Overview
An unreactive pupil suggests injury or compression of the third cranial nerve and by proxy, the upper brainstem. Fixed and dilated pupils suggest serious underlying pathology and can indicate a poor prognosis, especially if bilateral.
Causes
Unilateral unreactive pupil
Some causes are:
- Direct trauma
- Intracranial haemorrhage
- Subarachnoid haemorrhage
- Oculomotor nerve palsy
- Posterior communicating artery aneurysm
- This usually has associated diplopia
Bilateral unreactive pupils
- Severe intracranial pathology e.g. trauma/haemorrhage
- Diffuse brain injury
- Brain death
- Brainstem herniation
