Validation of Presurgical Motor Mapping With Transcranial Magnetic Stimulation (TMS) in Patients With Epilepsy

This study will be an open-label feasibility study which applies nTMS to subjects with incoming epilepsy surgery and pre-surgical motor mapping. No study-related medication changes are expected -- participants will remain compliant with their regular anticonvulsant regimen throughout each study phase. All patients will have undergone a complete history and neurological exam as part of their routine clinical care at the New York University (NYU) Comprehensive Epilepsy Center.

Fourteen (14) patients will undergo epilepsy surgery with expected subdural grid coverage over primary motor cortex. Potential subjects will be identified at the weekly multi-disciplinary epilepsy conference. Subjects must have a recent (<2 years) MRI scan, and registration of the TMS coil to the MRI scan via the Brainsight neuronavigation system will be utilized to guide TMS coil placement (Gugino et al 2001). When a presurgical fMRI (functional magnetic resonance imaging) is available which demonstrates the patient's hand knob, the fMRI will be used with the Brainsight neuronavigation system. Subjects will be recruited and consented during a presurgical clinical visit where the patient's primary epileptologist will introduce members of the research team.

nTMS mapping

Patients will receive a session of single-pulse TMS mapping of the motor area, at the outpatient TMS clinic at NYU Neurology Ambulatory Care Center, at 240 E 38th St 20th Floor prior their epilepsy surgery according to the following procedures:

1. Determination of the motor threshold by (1) finding the most excitable region in the hand knob which elicits the strongest compound muscle action potential (CMAP) in the APB muscle; (2) finding the motor threshold by determining output stimulation intensity which generates peak to peak CMAP response above 50 mV (Millivolts) in 5/10 stimulation cycles (Rossini et al., 1994).
2. Concurrent EMG will be measured with electrodes placed at APB (abductor policis brevis atrial premature beat), abductor digiti minimi, flexor carpiradialis muscles. Reference electrode will be placed at the ipsilateral elbow above the brachial biceps muscle.
3. Mapping of the upper extremity. After determination of the MT (motor threshold), mapping of the UE(Upper Extremity) will be performed at 110% of the rMT (resting motor threshold). All positive and negative stimulation sites will be recorded and saved. Patients will be closely monitored during TMS stimulation. Each subject will have a complete neurological examined by a neurologist before and immediately after nTMS. Patients will also be provided a side effects questionnaire after TMS mapping. Patients will then be asked to keep a 7 day seizure diary after the nTMS session.