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Cukiert A; Burattini JA; Mariani PP; Seda L; Forster CR; Cukiert CM; Argentoni-Baldochi M; Baise-Zung C; Mello VA.
Epilepsy Surgery Program, Hospital Brigadeiro, São Paulo SP, Brazil
Rationale: DBS for treatment of refractory epilepsy has been increasingly studied over the last decade. Presumably, DBS works by interfering both on the epileptic activity spreading pathways and subcortical epileptic activity generators or modulators. The patient usually remains unaware of the “on” and “off” phases during DBS while using typical DBS settings (up to 2-3V). On the other hand, higher voltage stimulation is used intra-operatively to ascertain electrode positioning (up to 8V). In the awaken patient, extremely high-voltage stimulation is not tolerated by the patient, but intermediate voltage-stimulation might trigger parcellar or partial seizures.
Methods: Two patients submitted to DBS were studied. Patient 1 had the diagnosis of Lennox-Gastaut syndrome and frequent tonic seizures. He was submitted to bilateral thalamic centro-median nuclei implantation. Patient 2 had bi-temporal lobe refractory epilepsy with epigastric simple partial and complex partial seizures. She was submitted to bilateral thalamic ventral-anterior nuclei implantation. Both patients were stimulated during one minute with varying voltage, 100 Hz and 300usec pulses.
Results: None of the patients tolerated an 8V stimulation while awaken. They complained of headache or bilateral and diffuse uncomfortable sensations in the body. On the other hand, stimulation using pulses with 4-6 V was able to trigger parcellar or partial habitual seizures in both patients. Patient 1 disclosed a parcellar seizure identical to the beginning of his habitual tonic seizures (tonic head extension) during the first 10 sec of the stimulation. Interestingly, this clinical manifestation subsided as stimulation continued over 1 minute, but it could be elicited at the beginning of each stimulation cycle. Patient 2 typically felt her “aura” (epigastric sensation) at the beginning of high voltage stimulation. Contrary to what was seen in patient 1, this sensation persisted during all the stimulation (“on”) cycle.
Discussion: We were able to demonstrate that in both patients the stimulation of the selected target did interfere with the on-going epileptic activity. Further studies would be needed to additionally refine the stimulation parameters so that DBS could yield the best clinical outcome.