Posterior Communicating Artery (PCOM) Aneurysm
Background
- Acute CN III palsy with ipsilateral pupil dilation is PCOM aneurysm until proven otherwise
- Aneurysm compresses the outer fibers (pupillomotor) of CN III → dilation
- In contrast to CN III palsy due to diabetes mellitus or hypertension in which pupil is spared
Clinical Features
- Inhibition of ipsilateral medial gaze, upward gaze, downward gaze, ptosis
- Lateral gaze (abduction) is preserved
- Ipsilateral dilated pupil
Differential Diagnosis
Binocular Diplopia
- Basilar Artery Thrombosis
- Posterior communicating artery (PCOM) aneurysm
- Vertebral artery dissection
- Myasthenia Gravis[1]
- Lambert-Eaton Syndrome
- Botulism
- Cavernous sinus thrombosis
- Intracranial mass, brainstem mass
- Miller Fischer variant Guillain-Barre[2]
- MS
- Hyperthyroid Proptosis
- Basilar Meningitis
- CVA
- Muscular Entrapment from Trauma
- Third nerve palsy
Evaluation
Management
- Emergent BP reduction if hypertensive
- Neuroimaging
- Neurosurgical consult