INFERIOR DIVISION PARESIS OF THE OCULOMOTOR NERVE CAUSED BY BASILAR ARTERY ANEURYSM

A 60-year-old woman with progressive ataxia and progressive diplopia on downgaze was found to have a paresis of the inferior division oculomotor nerve. There was no ptosis or signs of aberrant regeneration. A large aneurysm at the tip of the basilar artery was discovered which invaginated the midbrain. Although inferior division oculomotor nerve palsy is rare and has not been considered to be caused by aneurysms, it should not always be considered benign, especially if there is progression or association with other neurologic signs. This case also helps to further delineate the topical organization of the oculomotor nerve fascicle.