Acute ptosis with diplopia: aneurysmal versus ischaemic cause

What it is

Acute ptosis with diplopia is an oculomotor nerve palsy, and it is a neuro-ophthalmic emergency. Everything turns on the pupil:

• Pupillary involving: a compressive lesion, most commonly a PCOM aneurysm.
• Pupillary sparing: ischaemia due to DM, HTN, hyperlipidaemia and smoking.

How it presents

The history is of ptosis and diplopia over about 2 days. Pain is subjective and can occur with both types, so it does not separate them.

On examination there is ophthalmoplegia, with or without anisocoria, and the eye is otherwise normal. VA can be 6/6, and the eye sits abducted and depressed.

Anisocoria in a smoker with this history suggests an expanding intracranial aneurysm, which will rupture within hours or days. The same history in a diabetic and hypertensive patient, with no anisocoria, suggests the ischaemic type.