Evaluating the feasibility of measures of motor threshold and cortical silent period as predictors of outcome after temporal lobe epilepsy surgery

INTRODUCTION Although it is well known that ES alters cortical excitability, little is known about the relationship between ES outcome and cortical excitability. Transcranial magnetic stimulation has been successfully used to evaluate cortical excitability in epilepsy patients. The present study aimed to assess the value of the motor threshold (MT) and cortical silent period (CSP) as predictors of the outcome of temporal lobe epilepsy surgery (TLES). MATERIALS AND METHODS Epileptic foci in the epilepsy patients were identified via video-electroencephalography (v-EEG) monitoring, brain magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and positron emission tomography (PET), and neurophysiological testing. MT, CSP-150, and CSP-max were measured in 10 epilepsy patients on both the ipsilateral and contralateral side of the epileptic focus 1 week before and 3 months after TLES. Pre- and post-operative MT and CSP measurements were compared, and the results were interpreted based on the clinical outcome of TLES. RESULTS Mean follow-up period was 28.8 months. In all, 8 patients were seizure-free post TLES, whereas in 2 patients seizures persisted. No significant differences were observed in ipsilateral or contralateral hemisphere MT measurements before and after surgery. Both CSP-150 and CSP-max values in the non-focal hemispheres decreased in the 8 patients that were seizure-free post TLES, whereas no differences were observed in the 2 patients with seizures that persisted post TLES. CONCLUSIONS The present findings indicate that monitoring pre- and post-TLES CSP changes may be predictive of the early clinical outcome of TLES.