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Open Myelomeningocele
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SPINAL DYSRAPHISM
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OPEN MYELOMENINGOCELE Yoon Sun Hahn, MD, FAAP, FACS
EMBRYOLOGIC CONSIDERATION OF THE DEFINITION
Most researchers agree that the embryonic origin of spina bifida stems from a sequence of abnormalities that takes place at 26 to 28 days' gestation.54,56 Malformations that arise during this period are termed net~rtilationdefects; those appearing after 28 days' gestation, during the canalization stage (29 to 48 days), are known as postnet~rulation defects. During the gestational period of 22 to 23 days, the neural groove deepens, and the neural folds meet in the dorsal midline to form the first neural tube. Initially the neural tube closes at the third or fourth somite, the future cervicomedullary junction, before it extends simultaneously in cephalic and caudal directions. The ectoderm that is contiguous with the lateral edge of the neural folds closes in the midline, and the cutaneous ectoderm is similarly drawn medially and fuses along the midline. Shortly thereafter, the cutaneous ectoderm separates from the neural tube. Ultimately, mesoderm interposes itself to form dermal appendages, muscles, and skeletal structures. On days 24 and 25 of gestation, the future thoracic spinal cord forms caudally while the neural tube completes its cephalad closure at the rostra1 opening, which is the anterior neuropore at the level of the future lamina terminalis. Finally, on days 26 and 27, the caudal end of the neural tube closes at spinal
cord segment L-1 or L-2 (with a range of error of two segments above or below).24The process of neurulation ends with the formation of the lumbar segments of the cord. The more caudal portions of the cord develop during the next stage, canalization, at 28 to 48 days' gestation.12,22 The process of canalization is less precise than that of neurulation. During this stage, the terminal ventricles that mark the future conus medullaris, filum terminale, lumbosacral lipoma, lipomyelomeningocele, and the fork of the central canal have their origin.21, 22, 25 Defects during neurulation lead to an open myelomeningocele. The cranial counterparts of these defects are anencephaly and cranioschisis. Postneurulation defects include skincovered variants of spina bifida, such as meningocele, lipomyelomeningocele, dermal sinus tract, and dia~tematornyelia.~~ Some of the forms of spina bifida may relate to abnormal development of the neural tube, separation of the superficial cutaneous ectoderm, or migration of the mesoderm toward the space between the superficial cutaneous ectoderm and the ne~roectoderm.~~ The term open myeloineningocele denotes the most common form of neural tube defect and is used synonymously with spina bifida aperta or spina bifida cystica. As the latter term implies, the spine has a cystic appearance, even if it collapses because of the leakage of cerebrospinal fluid. Typically a neural placode (plaque), which is unfolded neural tissue
From the Departments of Neurological Surgery and Pediatrics, Loyola University Medical Center of Chicago, Maywood, Illinois
NEUROSURGERY CLINICS OF NORTH AMERICA VOLUME 6 . NUMBER 2 APRIL 1995
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(usually abnormal conus medullaris), appears at the center. In the center of the placode, a midline groove, the central canal of the spinal cord, may be seen (Fig. 1). The rostral end enters the central canal of the normal spinal cord. Often, cerebrospinal fluid leaks from the rostral portion of the groove, which is the caudal vortion of the intact central canal. Neuronal counts in the lumbosacral spinal cords of children with myelomeningocele show dysplastic axons, cells, gliosis, or a reduction in size of the peripheral nerves.43 The neural placode is usually exposed at the center of the cystic dome but sometimes is covered by a thin epithelial layer. Varying degrees of epithelialization may be present from the periphery inward to the lateral margin of the neural placode (Fig. 2). Arachnoid pia reflect from this boundary, along with rudimentary dura splayed laterally where the dura meets the dorsal muscle fascia. At the rostral end of the cystic sac, the normal spinal cord can be traced as it exits from the spinal canal. Caudally the placode may end within the meningeal sac or extend as a thickened filum; the actual circumstance is determined by the level of the lesion. The ventral and dorsal roots are found primarily on the venI
Figure 2. Myelomeningocele showing three different zones: (a) neural placode zone; (b) pia-arachnoid epithelial zone; and (C) cutaneous zone.
tral surface of the neural placode. The dorsal roots exit the lateral anterior half of the spinal cord, whereas the ventral roots exit the medial anterior neural placode. The nerve roots exit at an angle more tangential than that of the normal rostral nerve roots.8 In addition, aberrant roots run laterally or dorsally toward the dural encasement and end blindly in the dura, the paravertebral muscle layer, or the epithelial layer. Anomalous blood vessels, usually veins, are noticeable at the inner wall of the arachnoid or dura, but they most likely have no anatomic significance. Often the cutaneous layer lacks a full thickness of skin that may continue into the center and become a thin epithelial layer, through which cerebrospinal fluid is visible if the sac is not ruptured (see Figs. 1 and 2). The most common sites of spinal cord lesions are the distal thoracic, lumbar, or sacral areas; more than 85% of myelomeningoceles and meningoceles are found at these levels.27 About 10% are detected in the thoracic area, and an additional 5% are found in the cervical area.27Occasionally, more than one lesion appears on the spinal axis. There may be as many as three, with the more caudal one being larger and more clinically significant.16,53 ASSOCIATED ANOMALIES
Figure 1. Neural placode with open central canal (arrow a), and midline groove (arrow b). Notice the abnormal wandering veins.
A multitude of associated anomalies are possible in a child with open myelomeningo-
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cele. Vertebral anomalies include (1) an absence of the spinous processes and laminae, or rudimentary laminae; (2) a reduction in the anteroposterior size of the vertebral body to become more or less ovoid; (3) an increase of the interpedicular distance; (4) decreased height of the pedicle; (5) laterally extended large transverse processes; (6) hemivertebrae; (7) partial or complete vertebral fusion; and (8) fusion of transverse processes. In its worst form, the spinal axis may appear telescoped so that the head seems to be impacted on the trunk and the lumbar spine almost nonexistent.'" A nearly constant pair of anomalies of the neuraxis in children with myelomeningocele are Arnold-Chiari malformation and demonstrable obstruction of the flow of cerebrospinal fluid within the ventricles." Hydrocephalus is present in 80% of children with myelomeningocele, along with associated brain anomalies, such as microgyria, polygyria, enlargement of the massa intermedia, agenesis or dysgenesis of the corpus callosum, and cerebellar dysgenesis and ArnoldChiari malformation type 11. This malformation denotes anomalies of the hindbrain almost always associated with myelomeningocele. The midbrain, especially the tectal area, is beaked, and the aqueduct of Sylvius is anomalous. The pons and medulla oblongata are bowed posteriorly and often extend into the rostral cervical canal along with the cerebellar vermis and tonsils. Skull anomalies include craniolacuna, a small posterior fossa with an enlarged foramen magnum, a lowset tentorium, low-lying torcular Herophili, and an anomalous dural sinus in the posterior fossa. Spinal cord anomalies other than open myelomeningocele include hydromyelia, diplomyelia, diastematomyelia, and defective myelinization; these were found in 88% of 25 autopsy cases." Brain stem malformations, such as hypoplasia or aplasia of cranial nerve nuclei, olives, basal pontine nuclei, tegmentum, or defective myelinization, were found in 76% of the same series." Other more common anomalies are in the ventricular system (92% of 25 autopsy cases) and include aqueductal stenosis, forking and atresia, or third ventricle atresia and fourth ventricle stenosis." Other common anomalies noticed in the cerebrum are heterotopias, polymicrogyria,
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corpus callosum dysgenesis or agenesis, and cerebellar dysgenesis (72% to 92% of autopsy cases)." Rorke and colleague^^^ found cerebellar dysplasia in some form in 84% of brains of normal infants. Associated systemic anomalies appear in the gastrointestinal, pulmonary, and cardiovascular systems; the craniofacial anomalies that appear are relatively infrequent. The most common anomalies in the genitourinary system are hydroureter or hydronephrosis. Gastrointestinal anomalies include inguinal hernia, Meckel's diverticulum, malrotation omphalocele, and imperforate anus. Cardiovascular anomalies include ventricular or atrial septa1 defects, patent ductus, and coarctation of the aorta2 Any combination of the anomalies described is possible in a child with open myelomeningocele. These children may also have additional lesions, such as dermoid cyst, intraspinal lipoma, epidermoid, dermal sinus, or even a small meningocele manque as a second lesion at the rostral spinal levell%r encephalocele (Fig. 3).In these circumstances, treatment priority is given to the life-threatening lesion or secondarily to the one that contributes to the most neurologic deficit^.^" CLINICAL ASSESSMENT
The earliest recorded surgical treatment of a child with spina bifida may have been when Forestus ligated a sac in 1610.44In 1929, Fraser9 reported long-term follow-up results for 131 children with myelomeningocele who were treated with some type of surgery. Sixty-three percent were discharged from the hospital, and 23% were alive at the time of the report. Surgeons began to consider operative closure of myelomeningocele with the advent of antibiotics and aseptic surgical techniques. Candidates for surgery had to be selected carefully, particularly among children with associated lesions such as hydrocephalus, high lumbar involvement, or extensive kyphosis associated with anomalies of major org a n ~Surgery . ~ ~ was usually delayed until the lesion was covered with epithelial t i s s ~ e . ' ~ , ~ ~ Despite these early reports, many investigators found that significant numbers of children who did not undergo treatment survived. Furthermore, when comparing the results in selected patient populations with
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Figure 3. A newborn child with associated lesions of myelomeningocele and encephalocele.
those in unselected populations, McLone and colleague^^^,^^ found that the results were distinctly better for the unselected patients than the highly selected series reported by L ~ r b e r These . ~ ~ results were based on continence, renal function, ambulation, IQ, and mortality. Quite simply, a selection process for providing treatment cannot be supported by clinical experience or ethical principle^.^^ Treatment and comprehensive continuing care are now of high quality, and most treatment centers provide aggressive multidisciplinary care from infancy through adulthood. Thus, the potential for a rewarding and meaningful existence extends to all patients with spina bifida and puts the selection discussion to rest. PREOPERATIVE TREATMENT Prenatal Care
With the advent of prenatal care, including alpha-fetoprotein analysis, amniocentesis, and ultrasound imaging, an increased number of fetuses with spina bifida are identified during intrauterine life, and obstetricians commonly refer the mother and family to specialized teams that include a pediatric neurosurgeon, neonatologist, social worker, and myelomeningocele (spina bifida) team coordinator. This referral allows postnatal treatment, including surgery, to be planned in a timely fashion and begun immediately after delivery. The prenatal sessions should
inform the mother and family about myelomeningocele; surgical treatment; and associated anomalies such as hydrocephalus, surgery to divert cerebrospinal fluid, Arnold-Chiari malformation, hydromyelia, and tethered cord. Most pediatricians and pediatric neurosurgeons agree that closure of the open myelomeningocele within the first 24 to 48 hours after birth decreases morbidity and mortality rates.
Postnatal Care
Immediately after the child is born, the myelomeningocele is covered with a sterile dressing (wet or nonadherent dressing) before the infant is transferred to the neonatal intensive care unit. Normothermia is rigorously maintained through continuous temperature monitoring. The child is kept in a prone or lateral recumbent position to protect the neural tissue. An initial evaluation is performed by the neonatologist and pediatric neurosurgeon to assess the degree of neurologic deficit; the child's functional level; and associated concerns such as hydrocephalus and cardiopulmonary, genitourinary, and gastrointestinal conditions that could interfere with surgery of the myelomeningocele. The examination of the lesion includes noting its circumference and shape, the placode, skin integrity, and the extent of the cutaneous and epithelialized layers. The spinal column is examined for evidence of early scoliosis, kypho-
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sis, and visible and palpable prominent laminae at the lateral margin of the lesion. To determine the level of neural involvement, the physician can begin by examining the sensory level, a test that requires the child to be relaxed and quiet. The sensory level can be determined by stimulating the distal to proximal dermatomal segments with pinpricks, noting whether the child responds by moving the face or upper or lower extremities, depending on the level of involvement. The sensory level is usually one or two segments higher than the anticipated motor level. The motor examination can be done with pinpricks over the child's torso or upper extremities. A child with a lesion at T-12 or above has flail legs. Hip flexion requires L-1 to L-3 function, whereas knee extension requires L-2 to L-4 function. Knee flexion demands function at L5-S2; plantar flexion demands function at S1-2. Plantar extension requires L4-5 function, toe extension requires ~ 5 1 ~and 1 , toe flexion requires S1-2 fun&ion. More than 90% of neonates with myelomeningocele have some form of neurogenic bladder, and one cannot always predict the degree of anal sphincter disturbance by the appearance of anal wink or sphincter tone. The constant leakage of meconium from a patulous anus usually predicts later difficulties. Dribbling of urine as the neonate cries or moves indicates future urinary incontinence, whereas periodic micturition with a good stream suggests a possibility of partial incontinen~e.~O A reliable determination of bladder function, however, often is not possible for months, even though the child's urologic capacity has been assessed early. A high percentage of children with neurogenic bladder are identified, and appropriate steps can be taken to ensure that the patient has a continent bladder. As the child develops, bladder and bowel training programs offer a possibility of achieving continence. RADIOGRAPHY AND NEUROIMAGING
Immediately after the child is born, the greatest concern is surgical closure of the open myelomeningocele. Ultrasound or computed tomography (CT) scans of the head furnish sufficient information for the surgeon to plan the approach. Other radiologic assess-
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ment of the child's nervous system is not usually required and has little influence on the initial surgery. A few days after the myelomeningocele is closed or cerebrospinal fluid diversion surgery is carried out, urologic and orthopedic care can begin. Because of the likely presence of associated anomalies, a diagnostic evaluation usually includes the head, spine, and hip. About 3O0/0 of children with a myelomeningocele have congenital scoliosis; half of these do not show evidence of the scoliosis until the ages of 5 to 10 years.1° Neurogenic hip and foot deformities are assessed along with joint mobility and loss of muscle bulk in the thighs and calves. Plain x-ray films do not provide information about anomalies of the neural structures, and CT scans or magnetic resonance images are preferred.
OPERATIVE TREATMENT
The neurologic deficits associated with myelomeningocele are usually permanent and irreversible. Exposing the neural tissue to trauma during birth potentially causes a shocklike state in the neural placode (spinal cord), which may be reversible with care and preservation of all viable neural tissue. Therefore, the goals of early operative care for a neonate with an open myelomeningocele are (1) preserving all viable neural tissue, (2) reconstituting the normal anatomic environment, and (3) minimizing the chance of infection or preventing ascending infection of the neural axis. The threat of superficial infection of the placode increases 72 hours after birth. Initiating surgery after that time carries a significant risk of meningitis, ventriculitis,16,34 decrease of motor function, and an increase in neurologic deficits in the survivors of delayed closure. Closure is usually delayed to allow time for physicians to instruct the family and for the parents to feel they are partic&ating in the initial decision-making process. This may be an ideal situation if delayed closure produces morbidity and mortality rates similar to those of early closure. The fundamental goals for surgical closure of the myelomeningocele are to (1) identify the neural placode, intermediate epithelial layer, skin, and the pia arachnoid and dura; (2) preserve neural tissues; (3) reconstitute the
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Figure 4. Myelomeningocele is covered with nonadherent-moistened sterile dressing and the rest of the skin is painted with aseptic solution.
normal neural environment-the pia-arachnoidal, dural, fascial, and skin layers; (4) complete skin closure; and (5) prevent leakage of cerebrospinal fluid. Preparation for surgery includes constant care of the neural placode, which should be covered with a moistened, nonadherent, aseptic dressing. The neonate is transferred to the surgical suite in an Isolette carrier while the body temperature is maintained and proper fluids are administered. The child can be intubated in either the lateral recum-
bent position or the supine position if the myelomeningocele is placed in the center of a doughnut-shaped sponge and the neural placode is not compressed. Temperature drift is controlled with a heating blanket, overhead heating lamp, and a warm operating room (78 to 80°F). The rectal route is less reliable than the oropharyngeal route for monitoring body temperature because the autonomic nervous system in the rectal area may also be damaged. Once the neonate is prone with appropriate rolls supporting the chest, the neural placode should be gently irrigated with normal saline and covered with a nonadherent moistened sterile dressing. The rest of the skin is scrubbed with an antiseptic agent (Fig. 4), and the entire wound except for the placode area and the surrounding skin is gently covered with an iodine-impregnated drape (Fig. 5). The surgeon begins the operation by identifying the margin of the neural placode, the central canal, and the primitive neural groove, which is in the midline of the placode and continues rostrally into the central canal. Cerebrospinal fluid can be seen flowing through the central canal. Surgical dissection begins under magnification, which facilitates the surgery and care of the neural tissue. Bipolar coagulation is essential; no monopolar coagulation is needed. Dissection begins in a circumferential fashion, dividing the placode from the epithelial layer. This division allows the surgeon to see the pia-arachnoid attached at the periphery of the neural
Figure 5. Neural placode is covered with nonadherent dressing and the entire field is draped with an iodine-impregnated drape.
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placode. Sharp dissection is warranted to decrease the future risk of inclusive epidermoid tumors. Developmentally the lateral edges of the ventral surface of the placode are the alar plate or the dorsal root entry zones. Dorsal nerve roots (sensory) are seen in these areas. The medial portion of the ventral surface of the placode is the basal plate, which contains the ventral nerve roots (motor). Thus, the piaarachnoid meets the neural placode at the lateral margin of the ventral surface of the placode. An understanding of this anatomy is essential to reconstituting - the spinal cord and its coverings. After the placode is dissected from the epithelial layer, the skin and the epithelial zone are grasped with hemostats and reflected laterally. This maneuver allows the surgeon to see the entire extension of the subarachnoid space on either side of the placode and dura, which also is everted. The dura is usually attached to the skin a few millimeters lateral to the lateral margin of the epithelial zone. Anomalous roots or rootlets, which usually end blindly in the dome or wall of the sac, can be seen and divided. Although the surgeon should attempt to preserve all small arteries and veins, one or two laterally displaced, engorged veins may have to be sacrificed to close the dura (Fig. 6, upper). Dissection of the dura starts from the lateral margin and moves toward both the rostral and the caudal poles. The junction of dura mater and skin is usually located just lateral to and beneath the point where the epithelium and skin are joined. The extradural space is entered and this plane, which is easily recognized as the dural flap, is dissected and rolled medially until the characteristic epidural fat is encountered within the spinal-canal. Unless it is flaccid or bulky, the neural tube usually can be reconstructed with 7-0 continuous sutures, starting from the rostra1 end and moving toward the caudal end. Care must be taken to suture the ~ia-arachnoid layer, but sutures must not be placed through the neural placode itself. Thus, the central canal is reconstructed in its entirety and the neural placode becomes a tube (Fig. 6, lower). Closing the placode into a tube and folding the arachnoid sac around this tube encloses the cord in an envelope of cerebrospinal fluid. This tubular reconstruction of the neural plac-
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Figure 6. A, Neural placode is dissected, dura is mobilized for closure. B, Using 7-0 suture, the edge of the neural placode is approximated in the midline to reconstruct neural placode into tube. (From McLone DG, Wilkins RH, Rangachary SS (eds): Neurosurgical Operative Atlas, vol 3, AANS, 1993, p 41 .)
ode might decrease the possibility of scarring and adherent neural elements that could later result in tethering of the spinal cord as the child grows.32 The dura is closed watertight, but this closure should not constrict the underlying neural elements. When insufficient dura is available to make a watertight closure, lyophilized dura, fascia lata, or lumbosacral muscle fascia can be used. The Valsalva maneuver is done to test the integrity of the dural coverage and watertight closure of the dura. At this point in the surgery, mobilizing and approximating paraspinal muscle fascia is optional. The skin is closed in the midsagittal plane wherever Iuossible. If midline closure is not possible, the skin may be closed in any direction in which it can be reapproximated easily. The skin must be well undermined and blunt dissection done between the muscle and subcutaneous layer so as to preserve maximum blood supply to the skin. The skin is then closed with interrupted sutures. Occasionally,
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good skin closure may be difficult or even impossible. Several surgical techniques have been used in this situation? including local rotated skin flaps, tissue expansi0n,5~relaxation of the lateral incisions with a skin graft13,38 and a Limberg-latissimus dorsi myocutaneous flap.28,40 Occasionally a child with a large defect and pronounced kyphosis needs surgery to reduce the vertebral angulation or a kyphect ~ m y .48~This ~ , surgery makes closure easier; corrects the angle of the back so as to give the child a flat back; and converts muscles from flexors of the spine to extensors, which may prevent progressive deformity of the spine. POSTOPERATIVE TREATMENT
Immediate postoperative care is directed toward preserving the integrity of the surgical wound without infection or leakage of cerebrospinal fluid. Fecal contamination is prevented by a plastic barrier placed between the anus and the wound. When surgery is finished, the child is placed in an Isolette sterile carrier for transfer to the neonatal intensive care unit. The child can be placed in the supine, prone, or lateral recumbent position. Daily inspection and care of the wound monitors signs of infection, healing of the wound, and leakage of cerebrospinal fluid. Antibiotics usually are not necessary. Meticulous closure of the dura and other layers significantly reduces the chance of cerebrospinal fluid leakage, but if fluid does leak within the first few days, additional sutures can be placed immediately. This secondary procedure usually ends the leakage. Hydrocephalus associated with myelomeningocele has been ascribed to aqueductal stenosis. Many surgeons, however, have noted that hydrocephalus is exacerbated by and becomes symptomatic after the myelomeningocele is closed. About 15% of patients with myelomeningocele are born with clinical signs of hydrocephalus, but 80% or more develop hydrocephalus in early infancy? In most instances, the clinical features of hydrocephalus become obvious within a week or two. The diagnosis is confirmed by CT or ultrasound, and a shunt, preferably a ventriculoperitoneal shunt, is inserted. This procedure not only relieves the ventricular pres-
sure, but also relieves pressure and tension on the myelomeningocele wound so that it can heal without cerebrospinal fluid leakage. Many infants with myelomeningocele have enlarged ventricles with no clinical features of increased intracranial pressure. When no overt clinical signs of hydrocephalus or a nonhealing wound are apparent, a team approach to assessment after surgery is recommended. Parents need guidance and help with their child; therefore, all members of the multidisciplinary team must be aware of the developmental problems the child faces and the emotions the parents often feel. Prenatal diagnosis by ultrasound and fetal alpha-fetoprotein allows an increasing number of pregnant mothers to be forewarned about and prepared for a child with a myelomeningocele. Even so, many parents experience immense emotional turmoil. Their primary concerns are about the child's survival, prognosis, disability, and intellectual development. Especially when the affected child is first-born, parents experience self-doubt and fears of inadequacy along with a profound guilt. The medical team must assure parents that these feelings are not unique to parents of children with myelomeningocele and that all parents feel guilt when their children are ill. To begin the infant's postsurgical care, a pediatric urologist examines the infant to determine the degree of sphincter impairment, bladder dysfunction, ureteral reflux, and infection and begins the intermittent catheterization program. Bowel management programs are easily achieved by supplementing proper nutrition, by using laxatives, and by taking advantage of the normal physiologic response of the gastrointestinal tract. A pediatric orthopedic surgeon evaluates spinal anomalies, such as scoliosis and neurogenic hip dislocation. The varieties of neurogenic clubfoot can be treated with a cast and stretches begun in the early stages of care. The neurosurgeon is most intimately involved in the child's care in the first 2 or 3 years of life. This closeness is then gradually supplanted by more involved orthopedic and urologic treatment. During the first few years, any illness the child has is often blamed on the shunt, even though the child may in fact have a middle ear or upper respiratory infection or gastroenteritis or urinary tract infection. Children with myelomeningocele are
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not more susceptible to illness than other children. EARLY COMPLICATIONS AND OUTCOME
The operative mortality rate for children undergoing repair of a myelomeningocele is approaching 0, with 95% or greater survival rates for the first 2 years of life.1,31,45 In 1964, Laurencez0reviewed the outcomes of 407 children cared for at a large children's hospital just before the shunt device was available. At that time, a newborn infant with myelomeningocele had a 29% chance of living to the age of 12 years. Infants who survived 4 months had a 51% chance of living to the age of 12. Those who survived to the age of 1 year had a 77% chance of surviving to the age of 12. The mortality rate began to level off at about 48 months. A similar leveling off of the mortality rate has been observed in recent studies. McLone and coworkers35reported an overall mortality rate of 15% in unselected patients followed for 8 to 12 years after closure of a myelomeningocele; a total of 10% died by the end of the third year, and 14% died by the end of the fifth year. The most common cause of death is related to hindbrain dysfunction (73O/0),2~, 35 and almost all children with myelomeningocele have occasional problems related to this dysfunction. Only about a third of those with hindbrain dysfunction, however, have some degree of suffering; 10% have mild dysfunction with inspiratory stridor, 9% have moderate dysfunction with inspiratory stridor and periodic apnea, and 13% have severe dysfunction with periodic apnea and gastroesophageal r e f l ~ x .35~ The ~ , natural history of hindbrain dysfunction in neonates appears to be one of gradual improvement over time in children who survive the acute problems. In the Toronto series,15,41 the surgical mortality rate of neonates with hindbrain dysfunction was 38%. In the Chicago the mortality rate was 34% in neonates with severe hindbrain dysfunction, most of whom received conservative nonsurgical treatment (four underwent surgery). These authors believe it is best to temporize as often as possible in such newborns and to operate only when no other course is possible.36 During the first 2 years, illnesses in a child with a shunt are frequently blamed on mal-
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function of the shunt; after this period, however, complaints usually level off, and the rate of shunt revision decreases. In the 5 to 10 years after the shunt is inserted, about half of those receiving shunts do not require revision; one third require one or two revisions, and the remain;ng 20% need three or more shunt revision^.'^, 36 An Arnold-Chiari malformation can cause symptoms such as prolonged feeding, occasional choking and regurgitation of food or fluid, or laryngeal stridor followed by a cyanotic attack or apnea. An Arnold-Chiari malformation is believed to be present in all children with myelomeningocele, but studies indicate that it becomes clinically significant in only 10% to 32% of these children, especially in those 3 months of age or younger.", 35, 41 The rates for wound infection range from 7% to 12% in patients in whom the myelomeningocele was closed early (within 48 hour^).^"^^ A higher rate of infection has been noted in patients who underwent delayed closure. Studies, however, have not shown any increase in neurologic defects caused by delayed closure of the l e ~ i o n . ~ Leakage of cerebrospinal fluid after closure of a myelomeningocele is reported to be as high as 17O/0.~~ Such a leak, however, was rarely associated with infection, usually closed spontaneously, and was thought to result from patulous dural closure to prevent a tethered spinal cord. Although the prognosis for intellectual development is difficult to determine for a given infant, it appears that children with myelomeningocele who do not have episodes of ventriculitis develop normal intelligence. Untreated hydrocephalus has an adverse effect on normal intellectual growth.1° Children with myelomeningocele and hydrocephalus who are treated aggressively, however, perform within the normal range on IQ test~:~,42 whereas only 31% of children with a shunt and infection of the central nervous system have IQ tests within the norm. Therefore, it appears that hydrocephalus alone does not significantly limit the normal development of intelligence. Nonverbal intelligence develops less well than verbal intelligen~e,~ but intelligence in general is not affected either by the type or number of shunt revision^.^,^^ The hand function and coordination in children with myelomeningocele may be significantly disturbed. These children may have
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delayed hand dominance, delayed use of the hands for balance, and difficulty with eyehand c~ordination.~~ These children may also have visual perception problems or memory deficits during crucial developmental phases6,47 Success with walking is subject to many of the same potentially limiting factors as intelligence. To stand erect requires a level of motor function at L-3; motor function at L-4 or L-5 is necessary for walking. As children with myelomeningocele age, the increase in their body weight may exceed the increase in their motor strength, creating difficulties in walking. For that reason, many become wheelchair bound or may require reciprocal braces, canes, and walkers. As a result, however, of improved recognition of myelomeningocele, treatment of tethered cord syndrome, the use of orthopedic procedures to prevent and treat scoliosis, care for deformities of the extremities, and the use of appropriate orthosis, about 80% of patients with myelomeningocele are able to walk.31,44, 45 Until the middle 1970s, children with myelomeningocele underwent a series of urologic procedures for urinary diversion. Since that time, the treatment of urinary incontinence has improved markedly because of the advent of clean intermittent catheterization and pharmacologic agents. Continence rates of 85% are now p ~ s s i b l e , ' ~and , ~ ~children , ~ ~ can stay dry for 3 or 4 hours. Sexual development and function require motor ability at the S-2 to S-4 level. Individual ability in sexual development is highly variable; despite certain lesions, reflex erection and ejaculation is possible.55In 1977, Shurtleff and S o u ~ reported a~~ that of 60 patients aged 16 to 24 years, 18% were sexually active. Counseling regarding sexual function is recommended for all patients with myelomeningocele. Optimal care of a patient with myelomeningocele requires a comprehensive coordinated plan of treatment. Because children with myelomeningocele have a variety of problems, their care requires a multidisciplinary team composed of a pediatric neurosurgeon, orthopedic surgeon, urologic surgeon, pediatrician, physiatrist, nurse, nutritionist, social worker, and neuropsychologist. All these individuals should be continuously involved in the care of the infant as he or she grows. One of the greatest obstacles children
with myelomeningocele face are psychosocial problems, which can originate within these children themselves and from their families and society. The stress of adjustment can be reduced by placing children into the mainstream of education, offering personal and family counseling, and working for increased public awareness of spina bifida. References 1. Ames MD, Schut L: Results of treatment of 171 consecutive myelomeningoceles-1963 to 1968. Pediatrics 50:466, 1972 2. Brown SF: Congenital malformations associated with myelomeningocele. J Iowa Med Soc 65:101, 1975 3. Chamey EB, Weller SC, Sutton LN: Management of the newborn with myelomeningocele: Time for a decision-making process. Pediatrics 75:58, 1985 4. Cheek WR, Laurent JP, Cech DA: Operative repair of lumbosacral myelomeningocele: Technical note. J Neurosurg 59:718, 1983 5. Cruz NI, Ariyan S, Duncan CC: Repair of lumbosacral myelomeningoceles with double Z-rhomboid flaps: Technical note. J Neurosurg 59:714, 1983 6. Cull C, Wyke MA: Memory function of children with spina bifida and shunted hydrocephalus. Dev Med Child Neurol26:177, 1984 7. Dennis M, Fitz CR, Netley CT: The intelligence of hydrocephalic children. Arch Neurol38:607, 1981 8. Emery JL, Lendon RG: The local cord lesion in neurospinal dysraphism (meningomyelocele). J Pathol 110:83, 1973 9. Fraser J: Spina bifida. Edinburgh Med J 36:284, 1929 10. French BN: Midline fusion defects and defects of formation. In Youmans JR (ed): Neurological Surgery, ed 2. Philadelpha, WB Saunders, 1982, p 1236 11. Gilbert JN, Jones KL, Rorke LB: Central nervous system anomalies with associated meningocele hydrocephalus, and the Arnold-Chiari malformation: Reappraisal of theories regarding the pathogenesis of posterior neural tube closure defects. Neurosurgery 18:559, 1986 12. Goldstein F, Kepes JJ: The role of traction in the development of the Arnold-Chiari malformation: An experimental study. J Neuropathol Exp Neurol 25:654, 1966 13. Gurdjian ES, Thomas LM: Operative Neurosurgery, ed 2. Baltimore, Williams & Wilkins, 1970 14. Hannigan KF: Teaching intermittent self-catheterization to young children with myelodysplasia. Dev Med Child Neurol21:365, 1979 15. Hoffman HJ, Park TS, Hendrick EB: Manifestazioni e trattamento della malformazione di Arnold-Chiari nel bambino con mielomeningocele. Iiz DiRocco M, Caldarelli M (eds): Mielomeningocele. Rome, Casa del Libro Editrice, 1983, p 251 16. Humphreys RP: Spinal dysraphism. In Wilkins RH, Rengachary SS (eds): Neurosurgery, vol3. New York, McGraw-Hill, 1985, pp 2041-2052 17. Ingraham FD, Swan H: Spina bifida and cranium bifidum: I. A survey of five hundred and forty-six cases. N Engl J Med 228:559, 1943 18. James CCM, Lassman LP: Spina Bifida Occulta: Or-
OPEN MYELOMENINGOCELE thopaedic, Radiological and Neurosurgical Aspects. New York, Grune & Stratton, 1981 19. Lapides J, Diokno AC, Lowe BS: Followup on unsterile, intermittent self-catheterization. J Urol 111:184, 1974 20. Laurence KM: The natural history of spina bifida cystica: Detailed analysis of 407 cases. Arch Dis Child 39:41, 1964 21. Lemire RJ: Variations in development of the caudal neural tube in human embryos (Horizons XIV-XXI). Teratology 2:361, 1969 22. Lemire RJ: Embryology of the central nervous system. 117 Davis JA, Dobbing J (eds): Scientific Foundations of Paediatrics. London, Heinemann Medical Books, 1981, p 547 23. Lemire RJ: Neural tube defects: Clinical correlations. Clin Neurosurg 30:165, 1983 24. Lemire RJ, Loeser JD, Leech RW: Normal and Abnormal Development of the Human Nervous System. Hagerstown, MD, Harper & Row, 1975 25. Lendon RG, Emery JL: Forking of the central canal in the equinal cord of children. J Anat 106:499, 1970 26. Lorber J: Results of treatment of myelomeningocele: An analysis of 524 unselected cases, with special reference to possible selection for treatment. Dev Med Child Neurol 13:279, 1971 27. Matson DD, Ingraham FD: Neurosurgery of Infancy and Childhood, ed 2. Springfield, Charles C. Thomas, 1969 28. McDevitt NB, Gillespie RP, Woosley RE: Closure of thoracic and lumbar dysgraphic defects using bilateral latissimus dorsi myocutaneous flap transfer with extended gluteal fasciocutaneous flaps. Childs Brain 9:394, 1982 29. McLone DG: Technique for closure of myelomeningocele. Childs Brain 6:65, 1980 30. McLone DG: Results of treatment of children born with a myelomeningocele. Clin Neurosurg 30:407, 1983 31. McLone DG: Treatment of myelomeningocele: Arguments against selection. Clin Neurosurg 33:359, 1986 32. McLone DG: Repair of the myelomeningocele. 111 Wilkins RH, Rengachary SS (eds): Neurosurgical Operative Atlas, vol3. Park Ridge, IL, American Association of Neurological Surgeons, 1993, p 41 33. McLone DG, Czyzewski D, Raimondi AJ: Central nervous system infections as a limiting factor in the intelligence of children with rnyelomeningocele. Pediatrics 70:338, 1982 34. McLone DG, Dias MS: Complications of myelomeningocele closure. Pediatr Neurosurg 17:267, 1991-92 35. McLone DG, Dias MS, Kaplan WE: Concepts in the management of spina bifida. In Humphreys R (ed): Concepts in Pediatric Neurosurgery, vol 5. Basel, S. Karger, 1985, p 97 36. McLone DG, Naidich TP: Myelomeningocele: Outcome and late complications. 111 McLaurin RL, Schut L, Venes JL (eds): Pediatric Neurosurgery, ed 2. Philadelphia, WB Saunders, 1989, p 53 37. McLone DG, Suna J, Collins JA: Neurulation: Biochemical and Morphological Studies on Primary and
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Secondary Neural Tube Defects. 01 Humphreys RP (ed): Concepts in Pediatric Neurosurgery, vol 4. Basel, S. Karger, 1983, p 15 38. Meacham WF, Dickins RD Jr: Midline fusion defects and defects of formation. Ilz Youmans JR (ed): Neurological Surgery. Philadelphia, WB Saunders, 1973, p 588 39. Moore JE: Spina bifida, with a report of three hundred and eighty-five cases treated by excision. Surg Gynecol Obstet 1:137, 1905 40. Munro IR, Neu BR, Humphreys RP: Limberg-latissimus dorsi myocutaneous flap for closure of myelomeningocele. Childs Brain 10:381, 1983 41. Park TS, Hoffman HJ, Hendrick EB: Experience with surgical decompression of the Arnold-Chiari malformation in young infants with myelomeningocele. Neurosurgery 13:147, 1983 42. Raimondi AJ, Soare P: Intellectual development in shunted hydrocephalic children. Am J Dis Child 127:664, 1974 43. Ralis Z, Ralis HM: Morphology of peripheral nerves in children with spina bifida. Dev Med Child Neurol 27(suppl):109, 1972 44. Reigel DH: Spinal bifida. In McLaurin R, Venes J, Schut L, Epstein F (eds): Pediatric Neurosurgery. Philadelphia, WB Saunders, 1989, p 35 45. Reigel DH, McLone DG: Myelomeningocele: Operative treatment and results. Iiz Marlin AE (ed): Concepts in Pediatric Neurosurgery, vol 8. Basel, S. Karger 1988, p 41 46. Rorke LB, Fogelson MH, Riggs HE: Cerebellar heterotopia in infancy. Dev Med Child Neurol10:644, 1968 47. Shaffer J, Wolfe L, Friedrich W: Developmental expectations: Intelligence and fine motor skills. 111 Shurtleff DB (ed): Myelodysplasias and Exstrophies: Significance, Prevention, and Treatment. New York, Grune & Stratton, 1986, p 359 48. Sharrard WJW: The segmental innervation of the lower limb muscles in man. Ann R Coll Surg Engl 35106, 1964 49. Shurtleff DB, Sousa JC: The adolescent with myelodysplasia: Development, achievement, sex and deterioration. In McLaurin RL (ed): Myelomeningocele. New York, Grune & Stratton, 1977, p 809 50. Stark GD: Neonatal assessment of the child with a myelomeningocele. Arch Dis Child 46:539, 1971 51. Stein SC, Schut L: Hydrocephalus in myelomeningocele. Childs Brain 5:413, 1979 52. Teichgraeber JF, Riley WB, Parks DH: Primary skin closure in large myelomeningoceles. Pediatr Neurosci 15:18, 1989 53. Tryfonas G: Three spina bifida defects in one child. J Pediatr Surg 8:75, 1973 54. Von Recklinghausen F: Untersuchungen iiber die spina bifida. Arch Path Anat 105:243, 1886 55. Wabrek AJ: Myelodysplasia and interpersonal and sexual aspects. I12 McLaurin RL (ed): Spina Bifida: A ~ u l t i d i s c ~ p l i n aApproach. r~ New &rk, Praeger, 1986, p 332 56. Warkany J: Morphogenesis of spina bifida. In McLaurin RL (ed): Myelomeningocele. New York, Grune & Stratton, 1977, p 31
Acld~essreprint reqtresfs to: Yoon S. Hahn, MD Loyola University Medical Center 2160 South First Avenue Maywood, IL 60153
SPINAL DYSRAPHISM
+ .20
OPEN MYELOMENINGOCELE Yoon Sun Hahn, MD, FAAP, FACS
EMBRYOLOGIC CONSIDERATION OF THE DEFINITION
Most researchers agree that the embryonic origin of spina bifida stems from a sequence of abnormalities that takes place at 26 to 28 days' gestation.54,56 Malformations that arise during this period are termed net~rtilationdefects; those appearing after 28 days' gestation, during the canalization stage (29 to 48 days), are known as postnet~rulation defects. During the gestational period of 22 to 23 days, the neural groove deepens, and the neural folds meet in the dorsal midline to form the first neural tube. Initially the neural tube closes at the third or fourth somite, the future cervicomedullary junction, before it extends simultaneously in cephalic and caudal directions. The ectoderm that is contiguous with the lateral edge of the neural folds closes in the midline, and the cutaneous ectoderm is similarly drawn medially and fuses along the midline. Shortly thereafter, the cutaneous ectoderm separates from the neural tube. Ultimately, mesoderm interposes itself to form dermal appendages, muscles, and skeletal structures. On days 24 and 25 of gestation, the future thoracic spinal cord forms caudally while the neural tube completes its cephalad closure at the rostra1 opening, which is the anterior neuropore at the level of the future lamina terminalis. Finally, on days 26 and 27, the caudal end of the neural tube closes at spinal
cord segment L-1 or L-2 (with a range of error of two segments above or below).24The process of neurulation ends with the formation of the lumbar segments of the cord. The more caudal portions of the cord develop during the next stage, canalization, at 28 to 48 days' gestation.12,22 The process of canalization is less precise than that of neurulation. During this stage, the terminal ventricles that mark the future conus medullaris, filum terminale, lumbosacral lipoma, lipomyelomeningocele, and the fork of the central canal have their origin.21, 22, 25 Defects during neurulation lead to an open myelomeningocele. The cranial counterparts of these defects are anencephaly and cranioschisis. Postneurulation defects include skincovered variants of spina bifida, such as meningocele, lipomyelomeningocele, dermal sinus tract, and dia~tematornyelia.~~ Some of the forms of spina bifida may relate to abnormal development of the neural tube, separation of the superficial cutaneous ectoderm, or migration of the mesoderm toward the space between the superficial cutaneous ectoderm and the ne~roectoderm.~~ The term open myeloineningocele denotes the most common form of neural tube defect and is used synonymously with spina bifida aperta or spina bifida cystica. As the latter term implies, the spine has a cystic appearance, even if it collapses because of the leakage of cerebrospinal fluid. Typically a neural placode (plaque), which is unfolded neural tissue
From the Departments of Neurological Surgery and Pediatrics, Loyola University Medical Center of Chicago, Maywood, Illinois
NEUROSURGERY CLINICS OF NORTH AMERICA VOLUME 6 . NUMBER 2 APRIL 1995
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(usually abnormal conus medullaris), appears at the center. In the center of the placode, a midline groove, the central canal of the spinal cord, may be seen (Fig. 1). The rostral end enters the central canal of the normal spinal cord. Often, cerebrospinal fluid leaks from the rostral portion of the groove, which is the caudal vortion of the intact central canal. Neuronal counts in the lumbosacral spinal cords of children with myelomeningocele show dysplastic axons, cells, gliosis, or a reduction in size of the peripheral nerves.43 The neural placode is usually exposed at the center of the cystic dome but sometimes is covered by a thin epithelial layer. Varying degrees of epithelialization may be present from the periphery inward to the lateral margin of the neural placode (Fig. 2). Arachnoid pia reflect from this boundary, along with rudimentary dura splayed laterally where the dura meets the dorsal muscle fascia. At the rostral end of the cystic sac, the normal spinal cord can be traced as it exits from the spinal canal. Caudally the placode may end within the meningeal sac or extend as a thickened filum; the actual circumstance is determined by the level of the lesion. The ventral and dorsal roots are found primarily on the venI
Figure 2. Myelomeningocele showing three different zones: (a) neural placode zone; (b) pia-arachnoid epithelial zone; and (C) cutaneous zone.
tral surface of the neural placode. The dorsal roots exit the lateral anterior half of the spinal cord, whereas the ventral roots exit the medial anterior neural placode. The nerve roots exit at an angle more tangential than that of the normal rostral nerve roots.8 In addition, aberrant roots run laterally or dorsally toward the dural encasement and end blindly in the dura, the paravertebral muscle layer, or the epithelial layer. Anomalous blood vessels, usually veins, are noticeable at the inner wall of the arachnoid or dura, but they most likely have no anatomic significance. Often the cutaneous layer lacks a full thickness of skin that may continue into the center and become a thin epithelial layer, through which cerebrospinal fluid is visible if the sac is not ruptured (see Figs. 1 and 2). The most common sites of spinal cord lesions are the distal thoracic, lumbar, or sacral areas; more than 85% of myelomeningoceles and meningoceles are found at these levels.27 About 10% are detected in the thoracic area, and an additional 5% are found in the cervical area.27Occasionally, more than one lesion appears on the spinal axis. There may be as many as three, with the more caudal one being larger and more clinically significant.16,53 ASSOCIATED ANOMALIES
Figure 1. Neural placode with open central canal (arrow a), and midline groove (arrow b). Notice the abnormal wandering veins.
A multitude of associated anomalies are possible in a child with open myelomeningo-
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cele. Vertebral anomalies include (1) an absence of the spinous processes and laminae, or rudimentary laminae; (2) a reduction in the anteroposterior size of the vertebral body to become more or less ovoid; (3) an increase of the interpedicular distance; (4) decreased height of the pedicle; (5) laterally extended large transverse processes; (6) hemivertebrae; (7) partial or complete vertebral fusion; and (8) fusion of transverse processes. In its worst form, the spinal axis may appear telescoped so that the head seems to be impacted on the trunk and the lumbar spine almost nonexistent.'" A nearly constant pair of anomalies of the neuraxis in children with myelomeningocele are Arnold-Chiari malformation and demonstrable obstruction of the flow of cerebrospinal fluid within the ventricles." Hydrocephalus is present in 80% of children with myelomeningocele, along with associated brain anomalies, such as microgyria, polygyria, enlargement of the massa intermedia, agenesis or dysgenesis of the corpus callosum, and cerebellar dysgenesis and ArnoldChiari malformation type 11. This malformation denotes anomalies of the hindbrain almost always associated with myelomeningocele. The midbrain, especially the tectal area, is beaked, and the aqueduct of Sylvius is anomalous. The pons and medulla oblongata are bowed posteriorly and often extend into the rostral cervical canal along with the cerebellar vermis and tonsils. Skull anomalies include craniolacuna, a small posterior fossa with an enlarged foramen magnum, a lowset tentorium, low-lying torcular Herophili, and an anomalous dural sinus in the posterior fossa. Spinal cord anomalies other than open myelomeningocele include hydromyelia, diplomyelia, diastematomyelia, and defective myelinization; these were found in 88% of 25 autopsy cases." Brain stem malformations, such as hypoplasia or aplasia of cranial nerve nuclei, olives, basal pontine nuclei, tegmentum, or defective myelinization, were found in 76% of the same series." Other more common anomalies are in the ventricular system (92% of 25 autopsy cases) and include aqueductal stenosis, forking and atresia, or third ventricle atresia and fourth ventricle stenosis." Other common anomalies noticed in the cerebrum are heterotopias, polymicrogyria,
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corpus callosum dysgenesis or agenesis, and cerebellar dysgenesis (72% to 92% of autopsy cases)." Rorke and colleague^^^ found cerebellar dysplasia in some form in 84% of brains of normal infants. Associated systemic anomalies appear in the gastrointestinal, pulmonary, and cardiovascular systems; the craniofacial anomalies that appear are relatively infrequent. The most common anomalies in the genitourinary system are hydroureter or hydronephrosis. Gastrointestinal anomalies include inguinal hernia, Meckel's diverticulum, malrotation omphalocele, and imperforate anus. Cardiovascular anomalies include ventricular or atrial septa1 defects, patent ductus, and coarctation of the aorta2 Any combination of the anomalies described is possible in a child with open myelomeningocele. These children may also have additional lesions, such as dermoid cyst, intraspinal lipoma, epidermoid, dermal sinus, or even a small meningocele manque as a second lesion at the rostral spinal levell%r encephalocele (Fig. 3).In these circumstances, treatment priority is given to the life-threatening lesion or secondarily to the one that contributes to the most neurologic deficit^.^" CLINICAL ASSESSMENT
The earliest recorded surgical treatment of a child with spina bifida may have been when Forestus ligated a sac in 1610.44In 1929, Fraser9 reported long-term follow-up results for 131 children with myelomeningocele who were treated with some type of surgery. Sixty-three percent were discharged from the hospital, and 23% were alive at the time of the report. Surgeons began to consider operative closure of myelomeningocele with the advent of antibiotics and aseptic surgical techniques. Candidates for surgery had to be selected carefully, particularly among children with associated lesions such as hydrocephalus, high lumbar involvement, or extensive kyphosis associated with anomalies of major org a n ~Surgery . ~ ~ was usually delayed until the lesion was covered with epithelial t i s s ~ e . ' ~ , ~ ~ Despite these early reports, many investigators found that significant numbers of children who did not undergo treatment survived. Furthermore, when comparing the results in selected patient populations with
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Figure 3. A newborn child with associated lesions of myelomeningocele and encephalocele.
those in unselected populations, McLone and colleague^^^,^^ found that the results were distinctly better for the unselected patients than the highly selected series reported by L ~ r b e r These . ~ ~ results were based on continence, renal function, ambulation, IQ, and mortality. Quite simply, a selection process for providing treatment cannot be supported by clinical experience or ethical principle^.^^ Treatment and comprehensive continuing care are now of high quality, and most treatment centers provide aggressive multidisciplinary care from infancy through adulthood. Thus, the potential for a rewarding and meaningful existence extends to all patients with spina bifida and puts the selection discussion to rest. PREOPERATIVE TREATMENT Prenatal Care
With the advent of prenatal care, including alpha-fetoprotein analysis, amniocentesis, and ultrasound imaging, an increased number of fetuses with spina bifida are identified during intrauterine life, and obstetricians commonly refer the mother and family to specialized teams that include a pediatric neurosurgeon, neonatologist, social worker, and myelomeningocele (spina bifida) team coordinator. This referral allows postnatal treatment, including surgery, to be planned in a timely fashion and begun immediately after delivery. The prenatal sessions should
inform the mother and family about myelomeningocele; surgical treatment; and associated anomalies such as hydrocephalus, surgery to divert cerebrospinal fluid, Arnold-Chiari malformation, hydromyelia, and tethered cord. Most pediatricians and pediatric neurosurgeons agree that closure of the open myelomeningocele within the first 24 to 48 hours after birth decreases morbidity and mortality rates.
Postnatal Care
Immediately after the child is born, the myelomeningocele is covered with a sterile dressing (wet or nonadherent dressing) before the infant is transferred to the neonatal intensive care unit. Normothermia is rigorously maintained through continuous temperature monitoring. The child is kept in a prone or lateral recumbent position to protect the neural tissue. An initial evaluation is performed by the neonatologist and pediatric neurosurgeon to assess the degree of neurologic deficit; the child's functional level; and associated concerns such as hydrocephalus and cardiopulmonary, genitourinary, and gastrointestinal conditions that could interfere with surgery of the myelomeningocele. The examination of the lesion includes noting its circumference and shape, the placode, skin integrity, and the extent of the cutaneous and epithelialized layers. The spinal column is examined for evidence of early scoliosis, kypho-
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sis, and visible and palpable prominent laminae at the lateral margin of the lesion. To determine the level of neural involvement, the physician can begin by examining the sensory level, a test that requires the child to be relaxed and quiet. The sensory level can be determined by stimulating the distal to proximal dermatomal segments with pinpricks, noting whether the child responds by moving the face or upper or lower extremities, depending on the level of involvement. The sensory level is usually one or two segments higher than the anticipated motor level. The motor examination can be done with pinpricks over the child's torso or upper extremities. A child with a lesion at T-12 or above has flail legs. Hip flexion requires L-1 to L-3 function, whereas knee extension requires L-2 to L-4 function. Knee flexion demands function at L5-S2; plantar flexion demands function at S1-2. Plantar extension requires L4-5 function, toe extension requires ~ 5 1 ~and 1 , toe flexion requires S1-2 fun&ion. More than 90% of neonates with myelomeningocele have some form of neurogenic bladder, and one cannot always predict the degree of anal sphincter disturbance by the appearance of anal wink or sphincter tone. The constant leakage of meconium from a patulous anus usually predicts later difficulties. Dribbling of urine as the neonate cries or moves indicates future urinary incontinence, whereas periodic micturition with a good stream suggests a possibility of partial incontinen~e.~O A reliable determination of bladder function, however, often is not possible for months, even though the child's urologic capacity has been assessed early. A high percentage of children with neurogenic bladder are identified, and appropriate steps can be taken to ensure that the patient has a continent bladder. As the child develops, bladder and bowel training programs offer a possibility of achieving continence. RADIOGRAPHY AND NEUROIMAGING
Immediately after the child is born, the greatest concern is surgical closure of the open myelomeningocele. Ultrasound or computed tomography (CT) scans of the head furnish sufficient information for the surgeon to plan the approach. Other radiologic assess-
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ment of the child's nervous system is not usually required and has little influence on the initial surgery. A few days after the myelomeningocele is closed or cerebrospinal fluid diversion surgery is carried out, urologic and orthopedic care can begin. Because of the likely presence of associated anomalies, a diagnostic evaluation usually includes the head, spine, and hip. About 3O0/0 of children with a myelomeningocele have congenital scoliosis; half of these do not show evidence of the scoliosis until the ages of 5 to 10 years.1° Neurogenic hip and foot deformities are assessed along with joint mobility and loss of muscle bulk in the thighs and calves. Plain x-ray films do not provide information about anomalies of the neural structures, and CT scans or magnetic resonance images are preferred.
OPERATIVE TREATMENT
The neurologic deficits associated with myelomeningocele are usually permanent and irreversible. Exposing the neural tissue to trauma during birth potentially causes a shocklike state in the neural placode (spinal cord), which may be reversible with care and preservation of all viable neural tissue. Therefore, the goals of early operative care for a neonate with an open myelomeningocele are (1) preserving all viable neural tissue, (2) reconstituting the normal anatomic environment, and (3) minimizing the chance of infection or preventing ascending infection of the neural axis. The threat of superficial infection of the placode increases 72 hours after birth. Initiating surgery after that time carries a significant risk of meningitis, ventriculitis,16,34 decrease of motor function, and an increase in neurologic deficits in the survivors of delayed closure. Closure is usually delayed to allow time for physicians to instruct the family and for the parents to feel they are partic&ating in the initial decision-making process. This may be an ideal situation if delayed closure produces morbidity and mortality rates similar to those of early closure. The fundamental goals for surgical closure of the myelomeningocele are to (1) identify the neural placode, intermediate epithelial layer, skin, and the pia arachnoid and dura; (2) preserve neural tissues; (3) reconstitute the
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Figure 4. Myelomeningocele is covered with nonadherent-moistened sterile dressing and the rest of the skin is painted with aseptic solution.
normal neural environment-the pia-arachnoidal, dural, fascial, and skin layers; (4) complete skin closure; and (5) prevent leakage of cerebrospinal fluid. Preparation for surgery includes constant care of the neural placode, which should be covered with a moistened, nonadherent, aseptic dressing. The neonate is transferred to the surgical suite in an Isolette carrier while the body temperature is maintained and proper fluids are administered. The child can be intubated in either the lateral recum-
bent position or the supine position if the myelomeningocele is placed in the center of a doughnut-shaped sponge and the neural placode is not compressed. Temperature drift is controlled with a heating blanket, overhead heating lamp, and a warm operating room (78 to 80°F). The rectal route is less reliable than the oropharyngeal route for monitoring body temperature because the autonomic nervous system in the rectal area may also be damaged. Once the neonate is prone with appropriate rolls supporting the chest, the neural placode should be gently irrigated with normal saline and covered with a nonadherent moistened sterile dressing. The rest of the skin is scrubbed with an antiseptic agent (Fig. 4), and the entire wound except for the placode area and the surrounding skin is gently covered with an iodine-impregnated drape (Fig. 5). The surgeon begins the operation by identifying the margin of the neural placode, the central canal, and the primitive neural groove, which is in the midline of the placode and continues rostrally into the central canal. Cerebrospinal fluid can be seen flowing through the central canal. Surgical dissection begins under magnification, which facilitates the surgery and care of the neural tissue. Bipolar coagulation is essential; no monopolar coagulation is needed. Dissection begins in a circumferential fashion, dividing the placode from the epithelial layer. This division allows the surgeon to see the pia-arachnoid attached at the periphery of the neural
Figure 5. Neural placode is covered with nonadherent dressing and the entire field is draped with an iodine-impregnated drape.
OPEN MYELOMENINGOCELE
placode. Sharp dissection is warranted to decrease the future risk of inclusive epidermoid tumors. Developmentally the lateral edges of the ventral surface of the placode are the alar plate or the dorsal root entry zones. Dorsal nerve roots (sensory) are seen in these areas. The medial portion of the ventral surface of the placode is the basal plate, which contains the ventral nerve roots (motor). Thus, the piaarachnoid meets the neural placode at the lateral margin of the ventral surface of the placode. An understanding of this anatomy is essential to reconstituting - the spinal cord and its coverings. After the placode is dissected from the epithelial layer, the skin and the epithelial zone are grasped with hemostats and reflected laterally. This maneuver allows the surgeon to see the entire extension of the subarachnoid space on either side of the placode and dura, which also is everted. The dura is usually attached to the skin a few millimeters lateral to the lateral margin of the epithelial zone. Anomalous roots or rootlets, which usually end blindly in the dome or wall of the sac, can be seen and divided. Although the surgeon should attempt to preserve all small arteries and veins, one or two laterally displaced, engorged veins may have to be sacrificed to close the dura (Fig. 6, upper). Dissection of the dura starts from the lateral margin and moves toward both the rostral and the caudal poles. The junction of dura mater and skin is usually located just lateral to and beneath the point where the epithelium and skin are joined. The extradural space is entered and this plane, which is easily recognized as the dural flap, is dissected and rolled medially until the characteristic epidural fat is encountered within the spinal-canal. Unless it is flaccid or bulky, the neural tube usually can be reconstructed with 7-0 continuous sutures, starting from the rostra1 end and moving toward the caudal end. Care must be taken to suture the ~ia-arachnoid layer, but sutures must not be placed through the neural placode itself. Thus, the central canal is reconstructed in its entirety and the neural placode becomes a tube (Fig. 6, lower). Closing the placode into a tube and folding the arachnoid sac around this tube encloses the cord in an envelope of cerebrospinal fluid. This tubular reconstruction of the neural plac-
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Figure 6. A, Neural placode is dissected, dura is mobilized for closure. B, Using 7-0 suture, the edge of the neural placode is approximated in the midline to reconstruct neural placode into tube. (From McLone DG, Wilkins RH, Rangachary SS (eds): Neurosurgical Operative Atlas, vol 3, AANS, 1993, p 41 .)
ode might decrease the possibility of scarring and adherent neural elements that could later result in tethering of the spinal cord as the child grows.32 The dura is closed watertight, but this closure should not constrict the underlying neural elements. When insufficient dura is available to make a watertight closure, lyophilized dura, fascia lata, or lumbosacral muscle fascia can be used. The Valsalva maneuver is done to test the integrity of the dural coverage and watertight closure of the dura. At this point in the surgery, mobilizing and approximating paraspinal muscle fascia is optional. The skin is closed in the midsagittal plane wherever Iuossible. If midline closure is not possible, the skin may be closed in any direction in which it can be reapproximated easily. The skin must be well undermined and blunt dissection done between the muscle and subcutaneous layer so as to preserve maximum blood supply to the skin. The skin is then closed with interrupted sutures. Occasionally,
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good skin closure may be difficult or even impossible. Several surgical techniques have been used in this situation? including local rotated skin flaps, tissue expansi0n,5~relaxation of the lateral incisions with a skin graft13,38 and a Limberg-latissimus dorsi myocutaneous flap.28,40 Occasionally a child with a large defect and pronounced kyphosis needs surgery to reduce the vertebral angulation or a kyphect ~ m y .48~This ~ , surgery makes closure easier; corrects the angle of the back so as to give the child a flat back; and converts muscles from flexors of the spine to extensors, which may prevent progressive deformity of the spine. POSTOPERATIVE TREATMENT
Immediate postoperative care is directed toward preserving the integrity of the surgical wound without infection or leakage of cerebrospinal fluid. Fecal contamination is prevented by a plastic barrier placed between the anus and the wound. When surgery is finished, the child is placed in an Isolette sterile carrier for transfer to the neonatal intensive care unit. The child can be placed in the supine, prone, or lateral recumbent position. Daily inspection and care of the wound monitors signs of infection, healing of the wound, and leakage of cerebrospinal fluid. Antibiotics usually are not necessary. Meticulous closure of the dura and other layers significantly reduces the chance of cerebrospinal fluid leakage, but if fluid does leak within the first few days, additional sutures can be placed immediately. This secondary procedure usually ends the leakage. Hydrocephalus associated with myelomeningocele has been ascribed to aqueductal stenosis. Many surgeons, however, have noted that hydrocephalus is exacerbated by and becomes symptomatic after the myelomeningocele is closed. About 15% of patients with myelomeningocele are born with clinical signs of hydrocephalus, but 80% or more develop hydrocephalus in early infancy? In most instances, the clinical features of hydrocephalus become obvious within a week or two. The diagnosis is confirmed by CT or ultrasound, and a shunt, preferably a ventriculoperitoneal shunt, is inserted. This procedure not only relieves the ventricular pres-
sure, but also relieves pressure and tension on the myelomeningocele wound so that it can heal without cerebrospinal fluid leakage. Many infants with myelomeningocele have enlarged ventricles with no clinical features of increased intracranial pressure. When no overt clinical signs of hydrocephalus or a nonhealing wound are apparent, a team approach to assessment after surgery is recommended. Parents need guidance and help with their child; therefore, all members of the multidisciplinary team must be aware of the developmental problems the child faces and the emotions the parents often feel. Prenatal diagnosis by ultrasound and fetal alpha-fetoprotein allows an increasing number of pregnant mothers to be forewarned about and prepared for a child with a myelomeningocele. Even so, many parents experience immense emotional turmoil. Their primary concerns are about the child's survival, prognosis, disability, and intellectual development. Especially when the affected child is first-born, parents experience self-doubt and fears of inadequacy along with a profound guilt. The medical team must assure parents that these feelings are not unique to parents of children with myelomeningocele and that all parents feel guilt when their children are ill. To begin the infant's postsurgical care, a pediatric urologist examines the infant to determine the degree of sphincter impairment, bladder dysfunction, ureteral reflux, and infection and begins the intermittent catheterization program. Bowel management programs are easily achieved by supplementing proper nutrition, by using laxatives, and by taking advantage of the normal physiologic response of the gastrointestinal tract. A pediatric orthopedic surgeon evaluates spinal anomalies, such as scoliosis and neurogenic hip dislocation. The varieties of neurogenic clubfoot can be treated with a cast and stretches begun in the early stages of care. The neurosurgeon is most intimately involved in the child's care in the first 2 or 3 years of life. This closeness is then gradually supplanted by more involved orthopedic and urologic treatment. During the first few years, any illness the child has is often blamed on the shunt, even though the child may in fact have a middle ear or upper respiratory infection or gastroenteritis or urinary tract infection. Children with myelomeningocele are
OPEN MYELOMENINGOCELE
not more susceptible to illness than other children. EARLY COMPLICATIONS AND OUTCOME
The operative mortality rate for children undergoing repair of a myelomeningocele is approaching 0, with 95% or greater survival rates for the first 2 years of life.1,31,45 In 1964, Laurencez0reviewed the outcomes of 407 children cared for at a large children's hospital just before the shunt device was available. At that time, a newborn infant with myelomeningocele had a 29% chance of living to the age of 12 years. Infants who survived 4 months had a 51% chance of living to the age of 12. Those who survived to the age of 1 year had a 77% chance of surviving to the age of 12. The mortality rate began to level off at about 48 months. A similar leveling off of the mortality rate has been observed in recent studies. McLone and coworkers35reported an overall mortality rate of 15% in unselected patients followed for 8 to 12 years after closure of a myelomeningocele; a total of 10% died by the end of the third year, and 14% died by the end of the fifth year. The most common cause of death is related to hindbrain dysfunction (73O/0),2~, 35 and almost all children with myelomeningocele have occasional problems related to this dysfunction. Only about a third of those with hindbrain dysfunction, however, have some degree of suffering; 10% have mild dysfunction with inspiratory stridor, 9% have moderate dysfunction with inspiratory stridor and periodic apnea, and 13% have severe dysfunction with periodic apnea and gastroesophageal r e f l ~ x .35~ The ~ , natural history of hindbrain dysfunction in neonates appears to be one of gradual improvement over time in children who survive the acute problems. In the Toronto series,15,41 the surgical mortality rate of neonates with hindbrain dysfunction was 38%. In the Chicago the mortality rate was 34% in neonates with severe hindbrain dysfunction, most of whom received conservative nonsurgical treatment (four underwent surgery). These authors believe it is best to temporize as often as possible in such newborns and to operate only when no other course is possible.36 During the first 2 years, illnesses in a child with a shunt are frequently blamed on mal-
239
function of the shunt; after this period, however, complaints usually level off, and the rate of shunt revision decreases. In the 5 to 10 years after the shunt is inserted, about half of those receiving shunts do not require revision; one third require one or two revisions, and the remain;ng 20% need three or more shunt revision^.'^, 36 An Arnold-Chiari malformation can cause symptoms such as prolonged feeding, occasional choking and regurgitation of food or fluid, or laryngeal stridor followed by a cyanotic attack or apnea. An Arnold-Chiari malformation is believed to be present in all children with myelomeningocele, but studies indicate that it becomes clinically significant in only 10% to 32% of these children, especially in those 3 months of age or younger.", 35, 41 The rates for wound infection range from 7% to 12% in patients in whom the myelomeningocele was closed early (within 48 hour^).^"^^ A higher rate of infection has been noted in patients who underwent delayed closure. Studies, however, have not shown any increase in neurologic defects caused by delayed closure of the l e ~ i o n . ~ Leakage of cerebrospinal fluid after closure of a myelomeningocele is reported to be as high as 17O/0.~~ Such a leak, however, was rarely associated with infection, usually closed spontaneously, and was thought to result from patulous dural closure to prevent a tethered spinal cord. Although the prognosis for intellectual development is difficult to determine for a given infant, it appears that children with myelomeningocele who do not have episodes of ventriculitis develop normal intelligence. Untreated hydrocephalus has an adverse effect on normal intellectual growth.1° Children with myelomeningocele and hydrocephalus who are treated aggressively, however, perform within the normal range on IQ test~:~,42 whereas only 31% of children with a shunt and infection of the central nervous system have IQ tests within the norm. Therefore, it appears that hydrocephalus alone does not significantly limit the normal development of intelligence. Nonverbal intelligence develops less well than verbal intelligen~e,~ but intelligence in general is not affected either by the type or number of shunt revision^.^,^^ The hand function and coordination in children with myelomeningocele may be significantly disturbed. These children may have
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delayed hand dominance, delayed use of the hands for balance, and difficulty with eyehand c~ordination.~~ These children may also have visual perception problems or memory deficits during crucial developmental phases6,47 Success with walking is subject to many of the same potentially limiting factors as intelligence. To stand erect requires a level of motor function at L-3; motor function at L-4 or L-5 is necessary for walking. As children with myelomeningocele age, the increase in their body weight may exceed the increase in their motor strength, creating difficulties in walking. For that reason, many become wheelchair bound or may require reciprocal braces, canes, and walkers. As a result, however, of improved recognition of myelomeningocele, treatment of tethered cord syndrome, the use of orthopedic procedures to prevent and treat scoliosis, care for deformities of the extremities, and the use of appropriate orthosis, about 80% of patients with myelomeningocele are able to walk.31,44, 45 Until the middle 1970s, children with myelomeningocele underwent a series of urologic procedures for urinary diversion. Since that time, the treatment of urinary incontinence has improved markedly because of the advent of clean intermittent catheterization and pharmacologic agents. Continence rates of 85% are now p ~ s s i b l e , ' ~and , ~ ~children , ~ ~ can stay dry for 3 or 4 hours. Sexual development and function require motor ability at the S-2 to S-4 level. Individual ability in sexual development is highly variable; despite certain lesions, reflex erection and ejaculation is possible.55In 1977, Shurtleff and S o u ~ reported a~~ that of 60 patients aged 16 to 24 years, 18% were sexually active. Counseling regarding sexual function is recommended for all patients with myelomeningocele. Optimal care of a patient with myelomeningocele requires a comprehensive coordinated plan of treatment. Because children with myelomeningocele have a variety of problems, their care requires a multidisciplinary team composed of a pediatric neurosurgeon, orthopedic surgeon, urologic surgeon, pediatrician, physiatrist, nurse, nutritionist, social worker, and neuropsychologist. All these individuals should be continuously involved in the care of the infant as he or she grows. One of the greatest obstacles children
with myelomeningocele face are psychosocial problems, which can originate within these children themselves and from their families and society. The stress of adjustment can be reduced by placing children into the mainstream of education, offering personal and family counseling, and working for increased public awareness of spina bifida. References 1. Ames MD, Schut L: Results of treatment of 171 consecutive myelomeningoceles-1963 to 1968. Pediatrics 50:466, 1972 2. Brown SF: Congenital malformations associated with myelomeningocele. J Iowa Med Soc 65:101, 1975 3. Chamey EB, Weller SC, Sutton LN: Management of the newborn with myelomeningocele: Time for a decision-making process. Pediatrics 75:58, 1985 4. Cheek WR, Laurent JP, Cech DA: Operative repair of lumbosacral myelomeningocele: Technical note. J Neurosurg 59:718, 1983 5. Cruz NI, Ariyan S, Duncan CC: Repair of lumbosacral myelomeningoceles with double Z-rhomboid flaps: Technical note. J Neurosurg 59:714, 1983 6. Cull C, Wyke MA: Memory function of children with spina bifida and shunted hydrocephalus. Dev Med Child Neurol26:177, 1984 7. Dennis M, Fitz CR, Netley CT: The intelligence of hydrocephalic children. Arch Neurol38:607, 1981 8. Emery JL, Lendon RG: The local cord lesion in neurospinal dysraphism (meningomyelocele). J Pathol 110:83, 1973 9. Fraser J: Spina bifida. Edinburgh Med J 36:284, 1929 10. French BN: Midline fusion defects and defects of formation. In Youmans JR (ed): Neurological Surgery, ed 2. Philadelpha, WB Saunders, 1982, p 1236 11. Gilbert JN, Jones KL, Rorke LB: Central nervous system anomalies with associated meningocele hydrocephalus, and the Arnold-Chiari malformation: Reappraisal of theories regarding the pathogenesis of posterior neural tube closure defects. Neurosurgery 18:559, 1986 12. Goldstein F, Kepes JJ: The role of traction in the development of the Arnold-Chiari malformation: An experimental study. J Neuropathol Exp Neurol 25:654, 1966 13. Gurdjian ES, Thomas LM: Operative Neurosurgery, ed 2. Baltimore, Williams & Wilkins, 1970 14. Hannigan KF: Teaching intermittent self-catheterization to young children with myelodysplasia. Dev Med Child Neurol21:365, 1979 15. Hoffman HJ, Park TS, Hendrick EB: Manifestazioni e trattamento della malformazione di Arnold-Chiari nel bambino con mielomeningocele. Iiz DiRocco M, Caldarelli M (eds): Mielomeningocele. Rome, Casa del Libro Editrice, 1983, p 251 16. Humphreys RP: Spinal dysraphism. In Wilkins RH, Rengachary SS (eds): Neurosurgery, vol3. New York, McGraw-Hill, 1985, pp 2041-2052 17. Ingraham FD, Swan H: Spina bifida and cranium bifidum: I. A survey of five hundred and forty-six cases. N Engl J Med 228:559, 1943 18. James CCM, Lassman LP: Spina Bifida Occulta: Or-
OPEN MYELOMENINGOCELE thopaedic, Radiological and Neurosurgical Aspects. New York, Grune & Stratton, 1981 19. Lapides J, Diokno AC, Lowe BS: Followup on unsterile, intermittent self-catheterization. J Urol 111:184, 1974 20. Laurence KM: The natural history of spina bifida cystica: Detailed analysis of 407 cases. Arch Dis Child 39:41, 1964 21. Lemire RJ: Variations in development of the caudal neural tube in human embryos (Horizons XIV-XXI). Teratology 2:361, 1969 22. Lemire RJ: Embryology of the central nervous system. 117 Davis JA, Dobbing J (eds): Scientific Foundations of Paediatrics. London, Heinemann Medical Books, 1981, p 547 23. Lemire RJ: Neural tube defects: Clinical correlations. Clin Neurosurg 30:165, 1983 24. Lemire RJ, Loeser JD, Leech RW: Normal and Abnormal Development of the Human Nervous System. Hagerstown, MD, Harper & Row, 1975 25. Lendon RG, Emery JL: Forking of the central canal in the equinal cord of children. J Anat 106:499, 1970 26. Lorber J: Results of treatment of myelomeningocele: An analysis of 524 unselected cases, with special reference to possible selection for treatment. Dev Med Child Neurol 13:279, 1971 27. Matson DD, Ingraham FD: Neurosurgery of Infancy and Childhood, ed 2. Springfield, Charles C. Thomas, 1969 28. McDevitt NB, Gillespie RP, Woosley RE: Closure of thoracic and lumbar dysgraphic defects using bilateral latissimus dorsi myocutaneous flap transfer with extended gluteal fasciocutaneous flaps. Childs Brain 9:394, 1982 29. McLone DG: Technique for closure of myelomeningocele. Childs Brain 6:65, 1980 30. McLone DG: Results of treatment of children born with a myelomeningocele. Clin Neurosurg 30:407, 1983 31. McLone DG: Treatment of myelomeningocele: Arguments against selection. Clin Neurosurg 33:359, 1986 32. McLone DG: Repair of the myelomeningocele. 111 Wilkins RH, Rengachary SS (eds): Neurosurgical Operative Atlas, vol3. Park Ridge, IL, American Association of Neurological Surgeons, 1993, p 41 33. McLone DG, Czyzewski D, Raimondi AJ: Central nervous system infections as a limiting factor in the intelligence of children with rnyelomeningocele. Pediatrics 70:338, 1982 34. McLone DG, Dias MS: Complications of myelomeningocele closure. Pediatr Neurosurg 17:267, 1991-92 35. McLone DG, Dias MS, Kaplan WE: Concepts in the management of spina bifida. In Humphreys R (ed): Concepts in Pediatric Neurosurgery, vol 5. Basel, S. Karger, 1985, p 97 36. McLone DG, Naidich TP: Myelomeningocele: Outcome and late complications. 111 McLaurin RL, Schut L, Venes JL (eds): Pediatric Neurosurgery, ed 2. Philadelphia, WB Saunders, 1989, p 53 37. McLone DG, Suna J, Collins JA: Neurulation: Biochemical and Morphological Studies on Primary and
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Secondary Neural Tube Defects. 01 Humphreys RP (ed): Concepts in Pediatric Neurosurgery, vol 4. Basel, S. Karger, 1983, p 15 38. Meacham WF, Dickins RD Jr: Midline fusion defects and defects of formation. Ilz Youmans JR (ed): Neurological Surgery. Philadelphia, WB Saunders, 1973, p 588 39. Moore JE: Spina bifida, with a report of three hundred and eighty-five cases treated by excision. Surg Gynecol Obstet 1:137, 1905 40. Munro IR, Neu BR, Humphreys RP: Limberg-latissimus dorsi myocutaneous flap for closure of myelomeningocele. Childs Brain 10:381, 1983 41. Park TS, Hoffman HJ, Hendrick EB: Experience with surgical decompression of the Arnold-Chiari malformation in young infants with myelomeningocele. Neurosurgery 13:147, 1983 42. Raimondi AJ, Soare P: Intellectual development in shunted hydrocephalic children. Am J Dis Child 127:664, 1974 43. Ralis Z, Ralis HM: Morphology of peripheral nerves in children with spina bifida. Dev Med Child Neurol 27(suppl):109, 1972 44. Reigel DH: Spinal bifida. In McLaurin R, Venes J, Schut L, Epstein F (eds): Pediatric Neurosurgery. Philadelphia, WB Saunders, 1989, p 35 45. Reigel DH, McLone DG: Myelomeningocele: Operative treatment and results. Iiz Marlin AE (ed): Concepts in Pediatric Neurosurgery, vol 8. Basel, S. Karger 1988, p 41 46. Rorke LB, Fogelson MH, Riggs HE: Cerebellar heterotopia in infancy. Dev Med Child Neurol10:644, 1968 47. Shaffer J, Wolfe L, Friedrich W: Developmental expectations: Intelligence and fine motor skills. 111 Shurtleff DB (ed): Myelodysplasias and Exstrophies: Significance, Prevention, and Treatment. New York, Grune & Stratton, 1986, p 359 48. Sharrard WJW: The segmental innervation of the lower limb muscles in man. Ann R Coll Surg Engl 35106, 1964 49. Shurtleff DB, Sousa JC: The adolescent with myelodysplasia: Development, achievement, sex and deterioration. In McLaurin RL (ed): Myelomeningocele. New York, Grune & Stratton, 1977, p 809 50. Stark GD: Neonatal assessment of the child with a myelomeningocele. Arch Dis Child 46:539, 1971 51. Stein SC, Schut L: Hydrocephalus in myelomeningocele. Childs Brain 5:413, 1979 52. Teichgraeber JF, Riley WB, Parks DH: Primary skin closure in large myelomeningoceles. Pediatr Neurosci 15:18, 1989 53. Tryfonas G: Three spina bifida defects in one child. J Pediatr Surg 8:75, 1973 54. Von Recklinghausen F: Untersuchungen iiber die spina bifida. Arch Path Anat 105:243, 1886 55. Wabrek AJ: Myelodysplasia and interpersonal and sexual aspects. I12 McLaurin RL (ed): Spina Bifida: A ~ u l t i d i s c ~ p l i n aApproach. r~ New &rk, Praeger, 1986, p 332 56. Warkany J: Morphogenesis of spina bifida. In McLaurin RL (ed): Myelomeningocele. New York, Grune & Stratton, 1977, p 31
Acld~essreprint reqtresfs to: Yoon S. Hahn, MD Loyola University Medical Center 2160 South First Avenue Maywood, IL 60153