Cortical motor and somatosensory representation: effect of cerebral lesions

Object. Changes in cortical representation in patients with cerebral lesion s 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. Methods. Fifty-one patients with supratentorial lesions were studied. Ninet een harbored noncentral lesions (no involvement of pre- or postcentral gyru s), whereas 32 had central lesions. Control studies consisted of stimulatio n of the hand contralateral to the unaffected hemisphere. Positron emission tomography activation studies were performed using the [O-15]H2O tracer. S omatosensory stimulation of the hand or foot was performed using a mechanic al 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 T-1-weighted magne tic resonance image. At the threshold selected, exclusive contralateral pri mary sensorimotor cortex activation was elicited in 100% of the control stu dies. A different pattern of cortical activation was associated with centra l lesions in 35 (78%) of 45 patients, which occurred significantly more oft en than with noncentral lesions (eight [31%] of 26 patients). The most comm on difference in the pattern of activation with central lesions was activat ion of cortical regions outside the central area (including the supplementa ry sensorimotor area and the secondary somatosensory cortex). No sensorimot or activation was observed in gyri adjacent to the pre- or postcentral gyru s. Conclusions. Central lesions are more frequently associated with altered pa tterns in activation than lesions in noncentral locations. Characteristic p atterns include activation of secondary sensorimotor areas. The absence of activation in gyri adjacent to the sensorimotor strip has clinical signific ance for the planning of resections in the central area.