Surgical treatment of central nervous system malformations

Handbook of Clinical Neurology, Vol. 87 (3rd series) Malformations of the Nervous System H. B. Sarnat, P. Curatolo, Editors # 2008 Elsevier B. V. All rights reserved

Chapter 31

Surgical treatment of central nervous system malformations LORENZO GENITORI *,1, PIER ARTURO DONATI1, FLAVIO GIORDANO1, MASSIMILIANO SANZO1, FEDERICO MUSSA1, LUIGI SARDO1, BARBARA SPACCA1, GIOVANNI DI PIETRO1, AND GIUSEPPE OLIVERI2 1

Department of Neurosurgery, Ospedale Pediatrico Meyer, Firenze, Italy 2

Department of Neurosurgery, Ospedale Le Scotte, Siena, Italy

31.1. Introduction The surgical treatment of CNS malformations is a big challenge for neurosurgeons. The developing technologies of new radiological imaging techniques, as well as surgical tools, and improving knowledge of such diseases have dramatically changed the opportunity to treat different malformations with better results and better quality of life for patients and family. Neuroendoscopy, for example, has radically changed the surgical approach to many cerebrospinal fluid (CSF)related diseases, giving, in some cases, an opportunity to treat the hydrocephalus in a minimally invasive and more physiological way. Nonetheless, new biomaterials such as resorbable plates and screws have changed the possibilities for surgical management of craniofacial diseases. This chapter aims to describe the current state of the art in the surgical management of CNS malformations on the basis of our experience and reviews of the pertinent literature (Table 31.1).

31.2. Management of hydrocephalus and CSF-related disturbances 31.2.1. Neuroendoscopy Neuroendoscopy appeared at the beginning of the last century and has begun to modify general neurosurgery during the last 10 years thanks to technological progress in optical fibers. Besides radically changing the neurosurgical treatment of hydrocephalus, nowadays neuroendoscopy is becoming an alternative and effective treatment for other intracerebral and periventricular lesions located into third and lateral ventricles, such as

arachnoid and colloid cysts. Furthermore neuroendoscopy allows biopsy and sometimes removal of intraand paraventricular tumors, including vascular malformations. The high incidence of hydrocephalus during childhood, isolated or associated with almost all the cerebral pathologies, makes neuroendoscopy a valid and suitable tool for its multimodal treatment. First, endoscopic third ventriculostomy (ETV) is today recognized as the gold standard treatment for obstructive hydrocephalus, both in children and infants, with an overall success rate of 75% in many published series (Sainte-Rose et al., 2001; Santamarta et al., 2005). Obstructive hydrocephalus due to aqueductal stenosis in children aged more than 1 year is characterized by 98% of patients shunt-free after ETV (Hellwig et al., 2005). Posterior fossa tumors with hydrocephalus should be treated first by ETV, followed by a direct approach to the tumor a few days later (Sainte-Rose et al., 2001). In infants the number of CSF shunting procedures has been reduced by neuroendoscopy. Posthemorrhagic hydrocephalus in preterm newborns can also sometimes be treated by neuroendoscopy instead of traditional techniques (Gorayeb et al., 2004). Indeed, in all cases of obstructive hydrocephalus (obstruction of the outlets of fourth ventricle, cysts, Chiari malformation, complex craniosynostosis) ETV may be considered the first-choice treatment (Decq et al., 2001). In case of shunt failure too, ETV can be proposed instead of ventriculo-peritoneal shunt revision, achieving an 82% success rate in terms of shunt-free children (Boschert et al., 2003). In shunted children affected by slit ventricle syndrome, ETV may be considered an alternative choice (Chernov et al., 2005).

*Correspondence to: Lorenzo Genitori, Department of Neurosurgery, Ospedale Pediatrico ‘Meyer’, Via Luca Giordano 13, Florence, Italy. E-mail: [email protected], Tel: þ39-055-566-2934 or þ39-348-443-1370.

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Table 31.1 Surgical procedures for CNS malformation in children 1996–2005 Procedure

N

%

Neuroendoscopy Shunting procedures Craniofacial repair for craniofacial dysmorphism Excision of encephalocele Posterior fossa decompression for Chiari type I anomaly Surgery for dysraphic state Fetal surgery

669 1385 353

25 51.9 13.3

20 129

0.7 4.8

111 3

4.2 0.1

31.2.1.1. Third ventriculocisternostomy Opening the floor of the third ventricle is a standard technique to put it in communication with the basal cisterns in order to divert CSF circulation from the aqueduct and the fourth ventricle. It is utilized for obstructive hydrocephalus due to aqueductal stenosis because of malformative pathology (aqueductal atresia, arachnoid cysts of lamina quadrigemina), tumors (posterior fossa, pineal or brainstem tumor, tectal hamartoma) and also in presence of aqueductal flow disturbance due to hemorrhages and/or infections. The surgical technique is standardized in all cases, using a rigid neuroendoscope of 9.5 F in outer diameter (about 2 mm) with a 30
angulated optic. The camera is oriented with the operative sheet. Under general anaesthesia the patient is positioned supine with the head slightly flexed and a precoronal 5 mm burr hole is made. After opening of the dural and arachnoidal surface, the endoscope is inserted ‘freehand’ without

Fig. 31.1. Endoscopic view of the floor of the third ventricle. The tuber cinereum and mammillary bodies are visible.

a stilet under direct view control. The presence of mandrin passed inside the operative channel prevents the passage of small brain particles into the endoscope during its introduction. After the lateral ventricle is reached and the foramen of Monro has been identified, the endoscope is passed into the third ventricle. Ventriculocisternostomy is always performed in the midline between the mammillary bodies and the tuber cinereum, as close as possible to the dorsum sellae, to avoid injury to the basilar artery complex (Fig. 31.1). The opening in the floor of the third ventricle is made with a 1 mm coagulator fiber followed by the insertion of a 2 Fr Fogarty balloon catheter inflated with 0.2 ml of saline solution in the cistern and then withdrawn into the third ventricle (Fig. 31.2). No forceps or blunt technique is used. After the perforation of the floor of the third ventricle, the neuroendoscope is always introduced through the stoma into the cisternal space to open the two layers of the Liliequist membrane,

Fig. 31.2. Endoscopic view. (A) Opening of the floor by coagulator. (B) The balloon of the Fogarty catheter is inflated through the stoma.

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phalic cisterns (Fig. 31.5); a suprasellar cyst may be marsupialized into the interpeduncular cistern while an interhemispheric cyst may be opened into the ventricular cavities (Abbott, 2004). A posterior fossa cyst (retrocerebellar, pontocerebellar angle, supracerebellar) may be marsupialized into the cisterna magna or into the pontocerebellar cisterns and the perimedullary cisternal spaces (Hopf and Perneczky, 1998). In case of endoscopic surgery failure, redo-endoscopy and direct microsurgical opening of the cyst through craniotomy are to be considered in the first instance; cystoperitoneal shunting today represents last-choice surgery (Pierre-Kahn et al., 2002). Fig. 31.3. Endoscopic view: the stoma is open between the third ventricle and the interpeduncular cistern

reaching the prepontine cistern after identification of the basilar artery. The endoscope is then retracted (Fig. 31.3). Irrigation is carried out carefully and manually if necessary; no continuous irrigation is used. The whole procedure is always carried out in a ‘freehand’ fashion and takes an average time of 30 min. 31.2.1.2. Septostomy Septostomy consists in opening the septum pellucidum (Fig. 31.4) in the case of monoventricular or biventricular hydrocephalus, or in fenestrating pathological septa inside the ventricles in multicystic hydrocephalus (Oi and Abbott, 2004). 31.2.1.3. Arachnoid cyst marsupialization This technique aims to open the wall of the cyst inside the CSF cisterns and/or ventricular cavities: for example, a temporo-silvian cyst can be put in communication with optical cistern, internal carotid artery and perimesence-

31.2.1.4. Placement of catheters In the presence of virtual ventricles or ventricles with multiple septations, neuroendoscopy enables a catheter to be placed in the selected place, also allowing its connection with an Ommaya reservoir for CSF tapping and/or delivering drugs (Oi and Abbott, 2004). 31.2.2. Shunting procedures The evacuation of superficial intracranial fluid in hydrocephalic children was described in detail for the first time in the 10th century by Abu Al-Kassim Khalaf ibn Abbas Al Zaharawi (936–1013). In 1893 the first permanent ventriculo-subarachnoid–subgaleal shunt was described by Mikulicz, who proposed a simultaneous ventriculostomy and drainage into the extrathecal low-pressure compartment. Between 1898 and 1925, lumboperitoneal and ventriculoperitoneal, ventriculovenous, ventriculopleural and ventriculoureteral shunts were invented but, in most cases, these systems had a high failure rate due to insufficient implant materials. Artificial CSF valves were proposed in 1948 by Ingram, by Bush at MIT in 1949 in collaboration with

Fig. 31.4. Endoscopic view: septostomy. (A) The Fogarty balloon is pushed through the septum pellucidum. (B) Opening between the two lateral ventricles.

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Fig. 31.5. MRI axial view. (A) Huge arachnoid cyst in the temporo-sylvian region with compression of the midline structures . (B) Postoperative (endoscopic approach). Note the almost complete disappearance of the cyst.

Matson, and by Nulsen and Spitz in Philadelphia (Aschoff et al., 1999). During the 1950s the Spitz– Holter shunt was developed, leading to a tremendous impact on neurosurgical procedures for hydrocephalus (Nulsen and Spitz, 1952). After a first generation of simple differential pressure valves, which are unable to drain physiologically in all body positions, a second generation of adjustable, autoregulating antisiphoning and gravitational valves was developed (Gruber et al., 1984). Many shunt systems also have a flexible flushing chamber (reservoir), which may be housed within the same unit as the valve or may be a separate unit along the shunt, depending on the design of the shunt system. Assuming that ‘the best shunt is no shunt’, none of the innumerable multicentric trials have showed that any shunting system is more effective than another. At the moment at least 127 different designs are available, but most of these are only clones (Drake and Kestle, 1996). 31.2.2.1. CSF shunt valves

ventricular pressure rises above the precalibrated opening pressure, allowing CSF outflow, and close when the pressure falls below the closing pressure of the valve (Pudenz, 1981). The limitation of standard differential valves is that the flow increases when the differential pressure increases (i.e. orthostatic pressure in standing position), leading to overdrainage complications (Pudenz and Foltz, 1991). 31.2.2.1.2 Programmable valves These valves have an adjustable ball–spring mechanism and operate as a differential device with the advantage that it is possible to modify the operating pressure of the valve once it has been implanted by means of an external device with a magnet placed on the skin (Benesch et al., 1994). Some authors have not reported higher efficacy and safety rates for these devices compared to precalibrated valves (Pollack et al., 1999). Other authors believe that this type of shunt is superior because ‘one cannot know in advance which case will turn out to be complicated’ (Zemack and Ramner, 2000).

31.2.2.1.1 Differential pressure pre-settled valves These valves are subdivided in four broad categories: slit valves, miter valves, diaphragm valves and ballin-cone valves (Drake and Saint-Rose, 1995). These systems have predefined operating pressures with three or five performance levels that vary from very low to high; differential pressure valves open when the intra-

31.2.2.1.3 Flow-regulating valves In these valves CSF flow through the device in correlation with variation of CSF pressure. In attempt to keep the CSF flow rate constant, the mechanism resistance increases as the pressure gradient increases (Hanlo et al., 2003).

SURGICAL TREATMENT OF CENTRAL NERVOUS SYSTEM MALFORMATIONS In conclusion, none of the described types of valve appears to be best for the initial treatment of pediatric hydrocephalus (Kestle et al., 2000). 31.2.2.2. Shunt surgery techniques Especially in children, the ventriculo-peritoneal route is preferred to the ventriculo-atrial route because it is easier to place and is followed by less morbidity (Hoffmann, 1982). Many studies have been carried out to evaluate the possibility of prevention and reversibility of pathological changes in hydrocephalic brain after shunting. In experimental models it has been demonstrated that, after early shunting, much damage to the gray (reduction of neuron size, disorientation, dendritic deterioration) and white matter (periventricular edema, axonal damage, demyelinization, gliosis) and brain metabolism can partially recover (Hakim and Hakim, 1984). 31.2.2.2.1. External ventricular drainage A short-term CSF shunt device may be needed for hydrocephalus following intraventricular hemorrhage, bacterial infection or after brain tumor surgery with a high risk of postoperative hydrocephalus. 31.2.2.2.2. Ventriculo-peritoneal shunt This is the most popular shunt procedure. The ventricular catheter is placed through an occipital or frontal burr hole and connected to the valve. The distal catheter is tunneled in the subcutaneous space and placed in the peritoneum. The advantages and disadvantages are as follows (Drake and Saint-Rose, 1995): Advantages:

 less morbidity from shunt infections  the possibility of placing a length of distal tubing to accommodate the patient’s distal growth Disadvantage: peritoneal adhesions or infection. The risk of seizures, which appears higher with frontal positioning, has been reported to be 5.5% in the first year after placement of a ventricular catheter. The risk rate drops to 1.1% after 3 years (Dan and Wade, 1986). 31.2.2.2.3. Ventriculo-atrial shunt This is a less commonly used procedure because of the high risk of infection (sepsis, pulmonary embolus, nephritis, cor pulmonaris and death) (Lundar et al., 1991). The shunt procedure is more demanding because the distal catheter is introduced into the transverse facial or jugular vein and the amount of distal tubing is standard and cannot be adapted to the child’s growth.

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31.2.2.3. Shunt complications CSF shunting represent the neurosurgical procedure with the highest failure rate (Drake and Saint-Rose, 1995). Most complications that require revision of the shunt occur between 6 months and 1 year after surgery (Sainte-Rose et al., 1991). The main causes of shunt dysfunction are:

 Obstruction  Infections  Mechanical problems (migration, disconnection, malpositioning)

 Other complications. Obstruction can occur in each component of the shunt device. The ventricular catheter may be obstructed by choroid plexus tissue or by the ventricular wall (Sainte-Rose, 1993). Blood cells, bacteria, proteins and other tissue debris may also block the ventricular catheter and/or the valve. Moreover, the tip of the peritoneal catheter may be obstructed by bowel loops, fat abdominal tissue and other abdominal pathologies (Drake and Saint-Rose, 1995). Shunt infection is usually caused by the child’s own bacterial organisms. The most frequent organism is Staphylococcus epidermidis, which is normally present on the surface of the child’s skin, in sweat glands and in hair follicles deep in the skin. These infections are most likely to occur 1 month after surgery and sometimes up to 6 months after surgery (Choux et al., 1992). Mechanical and other complications are described too. Shunts are very long-lasting systems, although their hardware may become disengaged as a result of the child’s growth, with migration into the body cavities where they were originally placed. The valve itself rarely breaks down because of mechanical malfunction even if the shunting device may over- or hypodrain CSF (Sgouros et al., 1995). The overdrainage may result in slit ventricles syndrome and/or subdural hematoma (Pudenz and Foltz, 1991); in these patients a cranial vault expansion and/or subtemporal decompression may be needed to achieve ventricular re-expansion (Epstein et al., 1988).

31.3. Craniofacial repair for craniofacial dysmorphism Surgical treatment of craniosynostosis aims to correct the deviated calvarial shape, to stop the compensatory growth and to modify its effects by normalizing the physiological functions. This can be achieved, but not always completely, by the ‘dynamization’ of the restricted skull growth and the redirection of the abnormally oriented growth vectors (David et al., 1982).

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In some craniosynostosis only affecting the cranial vault (scaphocephaly), a simple and wide suturectomy allows passive reshaping, especially in the first 2 months of life, utilizing the released directional vectors of growth with the final result of a good cranial expansion and cosmetic correction (Collmann et al., 1999). In other craniosynostosis involving the vault and the skull base simultaneously (e.g. brachycephaly, trigonocephaly, oxicephaly and most plagiocephaly), active reshaping is required by bringing vault regions into the desired position and remodeling shape, orientation and angles of the orbital bar (Genitori et al. 1995). The best time for this kind of correction is between the fourth and sixth months of life (Di Rocco et al., 1980). On the other hand, the management of complex craniofacial malformations (e.g. Crouzon, Apert and Pfeiffer syndromes, cloverleaf skull syndrome) is characterized by multistep surgery (Marchac et al., 1994). Initial anterior skull and orbital ridge remodeling with expansion and volumetric increase of the anterior cranial fossa aims to resolve intracranial hypertension, manage breathing and feeding problems and safeguard brain growth and visual function. Posterior skull expansion is sometimes needed when the occipital regions appear extremely flat; if Chiari type I anomaly coexists, occipital foramen opening may be combined (Cinalli et al., 1998). The second step is to address midfacial advancement, which is performed later, after the fourth year of life (Marchac et al., 1994). In cases of severe midfacial retrusion, causing psychological problems in pre- and school age, early maxillary distraction can be performed by means of mechanical devices that provide a progressive advancement and correction of the facial dysmorphism and subsequent enlargement of the nasal airway (Meling et al., 2004). This procedure is sometimes definitive or can prepare the child for subsequent programmed traditional midfacial advancement using the Le Fort III technique (Meazzini et al., 2005). Successively, when complete growth is achieved, treatment can be completed with rhinoplasty and canthopexy procedures (Tessier, 2000). 31.3.1. Preoperative assessment Early surgical correction is extremely important to achieve best functional and cosmetic result: the chance of an optimal aesthetic result decreases with child age especially after 12 months (Posnick, 2000). Unfortunately, toddlers in first months of life are characterized by ‘triple precariousness’ (large needs – insufficient supplies – inadequate control mechanisms) making

necessary an accurate clinical examination to detect concomitant pathologies (e.g. cardiopulmonary system, coagulopathies, etc.) and reduce anesthesiological and surgical risks (Di Rocco and Velardi, 2001). 31.3.2. Craniectomy and suturectomy This technique is only applied in infants in the first months of life with cranial deformities restricted to the vault (scaphocephaly). Goal of surgery is releasing the directional growth vectors in correspondence of the prematurely fused suture in order to allow a harmonic expansion of the brain. Vertex craniectomies, associated to strip craniotomies along coronal and lambdoid sutures must be preferred to small suturectomies to avoid precocious reossification. The bony defects will close by the end of the first year when the infant learns to walk. The advantage of this technique is represented by the possibility of a more precocious correction and a smaller skin incision (linear or Sshaped vertex incision) with reduced blood loss, the disadvantages are represented by a delayed cosmetic result (Jane and Persing, 1986). 31.3.3. Cranial vault remodeling When an immediate cosmetic result is required for scaphocephaly, more invasive procedures are employed. Many authors recommend the Marchac and Renier multisegment technique, which allows good cranial reshaping and volume expansion (Marchac and Renier, 1981). In these cases, in scaphocephalies we prefer the ‘Pi procedure’ described by Jane in 1986 (Jane and Persing, 1986) which accomplishes a satisfactory and immediate active remodeling of the cranial vault (Fig. 31.6). 31.3.4. Fronto-orbital advancement and remodeling This technique is used in various fashions for trigonocephaly, plagiocephaly (Fig. 31.7), brachycephaly and oxicephaly, to expand anterior cranial fossa and remodel frontal bone and orbital bar (Genitori et al., 1991, 1994). The procedure is characterized by a bicoronal skin incision, anterior lift of the scalp flap until orbital rims, elevation of the pericranium, detachment of the temporalis muscle and of the periosteum until the upper part of the orbital cavities and the frontozygomatic processes are exposed. A bifrontal bone flap, included between the coronal sutures and an horizontal line about 2.5 cm above the orbital rims, is then outlined and removed. The fronto-orbital bandeau is removed en bloc, avoiding to open the periorbital capsule, performing multiple osteotomies carried out along the orbital roofs, the frontozygomatic sutures,

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Fig. 31.6. Scaphocephaly. (A) Preoperative view from above. (B) Postoperative appearance after cranial vault remodeling (from above).

Fig. 31.7. Right anterior plagiocephaly. (A) Preoperative view. Note the facial scoliosis. (B) Postoperative (at 3 years). Note the symmetry of the craniofacial skull.

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Fig. 31.8. Brachycephaly. (A) Preoperative view. (B) Postoperative view after fronto-orbital advancement with bioresorbable plates and screws,

the lesser sphenoid wing, medially above the frontonasal suture and along the temporal bone with a fine oscillating saw or a chisel. At this point care is taken to detect dural lacerations and eventually repair them. The orbital bar is then bent by grooving the inner table or with a bender instrument, reshaped and repositioned with the new orientation and angle. A good stability especially in brachycephaly (Fig. 31.8) may be achieved with the use of bioresorbable lactic acid polymer plates (Kurpad et al., 2000). After its recontouring, the frontal bone is repositioned and ensured to the orbital bar or leaving it free to ‘float’ on the frontal lobes (Marchac et al., 1988). The temporal bone defect is filled advancing and rotating anteriorly the temporalis muscle. The bone surface is then covered by pericranium and the scalp is closed in layers. Treatment of anterior plagiocephaly can also be performed by advancing and remodeling the orbital bar only on the affected side (Genitori et al., 1994).

31.4. Excision of cephaloceles 31.4.1. Intrateutoria cephaloceles First question is deciding whether to treat or not a new-born with encephalocele (Brown and SheridanPereira, 1992). As a matter of fact, all meningoceles should be closed because they do not usually contain brain structures. On the other side, in case of large meningoencephaloceles with large amount of cerebral structures (sometimes exceeding the entire volume of

normal brain) and associated malformations, the surgical indication must be discussed with parents because of their poor prognosis. Prognostic factors to be considered are size of the encephalocele, the amount of vital brain tissue, the microcephaly and hydrocephalus associated. In these forms, the neurological outcome is usually dismal because of higher incidence of hydrocephalus and other brain malformations (Date et al., 1993). Goals of surgery are removing the sac with dysplastic tissue, preserving functional nerve structures and closing the malformation with not-dysplastic skin (McComb, 1996). In the early post-operative period, seizures, CSF collections, hydrocephalus and infection may occur (McComb, 1996). Seizures are due to presence of dysplastic and epileptogenic brain structures (Matson, 1969). It is usual to observe a CSF accumulation into the site of surgery. This ‘dead-space’ is to be avoided by compressive dressing: this phenomenon creates a ‘fifth’ ventricle which raises the risk of postoperative hydrocephalus (McComb, 1996). The hydrocephalus is more common in meningoencephaloceles than in meningocele being due to the loss of supplementary space of CSF accumulation and to coexistent subclinical infections (McLaurin, 1987). 31.4.2. Cranial vault cephaloceles Goal of surgery is cosmetic treatment without trying to remove all the intracranial portion of the content (McLaurin, 1964). Skin incision is tailored to the site

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Fig. 31.9. Three-dimensional CT (axial view). (A) Basal encephalocele. Note the opening of the base of the skull in the posterior ethmoidal and sphenoidal region. (B) Postoperative (transcranial route). Note the disappearance of the hole in the base.

and extension of the sac; the cranial defect is repaired with autologous bone. 31.4.3. Fronto-ethmoidal or sincipital encephaloceles The encephalocele is to be removed with its whole content by a subfrontal extradural route via an anterior bifrontal bone flap (David et al., 1984). The craniotomy is made just above anterior cranial fossa floor sometimes including a fronto-orbital osteotomy to dissect better the sac in a single-step procedure (Sargent et al., 1988). After sac excision and watertight dural closure with not-adsorbable suture, a cranial base plasty with a peduncularized autologous periosteum flap is created to seal the bony defect. A CSF leakage (rhinorrhea and/or CSF ‘tears’) may occur with risk of meningitis avoidable by an external lumbar drainage (McComb, 1996). 31.4.4. Basal encephaloceles The surgical management of trans-sphenoidal, intrasphenoidal and transethmoidal cephaloceles is still controversial because of its high morbidity, permanent impairment and mortality, especially in neonatal period and infancy (Yokota et al., 1986). The goal of surgery is the reduction of the prolapsed sac to lessen the traction on the vital structures, preserving their function and obtaining a watertight dural closure with reparation of the bone defect (Lai et al., 2002). The most important question still remaining is the route of the surgery: transcranial versus extracranial. As described by many authors, the transcranial transbasal route via a bifrontal

bone flap (Fig. 31.9) is followed by higher mortality and morbidity, especially in younger patients (Kai et al., 1996). On the other hand, since these lesions progressively enlarge, it is best to operate early in order to prevent further damage to the herniated brain tissue, preserve vision and avoid progressive respiratory distress (Abiko et al., 1988). Sometimes, urgent repair may be needed in patients with CSF leaks or hemorrhage after inadvertent removal of a cephalocele mimicking a nasal polyp (Choudhury and Taylor, 1982). So nowadays the extracranial approach is preferred even in infancy, especially in case of progressive and life-threatening symptoms (Kennedy et al., 1997). Different approaches may be performed: transpalatal, transnasal-transmaxillary, transnasal–trans-sphenoidal or combined approaches (Fig. 31.10). In the transpalatal approach, the sac can be easily viewed and dissected by paramedian splitting of the uvula and soft palate and partial osteotomy of the hard palate. The transnasal–transsphenoidal approach uses the well-known techniques of pituitary surgery to gain access to the sphenoid bone. In all these techniques, the common principle is not trying to push the whole sac inside the cranium but only to reduce the extent to which it stretches into the nasal cavity and epipharynx to stop traction on vital structures. Closure and reinforcing of the sac is made by application of multiple layers of oxidized cellulose and fibrin glue; the bone defect can be closed by autologous bone powder, nasal septum cartilage, autologous bone of nasal turbinates and sometimes other heterologous ossification inducers (Genitori et al., 2001). Reparation may be made through an endoscopic nasal approach, as described in an increasing number of cases reported in the literature (Lanza, 1996).

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Fig. 31.10. MRI (sagittal view). (A) Pure trans-sphenoidal encephalocele with third ventricular structures protruding into the epipharynx. (B) Postoperative aspect with complete reconstruction of the defect by an extracranial combined route.

31.4.5. Other forms of cranial dysraphism: atresic encephaloceles A horizontal skin incision in a rhomboidal fashion is made around the sac. The dysplastic skin is removed, with the nonvital inner tissue. The intracranial portion, if present, must be left in place. The cranial defect is closed by tubularizing the periosteum, which is then covered by autologous bony powder. The skin is closed with nonabsorbable sutures (McComb, 1996). 31.4.6. Congenital defects of the scalp (aplasia cutis congenita) Smaller lesions can be treated conservatively, waiting for spontaneous healing and epithelialization. Larger lesions must be repaired using rotational skin flaps, sometimes prepared in advance by implanting skin expanders. In cases of massive agenesis of the scalp, dessication and injury of the brain must be avoided by keeping the lesion moist (McComb, 1996).

31.5. Posterior fossa decompression for chiari type I anomaly In 1988 the American Association of Neurological Surgeons declared that, in Chiari I patients, posterior fossa decompression was always mandatory in the presence of signs of brainstem dysfunction, debatable in cases of mild symptoms and headache, and not recommended in asymptomatic patients (Haines and Berger, 1991). Today there is a general agreement that Chiari I anomaly characterized by cerebellar tonsil prolapse of at least 5 mm down to the foramen magnum, with appropriate symptoms, should be treated. In borderline cases (prolapse of 0–5 mm), the surgical indications must be eval-

uated in each individual clinical case. In cases of syringomyelia, surgery is mandatory even in the presence of limited tonsil descent to avoid further enlargement and clinical deterioration (Tubbs et al., 2003). The goal of surgery is to restore normal CSF flow, thus re-establishing a pressure balance between the intracranial and intraspinal subarachnoidal spaces by decompressing the inferior cerebellum and cervico-medullary region at the level of foramen magnum (Batzdorff, 1988). Nowadays, first-choice surgery consists of suboccipital craniectomy plus posterior C1 laminectomy both in simple Chiari I patients and in complicated cases with syringomyelia. The purpose of this simplified technique, first described by Isu, is to enlarge the posterior fossa at the level of the foramen magnum without complete dural opening (Isu et al., 1993). A midline vertical incision is made from just inferior to the inion to the C3 level. Myofascial dissection is carried out along the median raphe. Special care must be given to avoiding muscle dissection from C2 level (semispinalis cervicis and multifidus muscle) to prevent cervical instability and to reduce postoperative neck pain. Then a suboccipital craniectomy is carried out. The occipital bone is opened by a 3  3 cm suboccipital craniectomy performed using a high-speed drill and rongeurs to enlarge the foramen magnum. A posterior C1 laminectomy of about 2.5 cm is made. It is not necessary to extend the craniectomy laterally to reduce the surgical risk. A dense fibrous and constrictive band covers the atlanto-occipital membrane, causing intradural compression and arachnoid adhesion. This strip is cut and removed with the atlanto-occipital membrane until the outer dura is identified. This is bluntly dissected and sectioned until a good CSF pulsatility appears from the cisternal and medullary spaces. One must take care to respect the arachnoid layer as soon as it appears during

SURGICAL TREATMENT OF CENTRAL NERVOUS SYSTEM MALFORMATIONS the dissection of the outer layer of the dura (Genitori et al., 2000). In the past, other authors described many intradural procedures: opening of the dura in a Y fashion followed by a wide duraplasty graft (Batzdorff, 1996), dissection of arachnoid overlying the tonsils (Dyste and Menezes, 1988), coagulation of herniated cerebellar tonsils respecting the integrity of pia and arachnoid (Oakes, 1985), resection of cerebellar tonsils with subpial approach in cases of very high gliotic tonsils not reduced by simple coagulation (Fisher, 1995), obex occlusion with a piece of muscle (Hoffmann et al., 1987), section of filum terminale (Filizzolo et al., 1988). Surgical morbidity may take the form of vertebral artery damage, acute hydrocephalus, cerebellar ptosis, pseudomeningocele, CSF leakage, subdural collections, cervical instability and acute life-threatening signs of brainstem dysfunction (Tubbs et al., 2003). More aggressive surgery is followed by a higher rate of complications, especially pseudomeningocele (4%), CSF leakage (2%), aseptic meningitis (22%), acute hydrocephalus (1%), fluid collection in the operative wound and late arachnoid adhesions (Zerah, 1999). In modern series, authors like Zerah (1999) and Genitori et al. (2000) have stressed the good results of this technique, which is not associated with frequent compli-

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cations and is characterized by shorter hospitalization compared with the morbidity after surgery characterized by dural opening; surgical outcomes are good both in reducing syringomyelia and in improving its secondary effects such as scoliosis (Fig. 31.11). In any case, where there is clinical and/or radiological Chiari I recurrence or enlargement of syringomyelic cavities, dural expansion should be considered (Genitori et al., 2000). Recently, Milhorat and Bolognese (2003) have proposed intraoperative control using color Doppler ultrasonography (CDU) to tailor the extension of posterior fossa bony decompression and C1 laminectomy, and the eventual need for additional steps such as duraplasty and shrinkage or resection of the cerebellar tonsils. During the first surgical steps, CDU makes it possible to distinguish better all the posterior fossa structures, including aberrant vascular anatomy, asymmetrical herniations and neural displacement; this reduces the risk of surgical error, especially in patients undergoing reoperation with a lot of meningo-cerebral scarring (Milhorat and Bolognese, 2003). At the end of posterior fossa decompression, CDU serves to monitor whether the CSF circulation and pulsatility are restored by measuring CSF flow velocity and viewing CSF flow direction; optimal CSF flow has a peak

Fig. 31.11. MRI ( sagittal view). (A) Chiari type I anomaly. Note the cervical syringomyelia. (B) Postoperative, after posterior fossa decompression. Note the complete disappearance of the syringomyelia.

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velocity of 3–5 cm/s, bidirectional movement and a waveform exhibiting arterial, venous and respiratory variations (Milhorat and Bolognese, 2003). In presence of syringomyelia–hydromyelia, some authors have proposed putting a shunt between the fourth ventricle and the subarachnoidal spaces (Menezes et al., 1980) while others prefer to perform a syringostomy by myelotomy (Rhoton, 1976). Syringo-subarachnoid shunting using a small catheter has been also suggested, even though spinal cord injury has been described after insertion of catheter in the spinal cavity (Isu et al., 1990). A syringo-peritoneal or pleural shunt has been advocated because of the higher differential pressure compared with the subarachnoidal space (Barbaro et al., 1982). The catheter used is K- or T-shaped and 2 mm wide. The surgical technique consists of anchoring the catheter to the dura and placing its end in the planned cavity. The insertion of a valve device to regulate CSF drainage must be evaluated even if it is not usually employed (Batzdorff, 1988). Some technical reports describe the possibility of treating Chiari I anomaly by tapping the syringomyelial cavity via percutaneous aspiration after failure of previous treatment (Batzdorff, 1996). As regards the associated hydrocephalus, endoscopic third ventriculostomy is the first-choice surgery if hydrocephalus symptoms predominate (Decq et al., 2001). Posterior fossa surgery should be considered in the case of onset of Chiari symptoms even if hydrocephalus has been eliminated.

31.6. Surgery for dysraphic state 31.6.1. Closure of myelomeningocele (spina bifida aperta) Delivery by cesarean section is suggested to diminish local trauma to the malformation (Fig. 31.12). The mal-

Fig. 31.12. Myelomeningocele. Appearance of the placode before closure.

formation must be protected and kept moist using tulle gras (Genitori et al., 1993). At birth a number of precautions have to be taken to avoid hypothermia, hypovolemia and hypoglycemia (Reigel, 2001). A complete diagnostic work-up must be performed to evaluate the neurological status of the newborn and the associated problems (brain malformation, hydrocephalus, urological and orthopedic impairments) (Genitori et al., 1993). Surgery must be performed within the first 48 hours to avoid septic meningitis, sepsis and secondary injury to the placode requiring repair. Any delay after 72 hours increases this risk to 37% compared to 7% in cases of early closure (Charney et al., 1985). Neonatal meningitis is a serious complication because it impairs intellectual development (McLone et al., 1980). The neonate is positioned prone with all pressure points on smooth pads in a Trendelenburg position to reduce CSF leaking; warming tables are utilized. Tracheal intubation should be carried out in a donut position if possible to reduce trauma to the sac. The usual antiseptic drugs should be employed (i.e. povidone iodine must be avoided). Goals of surgery are: 1) identification of all anatomical planes according to the well-known embryological physiopathology; 2) reconstruction of the placode; 3) closure of meningeal coverings; 4) closure of the fascia and skin. The first step is an incision at the meningo-epithelial junction and dissection of the neural placode under the control of the operative microscope. Arachnoidal adhesions between the placode and underlying dura are lysed. Any other associated abnormalities must be identified and eventually removed (e.g. dermoids, lipomas, neuroenteric cysts, etc.). All residual epidermal and dermal elements must be removed to avoid the future formation of a dermoid or lipoma (McLone, 1998). At this stage, the placode is tubulized with nonabsorbable suture (nylon 5/0) and the recurrent spinal roots must be respected. The meningeal layer is then dissected as far as possible to cover the new spinal cord, aiming to maintain it submerged in CSF in order to avoid secondary tethering. Sometimes a duraplasty is created with an autologous flap (periosteum, fascia lata) or more frequently with artificial biocompatible material like PTFE (polytetra fluoroethilene). In a case with a huge kyphosis, kyphectomy is necessary during the first surgery to enable easy closure of the defect (Reigel, 1979). At the end of the procedure, a myofascial layer is prepared to cover the dura and the excess and dysplastic skin is excised before final closure is made with nonabsorbable sutures (nylon 3/0). A releasing incision in the fascia laterally away from the defect may be useful to obtain a tension-free closure. In the case of a large defect, the lumbo-sacral musculature is useful to create flaps to cover the malformations even if rotational flaps do not often function because

SURGICAL TREATMENT OF CENTRAL NERVOUS SYSTEM MALFORMATIONS of ischemia. Deep dissection of latissimus dorsi may be dangerous because of the risk of damage to retroperitoneal and pulmonary structures (Ramasatry and Cohen, 1995). In the early postoperative period the newborn must be carefully monitored. The recommended position is Trendelenburg prone or lateral protecting the wound from urine and fecal contamination. Periodical measurement of the cranial circumference and ultrasound tomography are performed to rule out hydrocephalus. Ventriculo-peritoneal shunting is mandatory at the first sign of hydrocephalus and/or in case of CSF leakage from the wound and/or brainstem dysfunction related to Chiari II. Endoscopic third ventriculostomy (ETV) achieves good results in secondary treatment of hydrocephalus in such children with shunt dysfunction (Jones et al., 1994). Surgery for Chiari type II anomaly should be considered if at least one of the four Griebel’s criteria is present (Griebel et al., 1990): 1) continuous stridor with respiratory difficulty; 2) recurrent ab ingestis pneumonia; 3) bradycardia or apnea; 4) cyanosis. The surgical technique involves wide dissection of the foramen magnum along with posterior C1 laminectomy; a large duraplasty is then constructed using autologous or artificial material (Genitori et al., 1993). However, this procedure is justified only if the hydrocephalus is well treated; in fact Chiari II may decompensate because of shunt dysfunction (Isu et al., 1990). Surgical mortality is near zero, while postoperative complications may be serious. The most frequent complication is wound dehiscence with CSF leak, followed by local infection (1–1.5%), neonatal sepsis, and all the other complications connected with shunt and posterior fossa surgery (Pang, 1995).

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on the dura. The laminae are repositioned, taking care to set them in the normal position, and sutured with resorbable 2/0 sutures. The fascia is closed. Subcutaneous tissue and skin are closed with the same suture (Chapman and Davis, 1993). 31.6.2.2. Caudal lipoma The paravertebral muscles are dissected off the laminae, very carefully in the zone of the schisis to avoid penetrating the dura. A two-level laminotomy is performed, above the lesion entry zone in the dura, if present. The surgical microscope is necessary to perform the next surgical step. The dura is opened in a craniocaudal fashion and suspended. Untethering is achieved by dividing the lipoma below the transitional zone, which is identified between the conus and lipoma to avoid neural elements (Choux et al., 1994). After division of the lipoma the cord often shows a remarkable degree of retraction. The dura is closed with a biocompatible artificial patch using a 5/0 running suture to avoid retethering between the scar and the dural elements (Fig. 31.13). The laminae are repositioned, setting them carefully in the normal position.

31.6.2. Detethering the spinal cord (occult spinal dysraphism) 31.6.2.1. Lipoma of the filum terminale The surgical approach starts with a skin incision in the midline; the subcutaneous layer is incised with a monopolar scalpel until the fascia is exposed. Then the paravertebral muscles are dissected off the laminae and a two- or three-level laminotomy is performed. Use of the surgical microscope is necessary to perform the next surgical step. The dura is opened in a craniocaudal fashion and suspended. At this point Trendelenburg position prevents loss of CSF and keeps the surgical field clear of CSF. The filum lipomatosus is identified, coagulated and sectioned using microscissors. Normally after this step there is a remarkable retraction of the proximal end of the filum. The dura is closed with a 5/0 Prolene running suture. Fibrin glue and oxidized cellulose are positioned

Fig. 31.13. MRI ( sagittal view). Dysraphic state. (A) Caudal lipoma, preoperative. (B) Postoperative. Note the detethering of the spinal cord.

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31.6.2.3. Lipomyelomeningocele

The surgical approach is planned on the basis of radiological evaluation (Fig. 31.15). The aim of surgery is untethering the spinal cord, using two different techniques according to the two types of split cord malformation (Pang, 1992). In type I split cord malformation the

osteocartilaginous spur must be removed while dealing with tight adhesions between the cord and dura. The skin incision is performed in the midline extending above and below the lesion. The laminae are dissected off the paravertebral muscles, starting where the spinous processes are normal. A minimal laminectomy is begun in a normal area to avoid the risk of kyphoscoliosis. The bony spur is then progressively exposed and removed after a subperiosteal dissection of the septum, avoiding lateral movements, which can injure the adjacent hemicords. The two dural sacs are progressively exposed and the dura is opened by an incision encircling the dural cleft and extended towards each extremity. The adhesions between the medial aspect of the hemicord and the dural sleeves must be progressively severed. The closure of the dura is performed with a duraplasty. In type II split cord malformation the procedure is simpler. The dural tube is single and the two hemicords with the median septum may have three different positions: 1) a complete fibrous septum transfixes the hemicords and is fixed on the ventral and dorsal surfaces of the dura; 2) the septum is ventral only, fixing the ventromedial aspect of the hemicords

Fig. 31.14. MRI (sagittal view). Dysraphic state. (A) Lipomyelomeningocele, preoperative. (B) Postoperative. The lipoma has not been completely removed, but the spinal cord is detethered.

Fig. 31.15. MRI (coronal view). Dysraphic state: diastematomyelia. Note the split cord malformation.

The initial surgical approach is the same as described for the other types of operation. At the level of the dura, it is important to distinguish the ‘normal dura’ from the capsule of the lipoma. The lipoma can be dissected and debulked using a CO2 laser or ultrasonic aspirator. It is not necessary to attempt to debulk it in the intramedullary space since it does not increase in size (Fig. 31.14). Careful dissection must be employed at the interface between the lipoma and the spinal cord. The filum can be identified and divided. In these cases, the detethering starts from the superficial planes. The nerve roots lie horizontally and cannot be liberated from the lateral surface of the lipoma (McLone, 2001). 31.6.2.4. Diastematomyelia

SURGICAL TREATMENT OF CENTRAL NERVOUS SYSTEM MALFORMATIONS to the dura; 3) the septum fixes the dorsal aspect of the hemicords (Pang, 1992). 31.6.2.5. Dermal sinus The skin incision is made around the dermal sinus opening. The tract itself is dissected free of the underlying subcutaneous tissues, down to the point where it pierces and penetrates the underlying muscular fascia. Every attempt is made to preserve the tract until the laminotomy is made at one or two levels above and below the tract where it enters the dura. Then the dura is opened in the cranial and caudal direction and two incisions are made around the stalk where it penetrates the dura. At this point, the stalk is sectioned and removed (Fig. 31.16). Associated lesions such as dermoids and lipomas should be removed using magnification under the operative microscope (Choux et al.,1994). Detethering of the spinal cord in other, rarer, forms of dysraphic-state-like neuroenteric cyst and anterior meningoceles should be treated in a multidisciplinary fashion with an anterior transabdominal and posterior approach that allows wide exposure of the malformation while preserving the surrounding neural structures (Fig. 31.17).

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31.7. Fetal surgery Fetal surgery represents a multidisciplinary approach to some CNS malformations and tumors diagnosed in utero (Flake and Harrison, 1995). Nowadays, these new techniques deal essentially with prenatal hydrocephalus (Cavalheiro et al., 2003) and myelomeningocele (Sutton et al., 2003) and are feasible thanks to a full collaboration between the obstetric surgeon, anesthesiologist and neurosurgeon (Hendrick et al., 1998). Prenatal imaging by fetal magnetic resonance imagine (MRI) is mandatory to gain a complete and precise evaluation of malformations (Oi et al., 1998). 31.7.1. Prenatal hydrocephalus The incidence of true fetal hydrocephalus ranges from 1 to 4:1000 births (Cavalheiro et al., 2003). In 70% of cases other CNS anomalies are associated (holoprosencephaly, Dandy–Walker complex, spina bifida, corpus callosum agenesia) and in 7–15% of fetuses systemic malformations coexist (Chervenak et al., 1985). In 3– 10% of cases different chromosomopathies have been screened, involving chromosomes 1, 6, 9, 13, 18, 21,

Fig. 31.16. Dysraphic state. (A) MRI (sagittal view). Dermal sinus and tract. (B) Intraoperative view. Note the stalk fixing the spinal cord.

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Fig. 31.17. MRI (sagittal view). Dysraphic state. (A) Neuroenteric cyst. (B) Postoperative appearance with removal of the cyst by an anterior approach.

22 or X (Strain et al., 1994). Fetal hydrocephalus may be due to ventricular obstruction (congenital tumors, intraventricular hemorrhage), CNS maldevelopment or acquired intrauterine damage (infections, hemorrhages) (Von Koch et al., 2003). The most frequent cause of isolated fetal hydrocephalus is aqueductal stenosis (Cavalheiro et al., 2003). In his ‘perspective classification of congenital hydrocephalus’, Oi divided prenatal hydrocephalus into four phases according to the gestational age of diagnosis (Oi et al., 1998). Phase II (22–31 weeks) corresponds to the period of ‘intrauterine preservation’; during this phase, if the hydrocephalus becomes progressive, the damage to CNS may be irreversible after birth. Between 22 and 31 weeks of gestational age, the fetal lungs are not sufficiently developed, requiring preservation in the uterus, and it is obvious that the earlier the onset of hydrocephalus the greater the damage to the developing CNS; hence the earlier the treatment the better the results from both motor and cognitive points of view (Weller and Shulman, 1972). Thus Phase II hydrocephalus is amenable to prenatal surgical treatment (Oi, 2001). Surgery is suggested only in case of hydrocephalus not associated with other systemic and/or brain malfor-

mations because surgical and patient outcomes are better (Cavalheiro et al., 2003). According to the guidelines of the International Fetal Surgery Registry (Harrison et al., 1982), the ideal candidate to be submitted to fetal surgery should have an isolated hydrocephalus from non-X-linked aqueductal stenosis diagnosed before 28 weeks gestation and before the cortical mantle thickness is less than 1.5 cm; the hydrocephalus must be moderate to severe and not associated with other fetal brain anomalies on MRI; its progression has been documented by periodic ultrasound tomography; infections and genetic anomalies must be ruled out by amniocentesis. Indeed, fetuses harboring hydrocephalus linked to another CNS malformation (e.g. Dandy–Walker complex, X-linked hydrocephalus) do not show improved intellectual outcome after fetal surgery (Von Koch et al., 2003). In the case of polymalformation hydrocephalus, termination of pregnancy should be suggested to the family. If the hydrocephalus is stable or resolving, the child is delivered at term and then treated (Von Koch et al., 2003). In the past, repeated cephalocentesis was performed to obtain temporary control until delivery was possible (Birnholz and Frigoletto, 1981) even if this technique involved a higher risk of fetus infection,

SURGICAL TREATMENT OF CENTRAL NERVOUS SYSTEM MALFORMATIONS hemorrhage and porencephaly (Cavalheiro et al., 2003). Today, fetal CSF shunting surgery is preferred, aiming to obtain temporary relief from intracranial pressure while waiting for the earliest possible delivery for definitive treatment in better general conditions (Von Koch et al., 2003). Ventriculo-amniotic shunts were proposed Clewell and colleagues (1982). This shunting technique is hindered by a high incidence of complications such as catheter obstruction, migration of the device into the amniotic cavity, and infection (Cavalheiro et al., 2003). Furthermore, fetal hydrocephalus is high-pressure but surrounded by a higher intrauterine pressure, which impedes its correct functioning (Oi et al., 1990). On this pathological basis Oi has proposed the use of a fetal-ventricular–maternalperitoneal shunt (Oi et al., 1989). Bruner has introduced a new type of ventriculo-amniotic shunting to improve the fixation (Bruner et al., 2001). As a rule, requirements for such shunts include a safe and simple insertion technique, valid scalp fixation and a one-way valve to prevent intraventricular reflux of amniotic fluid (Von Koch et al., 2003). As suggested by Cavalheiro et al. (2003) endoscopic third ventriculostomy may be considered in case of hydrocephalus due to pure aqueductal stenosis. 31.7.2. Myelomeningocele Much clinical and experimental evidence shows neurological deterioration in the affected fetus during pregnancy according to the ‘two hit’ hypothesis, the first hit being embryological spinal cord malformation (Heffez et al., 1990). Some reports have documented normal movement of the lower extremities in fetuses with spina bifida aperta before 17–20 weeks, followed by fairly complete paralysis in late gestation (Korenromp et al., 1986). This deterioration seems to be due to the exposure of nervous tissue to meconium and amniotic fluid (Drewek et al., 1997) and to direct trauma to the placode from the uterine wall during fetal movements (Hutchins et al., 1996). The amniotic fluid becomes more hypotonic thus more toxic as fetal urine output increases after kidney maturation, which takes place after 22 weeks gestation (Lind et al., 1972). Furthermore, there is evidence that the Chiari type II anomaly is also acquired as a result of the continuous CSF leakage from the placode, which leads to progressive hindbrain prolapse (Paek et al., 2000). These findings constitute the physiopathological background for myelomeningocele repair in utero (Heffez et al., 1990). According to a schedule promoted by three different institutions (Children’s Hospital of Philadelphia, Vanderbilt Medical University, University of California at Los Angeles) (Sutton

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et al., 2003), the selection criteria are: prenatal diagnosis between 16 and 25 weeks of gestation; level of the defect at S1 or above with documented leg motility on ultrasound and absence of foot deformity; absence of other fetal malformations or chromosomal anomalies; proposed date for surgery 26 weeks. The first cases were treated by an endoscopic technique pioneered by Copeland and colleagues (1993). This was performed between 22 and 24 weeks of gestation using a 4 mm rigid endoscope. First, the mother underwent laparotomy under general and epidural anesthesia, with exposure of the gravid uterus. Then, three endoscopic ports were inserted into the uterus (one for the endoscope and two operative channels for instruments). Because of its turbidity, amniotic fluid was tapped until the fetus was completely exposed and the fluid was replaced by carbon dioxide to maintain ambient intrauterine pressure. After positioning of the fetus, the placode was covered with a maternal split-thickness skin graft because it was not possible to use a standard skin suture. All the reconstruction was sealed by oxidized cellulose and fibrin glue (Bruner et al., 1999). The surgical results were not satisfactory because fetal morbidity and mortality, and maternal morbidity, were high: in the four cases treated by Tulipan and Bruner (Bruner et al., 1999) amnionitis, amniotic leakage, uterine dehiscence, placental abruption, preterm delivery and one death were observed. Furthermore, this technique was only palliative and not curative, as the skin graft was short-lived (Copeland et al., 1993). Accordingly, the technique of open intrauterine repair was developed, on the basis of experimental models suggesting that most secondary damage takes place during the third trimester of pregnancy (Tulipan and Bruner, 1998). The mother underwent cesarean section under general plus epidural anesthesia at 28– 30 weeks of gestation; this anesthetic combination seems to reduce the incidence of unwanted uterine contractions and allows sedation of the fetus too (Tulipan and Bruner, 2001). After the uterus is exteriorized through a Pfannenstiel’s incision and the fetus and placenta are localized by ultrasound scan, the Tulipan– Bruner trocar is inserted into the uterus (Bruner et al., 1999) to tap most of the amniotic fluid, which is conserved in warm syringes. A 5 cm incision is made in the uterus and the fetus is positioned with the placode in the middle of the hysterotomy (Fig. 31.18). The myelomeningocele is then closed using the standard neurosurgical technique with nonresorbable nylon 7/0 sutures for the placode tubulization and nylon 5/0 for the skin (Tulipan and Bruner, 2001). During the whole procedure, the fetal heartbeat is monitored by ultrasound and continuous electronic

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Fig. 31.18. Fetal surgery. Intrauterine repair of myelomeningocele. (A) Uterine incision and exposition of the fetal lesion. (B) Appearance after closure of the malformation (personal case).

fetal monitoring. The uterus is closed in layers with adsorbable sutures and the amniotic fluid is replaced, sometimes with saline solution until its turgor becomes similar to the preoperative state, in order to reduce the risk of uterine contractions (Tulipan and Bruner, 2001). The wall of the abdomen is closed in a standard fashion and the fetus continues to be monitored. The mother is administered tocolytic agents (indomethacin, terbutaline). In the postoperative period, both the mother and the fetus are periodically monitored until delivery by cesarean section, which is usually planned at 34–35 weeks gestation; delivery is anticipated only in the case of uncontrolled amniotic leak or premature contractions, trying to balance, in all cases, the risk of dehiscence of the hysterotomy and iatrogenic fetal immaturity (Tulipan and Bruner, 2001). In the series of 50 cases operated on by Tulipan and coworkers, surgical morbidity was low and included uterine contractions, placental abruption, amniotic leakage; uterine dehiscence with prolapse of the fetus into the peritoneal cavity was the most serious. In only one case did premature delivery occur. Surgical mortality in utero involved only one fetus (Tulipan and Bruner, 2001) even if, in other series, there is a perinatal mortality of about 6% due to the extreme prematurity (Johnson et al., 2003). Unwanted side effects of tocolytic therapy are possible in the mother, such as tachycardia, fever, dyspnea and pulmonary edema (Tulipan and Bruner, 2001). The newborn may show local dehiscence at the site of placode repair, which is usually managed conservatively (Tulipan and Bruner, 2001). The most encouraging surgical results are the lower incidence of Chiari II and of hydrocephalus (Tulipan and Bruner, 2001). Chiari type II anomaly after fetal surgery accounts for only 16% rather than the

described incidence of 95% (Tulipan and Bruner, 1999). Other studies have shown that hindbrain prolapse is reversed rather than prevented by fetal surgery: postoperative fetal MRI (Fig 31.19) at 3 weeks has well documented the ascent of these structures (Sutton et al., 1999). Resolution of Chiari II anomaly reduces the incidence of hydrocephalus to 42.7% from 90% (Sutton et al., 2003) thanks to restoration of CSF pathway at the level of the fourth ventricle outlets (Babcook et al., 1994). Despite a number of experimental and clinical studies to the contrary (Heffez et al., 1990; Massobrio and Genitori, 2003), Tulipan’s series did not show any neurological improvement, as

Fig. 31.19. Fetal surgery. MRI (sagittal view). (A) Appearance of fetal myelomeningocele. (B) After closure of the lesion. Note the ‘normal’ position of the spinal cord (personal case).

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Fig. 31.19. (Continued)

the neonates showed neurological impairment exactly corresponding to the level of the defect (Tulipan and Bruner, 2001). In some cases secondary, late tethering of the spinal cord has been described because of epidermoid inclusion cysts, which required further treatment (Mazzola et al., 2002).

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