Pure Motor Monoparesis Due to Ischemic Stroke

Abstract

Pure motor monoparesis (PMM), an isolated motor deficit that occurs after ischemic stroke (IS) in a single arm or leg without accompanying cranial or sensory dysfunction, is rare and easily misdiagnosed as other causes of weakness. Cortical infarctions of the precentral knob and the anterior cerebral artery territory (for upper and lower limbs, respectively) are the most commonly reported lesion sites in PMM. Other sites include the subcortex, corona radiata, internal capsule, and brainstem; these sites are cited less frequently than those afflicted by cortical infarctions. PMM shows a complex weakness pattern; however, distal-dominant weakness, as well as the absence of pyramidal signs is most commonly observed in PMM owing to IS. Nevertheless, the overall prognosis is generally good. Physicians should carefully assess acute monoparesis, particularly in elderly patients with conventional risk factors, and should include IS in the differential diagnosis. Diffusion-weighted imaging is the most useful tool for diagnosing PMM owing to IS.