Spontaneous chronic subdural hematoma as the cause of oculomotor cranial nerve palsy: A narrative review.

Acute complete third nerve palsy with pupillary involvement is usually caused by a posterior communicating artery aneurysm (i.e. "the rule of the pupil"). The pupillary fibers run peripherally in the third nerve and are thus susceptible to the external compression. Headache is usually present, and urgent diagnosis and treatment are warranted. Rarely, however, neuroimaging shows other causes of third nerve palsy. In this study, we perform a literature review of spontaneous chronic subdural hematoma that, although rarely, may cause an acute pupil-involving third nerve palsy as a false localizing sign. We review the localizing, nonlocalizing, and false localizing nature of ocular motor cranial nerve palsy in this setting.