Abstracts

Rationale: Repetitive transcranial magnetic stimulation (rTMS) is a technique for noninvasive focal brain stimulation where small intracranial electrical currents are generated by a powerful fluctuating extracranial magnetic field. rTMS can disrupt ongoing neuronal activity, or induce lasting changes in cortical excitability, and is emerging as a novel anticonvulsive therapy. Largely, rTMS is applied interictally to reduce seizure frequency – this is generally well-tolerated, although seizure induction by rTMS is a possible side-effect. Less often, rTMS has been used ictally to terminate ongoing seizures, as in instances of epilepsia partialis continua (EPC). Whether ictal rTMS is effective and safe has not been extensively studied. In particular, the question of whether rTMS can exacerbate ongoing seizures is among the safety concerns. Accordingly, we report our recent experience with rTMS in treatment of EPC, and summarize available published reports as an early step towards evaluating the safety and efficacy of rTMS in the treatment of ongoing focal seizures.Methods: Seven patients (six adult and one pediatric) with EPC due to mixed etiologies were treated with rTMS applied over the seizure focus as determined by seizure semiology and/or surface EEG. rTMS was delivered at or above motor threshold in high frequency (20- to 100-Hz) bursts or as prolonged low frequency (1-Hz) trains. Two patients were treated with prolonged daily 1-Hz rTMS for 9 and for 10 days, respectively. Clinical seizures were monitored in all by patient and caregiver report, and EEG was recorded in three of seven. To complement our data, we also performed a literature search to identify additional EPC cases treated with rTMS.Results: Ongoing seizures were suppressed after treatment in three of seven patients. Notably, in a patient with EPC due to a vascular malformation, continuous right hand movements of approximately 20-years duration were initially disrupted by high frequency (100-Hz) rTMS bursts, and a durable (>4 months) EPC suppression was achieved with daily 1-Hz rTMS. Seizures in one of the remaining four patients, a child with Rasmussen’s encephalitis, were suppressed only for the duration of the rTMS train, but resumed after treatment. Our literature search identified six additional reports of EPC treated with low frequency (0.5- to 1-Hz) or high frequency (6- to 20-Hz) rTMS trains. Clinical seizures were suppressed in three of six reported cases. Seizures were not exacerbated by rTMS either in our experience, or in the published reports. Side-effects were generally mild and well-tolerated – among these were transient head and limb pain, and limb stiffening during high-frequency rTMS trains.Conclusions: rTMS may be safe and effective in suppressing ongoing seizures associated with EPC. Encouragingly, we did not identify any instance of seizure exacerbation by either high- or low-frequency rTMS. We conclude that careful and controlled evaluation of the safety and efficacy of rTMS in the treatment of EPC is warranted.