A baby is born with an unusually large head. There are no other obvious abnormalities. Ultrasound of the head demonstrates hydrocephalus with marked enlargement of the lateral ventricles. Statistically, at which of the following sites has the obstruction MOST likely to have occurred?
The baby has hydrocephalus, which occurs when CSF production exceeds reabsorption. Usually, this happens when there is a block at some point in CSF circulation. The most common site of obstruction is in the aqueduct of Sylvius, but it may alternatively be at the outlets of the fouh ventricle (foramina of Luschka and Magendie), or in the subarachnoid spaces around the brainstem or near the hemispheres. Nonobstructive hydrocephalus can occur if meningeal inflammation causes excessive production of CSF. Ref: Waxman S.G. (2010). Chapter 11. Ventricles and Coverings of the Brain. In S.G. Waxman (Ed), Clinical Neuroanatomy, 26e.
Aqueduct of Sylvius
Foramen of Luschka
Foramen of Magendie
Subarachnoid space near brainstem