Obstructive hydrocephalus is present in
approximately 90% of patients and is often associated with cranial nerve
palsies. Most children have cerebellar signs (ataxia, nystagmus) and
evidence of long-tract signs (spasticity). Signs of raised intracranial
pressure (irritability, vomiting, convulsions), infantile hypotonia,
developmental delay, and mental retardation (in up to 70%). Associated
anomalies occur in almost 50% of cases. Agenesis of the corpus callosum
with associated mental retardation and interference with medullary control
of respiration leads to medullary failure. Pontine lesions involving the
apneustic center result in abnormal respiratory control (e.g.: apneas). The
clinical picture in older children involves delayed motor development with
poor coordination and gait control. Intellectual development is delayed, and
learning problems are frequently reported. Seizures have been reported in up
to 30% of patients. Extracerebral anomalies are present in approximately
one third of patients and include cleft palate, micrognathia, eye
abnormalities (increased intraocular pressure), skeletal abnormalities of
lumbar vertebrae, and polydactyly. Congenital cardiac defects have been
reported in approximately 15% (ventriculoseptal defect) of patients.
Renal abnormalities have been reported. Infundibular hematomas, posterior
fossa lymphomas, and syringomyelia are reported features that complicate
Dandy-Walker syndrome. The reported mortality rates vary from 26 to 50%.