High-Yield Neuroanatomy 5e

Development of the Nervous System 15
E. Dandy–Walker malformation has a frequency of 1:25,000. It may result from riboflavin inhibitors,
posterior fossa trauma, or viral infection (Figure 2-8).
F. Hydrocephalus—most commonly caused by stenosis of the cerebral aqueduct during development.
Excessive CSF accumulates in the ventricles and subarachnoid space. This condition may result
from maternal infection (cytomegalovirus and toxoplasmosis). The frequency is 1:1,000.
G. Fetal Alcohol Syndrome—the most common cause of mental retardation. It manifests with
microcephaly and congenital heart disease; holoprosencephaly is the most severe manifestation.
Lateral ventricle
Third ventricle/
thalamus
Cerebral aqueduct
Confluence of sinuses
Optic chiasm
Cerebellar vermis
Posterior fossa cyst
Mamillary body
A
Corpus callosum
Polymicrogyria
Superior sagittal sinus
Straight sinus
Lateral ventricle
Confluence of
sinuses
Massa intermedia
Thrid ventricle
Cerebellar vermis
Pons
Posterior fossa cyst
Medulla
B
Figure 2-8 Dandy–Walker malformation. Midsagittal section. An enormous dilation of the fourth ventricle results from
failure of the lateral foramina (of Luschka) and median foramen (of Magendie) to open. This condition is associated with
occipital meningocele, elevation of the confluence of the sinuses (torcular Herophili), agenesis of the cerebellar vermis, and
splenium of the corpus callosum. (Reprinted from Dudek RW, Fix JD. BRS Embryology. Baltimore, MD: Williams & Wilkins;
1997:97, with permission.)