Isolated Oculomotor Nerve Palsy as Presenting Symptom of Bilateral Chronic Subdural Hematomas: Two Consecutive Case Report and Review of the Literature

Abstract

Isolated oculomotor nerve palsy (ONP) is caused most commonly by vascular disease, posterior circulation aneurysms, and inflammatory or traumatic injury. ONP usually occurs in chronic subdural hematoma (CSDH) as a common sign of cerebral herniation that typically is associated with a deterioration of consciousness. We report 2 cases of bilateral CSDH who presented with ONP without deterioration of consciousness. An extensive literature review revealed this is an extremely rare finding. We also investigated all the possible pathogenic mechanisms producing nerve impairment and found a strong association with bilateral subdural hematoma. Vascular compression between posterior circulation arteries and tentorial edge abnormalities also could be involved. Vulnerability of the oculomotor nerve seems to be a necessary condition leading to clinical onset and is caused by predisposing factors to nerve damage, including vascular disease, head trauma, or herpes zoster infection. Although isolated ONP is a very rare presentation of CSDH, a differential diagnosis is absolutely necessary, because surgical treatment allows good recovery of third nerve palsy in most of the cases.