Hand Motor Recovery after Stroke: A Transcranial Magnetic Stimulation Mapping Study of Motor Output Areas and Their Relation to Functional Status

The respective contributions of the stroke and undamaged hemispheres to motor recovery after stroke remains controversial. The aim of this article is to evaluate the relationship between location and size of cortical motor areas and outcome after stroke. Twelve controls and 12 stroke patients were studied. Hand cortical motor output areas were determined using transcranial magnetic stimulation. Motor-evoked potentials were recorded simultaneously from both hands. Functional motor abilities were evaluated using well-validated measures. Surface area, weighted surface area, and center of gravity of motor output areas were calculated. Different patterns of motor output areas to the paretic hand were observed; there was no motor output from the stroke hemisphere in patients with poor outcome, contrasting to large motor output area in the stroke hemisphere in patients with good outcome, regardless of infarct size or location. A significant correlation was found between measures of motor outcome in the stroke-affected upper extremity and both the surface area and weight of the central motor output area in the stroke hemisphere. No ipsilateral motor response was obtained after stimulation of either hemisphere. These data support an association between preservation of cortical motor output area to the paretic hand in the stroke hemisphere and good motor outcome.