Effectiveness of vagal nerve stimulation (VNS) in patients with drop-attacks and different epileptic syndromes

PURPOSE The effectiveness of VNS was evaluated in thirty-nine encephalopatic patients with drug-resistant epilepsy characterized by multiple seizures and drop attacks. Twenty-five patients were affected by severe epilepsy with multiple independent spike foci (SE-MISF) and fourteen patients by Lennox-Gastaut syndrome (LGS). METHOD Changes in seizure frequency, cognition, adaptive behaviour and quality of life were assessed before and after VNS implant until three years. Outcome assessment for all seizure types included the number of seizures/month and the reduction in seizure frequency rate at each follow-up. Moreover, the effect of VNS on frequency, duration and intensity of drop attacks was separately addressed by a modification of McHugh scale. RESULTS VNS produced a mean seizure rate reduction of 41% at six months, 50% at twelve months, and 54% at thirty-six months. After one year of stimulation, thirteen patients with SE-MISF (52%) and three patients with LGS (21%) showed a reduction above 50% in all seizures' frequency rate. As for drop attacks, eight patients (20%) gained a reduction above 50%, while seven patients (17%) showed a reduction only in intensity and duration. Cognitive level and adaptive behaviour were unchanged, while a better quality of life was reported in half out of the patients. CONCLUSIONS VNS had a greater effect in reducing seizures frequency and drop attacks' intensity and duration in SE-MISF patients than LGS patients. An improved quality of life was observed also in those patients who only reduced the intensity and duration of drop attacks.