CLONIDINE AND METHOHEXITAL-INDUCED EPILEPTIC MAGNETOENCEPHALOGRAPHIC DISCHARGES IN PATIENTS WITH FOCAL EPILEPSIES

Purpose: During presurgical evaluation, 14 patients with medically int ractable focal epilepsies underwent magnetoencephalographic (MEG) reco rdings for focus localization. To increase the number of epileptic dis charges required for MEG analysis, we administered methohexital (MHT), a short-acting barbiturate known to provoke epileptic activity. We al so investigated the spike-provoking properties of clonidine in compari son with MHT. Methods: Patients were briefly anesthetized with intrave nously administered MHT after being premedicated orally with clonidine . Numbers and locations of epileptic MEG discharges were assessed afte r clonidine premedication as well as during MHT anesthesia. Results we re compared with baseline MEG recordings. Results: MHT increased the f requency of focal epileptic dis charges in 8 of 13 patients (1 of the 14 patients did not receive MHT after premedication with clonidine). P remedication with clonidine also increased focal epileptic discharges in 9 of 14 patients. The numbers of epileptic signals and numbers of s pikes contributing to MEG source localizations were significantly incr eased in MEG recordings under both treatment conditions (clonidine pre medication and MHT anesthesia) as compared with baseline MEG recording s. Conclusions: Our results confirmed the selective proconvulsive effe cts of MHT on the epileptic focus, as previously suggested by EEG and electrocorticographic (ECoG) investigations. However. our present data establish for the first time that clonidine increases epileptic activ ity in patients with seizure disorders and indicate thar clonidine is suitable as an activating agent for localization of epileptogenic foci by MEG. This effect of clonidine on specific epileptic activity also indicates that specific care must be taken when clonidine is used as a n antihypertensive drug in patients with seizure disorders.