Cortical motor and somatosensory representation: effect of cerebral lesions.

Abstract

Changes in cortical representation in patients with cerebral lesions may alter the correlation between cortical anatomy and function. This is of potential clinical significance when the extent of cortical resection is based on surface anatomical landmarks. Fifty-one patients with supratentorial lesions were studied. Nineteen harbored noncentral lesions (no involvement of pre- or postcentral gyrus), whereas 32 had central lesions. Control studies consisted of stimulation of the hand contralateral to the unaffected hemisphere. Positron emission tomography activation studies were performed using the [15O]H2O tracer. Somatosensory stimulation of the hand or foot was performed using a mechanical vibrator. Motor activation consisted of hand clenching or foot tapping. The t-statistic volumes were generated from images showing the mean change in regional cerebral blood flow, and coregistered with a T1-weighted magnetic resonance image. At the threshold selected, exclusive contralateral primary sensorimotor cortex activation was elicited in 100% of the control studies. A different pattern of cortical activation was associated with central lesions in 35 (78%) of 45 patients, which occurred significantly more often than with noncentral lesions (eight [31%] of 26 patients). The most common difference in the pattern of activation with central lesions was activation of cortical regions outside the central area (including the supplementary sensorimotor area and the secondary somatosensory cortex). No sensorimotor activation was observed in gyri adjacent to the pre- or postcentral gyrus. Central lesions are more frequently associated with altered patterns in activation than lesions in noncentral locations. Characteristic patterns include activation of secondary sensorimotor areas. The absence of activation in gyri adjacent to the sensorimotor strip has clinical significance for the planning of resections in the central area.