Abducens nerve palsy

What it is

Abducens nerve palsy is a neuro-ophthalmic emergency. Its causes fall into two:

1. Compressive, or IIH: increased ICP, usually in young patients.
2. Ischaemic, the most common: in older patients with ischaemic risk factors.

How it presents

There is diplopia with no pain, and it appears on looking to one side, with an extraocular movement abnormality. If there is headache, nausea or vomiting with it, think of increased ICP.