Dandy-Walker Malformation, Agenesis of Corpus Callosum, and Gray Matter Heterotopia
Findings:
The corpus callosum and cerebellar vermis are absent.
The lateral ventricles have a parallel configuration and are lined with
scattered nodules of tissue that are isointense to gray matter.
Discussion:
Callosal agenesis and heterotopias are discusssed elsewhere
(unknowns #39, #85). Dandy Walker complex is thought to be caused by developmental
atresia of the fourth ventricular foramina with resultant variable hypoplasia
of the cerebellar vermis and a posterior fossa cyst which communicates
with the fourth ventricle. The malformation is not inherited, but has numerous
associations as follows:
-macrocephaly, developmental delay, other non
CNS anomalies
-aqueductal stenosis, Aicardi syndrome, holoprosencephaly
-occipital encephalocele
-hydrocephalus (80%), migrational anomalies (5-10%)
-Klippel-Feil, callosal agenesis (30%), Ellis
van Creveld, others
The classic Dandy Walker malformation is associated with
torcular-lambdoid inversion, but this is not specific. Dandy Walker variants
are more common, are characterized by a more benign course with variable
hypoplasia of the vermis, and are not associated with T-L inversion.