Abstracts

Rationale: Epilepsy is the most common neurologic disease in childhood affecting 0.5 to 1% of all children. Vagal nerve stimulation (VNS) had been approved as an adjunctive therapy for drug resistant epilepsy in patients older than 12 years with partial onset seizures. However, it has been used off label in children younger than 12 years of age for the last years with several studies showing comparable efficacy and safety with that found in adults. This study reports the epilepsy-related profile and outcomes of children with drug resistant epilepsy and VNS implants in Puerto Rico.Methods: An observational retrospective design was performed. The study population included 28 children, 18 years old or younger, with drug resistant epilepsy that had VNS implanted between 2001 and 2013. There are 17 females (60.7%) and 11 males (39.3%). Data was collected from medical records. Mean duration of epilepsy by time of VNS implantation was 6.5 years (SD=3.80). Statistical data analysis included frequencies and percentages distribution, measures of central tendency and contingency tables with chi-square statistics.Results: The mean age at the moment of VNS implantation was 8 years old (SD=4.35). The median age at the onset of epilepsy was less than 1 year old (SD=3.75). Sixty percent (60.7%) of patients had symptomatic epilepsy while 35.7% were idiopathic and 3.6% cryptogenic. From those with symptomatic epilepsy, 21.4% had structural causes, with encephalomalacia (14.3%) being the most frequent, followed by cerebrovascular insults (7.1%) and cortical dysplasia (3.6%). A greater proportion of patients with VNS had multiple seizures types (53.6%), while 39.3% had isolated partial seizures and 7.1% isolated generalized tonic-clonic seizures. In patients with multiple types of seizures, partial seizures were the most frequent (35.7%), followed by atonic and atypical absence seizures (28.6% each), generalized tonic-clonic (25%), myoclonic (21.4%), tonic (17.9%) and clonic (3.6%) seizures. A high proportion of patients (68.0%) showed a seizure frequency reduction of 90% or more after 2-year follow-up of VNS implant; 78% of these had onset of epilepsy before 1 year old. All patients with multiple types of seizures had a seizure frequency reduction of 90% or more in at least one seizure type as compared to 22.2% of patients with isolated partial seizures (p<.001). At least 75% of patients with atonic and/or atypical absence seizures attained seizure freedom (p=0.26). None of the patients had complications associated with VNS up to 2 years after VNS implantation.Conclusions: These results suggest that VNS is a safe and effective therapeutic alternative for children with drug resistant epilepsy. Atonic and atypical absence seizure are the most responsive types. Given that the outcome variables were almost a constant (most patients present seizure frequency reduction and show no complications), we were not able to identify other possible predictors of effectiveness and safety within the variables analyzed.