Pure motor upper limb weakness and infarction in the precentral gyrus: mechanisms of stroke.

BACKGROUND Pure arm monoparesis is an uncommon presentation of stroke. Localization of the lesions is variable, including cortical, subcortical or deep brain infarcts. No particular risk factors or unifying mechanisms have been clearly identified. METHODS Seven patients (5 women, 2 men) presented with isolated arm weakness and brain magnetic resonance imaging (MRI) documented an infarct in the precentral gyrus. All were evaluated for stroke risk factors, had telemetry monitoring, transthoracic echocardiogram (TTE) and magnetic resonance angiography (MRA) of the head and neck. Transesophageal echocardiogram (TEE) was performed in three cases. Hyper-coagulable work-up was performed in one case. Trans-cranial Doppler was performed in one case. RESULTS Mean age was 73 years (range 55-88 years). Arm weakness in all patients was ranging from mild (-5/5) to moderate (2/5) and was predominantly distal (without plegia). None of the patients complained of limb pain or sensory deficit. Infarcts affected one gyrus (5/7) or, less often, 2 adjacent gyri (2/7), along the most distal aspect of the middle cerebral artery (MCA) territory. Risk factors included hypertension (6/7), diabetes (2/7), hyper-lipidemia (7/7), smoking (1/7) and prior TIA/stroke (3/7). The mechanisms of ischemic stroke were determined to be large artery atherosclerosis (2/5), cardioembolic (2/5), other determined etiology [hypoperfusion (1/5)] and undetermined etiology (2/5). CONCLUSIONS Our series of patients with small cortical infarcts and pure motor arm weakness show heterogeneous etiologies of stroke mechanisms and related long term outcomes. The risk factors appear to distribute as in most stroke populations, without a pattern specific to this unusual clinical presentation.