Pontine versus capsular pure motor hemiparesis.

We prospectively studied 21 patients with pure motor hemiparesis (PMH). CT showed a capsular lesion consistent with the clinical syndrome in 15 patients (71%) and was repeatedly negative in the remaining six (29%). In all six patients with repeatedly negative CT, MRI showed a pontine paramedian infarct as the notable cause of PMH. Clinical findings could not definitely distinguish between capsular and pontine PMH, but the combination of dysarthria and a history of previous transient gait abnormality or vertigo favored a pontine location. Outcome at 3 months was characterized by persistent, moderate to severe disability in 86% of patients with pontine PMH versus 46% in capsular PMH. Based on MRI and magnetic resonance angiographic findings, the presumed mechanism of pontine ischemic lesions was a lacunar process in most instances (86%).