Third nerve palsy as the sole manifestation of midbrain ischemia

Thirty-seven patients with risk factors for the development of cerebrovascular diseases had sudden onset isolated third nerve palsy and abnormal masseter reflex and/or electro-oculographic findings indicating a causative midbrain lesion. Improvement or recovery of the third nerve palsies was accompanied by improvement or recovery of the abnormal electro-physiologic findings pointing to their functional significance. Magnetic resonance imaging (MRI) in 29 of these patients demonstrated corresponding ischemic midbrain lesions in eight, ipsilateral in five patients, bilateral in three. In another three patients with MRI proven midbrain lesions (ipsilateral in two, bilateral in one) electrophysiological examinations were normal. Computer assisted tomography in 27 patients showed no brainstem lesion.