Neurosurgery 92:186–194, 2023
Direct cortical stimulation of the mesial frontal premotor cortex, including the supplementary motor area (SMA), is challenging in humans. Limited access to these brain regions impedes understanding of human premotor cortex functional organization and somatotopy.
OBJECTIVE: To test whether seizure onset within the SMA was associated with functional remapping of mesial frontal premotor areas in a cohort of patients with epilepsy who underwent awake brain mapping after implantation of interhemispheric subdural electrodes.
METHODS: Stimulation trials from 646 interhemispheric subdural electrodes were analyzed and compared between patients who had seizure onset in the SMA (n = 13) vs patients who had seizure onset outside of the SMA (n = 12). 1:1 matching with replacement between SMA and non-SMA data sets was used to ensure similar spatial distribution of electrodes. Centroids and 95% conﬁdence regions were computed for clustered head, trunk, upper extremity, lower extremity, and vision responses. A generalized linear mixedeffects model was used to test for signiﬁcant differences in the resulting functional maps. Clinical, radiographic, and histopathologic data were reviewed.
RESULTS: After analyzing direct cortical stimulation trials from interhemispheric electrodes, we found signiﬁcant displacement of the head and trunk responses in SMA compared with non-SMA patients (P < .01 for both). These differences remained signiﬁcant after accounting for structural lesions, preexisting motor deﬁcits, and seizure outcome.
CONCLUSION: The somatotopy of the mesial frontal premotor regions is signiﬁcantly altered in patients who have SMA-onset seizures compared with patients who have seizure onset outside of the SMA, suggesting that functional remapping can occur in these brain regions.
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