Pupil-sparing, painless compression of the oculomotor nerve by expanding basilar artery aneurysm: a case of ocular pseudomyasthenia.

BACKGROUND

Oculomotor nerve paresis may have relatively benign but also life-threatening causes. Distinguishing between these is of great clinical importance.

OBJECTIVE

To reveal a potential pitfall of the clinical evaluation of oculomotor nerve paresis.

PATIENT: Single case observation.

RESULTS

A 56-year-old man had fluctuating diplopia and fatigable ptosis, promptly relieved by intravenous edrophonium, leading to the diagnosis of ocular myasthenia gravis. His pupillary function was intact. A few days after the initial diagnosis, he suffered a subarachnoid hemorrhage secondary to the rupture of a basilar artery aneurysm. His ocular symptoms were related to aneurysmal oculomotor nerve compression.

CONCLUSION

Patients with oculomotor nerve dysfunction need more detailed evaluation because the underlying cause cannot be safely determined on a clinical basis.