Isolated non-pupil sparing oculomotor nerve palsy.

This report examines a longstanding clinical dictum that maintains that mononeuropathy of the oculomotor nerve with pupillary sparing is most likely secondary to an ischemic vasculopathy, while oculomotor nerve mononeuropathy associated with pupil dysfunction is considered to be secondary to a subarachnoid aneurysm until proven otherwise. A sixty two year old female diabetic patient taking hormone supplements developed acute right third nerve palsy with partial pupillary involvement, and pre-orbital eye pain. Although an ischemic etiology was suspected, MRI and cerebral angiography were performed to rule out an aneurysmal etiology. Neuro-radiologic testing revealed no intercranial pathology, suggesting isolated, self-limited , microvascular etiology of the oculomotor nerve palsy. The mononeuropathy gradually resolved over the next eight weeks. This case demonstrates that ischemic oculomotor nerve palsy may present with pupillary dysfunction, contradicting the clinical dictum maintaining that spared pupils are associated with aschemia and affected pupils are associated with aneurysm in acute, isolated oculomotor nerve palsy. The discussion section covers isolated oculomotor nerve palsy and its related pupillary postures and offers possible patho-physiologic explanations for the various relationships