The four types of hydrocephalus are communicating, noncommunicating, ex vacuo, and normal pressure. Diagnosis is typically made by physical examination and medical imaging.

Hydrocephalus ex vacuo also refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy (as it occurs in dementias), post-traumatic brain injuries and even in some psychiatric disorders, such as schizophrenia. As opposed to hydrocephalus, this is a compensatory enlargement of the CSF-spaces in response to brain parenchyma loss; it is not the result of increased CSF pressure.

https://en.wikipedia.org/wiki/Hydrocephalus#Type

Think ex vauco for = fake IE: The ventricles appear to be big but in reality it just looks a lot bigger because its being compared against a atrophic brain from something like (Alzheimers, advanced HIV, Pick disease, Huntingtons).

Communicating hydrocephalus is due to decreased CSF absorption by arachnoid granulations which causes ICP --> papilledema and herniation.

Normal pressure hydrocephalus affects the elderly and causes "Wet, wobby, wacky"