P11.10.B THE SYNDROME OF THE SUPPLEMENTARY MOTOR AREA: CLINICAL COURSE AND PREDICTORS OF OUTCOME AFTER RESECTION OF PREMOTOR LESIONS

Abstract BACKGROUND The syndrome of the supplementary motor area (SMA) frequently occurs after resection of lesions in the premotor cortex or its associated white matter tracts. Brain plasticity involving the interhemispheric connectivity including the contralateral SMA region might be crucially involved in the development of and recovery from SMA syndrome. We herein aimed to identify predictors of outcome by quantifying pre-operative structural alterations in the non-affected contralateral hemisphere. METHODS We retrospectively searched our institutional database for patients developing SMA syndrome after undergoing resection of lesions localized in the SMA region between 2013 and 2023. Clinical characteristics, imaging data, and neurological outcomes were collected. Structural network analysis was performed using the previously validated morphometric inverse divergence (MIND) network. MIND estimates a patient’s axonal connectivity and cortical cytoarchitectonics based upon the comparison of the patient’s MRI with a large cohort of more than 10,000 healthy controls. RESULTS We identified 27 patients with a mean age of 39.2 ± 17.7 years who developed SMA syndrome following resection of premotor lesions, including 13/27 patients (48.1%) who underwent tumor resection for primary brain tumors and 14/27 patients (51.9%) who underwent focal resection for intractable lesional epilepsy. Postoperative SMA syndrome was most characterized by contralateral upper extremity hemiparesis (19/27 patients, 70.4%) and aphasia in case dominant hemisphere involvement (13/13 patients, 100%). Patients with a primary brain tumor had generally more severe symptoms, and were less likely to fully recover from SMA syndrome after 7 days compared to epilepsy patients (full recovery: 2/13 [15.4%] versus 9/14 [64.3%] patients, p = 0.018). At last follow-up after a median time of 5 months (IR 3-16 months), most patients (23/27, 85.2%) experienced a full recovery of SMA syndrome, with no difference between patients with tumors or epilepsy (p = 0.999). Preoperative contralateral intra-hemispheric connectivity was similar between patients receiving tumor or focal resection (0.183 vs 0.177, p = 0.295). However, imaging analyses point towards baseline affection of the SMA connectivity network in patients with brain tumors as characterized by reduced cortical thickness of the contralateral frontal lobe and the cingulate gyrus compared to epilepsy patients. CONCLUSION While full recovery from SMA syndrome is common, SMA syndrome is frequently less severe and more transient in patients with epilepsy. This might be due to more severe affection of contralateral SMA network in tumor patients due to the infiltrative nature of the disease. Imaging analyses might assist in identifying network affections at baseline to guide informed discussions with patients and caregivers.