Isolated oculomotor nerve palsy in spontaneous internal carotid artery dissection: case report

Partial oculosympathetic palsy followed by ischemic manifestations in brain or retina are the main symptoms of extracranial internal carotid artery (ICA) dissection. Unusually, cranial nerves may be affected. Isolated oculomotor nerve palsy is found only rarely.

We present a 50-year-old nondiabetic man who experienced acute onset of right occipital headache which spread to the right retro-orbital region. Five days later he noticed diplopia and right blurred vision sensation. Neurologic examination disclosed only impaired adduction and upward gaze of right eye, slight ipsilateral pupillary dilatation, without ptosis. Brain MRI was normal. Angiography showed right internal carotid artery dissection with forward occlusion to the base of the skull. Intravenous heparin followed by warfarin was prescribed. The headache and the oculomotor nerve deficit gradually resolved in the next three weeks.

Isolated oculomotor nerve palsy is underrecognized as a clinical presentation of extracranial ICA dissection. If the angiographic evaluation is incomplete without careful study of extracranial arteries, misdiagnosis may lead to failure to initiate early treatment to prevent thromboembolic complications. For this reason we draw attention to the need for careful evaluation of cervical arteries in patients with oculomotor nerve palsy. Mechanical compression or stretching of the third nerve are possible mechanisms, but the direct impairment of the blood supply to the third nerve seems to be the most plausible explanation.