Treatment options for Dandy–Walker malformation

J Neurosurg (5 Suppl Pediatrics) 105:348–356, 2006

348 J. Neurosurg: Pediatrics / Volume 105 / November, 2006

N 1914 Dandy and Blackfan8 described a congenitalmalformation of the central nervous system comprisingdilation of the fourth ventricle, hypoplasia of the cere-

bellar vermis, and hydrocephalus. Forty years later Benda3

termed the lesion “Dandy–Walker malformation” to ac-knowledge contributions made by Taggart and Walker in1942.

Considerable debate exists in the contemporary literatureregarding the ideal management of DWMs.2,4,6,9,10,13,15,21,28 Inthe past two decades surgical management has shifted fromcraniectomy and membrane excision to shunt placement.There has been a considerable decrease in morbidity andmortality rates since shunts have been used to treat DWM;however, shunt-treated patients become dependent on thedevice and multiple surgeries are required in these patientsto correct shunt-associated failures and complications. Withthe increased use of the neuroendoscope in the treatment of

obstructive hydrocephalus, it is possible that many of thesechildren can become shunt independent and be at less riskfor morbidity and mortality. In this paper we review our 16-year experience at the National Institute of Mental Healthand Neurosciences, Bangalore, India, in treating childrenwith DWM, and we compare the various management op-tions used during this period.

Clinical Material and Methods

We retrospectively studied the cases of 72 children whohad undergone surgery for DWM or a Dandy–Walker vari-ant at the National Institute of Mental Health and Neuro-sciences between January 1986 and July 2002. Patients inwhom there was neuroimaging evidence of posterior fossaarachnoid cysts or mega cisterna magna were excluded fromthe study. Developmental assessments were performed pre-operatively, whenever possible, and postoperatively. Whenavailable, preoperative and postoperative neuroimages werecompared to evaluate any reduction in ventricle and cystsizes.

Treatment options for Dandy–Walker malformation

AARON MOHANTY, M.CH., ARUNDHATI BISWAS, M.CH., SATYANARAYANA SATISH, M.CH.,SHANTI SHANKAR PRAHARAJ, M.CH., AND KOLLURI V. R. SASTRY, M.CH.

Department of Neurosurgery, National Institute of Mental Health and Neuro Sciences, Bangalore,India; and Department of Neurosurgery, University of Texas Health Sciences Center at Houston,Texas

Object. The aim of this study was to assess the efficacy of various treatment options available for children withDandy–Walker malformation (DWM) and to evaluate the role of endoscopic procedures in the treatment of this dis-order.

Methods. The authors conducted a retrospective review of 72 children who underwent surgical treatment for DWMduring a 16-year period. All patients underwent computed tomography scanning, and 26 underwent magnetic reso-nance (MR) imaging. The initial surgical treatment included ventriculoperitoneal (VP) shunt placement in 21 patients,cystoperitoneal (CP) shunt placement in 24, and combined VP and CP shunt insertion in three. Twenty-one patientsunderwent endoscopic procedures (endoscopic third ventriculostomy [ETV] alone in 16 patients, ETV with aqueduc-tal stent placement in three, and ETV with fenestration of the occluding membrane in two). Three patients underwentmembrane excision via a posterior fossa craniectomy. In the 26 patients who had undergone preoperative MR imag-ing, aqueductal patency was noted in 23 and aqueductal obstruction in three. These three patients underwent placementof a stent from the third ventricle to the posterior fossa cyst in addition to the ETV procedure.

During the follow-up period, 12 patients with a CP shunt and four with a VP shunt experienced shunt malfunctionsthat required revision. Four patients with a CP shunt also required placement of a VP shunt. In addition, five of the 21ETVs failed, requiring VP shunt insertion. A reduction in ventricle size noted on postoperative images occurred morefrequently in patients with a VP shunt, whereas a reduction in cyst size was more appreciable in patients with a CPshunt. Successful ETV resulted in a slight decrease in ventricle size and varying degrees of reduction in cyst size.

Conclusions. Endoscopic procedures may be considered an acceptable alternative in children with DWM. Theauthors propose a treatment protocol based on preoperative MR imaging findings of associated aqueductal stenosis.

KEY WORDS • Dandy–Walker malformation • hydrocephalus • aqueductoplasty •endoscopic third ventriculostomy • shunt • pediatric neurosurgery

I

Abbreviations used in this paper: CP = cystoperitoneal; CSF =cerebrospinal fluid; CT = computed tomography; DWM = Dandy–Walker malformation; ETV = endoscopic third ventriculostomy;MR = magnetic resonance; VP = ventriculoperitoneal.

Nine patients were lost to follow up, and two died duringthe follow-up period. The remaining patients were observedfor a period ranging from 6 months to 14 years (mean 48months). The follow-up period for the patients who under-went endoscopic procedures ranged from 6 to 52 months(mean 30.9 months). The mean follow-up periods for pa-tients treated with CP shunts and those treated with VPshunts were 56.5 months (range 14–120 months) and 64months (range 14–168 months), respectively. The patientswho underwent membrane excision as the primary proce-dure participated in follow up for a mean of 27 months(range 12–42 months).

Patient Population

Of the 72 children (42 boys and 30 girls [male/female ra-tio 1.4:1]), 36 (50%) were younger than 1 year of age (Ta-ble 1). Six children were between 11 and 18 years of age atpresentation; all had symptoms in early childhood, suggest-ing a delayed referral pattern.

Clinical Presentation

Macrocrania was the most common clinical presentation(82%; Table 1). Delayed developmental milestones (36%)and features of raised intracranial tension (25%) were alsocommon presenting symptoms. Five children (7%) experi-enced seizures. Associated foot deformity was present inthree children, associated occipital encephalocele in three,and myelomeningocele in one patient.

Neuroimaging Evaluation

All patients underwent preoperative CT scanning. Theseimages did not reveal hydrocephalus in four children, where-as varying degrees of ventriculomegaly were exhibited inthe remaining patients. Additionally, MR imaging was per-formed in 26 children, revealing aqueductal patency in 23and aqueductal stenosis in three (Fig. 1).

Initial Surgical Treatment

The initial surgical treatment plan was based on findingsfrom the neuroimaging evaluation, which included the ab-

sence or presence of hydrocephalus, the degree of ventric-ulomegaly, and the surgical practice prevalent during thatperiod. Ventriculoperitoneal shunts were placed in 21 pa-tients (29%), CP shunts in 24 (33%), and combined shuntsin three (4%). Endoscopic procedures were performed in 21patients (29%), and the obstructing membrane was excisedvia an open surgical technique in three (4%) (Table 2). Inthe three patients who underwent placement of combinedVP and CP shunts as the initial procedure, both proximalcatheters were connected by a single distal peritoneal cath-eter with a Y connector. The endoscopic procedures were

J. Neurosurg: Pediatrics / Volume 105 / November, 2006

Dandy–Walker malformation

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TABLE 1Age distribution and clinical presentation in

72 patients who presented with DWM

Variable No. of Patients

age distribution (yrs),1 361–2 143–5 126–10 411–18 6

clinical presentationmacrocrania 59delayed milestones 26increased intracranial tension 18sunset sign 21seizures 5spasticity 9hydrocephalus 3large posterior fossa 6lethargy 3

FIG. 1. Sagittal T1-weighted MR images demonstrating largeposterior fossa cysts with a patent aqueduct (upper) and an obstruct-ed aqueduct (lower).

performed in the latter part of the study period when endo-scopic surgery was standardized and had become a well-accepted method for treating obstructive hydrocephalus.These procedures included ETV alone in 16 children, ETVplus fenestration of the occluding membrane in two, andETV plus ventricle–cyst stent placement in three patients.

The ETV was performed in the region of the tuber cine-reum in the conventional manner with the aid of a rigid-rodneuroendoscope. A flexible neuroendoscope was also usedif deemed necessary. During the procedure the aqueductopening was inspected for any obstruction or stenosis. Anattempt was made to fenestrate the occluding membraneonly if it could be visualized and the fenestration safely per-formed. On inspection the aqueduct was found to be wide-ly patent in all but three patients. These three patients withaqueductal stenosis underwent placement of a stent extend-ing from the third ventricle to the posterior fossa cyst in addition to ETV. The details of the procedure have been de-scribed elsewhere.12,26 In two patients the obstructing mem-brane could be fenestrated at the time of surgery.

Postoperative Period, Complications, and SubsequentSurgeries

During the postoperative period, peritubal CSF collectionor CSF leakage from the ventriculostomy site was evident in15 patients (Table 3). Of these patients a CP shunt had beenplaced in seven (47%) and a VP shunt in three (20%); endo-scopic procedures had been performed in the remaining five(33%). The CSF leakage was treated by shunt revision or intermittent CSF drainage through the patent anterior fon-tanelle in patients who underwent endoscopic procedures.Subdural hematomas developed in two patients with VPshunts and required evacuation.

In 25 patients (35%) the procedure failed (Table 4). Itwas evident in 12 (50%) of 24 patients who had a CP shunt;33% of the failures manifested within 1 week of surgeryand 67% within 6 months. The failure rate for VP shuntswas 19% (four of 21), all failures occurred within 6 monthsafter the initial placement. Endoscopic procedures failed insix patients (24%), five of whom underwent placement ofa VP shunt (Tables 2 and 4). In one patient who had under-gone ventricle–cyst stent placement, the stent became mal-positioned and required repositioning.

Four patients in whom a CP shunt was initially implant-ed later underwent placement of a VP shunt. In one patient

with a CP shunt, ETV was performed to treat subsequentshunt failure. One of the three patients in whom the mem-brane had been excised (Table 2) underwent VP shunt in-sertion to treat persistent hydrocephalus. Of the three pa-tients who had aqueductal stenosis associated with DWMand had undergone ETV and ventricle–cyst stent place-ment, the ETV failed in one; placement of a VP shunt wasrequired in this patient. Patency of the aqueductal stent wasconfirmed in all patients on follow-up MR imaging flowstudies or iohexol CT ventriculography.26

Neuroimaging-Documented Improvement

Preoperative and postoperative images were availablefor review in 43 patients (Table 5). The CT scan or MR im-age obtained at the last follow-up visit was compared withthe preoperative images to assess cyst and ventricle size re-duction. This decrease was classified as significant (.60%), moderate (30–60%), or slight (, 30%) dependingon the size observed on the postoperative images. The cystvolume was measured using the Cavalieri direct estimatormethod.7 The measurements were made by placing a pointgrid over the images of interest and counting the number ofdots enclosed by the area. The total number of dots coveredby all the slices were summed and a volume represented byeach dot was calculated, allowing simple calculation of thecyst or ventricle volume. This method for determining vol-ume has been shown to be reliable and comparable to oth-ers in which a sophisticated three-dimensional computer-based technique is used.7

A remarkable (moderate to significant) reduction in ven-

A. Mohanty, et al.


TABLE 2Surgical procedures performed in 72 patients with DWM

No. of Ops

Procedure Initial Final

shunt placementVP 21 28CP 24 17VP & CP 3 7

endoscopic procedureETV alone 16 12ETV & membrane fenestration 2 2ETV & stent placement 3 2

VP & stent placement 0 1membrane excision 3 2VP & membrane excision 0 1

TABLE 3Surgical complications in patients with DWM*

No. of Complications by Procedure

Endoscopic MembraneComplication VPS CPS Procedure VPS & CPS Excision

CSF leakage/collection 3 7 5 0 0SDH 2 0 0 0 0shunt malfunction 4 12 0 2 0shunt infection 0 1 0 0 0

* CPS = CP shunt; SDH = subdural hematoma; VPS = VP shunt.

TABLE 4Procedural failures in 25 patients with DWM

No. of Procedures

Type of Shunt

Endoscopic MembraneTime to Failure VP CP VP & CP Procedures Excision

total no. of patients 21 24 3 21 3no. of failed procedures

,1 wk 2 4 0 1* 01–4 wks 1 1 1 3 11–6 mos 1 3 0 2 06 mos–,1 yr 0 0 0 0 01–2 yrs 0 0 0 0 03–5 yrs 0 2 0 0 06–10 yrs 0 2 0 0 1

* One patient had a malpositioned stent that required repositioning.

tricle size was obtained in 88% of children with a VP shuntcompared with 38% of those with a CP shunt. On the otherhand, a relatively marked reduction in cyst size was dem-onstrated in 88% of patients with CP shunts and 62% ofthose with VP shunts (Figs. 2 and 3). Of the 16 patients wholater underwent endoscopic procedures, a slight reductionin ventricle size was noted in all, and the cyst volume de-creased in varying degrees (Fig. 4). Repeated MR imagingstudies performed in these patients demonstrated a goodflow void at the third ventriculostomy site, suggesting afunctioning ventriculostomy (Fig. 5).

Developmental Assessment

Developmental and neuropsychological assessmentcould be performed in 45 patients during both the pre- andpostoperative periods. Of these patients 22 (49%) exhibitedage-appropriate development, whereas 13 (29%) had a milddelay and 10 a significant delay in reaching their devel-opmental milestones. We did not observe any specific trendof developmental delay in the various treatment groups.

Discussion

Although initially described by Sutton in 1887, credit isattributed to Dandy and Blackfan8 for recognizing the mal-formation comprising cyst dilation of the fourth ventricle,cerebellar vermian dysgenesis, and hydrocephalus. Initiallythis disorder was considered to be due to atresia of the for-amina of Magendie and Luschka. Later Benda3 suggestedthat DWM was possibly due to failure of the normal regres-sive changes in the posterior medullary velum combinedwith a congenital absence of the cerebellar vermis, thus re-sulting in cyst formation at the caudal end of the fourth ven-tricle. Currently, DWM is considered to be the result ofmaldevelopment in the region of the fourth ventricle and isnot limited to foraminal atresia. The presence of a posteri-or fossa cyst with varying degrees of dysgenesis of the ce-rebellar vermis is considered essential for the diagnosis ofthis disorder, although hydrocephalus and associated en-largement of the posterior fossa with elevation of the tento-rium may also be present to a varying extent.

In the present paper we describe a retrospective study ofpatients treated during a 16-year period (January 1986–July2002). Considerable advancements in neuroimaging andsurgical techniques were witnessed during this time span,necessitating a change in treatment options for patients withDWM. Because the study population comprised patientstreated by several neurosurgeons during a period of almosttwo decades, we realize that a definite conclusion of supe-riority of one treatment option over another is difficult toestablish. In this study, however, we have attempted to com-pare the various management strategies currently availablefor treatment of children with DWM and Dandy–Walkervariants.

Of the several subgroups of patients with posterior fossacysts, we excluded those harboring arachnoid cysts andmega cisterna magna. On reviewing the literature, we foundthat surgeons prefer to treat posterior fossa arachnoid cystsvia cyst excision and CP shunt insertion, whereas they pre-fer to manage mega cisterna magna conservatively. Weincluded patients with DWM and Dandy–Walker variantsin our study because the management options are quite sim-ilar for both conditions.

Hydrocephalus and Aqueductal Patency

In the present series 68 children (94%) had associatedhydrocephalus at the time of diagnosis. In several earlierpublications investigators have stated this incidence to be86 to 94%.2,9,28 However, in another previous study therewas no evidence of hydrocephalus on prenatal ultrasono-graphic studies in 80% of patients with DWM, suggestingits probable development during the neonatal period.15

Initial aqueductal patency is of considerable importance,given that it often dictates the surgical plan. Detection ofassociated aqueductal stenosis on preoperative neuroim-ages warrants combined VP–CP shunt placement becauseboth the ventricle and cyst need to be drained to prevent atranstentorial pressure gradient and its resulting complica-tions. Asai, et al.,2 noted initial aqueductal patency in 19patients who underwent preoperative ventriculography orMR imaging. Similar findings have been reported by oth-ers.23 In another study, the authors retrospectively conclud-ed that two of their 35 patients with DWM might have anassociated aqueductal stenosis.9 However, Edwards andRafel10 stated that aqueductal patency is rare in their expe-rience and have suggested simultaneous drainage of bothcompartments as the initial procedure. In the present seriesa patent aqueduct was observed in 18 of the 21 patientswho underwent preoperative MR imaging. During the en-doscopic procedure a specific attempt was made to visual-ize the aqueduct. Aqueductal patency was confirmed in allpatients in whom preoperative MR images had demon-strated a patent aqueduct.

Initial Surgical Treatment and the Role of Shunts

The choice of the initial surgical treatment remains underdebate. Excision of the obstructing membrane, once advo-cated, is currently not considered the initial procedure ofchoice due to its associated risks of morbidity and mortali-ty. In patients who experience frequent shunt malfunctions,however, this procedure may be considered an alternativeto shunt placement,1 and it has also been found to be bene-ficial in older children.20 Shunt placement is currently con-



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TABLE 5Neuroimaging-documented improvementin cyst and ventricle size in 43 patients*

Size Reduction (no. of patients)

Structure & Treatment Significant Moderate Slight

cystVP shunt 1 9 6CP shunt 5 2 1VP & CP shunt 1 0 1ETV 2 5 9membrane excision 1 0 0

ventricleVP shunt 5 9 2CP shunt 0 3 5VP & CP shunt 0 1 1ETV 0 7 9membrane excision 0 0 1

* Both pre- and postoperative neuroimages were available in these pa-tients.

sidered the surgical procedure of choice; however, there hasbeen considerable debate on the type of shunt to be placed.Various authors have advocated VP and CP shunt insertion,either alone or in combination. Ventriculoperitoneal shuntsare easier to place, have a relatively low incidence of mal-position or migration, and can be used in cases of signifi-cant hydrocephalus. Carmel and colleagues6 have suggest-ed creation of a free communication between the supra- andinfratentorial compartments, and recommend draining thelateral ventricles to achieve early decompression, ensuringa satisfactory cognitive development. Early decompression

of ventriculomegaly is essential for satisfactory cognitivedevelopment, and the presence of a VP shunt suffices inmost cases. Bindal, et al.,4 did not find any statistically sig-nificant difference between outcomes in children with CPshunts and those with VP shunts; however, they recom-mended that VP shunt placement should be the initial treat-ment of choice, given that the complication rate associatedwith that treatment is lower than the rate associated with CPshunts. Similar views also have been expressed by Gerstzenand Albright.13 Nonetheless, transtentorial upward hernia-tion29,30 and acquired aqueductal stenosis2 resulting in an

A. Mohanty, et al.


FIG. 2. Preoperative (A and B) and postoperative (C and D) CT scans obtained in a patient with a Dandy–Walker vari-ant who had undergone placement of a CP shunt. Note the significant reduction in cyst size and the moderate reduction inventricle size.

isolated fourth ventricle have been reported after ventricu-lar shunt insertion. In a previous paper, development of de-layed secondary aqueductal stenosis and an isolated fourthventricle requiring additional CP shunt placement was re-ported in nine (43%) of 21 patients who had undergone ini-tial placement of a VP or ventriculoatrial shunt.2 In anotherstudy, ventricular shunts were found to be unsuccessful indraining both cavities in 77% of patients.28

Cystoperitoneal shunts are currently favored by manyauthors.2,9,15,22,32 A CP shunt drains both the cyst and ventri-cles adequately in the majority of cases. In a series of 10patients who underwent CP shunt placement described byAsai and colleagues,2 ventricle and cyst size reduction wasnoted in all 10 patients. Nevertheless, CP shunts are asso-ciated with the following complications: difficult place-ment of the proximal end,9 frequent disconnection andmigration,9 development of posterior fossa hematomas4 andbrainstem tethering,20 the need for frequent revisions,13 andan increased incidence of CSF leakage during the postop-erative period.6 A few deaths have also been attributed toposterior fossa hematomas due to CP shunts.4

Authors have advocated combined shunt placement in thelateral ventricle and the posterior fossa cyst to equalize pres-sure across the tentorium.28,29,34 Osenbach and Menezes28 re-ported a 92% success rate when using combined shunts.Some authors have reported simultaneous drainage of boththe lateral ventricle and the posterior fossa cyst when sepa-rate proximal catheters have been placed and connected bya Y connector to a single distal valve and peritoneal cathe-ter,29,31 whereas others have advocated placement of two dif-ferent catheters to equalize the pressure across the tentori-um.25 However, it has been suggested that combined shuntplacement can cause development of secondary aqueductalstenosis because CSF flow through the aqueduct is greatlyreduced.2

In the present study, a relatively lower complication ratewas observed in patients with a VP shunt than in those witha CP shunt. Cerebrospinal fluid leakage and peritubal CSFcollection occurred more often in patients with CP shuntsthan in those with VP shunts. Furthermore, the incidence ofmalfunctioning of the CP shunts was higher than that of theVP shunts. The CP shunts malfunctioned in one third of the



353

FIG. 3. Preoperative (A and B) and postoperative (C and D) CT scans obtained in a child with DWM who had under-gone placement of a VP shunt. Note the significant decompression of the dilated ventricles with a residual posterior fossacyst.

patients within 1 week and in another third between 1 and6 months after placement.

Neuroimaging-Documented Improvement

Authors of several studies have addressed the extent ofneuroimaging-documented improvement during the fol-low-up period after shunt placement.2,9 In a study of 35patients, the cyst size decreased in 74% of the patients whounderwent CP shunt placement, whereas the ventricle sizedecreased in 68%. On the other hand, placement of a VPshunt caused a reduction in the sizes of ventricles and cystsin 41 and 31% of patients, respectively.9 Asai, et al.,2 de-scribed cyst size reduction in all patients with CP shuntscompared with 62% of patients with VP shunts. In the pre-sent series, of the patients with VP shunts a satisfactory re-duction in cyst and ventricle sizes was exhibited in 62 and88%, respectively, whereas in patients with CP shunts thecyst size decreased more than the ventricle size. In the ma-jority of patients who underwent endoscopic procedures, aslight to moderate reduction was exhibited in both ventric-ular and cyst sizes.

In the present series, 10 patients were 6 years or older atthe time of their initial surgery. In view of these cases ofchronic ventriculomegaly, a significant reduction in ventri-cle size following the procedure would be difficult to ex-pect. Forty-three of the 72 patients underwent pre- and post-operative neuroimaging performed at suitable intervals andthe images were available for comparison. Given that theETV procedure has only been performed fairly recently,neuroimages were available for most patients who under-went ETV. On the other hand, in some of the patients withVP and CP shunts neuroimages were not available for acomparison (Table 5). Although the lack of imaging docu-mentation appears to be a flaw in the study, we do not be-lieve that it significantly biased the results.

Correlation Between the Type of Shunt and FunctionalOutcome

In their study, Golden and associates14 suggested that re-establishment of the posterior fossa architecture was associ-ated with a favorable prognosis: 89% of their patients witha developmentally normal intellect had undergone at least

A. Mohanty, et al.


FIG. 4. Preoperative (A) and postoperative (B) sagittal MR images obtained in a patient with a Dandy–Walker variantwho underwent ETV. Note the slight reduction in cyst size as evidenced by the decompressed and relaxed cerebellar ver-mis and the reduction in the fourth ventricle size. Preoperative (C and D) and postoperative (E and F) CT scans revealinga slight reduction in the cyst and ventricle sizes.

partial restoration of the posterior fossa structures to nor-mality. However, these findings have not been substantiat-ed. Bindal and colleagues4 did not find any statistical sig-nificance in outcomes between the type of shunt placed andthe patients’ intellectual and functional outcomes. They alsonoted that although 38% of patients with one shunt had toundergo placement of an additional shunt, it was uncertainwhether the efficacy of this aggressive procedure had anyimpact on the final outcome. After reviewing the data in 35patients with DWM, Domingo and Peter9 noted a greaterreduction in cyst size in those with a CP shunt. However, abetter outcome could not be correlated with the amount ofreduction in cyst size. In a thoughtful and carefully analyzedstudy, Gerstzen and Albright13 did not find a correlation be-tween the residual cerebellar size and the cerebellar andintellectual deficits exhibited by the patient. Furthermore,they could not demonstrate any correlation between the lo-cation of the shunt and the subsequent cerebellar size onpostoperative neuroimages. Although the correlation be-tween a developmental delay and the type of shunt treat-ment was not a specific aim of our study, we did not observethis association.

Endoscopic Procedures Used in Treating DWM

Although ETV has been widely used to treat obstructivehydrocephalus due to aqueductal stenosis, no authors havespecifically mentioned the use of ETV to treat DWM. Au-thors of a few reports, however, have described using per-cutaneous third ventriculostomy for treating this condi-tion.2,15,16 Asai, et al.,2 reported on two patients who hadpresented with shunt malfunction and then underwent thisprocedure. Hydrocephalus improved in both; the cyst sizereduced in one and remained unchanged in the other. Three(50%) of six patients treated by Hirsch and associates15 us-

ing percutaneous ventriculostomy experienced improvedhydrocephalus. McLaurin and Crone24 described using anendoscope to connect the third and the fourth ventricles,thereby facilitating the use of a single shunt system. Buxtonand coworkers5 performed ETV in three patients, one ofwhom experienced procedural failure during the postopera-tive period.

In the present series, 21 patients underwent endoscopicprocedures. In cases of aqueductal patency, ETV was theprocedure of choice; however, in cases of aqueductal ob-struction, placement of a ventricle–cyst stent was combinedwith ETV. This combined treatment was performed to en-sure a patent communication between the supratentorial andthe infratentorial compartments, thus preventing develop-ment of a transtentorial herniation. The five patients whoexperienced a CSF leak following ETV were treated withintermittent CSF drainage. In these patients there was aninsufficient cortical mantle to provide adequate tamponadeto prevent CSF egress at the insertion site of the endoscope.The five ETV failures occurred between 1 and 6 monthspostoperatively and caused patient irritability and a persis-tent increase in head circumference that required shunt in-sertion.

In cases of obstructive hydrocephalus, the success rate ofETV ranges between 23 and 80%; the lower rates are seenin infants and younger children.5,17,18 The 24% failure rate ofendoscopic procedures in the present study is in accordancewith the failure of ETV for treating obstructive hydroceph-alus in children. After a successful ventriculostomy a slightreduction (16–35%) in ventricle size has been documentedin previous studies.19,33 A generous residual ventriculomeg-aly seen after a successful third ventriculostomy may pre-vent secondary aqueductal stenosis, which has been re-ported to occur due to marked reduction in ventricle sizefollowing VP shunt insertion.11 In the present study, sec-ondary aqueductal stenosis was not encountered during thefollow-up period. In a related report in which the authorsdescribed the successful use of ETV in treating a fourthventricle outlet obstruction, isolation of the fourth ventriclewas not observed during the follow-up period.27

Suggested Management Protocol

In patients with DVM the presence of an aqueductal ob-struction, as noted on preoperative neuroimages, should bethe deciding factor in determining the treatment method.The presence of an aqueductal obstruction warrants simul-taneous drainage of the supra- and infratentorial compart-ments to prevent a transtentorial pressure gradient.

With the advent of neuroendoscopic techniques, ETVappears to be reasonable as the initial treatment option forpatients with DWM and is usually adequate in patients witha patent aqueduct. A VP or CP shunt may be considered ifthe ETV fails. However, in the less frequent case of an as-sociated aqueductal stenosis, communication between bothcompartments would warrant an aqueductoplasty or a stentplacement in addition to third ventriculostomy.

Conclusions

The role of shunts in treating patients with DWM hasbeen well established. Shunt use has considerably reducedmortality and morbidity rates compared with the open sur-



355

FIG. 5. Postoperative MR image obtained in a child with aDWM who had undergone an ETV. A good flow void through thethird ventriculostomy is demonstrated.

gical procedures that have been in practice in the past fewdecades. However, frequent device malfunction and per-manent shunt dependency have been a constant problemwith shunt insertion. With the growing popularity of neuro-endoscopy in managing obstructive hydrocephalus, endo-scopic procedures for DWM may become more widely fa-vored than shunt placement. A longer follow-up period andmore widespread experience, however, are warranted.

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Manuscript received April 12, 2005.Accepted in final form August 16, 2006.Address reprint requests to: Aaron Mohanty, M.Ch., Department

of Neurosurgery, University of Texas Health Sciences Center at Hous-ton, 6410 Fannin #1020, Houston, Texas 77030. email: [email protected].

A. Mohanty, et al.


Treatment options for Dandy–Walker malformation

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