Isolated Cranial Nerve-III Palsy Secondary to Perimesencephalic Subarachnoid Hemorrhage

We describe isolated cranial nerve-III palsy as a rare clinical finding in a patient with perimesencephalic subarachnoid hemorrhage. In this unusual case, the patient presented with complete cranial nerve-III palsy including ptosis and pupillary involvement. Initial studies revealed subarachnoid hemorrhage in the perimesencephalic, prepontine, and interpeduncular cisterns. Angiographic studies were negative for an intracranial aneurysm. The patient's neurological deficits improved with no residual deficits on follow-up several months after initial presentation. Our case report supports the notion that patients with perimesencephalic subarachnoid hemorrhage have an excellent prognosis. Our report further adds a case of isolated cranial nerve-III palsy as a rare initial presentation of this type of bleeding, adding to the limited body of the literature.