Pupil sparing incomplete third nerve palsy secondary to a cavernous sinus meningioma: challenges in management

The diagnosis of incomplete third nerve palsy can be clinically challenging because the aetiologies, as well as presentations, can be variable and subtle. The optometric clinician should be familiar with the association of third nerve palsy with compressive lesions, including the clinical presentations and management of these patients.

We present a 68-year-old hypertensive male complaining of intermittent diplopia for the previous six months. Neurological examination revealed a mild deficit in adduction, reduced range of vertical motility and questionable ptosis, all limited to the OD. No pupillary involvement was noted. MRI revealed a cavernous sinus meningioma. The patient elected against surgery, choosing MRI every six months.

Due to the subtle clinical presentation of incomplete pupil sparing third nerve palsy, this ophthalmoplegia may be easily overlooked. The associated aetiologies of palsy of cranial nerve three (CN3) carry increased risk of morbidity and mortality. Management should include evaluation for mass lesions and/or vascular aetiologies, regardless of pupillary involvement.