Clinical course of young patients with Dravet syndrome after vagal nerve stimulation

Medical treatment of Dravet syndrome is disappointing. Ketogenic Diet and neurostimulation procedures as Vagus Nerve Stimulation (VNS) and Deep Brain Stimulation are in ongoing evaluation. In the present study, the long-term effectiveness of VNS on seizures, cognition and behavior was retrospectively evaluated in eight young patients with DS and medically refractory epilepsy (mean age at VNS implant: 10.28 years, range: 5-25). The average duration of treatment was 54 months (range: 12-120). Compared to baseline (mean: 55; standard deviation: 83, range: 4-200), the mean number of monthly seizures after VNS implantation was 39 ± 67 at 3 months, 42 ± 67 at 6 months and 38 ± 69 at twelve months (not significant comparisons). In particular, VNS produced a mean seizure rate reduction of 12% at three months, 6% at six months, and 31% at twelve months. All patients but three experienced some reduction in seizure burden (range: 33-61%) at twelve months. Seizure outcome after one year of stimulation was rated as Mc Hugh class II (50-79% reduction in seizure frequency) in four patients, class III (<50% reduction) in one patient and class V (no improvement) in three patients. In this small case series of patients with DS, VNS therapy had a clinically significant effect in reducing seizures at twelve months in four of the eight patients. Even in patients in whom seizure reduction was not dramatic, a slight improvement in alertness and communicative skills was seen. The long-term clinical course of two selected cases is discussed.