Diagnosis and neuroimaging of acute stroke producing distal arm monoparesis

Strokes which result in the isolated, pure motor weakness of an upper extremity are unusual and under-recognized cerebrovascular syndromes. Few reports in the literature describe the syndrome adequately or provide substantive clinical or anatomical correlation. Moreover, it may be misdiagnosed as a disorder of the peripheral nervous system because of the lack of pyramidal tract signs or the involvement of speech, the face, or lower limbs. We describe 35 patients who presented with sudden isolated pure motor weakness of an arm or hand caused by stroke, and provide clinical anatomic correlation of the lesion, stroke etiology, and outcome. Between December 1997 and November 2002, we prospectively identified 35 cases of distal arm monoparesis (DAMP) from among 4818 acute stroke and stroke related admissions to the Lehigh Valley Hospital. We included all patients with isolated weakness of one arm or hand unassociated with objective sensory, coordination, or language deficit, and no significant involvement of speech, the ipsilateral face, or leg. We examined clinical features, neuroimaging, etiology of stroke, and the prognosis of patients with the syndrome over a mean follow-up of 1.7 years. DAMP is an unusual form of cortical infarct which occurs in the parietal lobe or central sulcus region, comprising less than 1% of stroke cases. The infarcts are not caused by classical deep white matter lacunar infarctions, and are clearly delineated as superficial small cortical infarcts by magnetic resonance imaging (MRI)/diffusion-weighted imaging (DWI). Although the prognosis for recovery is uniformly good, the recurrent stroke risk was 14% over 1.7 year mean follow-up.