“Supplementary motor area (SMA) seizure” rather than “SMA epilepsy” in optimal surgical candidates: a document of subdural mapping

Abstract

Purpose: To clarify the relationship between epileptogenic zone and supplementary motor area (SMA) in patients who were regarded as the optimal surgical candidates for their intractable SMA seizures. Methods: We analyzed the epileptogenic zone at/or adjacent to the SMA in four patients with clinical SMA seizures. All four patients had noninvasive presurgical evaluations (long-term video/EEG monitoring, MRI, and neuroimaging with radioisotopes), which provided convergent results between ictal semiology and the epileptogenic area, and thus, they had chronically implanted subdural electrodes, and finally had focus resection with a follow-up period of more than 2 years. Results: Three patients had lesions shown by MRI outside the SMA, and one patient had a lesion within the SMA. Interictal epileptiform discharges were seen at/or outside the SMA. Ictal EEG pattern originated from the SMA in one patient, from the high lateral frontal area in two patients, and from the precuneus in one patient. In the latter three patients, the ictal EEG pattern immediately spread to the SMA. Those ictal onset zones were consistently localized within/or just adjacent to the lesions revealed by MRI. Only one patient had SMA resection, and three had the resection of epileptogenic zone by preserving the SMA. No neurological deficits developed and good seizure control was achieved. Conclusion: Among surgical candidates for intractable SMA seizures, frontal cortex other than SMA or even parietal cortex can be epileptogenic, and thus, the SMA itself may not necessarily have to be resected. This notion is clinically important when selecting surgical candidates as well as when planning presurgical invasive evaluation in patients with intractable SMA seizures.