The electrophysiological effects of multiple subpial transection (MST) in an experimental model of epilepsy induced by cortical stimulation.

Multiple subpial transection (MST) is an effective surgical therapy for patients with intractable seizures whose epileptogenic lesions lie in the cortex and are unresectable. Morrell developed this procedure and reported clinical results obtained using it. However, only the disappearance of epileptiform discharges after MST in an experimental model of epilepsy has been demonstrated. The aim of this study was to establish the histological changes caused by MST and evaluate the effects of this procedure on interneuronal discharge spread in an epilepsy model, i.e. acute cortical kindling in rabbits. Histologically, vertical cracks in the transected cortex with mild gliosis and very little tissue disruption were observed. Horizontal fibers across the crack had been transected, whereas vertical fibers and neuronal cell bodies were preserved. The stimulation-induced after-discharges (ADs) were analyzed: cortical hyperactivity across the transected zone was reduced significantly earlier than that in the control group. Propagation of ADs induced by the kindling effect was also inhibited. These results suggest that MST interrupts not only neuronal synchronization, but also excitatory interneuronal conduction, in this epilepsy model.