Multiple subpial cortical transaction (MST) for the treatment of extensive seizure foci

Multiple subpial transaction (MST) was used to treat 7 patients who had intractable epilepsy with extensive seizure foci involving more than one lobe and both hemispheres, and who have had a follow-up of at least 2 years. The longest follow-up is 61 months, with a median of 43 months. Preoperative investigations included magnetic resonance scans, positron emission tomography scans, single photon emission computed tomography scans, and video-EEG monitoring with scalp and subdural electrodes. Two patients' seizure foci were in both hemispheres, and 5 patients' foci were in 2 lobes of 1 hemisphere. The motor cortex was involved in 5 patients and the speech areas in 1 patient. MST at an interval of 4 mm was performed over all areas that showed seizure foci. Two patients are free of seizures, 1 patient is free of seizures involving the operated hemisphere, 1 has rare seizures, 1 has >90% reduction in seizure frequency, 1 has >70% reduction in seizure frequency, and 1 did not respond to MST. MST alone was able to control seizures to varying degrees, without producing a permanent deficit, in 84% of patients with intractable seizures originating from large areas of the cortex.