Prompt recognition of aneurysmal compression in isolated oculomotor nerve palsy: A case of favourable visual and clinical outcomes

Oculomotor nerve palsy can be associated with life-threatening pathology, especially when caused by an intracranial aneurysm, requiring urgent recognition and intervention. We report a 57-year-old man with diabetes, hypertension, and dyslipidemia who presented with a three-day history of left ptosis and diplopia, preceded by headache one month earlier. Visual acuity was 6/7.5 in the right eye and 6/10 in the left eye. Examination showed complete left ptosis, a "down-and-out" eye position with preserved abduction, and anisocoria with a 7mm pupil. Initial contrast enhanced CT was unremarkable, but CT angiography revealed a saccular aneurysm of the left internal carotid artery causing mass effect. The patient underwent aneurysm clipping on day five. Postoperatively, visual acuity improved with partial resolution of ptosis, normalization of pupil size, and improved diplopia, highlighting the importance of prompt vascular imaging and timely neurosurgical management.