Clinical study of twenty-one patients with pure midbrain infarction.

We investigated the neurological and MRI findings of 21 patients with pure midbrain infarction. The locations of the infarcts were classified into paramedian (PM) area (13 patients), lateral area (6 patients), and PM and lateral areas (1 patient), based on the distribution of each penetrating artery of the midbrain. The infarction of 1 patient showed bilateral multiple lesions. In the PM area group, 12 patients showed eye movement disorders and truncal and gait ataxia. Eye movement disorders consisted of medial longitudinal fasciculus syndrome, oculomotor nerve palsy, and bilateral vertical gaze palsy. The infarcts of the 2 patients with bilateral vertical gaze palsy were located in the PM area on both sides. Eye movement disorders and truncal and gait ataxia were prominent in the PM area group. Ataxic hemiparesis was shown in 2 patients of the PM area group and 4 patients of the lateral area group. We showed that ataxic hemiparesis also occurred in PM area infarction, although ataxic hemiparesis was a prominent feature of lateral area infarction.