High-Yield Neuroanatomy 5e

16 Chapter 2
H. Holoprosencephaly results from failure of midline cleavage of the embryonic forebrain. The
telencephalon contains a singular ventricular cavity. Holoprosencephaly is seen in trisomy 13 (Patau
syndrome); the corpus callosum may be absent. Holoprosencephaly is the most severe manifestation of
fetal alcohol syndrome.
I. Hydranencephaly results from bilateral hemispheric infarction secondary to occlusion of the
carotid arteries. The hemispheres are replaced by hugely dilated ventricles.
CASE 2-1
A mother brings her newborn infant to the clinic because the infant’s “legs don’t seem to work right.” The
infant was delivered at home without antenatal care. What is the most likely diagnosis?
Relevant Physical Exam Findings
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Tufts of hair in the lumbosacral region
Clubfoot (Talipes equinovarus)
Chronic upper motor neuron signs, including spasticity, weakness, and fatigability
Diagnosis
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Spina bifida occulta results from incomplete closure of the neural tube during week 4 of embryonic
development. This type of neural tube defect often affects tissues overlying the spinal cord, including the
vertebral column and skin.