We report three cases of isolated oculomotor nerve palsy caused by paranasal disease. All patients complained of double vision but showed no sign of brain aneurysm or diabetes mellitus. These patients had unilateral disturbance of ocular movement and ptosis, but there was no visual impairment on opthalmologic examination. In two cases, computed tomography (CT) demonstrated soft tissue density (STD) in the posterior ethmoid and sphenoid sinuses and also inside the ipsilateral anterior clinoid process (ACP) of the sphenoid bone. In the other case, CT and magnetic resonance imaging showed STD in the ethmoid sinus and pneumatization in the ACP. In all cases, a bony defect was identified at the inferior wall in ACP, adjacent to the superior orbital fissure. We performed endoscopic sphenoidectomy in two cases and conservatively treated the other case with steroid and antibiotics. In all three cases, ocular movement became normal approximately one month later. Since the oculomotor nerve coursed just under the pneumatized ACP in these cases, we speculated that compression and/or inflammation through the ACP might have induced oculomotor nerve palsy.
