Pure Motor Upper Limb Weakness and Infarction in the Precentral Gyrus: Mechanisms of Stroke

Abstract

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(5women, 2men) presentedwith isolated armweakness 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-cranialDoppler
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