Somatotopy of the Supplementary Motor Area: Evidence from Correlation of the Extent of Surgical Resection with the Clinical Patterns of Deficit

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Abstract
This study, which aimed to confirm or invalidate the somatotopic organization of the supplementary motor area (SMA), correlates the pattern of clinical symptoms observed after SMA removal with the extent of resection. Eleven patients with medial precentral glioma underwent partial or complete tumoral resection of the SMA. Seven patients underwent preoperative functional magnetic resonance imaging that incorporated speech and motor tasks. During the operation, the primary motor and speech areas and pathways (in the dominant side) were identified by use of intraoperative direct cortical or subcortical stimulation, and these areas were respected. SMA resection resulted in motor deficits, language deficits, or both; the deficits were always regressive, and they corresponded to the SMA syndrome. The topography and severity of these deficits were correlated to the extent of the SMA resection. The location of the deficit corresponded to SMA somatotopy: the representations of the lower limb, the upper limb, the face, and language (in the left-dominant SMA) were located from posterior to anterior. This somatotopy was also observed with functional magnetic resonance imaging. Correlation between clinical patterns of deficit and the extent of SMA resection, guided by means of pre- and intraoperative functional methods, provides strong arguments in favor of somatotopy in this area. This knowledge should allow clinicians to base preoperative predictions of the pattern of postsurgical deficit and recovery on the planned resection, thus allowing them to inform patients accurately before the procedure.