Hydrocephalus

===Noncommunicating===
Noncommunicating hydrocephalus, or obstructive hydrocephalus, is caused by an obstruction to the flow of CSF.<ref>{{Cite web |date=2020-02-21 |title=Communicating and Non-communicating Hydrocephalus {{!}} Helpful |url=https://www.hydroassoc.org/communicating-non-communicating-hydrocephalus/ |access-date=2022-05-17 |website=www.hydroassoc.org |language=en-US}}</ref>
* [[Interventricular foramina (neural anatomy)|Foramen of Monro]] obstruction may lead to dilation of one, or if large enough (e.g., in [[colloid cyst]]), both lateral ventricles.
* The [[Cerebral aqueduct|aqueduct of Sylvius]], normally narrow, may be obstructed by a number of genetic or acquired lesions (e.g., atresia, [[ependymitis]], hemorrhage, or tumor) and lead to dilation of both lateral ventricles, as well as the [[third ventricle]].
* [[Fourth ventricle]] obstruction leads to dilatation of the aqueduct, as well as the lateral and third ventricles (e.g., [[Chiari malformation]]).
* The [[foramina of Luschka]] and [[Median aperture|foramen of Magendie]] may be obstructed due to congenital malformation (e.g., [[Dandy–Walker malformation]]).