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Surgical experience of syringomyelia with reference to the findings of magnetic resonance imaging
Journal of Clinical Neuroscience (2004) 11(3), 273–279 0967-5868/$ - see front matter ª 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2003.02.015
Clinical Study
Surgical experience of syringomyelia with reference to the findings of magnetic resonance imaging Kazuhiko Kyoshima1 MD, Takayuki Kuroyanagi2 MD, Toshihide Toriyama3 MD, Takeomi Takizawa1 Yunoshin Hirooka1 MD, Hiroshi Miyama1 MD, Akihiko Tanabe1 MD, Susumu Oikawa1 MD
MD,
1 Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan, 2Division of Neurosurgery, Asama General Hospital, Iwamurada 1862-1, Saku 385-8558, Japan, 3Division of Neurosurgery, Komoro Kosei General Hospital, Yora-machi 3-2-31, Komoro 384-0006, Japan
Summary We present our surgical experience of 20 patients with syringomyelia, who were divided into two groups based on the findings of magnetic resonance (MR) imaging: a “non-visible cisterna magna” group, in which MR imaging did not reveal cerebrospinal fluid (CSF) in the cisterna magna, and a “visible cisterna magna” group. Patients with non-visible cisterna magna were associated with Chiari malformation (14 patients) or tight cisterna magna (4 patients) and underwent craniocervical decompression. Intradural exploration was performed when CSF movement in the cisterna magna or CSF outflow from the fourth ventricle appeared to be insufficient. It is important to confirm CSF outflow from the foramen of Magendie. Patients with visible cisterna magna were associated with tuberculous meningitis (2 patients) and underwent shunting procedures. Postoperatively, improvement in symptoms and a reduction in syrinx size were demonstrated in all patients except one. Two patients experienced recurrence of symptoms and syrinx dilatation. ª 2003 Elsevier Ltd. All rights reserved. Keywords: syringomyelia, Chiari malformation, tight cisterna magna, magnetic resonance imaging, surgical treatment, classification
INTRODUCTION
Surgical procedure
Many surgical procedures have been reported to treat syringomyelia. However, the optimal surgical option is still controversial because of the uncertain pathogenesis of spinal cord cavitation. We focused on cerebrospinal fluid (CSF) flow at the level of the foramen magnum, especially in the cisterna magna, because most theories of the formation and developmental mechanism of spinal cord cavities are based on CSF dynamics associated with obstruction of the ventricular foramina and/or the subarachnoid space around the brainstem at the level of the foramen magnum. We report our surgical experience of syringomyelia with reference to the findings of magnetic resonance (MR) imaging.
The main surgical procedures for patients with non-visible cisterna magna were as follows: (1) wide opening of the foramen magnum (foramen magnum decompression), via a suboccipital craniectomy with or without upper cervical laminectomy; (2) peeling off of the outer layer of the dura mater and confirmation of sufficient CSF flow from the foramen of Magendie, established by visualization through the thinned-out and transparent dura under an operating microscope or by Doppler ultrasonography; (3) opening of the dura leaving the arachnoid intact; (4) opening of the arachnoid membrane and dissection of arachnoid adhesions over and around the foramen of Magendie, or opening of the outlet foramen, in cases when the CSF flow from the foramen was insufficient; (5) lateral displacement of the cerebellar tonsil(s) by tenting it to the dura to leave the foramen of Magendie open for further outlet widening when the external decompression was deemed to be insufficient; and (6) duraplasty using allograft or artificial materials. Patients with visible cisterna magna underwent shunting procedures.
CLINICAL MATERIAL AND METHODS We operated on 20 patients with syringomyelia for progressive symptoms, except for one case because of scoliosis, between 1988 and 1999. The patients were 13 females (3 pediatric patients) and 7 males (3 pediatric patients) ranging in age at surgery from 10 to 54 years (mean 33 years). All patients underwent MR imaging of the craniocervical junction and the entire spinal cord to delineate pathogenic lesions that can cause spinal cord cavitation. Syringes related to spinal intramedullary or posterior fossa tumors were excluded. Based on MR findings, the patients were divided into two groups: a “non-visible cisterna magna” group, in which MR imaging did not reveal CSF in the cisterna magna, and a “visible cisterna magna” group, in which the CSF in the cisterna magna was visible. The clinical features of the patients are summarized in Table 1 (the patients with tight cisterna magna were reported elsewhere.1 ) Received 17 October 2002 Accepted 19 February 2003 Correspondence to: Kazuhiko Kyoshima MD, Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan. Tel.: +1-81-263-37-2688; Fax: +1-81-263-37-0480; E-mail: [email protected]
REPRESENTATIVE CASES Non-visible cisterna magna Case 4 An 18-years-old male presented with a 1-year history of thermohypesthesia in the left half of the body. Preoperative neurological findings revealed thermohypesthesia and hypalgesia in the left body, doubtful hemiparesis in the right side with hyperreflexia. MR imaging revealed a syrinx extending from C1 to T7 with a cystic-like dilatation at the C1 level and a Chiari malformation (Fig. 1). An X-ray film showed scoliosis of the thoracic spine. At surgery, foramen magnum decompression with C1 and partial C2 laminectomies was performed, and the dura was opened leaving the arachnoid membrane intact, resulted in good CSF flowing from the foramen of Magendie. Postoperatively, symptomatic improvement and a reduction in size of the syrinx and cystic dilatation were observed (Fig. 1). 273
274 Kyoshima et al.
Table 1 Case No.
Summary of clinical features of patients with syringomyelia Age (years) & sex
Preoperative symptoms and signs
Location of syrinx
Surgical procedures
C1–T5
FMD, C1, OA, DT, DP, obex plugging FMD, C1, Peel-off, DP FMD, C1, Peel-off, DP
Non-visible cisterna magna Chiari malformation 1 37 M Sensory impairment in rt arm, rt hemiparesis 2
37 F
Trunkal pain
C2–C7
3
16 M
rt Hemiparesis, sensory impairment in rt arm, scoliosis
C1-T11
4
18 M
C1–T7
5
30 F
6
51 F
lt Hemisensory impairment, slight rt hemiparesis, scoliosis Headache, numbness in rt arm, nystagmus, trunkal ataxia, hydrocephalus Sensory impairment in both arms(lt > rt), muscle weakness & Atorphy in lt hand # Worsening motor weakness in lt hand
C1–C7 C1–T9 C1–T12
7
19 F
rt Hemisensory impairment, scoliosis
C3–T6
8
19 F
C1–T10
9
33 F
Sensory impairment in rt arm, finger weakness in rt hand lt Trunkal sensory impairment
10 11
30 F 23 F
C2–T3 C4–T10
12
54 F
rt Hemiparesis, rt hemisensory impairment Numbness & sensory impairment in lt trunk and lt upper extremity Sensory impairment in both arms
13
10 M
Scoliosis
C2–T8
14
45 F
Slight lt hemiparesis, slight hypalgesia in lt face
C1–T8
Tight cisterna magna 15 52 F
rt Hemisensory impairment (touch and pain including face) Weakness & sensory impairment in rt arm
C6–T12
C2–T11
Holocord
FMD, PC1, Peel-off, DP FMD, PC1, Peel-off, DP FMD, C1, OD, DP FMD, C1, Peer-off, DP FMD, C1,OD, DP FMD, C1()), dural band cutting FMD, C1, Peel-off, DP FMD, C1, OA, AD, DT, DP FMD, C1, OA, AD, DT, DP FMD, C1, Peel-off, DP
16
49 M
17
16 F
Hypalgesia in both extremities, analgesia in both hands & feet, scoliosis, hydrocephalus
18
34 F
Weakness & muscle atrophy in lt arm, hypalgesia in lt leg, scoliosis # Worsening motor weakness in in lt arm
C1–T9 C1–T11
FMD, PC1, Peel-off, DP SS shunting
Numbness in rt leg, gait disturbance (normal subarachnoid) Clumsiness and motor weakness in both hands, paraplesia (whole arachnoid obstruction)
C6–T8
SS shunting
Visible cistena magna 19 38 M 20
48 M
Medulla -T12 (syringobulbia) Holocord
FMD, C1, PC2, OD, DP FMD, C1, PC2, OA, M-tomy, DP FMD, C1()), Peel-off, DP Wider FMD, C1, OA, DP FMD, C1()), Peel-off, DP
Holocord (C1–L1)
FMD, C1, PC2, OA, SC shunting
Treatment results
Follow-up period (years)
Symptoms
Syrinx size
Diminish
Decreased
13.3
Diminish
Decreased
10
Improved* (slightly)
Decreased
11
Improved
Almost
10
Improved
Decreased
8
Improved (slightly) Improved (slightly) Improved (slightly)
Decreased (slightly) Decreased
3.3
Almost
5
Improved
Decreased
5
Improved
Disappeared
5.3
Improved** Improved*** (slightly) Improved (slightly) –
Decreased Decreased
1 4.3
Decreased
3
Almost
3
Improved
Decreased
2
Improved
Decreased
11
Improved
Decreased
10
Improved, asympt cbll ptosis Improved (temporary) Improved (slightly)
Decreased
9
Decreased (temporary) Almost
2.5
Decreased
9
No change
7
Improved (slightly) No change
3
7
AD ¼ arachnoid dissection; C1 and C1()) ¼ with and without C1 laminectomy, respectively; DP ¼ duraplasty, DT ¼ displacement of the tonsil(s); FMD ¼ foramen magnum decompression; M-tomy ¼ membranectomy of the foramen of Magendie; OA ¼ opening the arachnoid membrane; OD ¼ opening the dura leaving the arachnoid membrane intact; PC1 and PC2 ¼ partial laminectomy of upper half of C1 and C2, respectively; Peel-off ¼ peeling off of the outer layer of the dura; SC shunting ¼ syringocisterna shunting; SS shunting ¼ syrinosubarachnoid shunting; almost ¼ almost disappeared; # ¼ second operation; * ¼ remaining motor weakness of rt hand; ** ¼ remaining hemi-numbness; *** ¼ disappearance of numbness only; asympt cbll ptosis ¼ asymptomatic cerebellar ptosis. The cases of tight cisterna magna were reported elsewhere.1
Case 5 A 30-years-old female, who had a 1-month history of headache, nausea, vomiting and numbness of the right upper extremity after the first delivery 1.5 years prior to admission, had complained of the same symptoms again from 7 months previously. Preoperative neurological examination showed bilateral papilloedema, occasional horizontal nystagmus and unstable tandem gait. Neuroimaging revealed a Chiari malformation, hydrocephalus and a Journal of Clinical Neuroscience (2004) 11(3), 273–279
syrinx. The syrinx consisted of two parts: the upper segment was located from C1 to C2 showing CSF-like intensity, and the lower segment was from C2 to C7 showing iso- to high-intensity on MR imaging (Fig. 2). Due to the heterogeneous feature, a spinal cord tumor was suggested but MR imaging demonstrated no intramedullary tumor (Fig. 2). At surgery, foramen magnum decompression and C1 and partial C2 laminectomies were performed. When the dura was opened, no marked CSF flow from the foraª 2003 Elsevier Ltd. All rights reserved.
Surgical experience of syringomyelia 275
Fig. 1 Case 4. Left and Middle: Preoperative MR imaging revealing a syrinx extending from C1 to T7 with a cystic-like dilatation at the C1 level and a Chiari malformation. Right: Postoperative imaging presenting a reduction in the size of the syrinx and cystic dilatation. MR ¼ magnetic resonance.
men of Magendie was observed and the foramen of Magendie was obstructed by a membranous structure, which was subsequently opened widely. Postoperatively the patient showed symptomatic improvement and neuroimaging revealed a reduction in syrinx and ventricle sizes (Fig. 2). Case 6 A 51-years-old female underwent decompression surgery of the left ulnar nerve 1.7 years prior to admission because of bilateral sensory impairment of both hands, but was followed by progressive motor weakness and sensory disturbance of the left upper extremity. Preoperatively, the patient showed sensory disturbance and motor weakness of her upper extremities with muscle atrophy of the left hand. Preoperative MR imaging revealed a syrinx extending from C1 to T9 and a Chiari malformation (Fig. 3(a)). The patient underwent foramen magnum decompression without C1 laminectomy. After peeling off of the outer layer of the dura, a relatively good CSF flow from the foramen of Magendie was
observed through the thinned-out dura. Postoperatively, the patient gained smoothness of finger movement and warm sensation with some improvement of sensation, and MR imaging revealed some decrease in syrinx size but the cisterna magna was still tight (Fig. 3(b)). Approximately 3 years postoperatively, motor weakness of the left upper extremity was aggravated and MR imaging demonstrated an enlargement of the syrinx (Fig. 3(c)). The patient underwent intradural exposure in addition to C1 laminectomy. A thick and hard scar like tissue was observed at the craniocervical junction. When the dura was opened there was no adhesion around the foramen of Magendie and good CSF flow was observed from the fourth ventricle but the tonsils were situated over the foramen of Magendie and the right tonsil apparently veiled the foramen. Postoperatively, MR imaging revealed a reduction in syrinx size (Fig. 3(d)), accompanied with slight symptomatic improvement. The cause of syrinx recurrence would be due to recompression of the tonsils by the thickened scar tissue located immediately over them.
Fig. 2 Case 5. Left: Preoperative enhanced MR imaging reveling a syrinx located from C1 to C7, a Chiari malformation and ventricular dilatation. Note that the syrinx consists of two parts: the upper segment located from C1 to C2 showing CSF-like intensity, and the lower segment from C2 to C7 showing iso- to high-intensity without suspecting a tumor shadow. Middle and Right: Postoperative imaging presenting a reduction in syrinx and ventricle sizes. MR ¼ magnetic resonance, CSF ¼ cerebrospinal fluid.
ª 2003 Elsevier Ltd. All rights reserved.
Journal of Clinical Neuroscience (2004) 11(3), 273–279
276 Kyoshima et al.
Fig. 3 Case 6. (a) Preoperative MR imaging revealing a syrinx extending from C1 to T9 and a Chiari malformation. The patient underwent foramen magnum decompression without C1 laminectomy. (b) Postoperative imaging presenting some decrease in syrinx size. (c) MR imaging obtained approximately 3 years postoperatively demonstrating an enlargement of the syrinx. Note that the cisterna magna remains tight and not visible. (d): MR imaging after reoperation revealing a reduction in syrinx size. MR ¼ magnetic resonance.
Visible cisterna magna Case 19 A 38-years-old male with a history of tuberculous meningitis at the age of 4 years had complained of gait disturbance and numbness of the right leg from 5 years prior to admission. Preoperative MR imaging revealed a syrinx extending from C6 to T8 with no abnormality at the posterior fossa (Fig. 4). Myelography showed no obstruction of the spinal and intracranial subarachnoid spaces. Syringosubarachnoid (S-S) shunting was performed via T1–T2 laminectomy. There was no marked adhesion of the spinal subarachnoid space. Postoperatively, MR imaging revealed a reduction of syrinx size (Fig. 4) whereas no marked improvement was seen except some sensory improvement. RESULTS The follow-up period after each operation ranged from 1 to 13.3 years (mean approximately 6.5 years). Postoperatively, improvement in symptoms and a reduction in syrinx size were demonstrated in all patients except for one with visible cisterna magna
(case 20), who had a long history of severe neurological deficits. No progressive symptoms or increase in syrinx size was demonstrated during the follow-up period except for 2 patients (cases 6 and 18), who required reoperation because of recurrence of symptoms and syrinx dilatation, resulted in a reduction in syrinx size and slight symptomatic improvement. Of 20 patients, 18 patients were assigned to the non-visible cisterna magna group and 2 patients to the visible cisterna magna group. The patients with non-visible cisterna magna were associated with Chiari malformation (14 patients) or tight cisterna magna (4 patients), and the patients with visible cisterna magna were associated with tuberculous meningitis (2 patients), one of whom revealed a spinal subarachnoid block on myelography (case 20). In the patients with the non-visible cisterna magna, all underwent foramen magnum decompression with the assurance of sufficient CSF flow from the foramen of Magendie, and showed clinical improvement postoperatively; laminectomy was not performed in 3 cases (cases 6, 7 and 13), one because of aplasia of the anterior C1 arch (case 13). Ten patients underwent peeling off of the outer layer of the dura only; 2 required reoperation of an intradural procedure (case 6) or
Fig. 4 Case 19. Left and Middle: Preoperative MR imaging revealing a syrinx extending from C6 to T8 with visible cisterna magna. Right: Postoperative imaging presenting a reduction of syrinx size. MR ¼ magnetic resonance.
Journal of Clinical Neuroscience (2004) 11(3), 273–279
ª 2003 Elsevier Ltd. All rights reserved.
Surgical experience of syringomyelia 277
S-S shunting (case 18). Four patients with non-visible cisterna magna (cases 1, 5, 15 and 16) underwent intradural procedures such as arachnoid dissection (cases 15 and 16), displacement of the tonsil(s) (cases 1, 15 and 16) and membranectomy of the foramen of Magendie (case 5). Three patients underwent opening of the dura leaving the arachnoid membrane intact (cases 4, 10 and 12) and one patient cutting of the dural band only (case 13). Obex plugging was performed in only one patient in the earliest case (case 1). Two patients showed hydrocephalus preoperatively, which responded to craniocervical decompression (case 17) and foraminal membranectomy (case 5). In the patients with the visible cisterna magna, one underwent S-S shunting because the subarachnoid space rostral to the syrinx was open by the preoperative myelography (case 19), and the other underwent syringocisterna shunting via suboccipital craniectomy (case 20). All but one of patients younger than 20 years of age and one adult patient had scoliosis. We did not experience any obvious surgery-associated complications. DISCUSSION Different surgical treatments have been recommended for spinal cord cavities in response to various pathogenic conditions such as foramen magnum or spinal lesions (organic syringomyelia), or unknown etiologies (idiopathic syringomyelia), and selection of the surgical procedure for syringomyelia remains controversial.2;3 Several theories have been proposed to explain the formation and development of syringomyelia associated with foramen magnum lesions, especially Chiari malformations. Congenital obstruction of the foramen of Magendie causes increases in intraventricular arterial CSF pressure waves, which forces the central canal to dilate via the obex (hydrodynamic theory).4;5 Otherwise, subarachnoid obstruction around the brainstem at the level of the foramen magnum causes increases in intracranial venous6–8 or arterial9 CSF pressure waves, which force CSF to push from the fourth ventricle into the central canal (craniospinal pressure dissociation),6–8 or cause reflux of CSF from the cisterna magna into the fourth ventricle forcing dilatation of the central canal.9 Alternatively, other studies proposed that increased venous,10;11 or arterial12;13 CSF pressure waves in the spinal subarachnoid space causes CSF to flow from the spinal subarachnoid space into the spinal cord through the perivascular or interstitial space creating a non-communicating parenchymal or central canal cavity (transcordal CSF infiltrating theory). The pathogenesis and developmental mechanism of spinal lesion-related cavities remains controversial. The initiation of spinal cavities was, however, thought to be a result from direct disruption, extramedullary compression damage, or necrosis of the spinal cord parenchyma. As developmental mechanisms, obstruction of the spinal subarachnoid space caused by extramedullary compression14–16;20 or arachnoiditis17–19 interferes with or increases CSF pressure waves,13;14;17–19 leading to transcordal CSF infiltration followed by parenchymal cavitation or central canal dilatation.14–16;18–20 Another proposal suggests that obstruction of the central canal for any reason may lead to fluid accumulation caudal to the blockage because there is a cephalad flow of CSFlike fluid in the central canal.2;21
strategies: (1) communicating syringes, which occur with hydrocephalus associated with identifiable pathologies including subarachnoid hemorrhage, meningitis and leptomeningeal neoplastic seeding, and are anatomically continuous with the forth ventricle; (2) non-communicating syringes, which are further divided into Chiari malformation with or without hydrocephalus, extramedullary compression lesions, spinal cord trauma, intramedullary tumors, infections, and multiple sclerosis; and (3) atrophic syringes, which occur with myelomalacia without indication of surgical intervention. In patients with syringomyelia with hydrocephalus, ventricular shunting is first recommended, and in those with Chiari malformation without hydrocephalus, posterior fossa decompression or syrinx shunting is first selected. Traumatic syringes are treated by syrinx shunting, and extramedullary compression-related or intramedullary tumor-related syringes are by excision of the lesions. Goel and Desai22 focusing on etiological factors and treatment considerations, classified syringomyelic patients, excluding those with posttraumatic and spina bifida-related syringes, into three groups. Group I, in which there is no definite demonstrable etiological factor, and S-S shunting is the ideal form of treatment; Group II, which had basilar invagination and/or Chiari malformation, and foramen magnum bony decompression is satisfactory and physiological; Group III, in which the syringes is secondary to an obvious etiology, such as a mass lesion either in the posterior cranial fossa or in the spine or a severe kyphotic spinal deformity, and the primary etiological problem is treated. We have classified syringomyelia, excluding intramedullary or posterior fossa tumor-related syrinx, into two groups focusing on the pathophysiological condition of CSF flow at the foramen magnum estimated by MR imaging, because in the majority of cases abnormal CSF dynamics in the cisterna magna has been generally thought to be the main factor in the pathogenesis of syringomyelia associated with foramen magnum lesions. One is the non-visible cisterna magna group, in which there is no effective subarachnoid space for the CSF in the cisterna magna on mid-sagittal MR imaging, and the other is the visible cisterna magna group, in which there is visible CSF in the cisterna magna. Syringes associated with non-visible cisterna magnum respond roughly to cavities associated with foramen magnum lesions such as Chiari malformation, tight cisterna magna,1 membranous occlusive lesions and basal arachnoiditis, whereas those with visible cisterna magna may include more diverse and complicated pathologies associated with spinal lesions such as trauma, arachnoiditis and extramedullary compression lesions, as well as with unknown etiologies. SURGICAL TREATMENT Numerous surgical interventions have been recommended for spinal cord cavities associated with foramen magnum lesions, especially Chiari malformations. They include drainage procedures of the ventricle or a syrinx, craniocervical decompression and direct syrinx decompression such as percutaneous aspiration of the syrinx,23–25 syringostomy,25;26 terminal ventriculostomy25;27–29 and endoscopic third ventriculostomy;30 drainage procedures and craniocervical decompression are, however, most frequently and widely adopted.
CLASSIFICATION Several classifications have been reported. However, classifications from the point of surgical treatment in relation to findings of MR imaging have been rarely proposed. Milhorat, et al.2 focusing on the pathological condition on MR imaging, classified all categories of syringes into three general types for specific treatment ª 2003 Elsevier Ltd. All rights reserved.
Drainage procedures Ventricular shunting has been recommended as the first procedure for syringes occurring with hydrocephalus and its effectiveness has been reported.2;8;29;31–33 However, it was noted that, even when a ventricular shunt is functioning, progression of spinal cord Journal of Clinical Neuroscience (2004) 11(3), 273–279
278 Kyoshima et al.
cavitation was eventually seen.34;35 Rhoton36 reported the development of a syrinx after shunt removal in a patient with mild hydrocephalus, although the ventricle size remained normal. He suggested that minimal pressure elevation may cause cord dilatation without causing ventricular dilatation in some patients. Oi et al.37 suggested that, under the intraluminal valvular mechanism, CSF may fill the central canal cavity during transient increases in intraventricular pressure, even though the decreasing intraventricular pressure, and isolation of a previously communicating holoneural canal system may occasionally develop via a similar mechanism that an isolated ventricle develops after ventricular shunting. Syrinx shunting procedures have been widely accepted for the treatment of any kind of cavity except those that are tumor related. S-S shunting has been reported to be the initial or an effective surgical procedure for syringomyelia associated with Chiari malformations, when symptoms of brainstem compression are not present.3;38–40 Some authors emphasize the effectiveness of syringoperitoneal (S-P) shunting.41–45 Other shunting procedures were reported such as syringopleural shunting,33;46;47 the thecoperitoneal shunting,48–50 syringocisternostomy (syringo-posterior fossa cistern shunting),51 lumboperitoneal shunting combined with myelotomy,52 and ventriculojugular shunting.53 S-S shunt is not indicated for cases in which the rostral part of the subarachnoid space is obstructed, for which cases S-P shunting is probably indicated.
flow from the fourth ventricle appeared to be insufficient. If arachnoiditis extends over the whole basal cistern, S-P shunting or syringocisternostomy will be necessary.51 Even in cases of hydrocephalus associated with non-visible cisterna magna, foramen magnum decompression may be responsible for resolving hydrocephalus. Two patients with hydrocephalus associated with Chiari malformation and tight cisterna magna responded to membranectomy of the foramen of Magendie and craniocervical decompression, respectively (cases 5 and 17). In case 6, although foramen magnum decompression with peeling off of the dura yielded some postoperative improvement in syrinx size and symptoms, the cisterna magna appeared to remain tight, suggesting insufficient CSF outflow from the fourth ventricle, so further intradural exploration by opening the arachnoid and establishing ventricular CSF outflow was performed to resolve this condition because of clinical recurrence. It is important not only to perform craniocervical decompression but also to confirm CSF flow in the cisterna magna and outflow form the foramen of Magendie. For patients with the visible cisterna magna, S-S shunting was selected if the subarachnoid space rostral to the syrinx was open, if the rostral subarachnoid space is, however, obstructed, S-P shunting is indicated. In syrinx-causative spinal lesions, such as extramedullary compression or a spinal deformity, treatment of the primary etiological problem will be necessary.
Foramen magnum decompression Various kinds of procedures or operative steps of craniocervical decompression with variations or combinations have been reported to resolve abnormal CSF dynamics at the foramen magnum. They include the following: (1) bony decompression via suboccipital craniectomy alone22 or with upper cervical laminectomy of C1–C2 or below; (2) opening both layers of the dura mater and the arachnoid, opening the dura but leaving the arachnoid intact,13;54–56 or removal of the outer layer of the dura57 and its modification as transverse microincisions of the outer layer of the dura;58 (3) surgical lyses of arachnoid adhesions, if present, to open the fourth ventricular outlet;2;34;44;59–61 (4) lateral displacement of the tonsils to leave the exit of the fourth ventricle open;3 or stitching the tonsils to the dura62 with simultaneous or alternative shunting from the fourth ventricle to the subarachnoid space using a Silastic tube27;36;44;60;63 and additional S-S shunting of the cavity;36 (5) intradural decompression such as subpial suction or concomitant hollowing of the herniated tonsils,6;8;64 or amputation of the cerebellar tonsils,2;3;59;65 when surgical decompression is considered insufficient;3 (6) with or without obex plugging: the plugging procedure is seldom performed nowadays;62 (7) combination with syringostomy;55 (8) duraplasty or leaving the dura open;3;6;8;25 and (9) replacement of an occipital bone flap.62 Idiopathic cavities have been treated by syrinx shunting such as S-S40;66 and S-P41–43;45;67 shunting. However, selection of the surgical procedure for syringomyelia remains controversial. The aim of surgery for syringomyelia with the non-visible cisterna magna is to restore appropriate CSF flow from the foramen of Magendie, or to obtain CFS pathways in the intracranial subarachnoid space at the foramen magnum, and to reconstruct the cisterna magna as a CSF pooling space to avoid arachnoid adhesion or extradural compression. For patients with the non-visible cisterna magna craniocervical bony decompression was first performed followed by a procedure of peeling off the outer dural layer;57 even in cases of tight cisterna magna, a C1 laminectomy will be necessary to provide sufficient decompression at the foramen magnum.1 Intradural procedures such as dural opening and lysis of the arachnoid adhesion were performed only when CSF movement in the cisterna magna as well as CSF outJournal of Clinical Neuroscience (2004) 11(3), 273–279
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45. Suzuki M, Davis C, Symon L, Gentili F. Syringoperitoneal shunt for treatment of cord cavitation. J Neurol Neurosurg Psychiatry 1985; 48: 620–627. 46. Sgouros S, Williams B. A critical appraisal of drainage in syringomyelia. J Neurosurg 1995; 82: 1–10. 47. Williams B, Page N. Surgical treatment of syringomyelia with syringopleural shunting. Br J Neurosurg 1987; 1: 63–80. 48. Pillay PK. Thecoperitoneal shunting for syringomyelia. J Neurosurg 1991; 75: 835–836. 49. Vassilouthis J, Papandreou A, Anagnostaras S, Pappas J. Thecoperitoneal shunt for syringomyelia: report of three cases. Neurosurgery 1993; 33: 324–328. 50. Vengsarkar US, Panchal VG, Tripathi PD, Patkar SV, Agarwal A, Doshi PK, Kamat MM. Percutaneous thecoperitoneal shunt for syringomyelia. Report of three cases. J Neurosurg 1991; 74: 827–831. 51. Milhorat TH, Johnson WD, Miller JI. Syrinx shunt to posterior fossa cisterns (syringocisternostomy) for bypassing obstructions of upper cervical theca. J Neurosurg 1992; 77: 871–874. 52. Park TS, Cail WS, Broaddus WC, Walker MG. Lumboperitoneal shunt combined with myelotomy for treatment of syringohydromyelia. J Neurosurg 1989; 70: 721–727. 53. Conway LW. Hydrodynamic studies in syringomyelia. J Neurosurg 1967; 27: 501–514. 54. Hida K, Iwasaki Y, Koyanagi I, Sawamura Y, Abe H. Surgical indication and results of foramen magnum decompression versus syringosubarachnoid shunting for syringomyelia associated with Chiari I malformation. Neurosurgery 1995; 37: 673–679. 55. Logue V, Edwards MR. Syringomyelia and its surgical treatment – an analysis of 75 patients. J Neurol Neurosurg Psychiatry 1981; 44: 273–284. 56. Sahuquillo J, Rubio E, Poca MA, Rovira A, Rodriguez-Baeza A, Cervera C. Posterior fossa reconstruction: a surgical technique for the treatment of Chiari I malformation and Chiari I/syringomyelia complex–preliminary results and magnetic resonance imaging quantitative assessment of hindbrain migration. Neurosurgery 1994; 35: 874–885. 57. Isu T, Sasaki H, Takamura H, Kobayashi N. Foramen magnum decompression with removal of the outer layer of the dura as treatment for syringomyelia occurring with Chiari I malformation. Neurosurgery 1993; 33: 844–850. 58. Gambardella G, Caruso G, Caffo M, Germano A, La Rosa G, Tomasello F. Transverse microincisions of the outer layer of the dura mater combined with foramen magnum decompression as treatment for syringomyelia with Chiari I malformation. Acta Neurochir 1998; 140: 134–139. 59. Bertrand G. Dynamic factors in the evolution of syringomyelia and syringobulbia. Clin Neurosurg 1973; 20: 322–333. 60. Dyste GN, Menezes AH, VanGilder JC. Symptomatic Chiari malformations. An analysis of presentation, management, and long-term outcome. J Neurosurg 1989; 71: 159–168. 61. Pillay PK, Awad IA, Little JR, Hahn JF. Surgical management of syringomyelia: a five year experience in the era of magnetic resonance imaging. Neurol Res 1991; 13: 3–9. 62. Vanaclocha V, Saiz-Sapena N, Garcia-Casasola MC. Surgical technique for cranio-cervical decompression in syringomyelia associated with Chiari type I malformation. Acta Neurochir 1997; 139: 529–539. 63. Batzdorf U. Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 1988; 68: 726–730. 64. Raftopoulos C, Sanchez A, Matos C, Baleriaux D, Bank WO, Brotchi J. Hydrosyringomyelia-Chiari I complex. Prospective evaluation of a modified foramen magnum decompression procedure: preliminary results. Surg Neurol 1993; 39: 163–169. 65. Iskandar BJ, Hedlund GL, Grabb PA, Oakes WJ. The resolution of syringohydromyelia without hindbrain herniation after posterior fossa decompression. J Neurosurg 1998; 89: 212–216. 66. Vaquero J, Martinez R, Salazar J, Santos H. Syringosubarachnoid shunt for treatment of syringomyelia. Acta Neurochir 1987; 84: 105–109. 67. Phillips TW, Kindt GW. Syringoperitoneal shunt for syringomyelia: a preliminary report. Surg Neurol 1981; 16: 462–466.
Journal of Clinical Neuroscience (2004) 11(3), 273–279
Clinical Study
Surgical experience of syringomyelia with reference to the findings of magnetic resonance imaging Kazuhiko Kyoshima1 MD, Takayuki Kuroyanagi2 MD, Toshihide Toriyama3 MD, Takeomi Takizawa1 Yunoshin Hirooka1 MD, Hiroshi Miyama1 MD, Akihiko Tanabe1 MD, Susumu Oikawa1 MD
MD,
1 Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan, 2Division of Neurosurgery, Asama General Hospital, Iwamurada 1862-1, Saku 385-8558, Japan, 3Division of Neurosurgery, Komoro Kosei General Hospital, Yora-machi 3-2-31, Komoro 384-0006, Japan
Summary We present our surgical experience of 20 patients with syringomyelia, who were divided into two groups based on the findings of magnetic resonance (MR) imaging: a “non-visible cisterna magna” group, in which MR imaging did not reveal cerebrospinal fluid (CSF) in the cisterna magna, and a “visible cisterna magna” group. Patients with non-visible cisterna magna were associated with Chiari malformation (14 patients) or tight cisterna magna (4 patients) and underwent craniocervical decompression. Intradural exploration was performed when CSF movement in the cisterna magna or CSF outflow from the fourth ventricle appeared to be insufficient. It is important to confirm CSF outflow from the foramen of Magendie. Patients with visible cisterna magna were associated with tuberculous meningitis (2 patients) and underwent shunting procedures. Postoperatively, improvement in symptoms and a reduction in syrinx size were demonstrated in all patients except one. Two patients experienced recurrence of symptoms and syrinx dilatation. ª 2003 Elsevier Ltd. All rights reserved. Keywords: syringomyelia, Chiari malformation, tight cisterna magna, magnetic resonance imaging, surgical treatment, classification
INTRODUCTION
Surgical procedure
Many surgical procedures have been reported to treat syringomyelia. However, the optimal surgical option is still controversial because of the uncertain pathogenesis of spinal cord cavitation. We focused on cerebrospinal fluid (CSF) flow at the level of the foramen magnum, especially in the cisterna magna, because most theories of the formation and developmental mechanism of spinal cord cavities are based on CSF dynamics associated with obstruction of the ventricular foramina and/or the subarachnoid space around the brainstem at the level of the foramen magnum. We report our surgical experience of syringomyelia with reference to the findings of magnetic resonance (MR) imaging.
The main surgical procedures for patients with non-visible cisterna magna were as follows: (1) wide opening of the foramen magnum (foramen magnum decompression), via a suboccipital craniectomy with or without upper cervical laminectomy; (2) peeling off of the outer layer of the dura mater and confirmation of sufficient CSF flow from the foramen of Magendie, established by visualization through the thinned-out and transparent dura under an operating microscope or by Doppler ultrasonography; (3) opening of the dura leaving the arachnoid intact; (4) opening of the arachnoid membrane and dissection of arachnoid adhesions over and around the foramen of Magendie, or opening of the outlet foramen, in cases when the CSF flow from the foramen was insufficient; (5) lateral displacement of the cerebellar tonsil(s) by tenting it to the dura to leave the foramen of Magendie open for further outlet widening when the external decompression was deemed to be insufficient; and (6) duraplasty using allograft or artificial materials. Patients with visible cisterna magna underwent shunting procedures.
CLINICAL MATERIAL AND METHODS We operated on 20 patients with syringomyelia for progressive symptoms, except for one case because of scoliosis, between 1988 and 1999. The patients were 13 females (3 pediatric patients) and 7 males (3 pediatric patients) ranging in age at surgery from 10 to 54 years (mean 33 years). All patients underwent MR imaging of the craniocervical junction and the entire spinal cord to delineate pathogenic lesions that can cause spinal cord cavitation. Syringes related to spinal intramedullary or posterior fossa tumors were excluded. Based on MR findings, the patients were divided into two groups: a “non-visible cisterna magna” group, in which MR imaging did not reveal CSF in the cisterna magna, and a “visible cisterna magna” group, in which the CSF in the cisterna magna was visible. The clinical features of the patients are summarized in Table 1 (the patients with tight cisterna magna were reported elsewhere.1 ) Received 17 October 2002 Accepted 19 February 2003 Correspondence to: Kazuhiko Kyoshima MD, Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan. Tel.: +1-81-263-37-2688; Fax: +1-81-263-37-0480; E-mail: [email protected]
REPRESENTATIVE CASES Non-visible cisterna magna Case 4 An 18-years-old male presented with a 1-year history of thermohypesthesia in the left half of the body. Preoperative neurological findings revealed thermohypesthesia and hypalgesia in the left body, doubtful hemiparesis in the right side with hyperreflexia. MR imaging revealed a syrinx extending from C1 to T7 with a cystic-like dilatation at the C1 level and a Chiari malformation (Fig. 1). An X-ray film showed scoliosis of the thoracic spine. At surgery, foramen magnum decompression with C1 and partial C2 laminectomies was performed, and the dura was opened leaving the arachnoid membrane intact, resulted in good CSF flowing from the foramen of Magendie. Postoperatively, symptomatic improvement and a reduction in size of the syrinx and cystic dilatation were observed (Fig. 1). 273
274 Kyoshima et al.
Table 1 Case No.
Summary of clinical features of patients with syringomyelia Age (years) & sex
Preoperative symptoms and signs
Location of syrinx
Surgical procedures
C1–T5
FMD, C1, OA, DT, DP, obex plugging FMD, C1, Peel-off, DP FMD, C1, Peel-off, DP
Non-visible cisterna magna Chiari malformation 1 37 M Sensory impairment in rt arm, rt hemiparesis 2
37 F
Trunkal pain
C2–C7
3
16 M
rt Hemiparesis, sensory impairment in rt arm, scoliosis
C1-T11
4
18 M
C1–T7
5
30 F
6
51 F
lt Hemisensory impairment, slight rt hemiparesis, scoliosis Headache, numbness in rt arm, nystagmus, trunkal ataxia, hydrocephalus Sensory impairment in both arms(lt > rt), muscle weakness & Atorphy in lt hand # Worsening motor weakness in lt hand
C1–C7 C1–T9 C1–T12
7
19 F
rt Hemisensory impairment, scoliosis
C3–T6
8
19 F
C1–T10
9
33 F
Sensory impairment in rt arm, finger weakness in rt hand lt Trunkal sensory impairment
10 11
30 F 23 F
C2–T3 C4–T10
12
54 F
rt Hemiparesis, rt hemisensory impairment Numbness & sensory impairment in lt trunk and lt upper extremity Sensory impairment in both arms
13
10 M
Scoliosis
C2–T8
14
45 F
Slight lt hemiparesis, slight hypalgesia in lt face
C1–T8
Tight cisterna magna 15 52 F
rt Hemisensory impairment (touch and pain including face) Weakness & sensory impairment in rt arm
C6–T12
C2–T11
Holocord
FMD, PC1, Peel-off, DP FMD, PC1, Peel-off, DP FMD, C1, OD, DP FMD, C1, Peer-off, DP FMD, C1,OD, DP FMD, C1()), dural band cutting FMD, C1, Peel-off, DP FMD, C1, OA, AD, DT, DP FMD, C1, OA, AD, DT, DP FMD, C1, Peel-off, DP
16
49 M
17
16 F
Hypalgesia in both extremities, analgesia in both hands & feet, scoliosis, hydrocephalus
18
34 F
Weakness & muscle atrophy in lt arm, hypalgesia in lt leg, scoliosis # Worsening motor weakness in in lt arm
C1–T9 C1–T11
FMD, PC1, Peel-off, DP SS shunting
Numbness in rt leg, gait disturbance (normal subarachnoid) Clumsiness and motor weakness in both hands, paraplesia (whole arachnoid obstruction)
C6–T8
SS shunting
Visible cistena magna 19 38 M 20
48 M
Medulla -T12 (syringobulbia) Holocord
FMD, C1, PC2, OD, DP FMD, C1, PC2, OA, M-tomy, DP FMD, C1()), Peel-off, DP Wider FMD, C1, OA, DP FMD, C1()), Peel-off, DP
Holocord (C1–L1)
FMD, C1, PC2, OA, SC shunting
Treatment results
Follow-up period (years)
Symptoms
Syrinx size
Diminish
Decreased
13.3
Diminish
Decreased
10
Improved* (slightly)
Decreased
11
Improved
Almost
10
Improved
Decreased
8
Improved (slightly) Improved (slightly) Improved (slightly)
Decreased (slightly) Decreased
3.3
Almost
5
Improved
Decreased
5
Improved
Disappeared
5.3
Improved** Improved*** (slightly) Improved (slightly) –
Decreased Decreased
1 4.3
Decreased
3
Almost
3
Improved
Decreased
2
Improved
Decreased
11
Improved
Decreased
10
Improved, asympt cbll ptosis Improved (temporary) Improved (slightly)
Decreased
9
Decreased (temporary) Almost
2.5
Decreased
9
No change
7
Improved (slightly) No change
3
7
AD ¼ arachnoid dissection; C1 and C1()) ¼ with and without C1 laminectomy, respectively; DP ¼ duraplasty, DT ¼ displacement of the tonsil(s); FMD ¼ foramen magnum decompression; M-tomy ¼ membranectomy of the foramen of Magendie; OA ¼ opening the arachnoid membrane; OD ¼ opening the dura leaving the arachnoid membrane intact; PC1 and PC2 ¼ partial laminectomy of upper half of C1 and C2, respectively; Peel-off ¼ peeling off of the outer layer of the dura; SC shunting ¼ syringocisterna shunting; SS shunting ¼ syrinosubarachnoid shunting; almost ¼ almost disappeared; # ¼ second operation; * ¼ remaining motor weakness of rt hand; ** ¼ remaining hemi-numbness; *** ¼ disappearance of numbness only; asympt cbll ptosis ¼ asymptomatic cerebellar ptosis. The cases of tight cisterna magna were reported elsewhere.1
Case 5 A 30-years-old female, who had a 1-month history of headache, nausea, vomiting and numbness of the right upper extremity after the first delivery 1.5 years prior to admission, had complained of the same symptoms again from 7 months previously. Preoperative neurological examination showed bilateral papilloedema, occasional horizontal nystagmus and unstable tandem gait. Neuroimaging revealed a Chiari malformation, hydrocephalus and a Journal of Clinical Neuroscience (2004) 11(3), 273–279
syrinx. The syrinx consisted of two parts: the upper segment was located from C1 to C2 showing CSF-like intensity, and the lower segment was from C2 to C7 showing iso- to high-intensity on MR imaging (Fig. 2). Due to the heterogeneous feature, a spinal cord tumor was suggested but MR imaging demonstrated no intramedullary tumor (Fig. 2). At surgery, foramen magnum decompression and C1 and partial C2 laminectomies were performed. When the dura was opened, no marked CSF flow from the foraª 2003 Elsevier Ltd. All rights reserved.
Surgical experience of syringomyelia 275
Fig. 1 Case 4. Left and Middle: Preoperative MR imaging revealing a syrinx extending from C1 to T7 with a cystic-like dilatation at the C1 level and a Chiari malformation. Right: Postoperative imaging presenting a reduction in the size of the syrinx and cystic dilatation. MR ¼ magnetic resonance.
men of Magendie was observed and the foramen of Magendie was obstructed by a membranous structure, which was subsequently opened widely. Postoperatively the patient showed symptomatic improvement and neuroimaging revealed a reduction in syrinx and ventricle sizes (Fig. 2). Case 6 A 51-years-old female underwent decompression surgery of the left ulnar nerve 1.7 years prior to admission because of bilateral sensory impairment of both hands, but was followed by progressive motor weakness and sensory disturbance of the left upper extremity. Preoperatively, the patient showed sensory disturbance and motor weakness of her upper extremities with muscle atrophy of the left hand. Preoperative MR imaging revealed a syrinx extending from C1 to T9 and a Chiari malformation (Fig. 3(a)). The patient underwent foramen magnum decompression without C1 laminectomy. After peeling off of the outer layer of the dura, a relatively good CSF flow from the foramen of Magendie was
observed through the thinned-out dura. Postoperatively, the patient gained smoothness of finger movement and warm sensation with some improvement of sensation, and MR imaging revealed some decrease in syrinx size but the cisterna magna was still tight (Fig. 3(b)). Approximately 3 years postoperatively, motor weakness of the left upper extremity was aggravated and MR imaging demonstrated an enlargement of the syrinx (Fig. 3(c)). The patient underwent intradural exposure in addition to C1 laminectomy. A thick and hard scar like tissue was observed at the craniocervical junction. When the dura was opened there was no adhesion around the foramen of Magendie and good CSF flow was observed from the fourth ventricle but the tonsils were situated over the foramen of Magendie and the right tonsil apparently veiled the foramen. Postoperatively, MR imaging revealed a reduction in syrinx size (Fig. 3(d)), accompanied with slight symptomatic improvement. The cause of syrinx recurrence would be due to recompression of the tonsils by the thickened scar tissue located immediately over them.
Fig. 2 Case 5. Left: Preoperative enhanced MR imaging reveling a syrinx located from C1 to C7, a Chiari malformation and ventricular dilatation. Note that the syrinx consists of two parts: the upper segment located from C1 to C2 showing CSF-like intensity, and the lower segment from C2 to C7 showing iso- to high-intensity without suspecting a tumor shadow. Middle and Right: Postoperative imaging presenting a reduction in syrinx and ventricle sizes. MR ¼ magnetic resonance, CSF ¼ cerebrospinal fluid.
ª 2003 Elsevier Ltd. All rights reserved.
Journal of Clinical Neuroscience (2004) 11(3), 273–279
276 Kyoshima et al.
Fig. 3 Case 6. (a) Preoperative MR imaging revealing a syrinx extending from C1 to T9 and a Chiari malformation. The patient underwent foramen magnum decompression without C1 laminectomy. (b) Postoperative imaging presenting some decrease in syrinx size. (c) MR imaging obtained approximately 3 years postoperatively demonstrating an enlargement of the syrinx. Note that the cisterna magna remains tight and not visible. (d): MR imaging after reoperation revealing a reduction in syrinx size. MR ¼ magnetic resonance.
Visible cisterna magna Case 19 A 38-years-old male with a history of tuberculous meningitis at the age of 4 years had complained of gait disturbance and numbness of the right leg from 5 years prior to admission. Preoperative MR imaging revealed a syrinx extending from C6 to T8 with no abnormality at the posterior fossa (Fig. 4). Myelography showed no obstruction of the spinal and intracranial subarachnoid spaces. Syringosubarachnoid (S-S) shunting was performed via T1–T2 laminectomy. There was no marked adhesion of the spinal subarachnoid space. Postoperatively, MR imaging revealed a reduction of syrinx size (Fig. 4) whereas no marked improvement was seen except some sensory improvement. RESULTS The follow-up period after each operation ranged from 1 to 13.3 years (mean approximately 6.5 years). Postoperatively, improvement in symptoms and a reduction in syrinx size were demonstrated in all patients except for one with visible cisterna magna
(case 20), who had a long history of severe neurological deficits. No progressive symptoms or increase in syrinx size was demonstrated during the follow-up period except for 2 patients (cases 6 and 18), who required reoperation because of recurrence of symptoms and syrinx dilatation, resulted in a reduction in syrinx size and slight symptomatic improvement. Of 20 patients, 18 patients were assigned to the non-visible cisterna magna group and 2 patients to the visible cisterna magna group. The patients with non-visible cisterna magna were associated with Chiari malformation (14 patients) or tight cisterna magna (4 patients), and the patients with visible cisterna magna were associated with tuberculous meningitis (2 patients), one of whom revealed a spinal subarachnoid block on myelography (case 20). In the patients with the non-visible cisterna magna, all underwent foramen magnum decompression with the assurance of sufficient CSF flow from the foramen of Magendie, and showed clinical improvement postoperatively; laminectomy was not performed in 3 cases (cases 6, 7 and 13), one because of aplasia of the anterior C1 arch (case 13). Ten patients underwent peeling off of the outer layer of the dura only; 2 required reoperation of an intradural procedure (case 6) or
Fig. 4 Case 19. Left and Middle: Preoperative MR imaging revealing a syrinx extending from C6 to T8 with visible cisterna magna. Right: Postoperative imaging presenting a reduction of syrinx size. MR ¼ magnetic resonance.
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S-S shunting (case 18). Four patients with non-visible cisterna magna (cases 1, 5, 15 and 16) underwent intradural procedures such as arachnoid dissection (cases 15 and 16), displacement of the tonsil(s) (cases 1, 15 and 16) and membranectomy of the foramen of Magendie (case 5). Three patients underwent opening of the dura leaving the arachnoid membrane intact (cases 4, 10 and 12) and one patient cutting of the dural band only (case 13). Obex plugging was performed in only one patient in the earliest case (case 1). Two patients showed hydrocephalus preoperatively, which responded to craniocervical decompression (case 17) and foraminal membranectomy (case 5). In the patients with the visible cisterna magna, one underwent S-S shunting because the subarachnoid space rostral to the syrinx was open by the preoperative myelography (case 19), and the other underwent syringocisterna shunting via suboccipital craniectomy (case 20). All but one of patients younger than 20 years of age and one adult patient had scoliosis. We did not experience any obvious surgery-associated complications. DISCUSSION Different surgical treatments have been recommended for spinal cord cavities in response to various pathogenic conditions such as foramen magnum or spinal lesions (organic syringomyelia), or unknown etiologies (idiopathic syringomyelia), and selection of the surgical procedure for syringomyelia remains controversial.2;3 Several theories have been proposed to explain the formation and development of syringomyelia associated with foramen magnum lesions, especially Chiari malformations. Congenital obstruction of the foramen of Magendie causes increases in intraventricular arterial CSF pressure waves, which forces the central canal to dilate via the obex (hydrodynamic theory).4;5 Otherwise, subarachnoid obstruction around the brainstem at the level of the foramen magnum causes increases in intracranial venous6–8 or arterial9 CSF pressure waves, which force CSF to push from the fourth ventricle into the central canal (craniospinal pressure dissociation),6–8 or cause reflux of CSF from the cisterna magna into the fourth ventricle forcing dilatation of the central canal.9 Alternatively, other studies proposed that increased venous,10;11 or arterial12;13 CSF pressure waves in the spinal subarachnoid space causes CSF to flow from the spinal subarachnoid space into the spinal cord through the perivascular or interstitial space creating a non-communicating parenchymal or central canal cavity (transcordal CSF infiltrating theory). The pathogenesis and developmental mechanism of spinal lesion-related cavities remains controversial. The initiation of spinal cavities was, however, thought to be a result from direct disruption, extramedullary compression damage, or necrosis of the spinal cord parenchyma. As developmental mechanisms, obstruction of the spinal subarachnoid space caused by extramedullary compression14–16;20 or arachnoiditis17–19 interferes with or increases CSF pressure waves,13;14;17–19 leading to transcordal CSF infiltration followed by parenchymal cavitation or central canal dilatation.14–16;18–20 Another proposal suggests that obstruction of the central canal for any reason may lead to fluid accumulation caudal to the blockage because there is a cephalad flow of CSFlike fluid in the central canal.2;21
strategies: (1) communicating syringes, which occur with hydrocephalus associated with identifiable pathologies including subarachnoid hemorrhage, meningitis and leptomeningeal neoplastic seeding, and are anatomically continuous with the forth ventricle; (2) non-communicating syringes, which are further divided into Chiari malformation with or without hydrocephalus, extramedullary compression lesions, spinal cord trauma, intramedullary tumors, infections, and multiple sclerosis; and (3) atrophic syringes, which occur with myelomalacia without indication of surgical intervention. In patients with syringomyelia with hydrocephalus, ventricular shunting is first recommended, and in those with Chiari malformation without hydrocephalus, posterior fossa decompression or syrinx shunting is first selected. Traumatic syringes are treated by syrinx shunting, and extramedullary compression-related or intramedullary tumor-related syringes are by excision of the lesions. Goel and Desai22 focusing on etiological factors and treatment considerations, classified syringomyelic patients, excluding those with posttraumatic and spina bifida-related syringes, into three groups. Group I, in which there is no definite demonstrable etiological factor, and S-S shunting is the ideal form of treatment; Group II, which had basilar invagination and/or Chiari malformation, and foramen magnum bony decompression is satisfactory and physiological; Group III, in which the syringes is secondary to an obvious etiology, such as a mass lesion either in the posterior cranial fossa or in the spine or a severe kyphotic spinal deformity, and the primary etiological problem is treated. We have classified syringomyelia, excluding intramedullary or posterior fossa tumor-related syrinx, into two groups focusing on the pathophysiological condition of CSF flow at the foramen magnum estimated by MR imaging, because in the majority of cases abnormal CSF dynamics in the cisterna magna has been generally thought to be the main factor in the pathogenesis of syringomyelia associated with foramen magnum lesions. One is the non-visible cisterna magna group, in which there is no effective subarachnoid space for the CSF in the cisterna magna on mid-sagittal MR imaging, and the other is the visible cisterna magna group, in which there is visible CSF in the cisterna magna. Syringes associated with non-visible cisterna magnum respond roughly to cavities associated with foramen magnum lesions such as Chiari malformation, tight cisterna magna,1 membranous occlusive lesions and basal arachnoiditis, whereas those with visible cisterna magna may include more diverse and complicated pathologies associated with spinal lesions such as trauma, arachnoiditis and extramedullary compression lesions, as well as with unknown etiologies. SURGICAL TREATMENT Numerous surgical interventions have been recommended for spinal cord cavities associated with foramen magnum lesions, especially Chiari malformations. They include drainage procedures of the ventricle or a syrinx, craniocervical decompression and direct syrinx decompression such as percutaneous aspiration of the syrinx,23–25 syringostomy,25;26 terminal ventriculostomy25;27–29 and endoscopic third ventriculostomy;30 drainage procedures and craniocervical decompression are, however, most frequently and widely adopted.
CLASSIFICATION Several classifications have been reported. However, classifications from the point of surgical treatment in relation to findings of MR imaging have been rarely proposed. Milhorat, et al.2 focusing on the pathological condition on MR imaging, classified all categories of syringes into three general types for specific treatment ª 2003 Elsevier Ltd. All rights reserved.
Drainage procedures Ventricular shunting has been recommended as the first procedure for syringes occurring with hydrocephalus and its effectiveness has been reported.2;8;29;31–33 However, it was noted that, even when a ventricular shunt is functioning, progression of spinal cord Journal of Clinical Neuroscience (2004) 11(3), 273–279
278 Kyoshima et al.
cavitation was eventually seen.34;35 Rhoton36 reported the development of a syrinx after shunt removal in a patient with mild hydrocephalus, although the ventricle size remained normal. He suggested that minimal pressure elevation may cause cord dilatation without causing ventricular dilatation in some patients. Oi et al.37 suggested that, under the intraluminal valvular mechanism, CSF may fill the central canal cavity during transient increases in intraventricular pressure, even though the decreasing intraventricular pressure, and isolation of a previously communicating holoneural canal system may occasionally develop via a similar mechanism that an isolated ventricle develops after ventricular shunting. Syrinx shunting procedures have been widely accepted for the treatment of any kind of cavity except those that are tumor related. S-S shunting has been reported to be the initial or an effective surgical procedure for syringomyelia associated with Chiari malformations, when symptoms of brainstem compression are not present.3;38–40 Some authors emphasize the effectiveness of syringoperitoneal (S-P) shunting.41–45 Other shunting procedures were reported such as syringopleural shunting,33;46;47 the thecoperitoneal shunting,48–50 syringocisternostomy (syringo-posterior fossa cistern shunting),51 lumboperitoneal shunting combined with myelotomy,52 and ventriculojugular shunting.53 S-S shunt is not indicated for cases in which the rostral part of the subarachnoid space is obstructed, for which cases S-P shunting is probably indicated.
flow from the fourth ventricle appeared to be insufficient. If arachnoiditis extends over the whole basal cistern, S-P shunting or syringocisternostomy will be necessary.51 Even in cases of hydrocephalus associated with non-visible cisterna magna, foramen magnum decompression may be responsible for resolving hydrocephalus. Two patients with hydrocephalus associated with Chiari malformation and tight cisterna magna responded to membranectomy of the foramen of Magendie and craniocervical decompression, respectively (cases 5 and 17). In case 6, although foramen magnum decompression with peeling off of the dura yielded some postoperative improvement in syrinx size and symptoms, the cisterna magna appeared to remain tight, suggesting insufficient CSF outflow from the fourth ventricle, so further intradural exploration by opening the arachnoid and establishing ventricular CSF outflow was performed to resolve this condition because of clinical recurrence. It is important not only to perform craniocervical decompression but also to confirm CSF flow in the cisterna magna and outflow form the foramen of Magendie. For patients with the visible cisterna magna, S-S shunting was selected if the subarachnoid space rostral to the syrinx was open, if the rostral subarachnoid space is, however, obstructed, S-P shunting is indicated. In syrinx-causative spinal lesions, such as extramedullary compression or a spinal deformity, treatment of the primary etiological problem will be necessary.
Foramen magnum decompression Various kinds of procedures or operative steps of craniocervical decompression with variations or combinations have been reported to resolve abnormal CSF dynamics at the foramen magnum. They include the following: (1) bony decompression via suboccipital craniectomy alone22 or with upper cervical laminectomy of C1–C2 or below; (2) opening both layers of the dura mater and the arachnoid, opening the dura but leaving the arachnoid intact,13;54–56 or removal of the outer layer of the dura57 and its modification as transverse microincisions of the outer layer of the dura;58 (3) surgical lyses of arachnoid adhesions, if present, to open the fourth ventricular outlet;2;34;44;59–61 (4) lateral displacement of the tonsils to leave the exit of the fourth ventricle open;3 or stitching the tonsils to the dura62 with simultaneous or alternative shunting from the fourth ventricle to the subarachnoid space using a Silastic tube27;36;44;60;63 and additional S-S shunting of the cavity;36 (5) intradural decompression such as subpial suction or concomitant hollowing of the herniated tonsils,6;8;64 or amputation of the cerebellar tonsils,2;3;59;65 when surgical decompression is considered insufficient;3 (6) with or without obex plugging: the plugging procedure is seldom performed nowadays;62 (7) combination with syringostomy;55 (8) duraplasty or leaving the dura open;3;6;8;25 and (9) replacement of an occipital bone flap.62 Idiopathic cavities have been treated by syrinx shunting such as S-S40;66 and S-P41–43;45;67 shunting. However, selection of the surgical procedure for syringomyelia remains controversial. The aim of surgery for syringomyelia with the non-visible cisterna magna is to restore appropriate CSF flow from the foramen of Magendie, or to obtain CFS pathways in the intracranial subarachnoid space at the foramen magnum, and to reconstruct the cisterna magna as a CSF pooling space to avoid arachnoid adhesion or extradural compression. For patients with the non-visible cisterna magna craniocervical bony decompression was first performed followed by a procedure of peeling off the outer dural layer;57 even in cases of tight cisterna magna, a C1 laminectomy will be necessary to provide sufficient decompression at the foramen magnum.1 Intradural procedures such as dural opening and lysis of the arachnoid adhesion were performed only when CSF movement in the cisterna magna as well as CSF outJournal of Clinical Neuroscience (2004) 11(3), 273–279
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