Cortical stimulation and epileptic seizure: A study of the potential risk in primates

OBJECTIVE: The recent successful development of chronic stimulation of the motor cortex as a treatment for neuropathic and central pain does not exclu de the possibility of eventual side effects, such as epileptic seizure or a lowering of the epileptic threshold. This study evaluates the behavioral a nd electroencephalographic impact of this treatment in three normal monkeys . RESULTS: None of the monkeys presented epileptic behavior or abnormal elect roencephalographic activity at parameters of stimulation currently used in clinical series, i.e., frequency and pulse duration of approximately 40 Hz and 90 microseconds, respectively, and an intensity just under the threshol d for inducing muscle twitch in painful areas. Higher intensities did, howe ver, induce reversible epileptic seizure. There was, nonetheless, no modifi cation of the epileptic threshold, because even after these seizures, inter mittent light stimulation elicited no abnormal electroencephalographic acti vity. CONCLUSION: It thus seems that motor cortex stimulation does not induce epi leptic complications when the classic clinical criteria of stimulation are respected. Nevertheless, it would be wise to subject candidates for implant ation to intermittent light stimulation before and after a period of stimul ation to ascertain the innocuousness of the cortical stimulation.