Role of the supplementary motor area in motor deficit following medial frontal lobe surgery

Objective: Patients undergoing surgical resection of medial frontal lesions may present a transient postoperative deficit that remains largely unpredi ctable. The authors studied the role of the supplementary motor area (SMA) in the occurrence of this deficit using fMRI. Methods: Twenty-three patient s underwent a preoperative fMRI before resection of medial frontal lesions. Tasks included self-paced flexion/extension of the left and right hand, su ccessively. Preoperative fMRI data were compared with postoperative MRI dat a and with neurologic outcome. Results: Following surgery, 11 patients had a motor deficit from which all patients recovered within a few weeks or mon ths. The deficit was similar across patients, consisting of a global reduct ion in spontaneous movements contralateral to the operated side with variab le severity. SMA activation was observed in all patients, The deficit was o bserved when the area activated in the posterior part of the SMA (SMA prope r) was resected. Conclusions: fMRI is able to identify the area at risk in the SMA proper whose resection is highly related to the occurrence of the m otor deficit. The clinical characteristics of this deficit support the role of the SMA proper in the initiation and execution of the movement.