Hydrocephalus in cats

©Barnett, KC & Crispin, SM Feline Ophthalmology (2002) Saunders

Hydrocephalus denotes, in general terms, an increase in the volume of cerebrospinal fluid (CSF). Hydrocephalus in cats is likely to be either a congenital problem because of malformation and hypoplasia of brain tissue or acquired because of ischaemic encephalopathy, neoplasia or severe meningitis and ependymitis (e.g. feline infectious peritonitis).

Congenital hydrocephalus is associated with abnormal skull shape, including an enlarged calvaria with open sutures. The bony orbits are also enlarged and the globes are displaced ventrolaterally, probably as a consequence of the orbital malformation rather than neuropraxia (temporary failure of nerve conduction due to injury, compression or ischaemia). Teratogenic damage from drugs such as griseofulvin or infection with the feline panleukopenia virus may induce congenital hydrocephalus. 

Hydrocephalus occurring as a result of ischaemic encephalopathy is caused by a compensatory increase of CSF volume which fills the space resulting from tissue destruction. Neoplasia and severe inflammation usually produce hydrocephalus because of obstruction to the flow of CSF, or interference with its absorption.

The clinical signs are variable, although affected animals invariably demonstrate behavioural changes such as lethargy. Bilateral visual defects with a normal pupillary light response is the most common and consistent sign observed in affected cats. Depending on the cause, and whether or not CSF pressure is raised, other neuroophthalmological changes may be present. The management of hydrocephalus depends upon establishing the cause and specialist neurological advice will be needed; many cases are not amenable to treatment.