Motor cortex excitability in patients with focal epilepsy

We studied the excitability of the motor cortex using, transcranial magneti c stimulation (TMS) in patients with temporal and extratemporal epilepsy. W e applied single and paired-pulse TMS to 15 patients with temporal (n = 7). extratemporal (n = 6) and focal epilepsy lateralised to one hemisphere (n = 2). Patients had no antiepileptic drugs in the last 48 h and were seizure free for 4 h prior to testing. We determined the threshold for EMG respons es at rest (RMT), the cortically evoked silent period (CSSP) and intracorti cal inhibition (ICI, intervals of 2-4 ms) and facilitation (ICF, 7-15 ms) a nd compared the results to those obtained in 17 normal controls. ICI and IC F was reduced in both hemispheres (P < 0.01, ANOVA) compared to the control s. In the hemisphere of seizure origin ('abnormal') there was a reduction o f ICF (P < 0.01) and normal ICI, in the 'normal' hemisphere there was a red uced ICI (P < 0.01) and a slight reduction of ICF (P < 0.05). ICF on the 'a bnormal' side was reduced (P < 0.05) compared to the 'normal' hemisphere. R MT was increased in two patients, but group comparison of RMT and CSSP show ed no significant differences between patients and controls. The results su ggest a remote effect of epileptic activity onto the motor cortex leading t o an alteration of activity in local inhibitory circuits. (C) 2000 Elsevier Science B.V. All rights reserved.