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 unpredictable. The authors studied the role of the supplementary motor area (SMA) in the occurrence of this deficit using fMRI. METHODS: Twenty-three patients underwent a preoperative fMRI before resection of medial frontal lesions. Tasks included self-paced flexion/extension of the left and right hand, successively. Preoperative fMRI data were compared with postoperative MRI data and with neurologic outcome. RESULTS: Following surgery, 11 patients had a motor deficit from which all patients recovered within a few weeks or months. The deficit was similar across patients, consisting of a global reduction in spontaneous movements contralateral to the operated side with variable severity. SMA activation was observed in all patients. The deficit was observed when the area activated in the posterior part of the SMA (SMA proper) 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 motor deficit. The clinical characteristics of this deficit support the role of the SMA proper in the initiation and execution of the movement.