Dandy-Walker Syndrome Dr Saeed Mokhtary Resident of Neurosurgery

HISTORY

The first autopsy description of such a clinical picture was offered in 1887 by Sutton. It was not until 1914 that Dandy and Blackfan realized an association between hydrocephalus and cystic fourth ventricular dilation in a 13-month old girl. The malformation was further characterized by Dandy in 1921 and by Taggart and Walker in 1942 as being related to congenital atresia of the fourth ventricular exit foramina. However, it was Benda in an autopsy series in 1954 who first used Dandy-Walker syndrome to describe this condition and offered a new theory on its etiology.

EMBRYOLOGY

Cerebellar development begins in the ninth week, when the cerebellar hemispheres develop and subsequently fusing to form the vermis. The choroid plexus of the fourth ventricle and the foramina of luschka and magendie form around the tenth week of gestation. Cerebrospinal fluid (csf) then accumulates within the fourth ventricle, forming this space. The cerebellar lobules develop in an anterior-to-posterior direction and are completely formed by week 18.

Persistence of the posterior medullary velum, which remains as a thick arachnoid and ectodermal membrane Dysgenetic development of the anterior membranous area of the rhombencephalon Developmental failure of the foramen of magendie is not necessary for the development of DWS

TERMINOLOGY AND DIFFERENTIAL DIAGNOSIS

Dandy Walker malformation (DWM) A large posterior fossa cyst communicating with the fourth ventricle Absence of a portion of the inferior vermis Hypoplasia, anterior rotation, and upward displacement of the remaining vermis Absence or flattening of the angle of the fastigium A large posterior fossa with torcular elevation Anterolateral displacement of the cerebellar hemispheres

Turcula vermis 4th ventricule

Primary Fissure F Pre-Pyramidal Fissure

Dandy-Walker variant (DWV) A milder spectrum of DWS-like signs that were not congruent with the classic definition, but a clear clinical separation has not been defined. An inferior cerebellar vermian defect and communication between a normal-sized cisterna magna and fourth ventricle.

Dandy-Walker complex (DWC) Continuum of posterior fossa anomalies Mild (mega–cisterna magna only) Moderate (mild hypoplasia of vermis, enlarged fourth ventricle) Severe (agenesis of vermis, dilation of posterior fossa cyst and fourth ventricle)

Mega–cisterna Magna

Agenesis Of Vermis Jubert Syndrome

CLINICAL FEATURES

Occur in 1 of 25,000 to 30,000 newborns The majority of patients presenting in the first YEAR(3 months) Hydrocephalus may not be present on prenatal imaging or at birth but has been reported to occur in roughly 80% of all patients with DWS

The most common postnatal presentation is macrocrania. Other signs and symptoms The sunset sign A large posterior fossa Seizures Spasticity Lethargy Delayed milestones Respiratory failure Apnea Deafness, Visual problems Increased intracranial pressure Older children and adults Headache Vomiting Cranial nerve palsies Nystagmus Ataxia

Numerous malformations are described in the literature in association with DWS and its variants. CNS anomalies (68%) Dysgenesis/agenesis of corpus callosum Occipital meningocele Systemic abnormalities (25%) Facial capillary hemangiomas Cardiac defects Atrial septal defect Patent ductus arteriosus Tetralogy of fallot Ventricular septal defect

Diagnostic tools

DIAGNOSIS Diagnosis of DWS is made on the basis of anatomic findings on imaging. MRI representing the gold standard CSF dynamics cine MRI sequences for detecting the etiology of hydrocephalus

PRENATAL IMAGING Ultrasound May be discordant with postnatal imaging or postmortem pathologic findings Fetal MRI Associated congenital abnormalities cognitive and developmental delays Insufficient for anatomic analysis of the vermis

GENETICS A disorder of genetic heterogeneity Chromosomal aberrations Occur in about 50% of cases Trisomy 13 Trisomy 18 Triploidy Inheritance patterns may be x-linked or autosomal recessive

TREATMENT

CYST MEMBRANE EXCISION To facilitate spinal fluid flow On the basis of the belief that hydrocephalus in DWS was due to obstruction of the foramina of luschka and magendie Poor efficacy (75% of patients still requiring a shunt) High mortality (10%) May rarely play a role in the treatment of DWS, particularly in older children or after multiple shunt failures.

DIVERSION OF CSF THROUGH SHUNTING The most widely accepted first-line treatment Controversy exists in terms of which shunting procedure yields the best results Shunting the supratentorial compartment Shunting the cerebellar cyst Shunting both compartments (dual shunt)

NEUROENDOSCOPIC INTERVENTION Endoscopic third ventriculostomy An aqueductal “stent” with shunting Endoscope-assisted transtentorial proximal catheter placement with shunting.

Assessment of aqueductal flow MRI and cine MRI VPS The primary option Safest and most effective treatment Endoscopic treatment Controversial Cyst treatment Reserved for refractory cases Presence of aqueductal stenosis ETV and aqueductal stenting or a dual shunt

PROGNOSIS

MORTALITY Has significantly decreased (from 100% in 1942 to 10% or less today) This improvement is likely due to advances in medical and surgical care and improved management of hydrocephalus. Death: Secondary to shunt malfunction or associated systemic anomalies.

ASSOCIATED CONDITIONS Seizures, hearing or visual problems, and other systemic or CNS abnormalities are predictive of worse outcome IQ 80 or more in 50% of long-term survivors, normal IQs in 30% vermian lobulation may be a useful prognostic factor of functional development