Abstracts

Rationale: DBS is being used in an increasing frequency to treat refractory focal and generalized epilepsy. Several targets have been used to treat different epileptic syndromes. At our center, we have used thalamic centro-median DBS (CM-DBS) to treat primary or secondary generalized epilepsy; thalamic anterior nucleus DBS (AN-DBS) to treat frontal lobe epilepsy or patients with failed temporal lobe surgery and hippocampal DBS (Hip-DBS) to treat temporal lobe epilepsy. We describe the microlesional, attentional, anticonvulsant and proconvulsant effects of thalamic and hippocampal deep brain stimulation.Methods: Twenty four adult refractory epilepsy patients were studied (7 with CM-DBS, 7 with AN-DBS, 10 with Hip-DBS). Patients were considered to have a microlesional effect when there was at least 50% of seizure frequency reduction postoperatively before turning on the generator. Attention status was rated pre- and post-operatively using the SNAP-IV questionnaire (attention-related questions). Patients kept a diary for seizure increase/decrease documentation. Patients were rated seizure-free or not seizure-free; mean seizure frequency counts were obtained. Results: Mean follow-up time was 13 months. CM-DBS, AN-DBS and Hip-DBS patients presented a microlesional effect in 84%, 16% and 66% of them, respectively (mean 1 month). Attention improved in 85%, 28% and 50% of the patients with CM-DBS, AN-DBS and Hip-DBS. Mean seizure frequency reduction was 70%, 60% and 90% for CM-DBS, AN-DBS and Hip-DBS. No patient submitted to CM-DBS remained seizure-free and 14% and 40% of the patients got seizure-free during AN-DBS and Hip-DBS, respectively. No patient with CM-DBS had seizure-frequency worsening, while 14% and 60% of the patients with AN-DBS and Hip-DBS did so after stimulation with intensity higher then 4.0V. Conclusions: Although targeting different epileptic syndromes, Hip-DBS was more effective in reducing seizure frequency then thalamic AN- and CM-DBS. Patients receiving CM-DBS presented with a striking improvement in attention that likely represent a parallel effect, since attention deficit improvement was noted before an anticonvulsant effect could be documented. The presence or not of microlesional effects might have importance while developing DBS clinical research protocols.