Dandy-Walker syndrome: different modalities of treatment and outcome in 42 cases

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1 Child s Nerv Syst (2001) 17: DOI /s ORIGINAL PAPER Raj Kumar Manoj Kumar Jain Devendra Kumar Chhabra Dandy-Walker syndrome: different modalities of treatment and outcome in 42 cases Received: 6 January 2000 Revised: 27 July 2000 Published online: 15 March 2001 Springer-Verlag 2001 R. Kumar ( ) M.K. Jain D.K. Chhabra Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow , India rajkumar@sgpgi.ac.in Tel.: Abstract Objects: Forty-two patients with Dandy-Walker syndrome who were treated with different surgical modalities over a period of 8 years, from 1988 to 1996, at the Sanjay Gandhi Post Graduate Institute of Medical Sciences were reviewed in the present study. Methods: All the patients presented with hydrocephalus at the time of diagnosis. Association of other CNS anomalies was detected in 9 (22%) patients. Vermian hypoplasia was present in 36 (88%) cases, while cerebellar hypoplasia was documented in 27 (59%) of these patients. The treatment modality for these cases has continued to change in our institution over the years. Initially the ventriculoperitoneal shunt was the treatment of choice and was performed in 28 (66%) patients. Subsequently shunting of the cyst to the peritoneal cavity was performed in 7 (16%) patients. More recently, 3 of our patients were treated by fenestration of the cyst membrane and 4 others (9%), by ventriculocystoperitoneal shunting procedures. In this study the additional insertion of cystoperitoneal shunts was required in 8 (27%) of the 28 patients who had primary ventriculoperitoneal shunt procedures, because of either nonresolution or reappearance of a posterior fossa cyst. Six out of the 7 cases of primary cystoperitoneal shunts required additional ventriculoperitoneal shunt diversion because of persistent ventricular dilatation. In the group of 4 patients with primary ventriculocystoperitoneal shunts, only 1 patient required shunt revision. The patients on whom cyst membrane fenestration was performed required no additional procedures, except for 1 who already had a ventriculoperitoneal shunt in situ. Conclusions: Therefore, 18 of the total 42 patients could ultimately be made asymptomatic by ventriculocystoperitoneal shunting for one or the other of these reasons. Keywords Dandy-Walker syndrome Ventriculoperitoneal shunt Cystoperitoneal shunt Ventriculocystoperitoneal shunt Introduction The Dandy-Walker malformation is classically described as a neuropathologic triad consisting of cystic dilatation of the fourth ventricle, hypoplasia of the cerebellar vermis, and hydrocephalus. This syndrome is commonly associated with enlarged posterior fossa, high torcula and higher displacement of cerebellar hemispheres. Other CNS anomalies, such as agyria, polymicrogyria, agenesis of corpus callosum, aqueductal stenosis and syringomyelia, demonstrated at autopsy have also been found to be associated with Dandy-Walker syndrome. The aetiology and pathogenesis of this condition have not yet been determined, but the presence of associated abnormalities is suggestive of an early embryonal developmental disturbance affecting more than just the poste-

2 349 rior fossa structures [6]. The Dandy-Walker syndrome is said to be associated with a high incidence of motor dysfunction and mental retardation, leading some to suggest that the prognosis for normal intellectual development is poor [15]. Surgical management of this condition has undergone a significant evolution since Dandy s original description of the condition as a clinical entity. However, modern surgical management of the Dandy-Walker syndrome is not uniform, and there is still controversy over the optimum method of treatment [12, 13]. In the present study we have tried to evaluate the results of different treatment modalities in 42 cases of Dandy-Walker syndrome, as our treatment policy has also undergone various changes since Initial treatments applied in this patient population were ventriculoperitoneal shunting in 28 patients (66%), cystoperitoneal shunting in 7 patients (16%), simultaneous ventriculocystoperitoneal shunting in 4 patients (9%), and fenestration of the membrane in 3 patients (7%). Clinical features, treatment, complications, and outcome in these cases are discussed in this paper. Clinical material Forty-two patients with the Dandy-Walker syndrome who were admitted to this institute between 1988 and 1996 were reviewed retrospectively. The age of the patients at the time of diagnosis ranged from 9 months to 12 years (mean age 3.8 years). Twelve cases (28%) were diagnosed before the age of 1 year, and 8 (19%), between the ages of 1 and 3 years. Fourteen cases (34%) belonged to the 3- to 5-years age group, and the remaining 8 patients (19%) were over the age of 5 years. Twentysix patients (61%) were male and 16 (39%) were female. The common presenting symptoms and signs in these patients were enlarged head in 16 patients (39%), bulging fontanel in 12 cases (28%), and upward gaze palsy in 8 patients (19%). All had secondary hydrocephalus (caused by atresia of foramina). However, the signs of cerebellar dysfunction were demonstrable in 18 cases (42%). Brain stem dysfunction was evident in 2 cases (5%) in the form of hemiparesis. Associated systemic and congenital anomalies were detected in 4 cases (9%). Two patients had equinovarus deformities of their feet. One patient (2%) had a polycystic kidney and in another (2%) strabismus was found on ocular examination. Radiological investigations The major diagnostic procedure, besides plain X-ray of the skull, was computed tomography in 38 cases (90%); in addition, a ventriculogram was done in 1 patient (2%) and MRI in 4 patients (9%). Large posterior fossa, dysgenesis of cerebellar vermis and cystic enlargement of the fourth ventricle were the positive findings recorded in all patients. All our patients had hydrocephalus, which was moderate in 20 cases (66%) and severe in 14 cases (34%). Agenesis of the corpus callosum was detected in 2 cases (5%), and 3 patients (7%) had associated occipital encephalocele. Porencephalic cysts were documented in 4 cases (9%). Surgical treatment and outcome Ventriculoperitoneal shunting was performed in 28 patients (66%), cystoperitoneal shunting in 7 patients (16%), simultaneous ventriculocystoperitoneal shunting in 4 patients (9%), and wide fenestration of the membrane of the posterior fossa cysts in 3 patients (7%). The 28 patients (66%) who underwent ventriculoperitoneal shunting as the primary modality of treatment showed improvement both in symptoms and signs and in the size of the lateral ventricle, but a decrease in posterior fossa cysts was seen in only 20 cases (56%). The rest [9] of these patients also required a cystoperitoneal shunt (with their independent separate tubing), since their symptoms of ataxia did not resolve because of either persisting or recurring posterior fossa cysts (Figs. 1, 2). These were the patients who had secondary aqueductal stenosis and an isolated fourth ventricle, which meant they required cystoperitoneal shunting in addition. Sixteen revisions had to be done in 12 of the 28 cases of ventriculoperitoneal shunting after an average of 3 years when they showed the reappearance of ventriculomegaly on repeat CT scan. Malfunctioning shunts were responsible for 12 shunt revisions (75%). Subdural collections were noticed in 2 patients (12%), and shunt infections were found in 2 other cases (12%). Thus, only 8 patients remained free of symptoms with ventriculoperitoneal shunts during their subsequent follow-up. Six (85%) of the 7 patients who underwent cystoperitoneal shunting required an additional ventriculoperitoneal shunt because their cysts were large and hydrocephalus, which had diminished initially, reappeared over a period of 2 4 years. Two of these (34%) presented with malpositioning of shunts with the shunt tips found to be outside the calvarium, and 4 patients (66%) had malfunctioning cystoperitoneal shunts. One out of the 4 (9%) patients who had combined ventriculocystoperitoneal shunts required revision because of a blocked lower end of the shunt, but had shown diminution of both cyst and hydrocephalus subsequent to revision. The procedure of wide fenestration of the cyst membrane was successful in treatment of both posterior fossa cysts and hydrocephalus in 2 out of the 3 patients. In 1 child, who had already undergone right ventriculoperitoneal shunting for his hydrocephalus (Dandy-Walker syndrome) 3 weeks after delivery, fenestration of a posterior fossa

3 350 Fig. 1 NCCT (head) of a child showing the decreased size of lateral ventricles but a persistent posterior fossa cyst although a wellfunctioning ventriculoperitoneal shunt is in place Fig. 2 CT (head) scan of the same child depicting resolution of a posterior fossa cyst following installation of a cystic shunt Fig. 3 Postoperative NCCT (head) of a child showing decompression of the posterior fossa cyst and fourth ventricle following wide fenestration of the cyst. Also note the smaller temporal horns cyst was carried out when he was 1.5 years of age, as he was found on follow-up to have developed gait ataxia. All 3 patients remained asymptomatic throughout a follow-up period (Fig. 3) of about 2 years. Small suboccipital craniectomy and intradural excision of the dorsal and inferior part of the membrane covering the posterior fossa cyst were carried out under the operating micro- scope. The fragments of membrane from the cyst wall were also excised from either side laterally to permit a free flow of CSF in the lateral cervicomedullary cistern. This procedure was performed to create openings at the fourth ventricular outlet in the presence of an intact distal pathway. A total of 14 patients ultimately received new ventriculocystoperitoneal shunts following their primary treatment with either ventriculoperitoneal shunts or cystoperitoneal shunts, and these children subsequently remained free of symptoms for about 3 years. Follow-up periods in these cases ranged from 1 year to 8 years, with a mean of 3.4 years. Discussion Dandy-Walker syndrome is characterized by: (1) Cystic dilatation of the fourth ventricle (2) Hypoplasia of the cerebellum (3) Hydrocephalus (4) Large posterior fossa (5) Atresia of the foramina of Magendie and Luschka However, not all these features need be present in all cases. Although Hart et al. state that hydrocephalus is essential for the diagnosis of Dandy-Walker syndrome [1], this has been refuted by Hirsch et al., who consider that hydrocephalus should not be included in the definition of this syndrome [9]. In 80% of their cases hydrocephalus was a postnatal complication of malformation, most often developing within 3 months of birth. In our series all patients presented with hydrocephalus, irrespective of their age. Systemic and other CNS anomalies associated with this syndrome are well documented. Hart et al. showed that 68% of their 28 patients had associated CNS anomalies [7]. Similarly, Sawaya and McLaurin reported that 48% of their 23 patients had CNS anomalies [15]. Clinically detectable associated anomalies are obviously less frequent than pathologically detectable anomalies [15]. Hoffman et al. found that 29% of their patients with Dandy-Walker syndrome had associated CNS anomalies [1]. In our study we found associated CNS anomalies in 43% of cases. In our series the incidence of occipital encephalocele (7%) was not as high as that documented by Hoffman et al. (20%). Hoffman et al. reported an 11.4% incidence of agenesis of corpus callosum, but we found this in only 2 cases (4%). The incidence of this syndrome is reported to be highest in infants under 1 year of age. As many as 89% of the patients were diagnosed when they were below 1 year of age in the series reported by Hoffman s group [1]. However, the majority of patients in our series presented at between 3 and 4 years of age. The most common symptoms and signs of Dandy-Walker syndrome are second-

4 351 ary to hydrocephalus, as seen in the present series. The clinical features related to posterior fossa abnormalities were present in only 18 (42%) of our 42 cases, as opposed to the series reported by Hawkin et al., where 73% of the patients had ataxia indicating posterior fossa abnormalities [8]. Despite advances in diagnostic modalities, the treatment still remains controversial. Foltz and Shurtleft and Hawkin et al. have pointed out that inserting a shunt into the lateral ventricle of a patient with hydrocephalus can lead to the development of acquired aqueductal stenosis [5, 8]. In the series investigated by Hoffman s group 6 patients out of 17 developed acquired aqueductal stenosis following ventriculoperitoneal shunting [1]. In our series 8 out of 28 patients required a cystoperitoneal shunt following a ventriculoperitoneal shunt over a span of 2 4 years, most probably as the result of the development of secondary aqueductal stenosis, as suggested by the reappearance of persistent posterior fossa cysts. Pillay et al. [13] reported upward transtentorial herniation following a ventriculoperitoneal shunt in cases of Dandy-Walker cysts. A keyhole configuration of the fourth ventricle seen on axial CT images of patients with Dandy-Walker cysts has been reported to be an indication of upward transtentorial herniation, an entity distinct from entrapped fourth ventricles of other causes and other posterior fossa cysts, which may also develop into upward transtentorial herniation. In the present series we did not find any upward transtentorial herniation following ventriculoperitoneal shunting, but there was progressive enlargement of posterior fossa cysts which required additional cystoperitoneal shunting. In contrast to upward transtentorial herniation with a ventriculoperitoneal shunt, a cystoperitoneal shunt alone leads to chronic cerebral herniation in shunted Dandy-Walker malformations, according to Naidich et al. [11]. They reported that in patients with the Dandy-Walker malformation, the high position of the tentorium, the wide incisura, the hypoplastic cerebellum and the large posterior fossa cyst predispose to chronic downward transincisural herniation of the cerebral hemisphere when the cystoperitoneal shunt reduces infratentorial volume and pressure. Such a predisposition is further aggravated by any application of suction to the cyst catheter and by any increase in supratentorial volume and pressure. Once established, the herniation may persist despite multiple shunt revisions, even after the restoration of normal pressure. The 7 patients in our study who underwent cystoperitoneal shunting did not develop chronic cerebral herniation. Although Manna et al. suggest the utilization of cystoperitoneal shunts when patency of aqueduct can be confirmed [10], our study lacked enough evidence to substantiate this viewpoint. None of our patients had undergone CSF flow dynamic studies to confirm the CSF flow velocity and its direction of flow at aqueductal level, which could have helped us further in decision making. The dynamics could have guided us in our treatment of 14 patients who ultimately required ventriculocystoperitoneal shunts. Combined ventriculoperitoneal and cystoperitoneal shunting appears to be a better option, according to Raimondi et al. [14]. They showed that the shunt should be inserted between the lateral ventricle and the cyst on one side and the peritoneal cavity on the other to avoid secondary aqueductal stenosis. The principle behind this technique has been to decompress the posterior fossa mass effect while decompressing the ventricles at the same time. This minimizes the risk of upward transtentorial herniation and chronic cerebral herniation. Domingo and Peter had found a high complication rate when double shunts were used [4]. Although the use of double shunting is not advocated as a primary mode of therapy, it may be required subsequently if secondary stenosis or shunt failure develops, according to Domingo and Peter [4]. Asai et al. have noted theoretically that a combined ventriculoperitoneal shunt and cystoperitoneal shunt can facilitate secondary aqueductal stenosis because it minimizes physiological CSF flow through the aqueduct [1]. Four of our patients had primarily undergone a combined ventriculocystoperitoneal shunt and only 1 of them had required shunt revision. Fourteen other patients had to undergo combined ventriculocystoperitoneal shunting subsequent to the failure of an isolated ventriculoperitoneal shunt or cystoperitoneal shunt and remained symptom free for about 3 years. Membrane excision was initially proposed by Dandy for the treatment of Dandy-Walker syndrome. The results using this form of therapy have been poor initially, with a high failure rate. This form of therapy was based on an assumption that the blocked outlets of the fourth ventricle were responsible for expansion of the fourth ventricle and supratentorial hydrocephalus [4]. Membrane excision, as proposed by Dandy and Blackfan, has fallen into disrepute because of a high mortality rate of 10% and a failure rate of 70% [3]. However, Udvarhelyi and Epstein still advocate this treatment by way of cyst wall excision in children aged over 3 years [16]. In our series, the 2 patients who had wide membrane fenestration as their primary modality of treatment were over 3 years old and had no complications following surgery. However, the third child had a pre-existing ventriculoperitoneal shunt and had also undergone membrane fenestration at 1.5 years of age. Since there were only 3 cases, it is difficult to comment on the complications and outcome. The present study failed to disclose any substantial evidence allowing us to call any of the available modalities of treatment in question, because of the nonavailability of dynamic CSF flow studies and aqueductal diameters. However, we conclude by saying that Dandy-Walker malformation in children below 3 years of age may be treated with combined cystoperitoneal and ventriculo-

5 352 peritoneal shunts with good results, while children over 3 years may benefit from cyst wall fenestration in view of the decreased mortality and morbidity in better equipped centres. This decision making could be more scientific if the dynamic CSF studies were done preoperatively. It becomes necessary to know not only the presence of flow but also the direction of CSF flow when the appropriate therapy has to be selected. We lack statistical evidence at this juncture, but theoretically it seems justifiable to perform cyst excision to offer a permanent cure in children over 3 years of age provided that downward CSF flow has been demonstrated at aqueductal level and below. In the absence of downward CSF flow or CSF flow at aqueductal level ventriculocystoperitoneal shunting remains an attractive and safe treatment option, although it cannot offer a permanent cure. We realize the importance of dynamic CSF studies and are planning a subsequent study in this area. References 1. Asai A, Hoffman J, Hendrick B, Humphrey P (1989) The Dandy-Walker syndrome: experience at the Hospital for Sick Children, Toronto. Pediatr Neurosci 15: Benda CE (1954) The Dandy-Walker syndrome or the so-called atresia at the foramen of Magendie. J Neuropathol Exp Neurol 13: Dandy WE, Blackfan KD (1914) Internal hydrocephalus. An experimental, clinical and pathological study. Am J Dis Child 3: Domingo Z, Peter J (1996) Midline developmental abnormalities of the posterior fossa: correlation of classification with outcome. Pediatr Neurosurg 24: Foltz EL, Shurtleft DB (1966) Conversion of communicating hydrocephalus to stenosis or occlusion of the aqueduct during ventricular shunt. J Neurosurg 24: Gardener E, Rahilly R, Prolo D (1975) The Dandy-Walker and Arnold-Chiari malformations. Arch Neurol 32: Hart MN, Malamud N, Ellis WG (1972) The Dandy-Walker syndrome: a clinicopathological study based on 28 cases. Neurology 22: Hawkins JC III, Hoffman HJ, Humphreys RP (1978) Isolated fourth ventricle as a complication of ventricular shunting. J Neurosurg 49: Hirsch J-F, Pierre-Kahn A, Renier D, Sainte Rose C, Hoppe-Hirsch E (1984) Dandy-Walker malformation. J Neurosurg 61: Maria BL, Zinrech SJ, Carson BC, Rosenbaum AE, Freeman JM (1987) Dandy-Walker syndrome revisited. Pediatr Neurosci 13: Naidich FP, Radkowski MA, McLone DG, Lashma J (1985) Chronic cerebral herniation in shunted Dandy-Walker malformation. Radiology 158: Osenbach K, Menezes H (1992) Diagnosis and management of the Dandy- Walker malformation: 30 years of experience. Pediatr Neurosurg 18: Pillay P, Barnett HG, Lanzeiri C, Cruse R (1989) Dandy-Walker cyst upward herniation: the role of MRI and double shunts. Pediatr Neurosci 15: Raimondi AJ, Samuelson G, Yazzagaray L, Norton T (1969) Atresia of the foramina of Luschka and Magendie: Dandy-Walker cyst. J Neurosurg 31: Sawaya R, McLaurin RL (1981) Dandy-Walker syndrome: clinical analysis of 23 cases. J Neurosurg 55: Udvarhelyi GB, Epstein MH (1975) The so-called Dandy-Walker syndrome: analysis of 12 operated cases. Child s Brain 1: