Abstracts

Rationale: The vagal nerve stimulator (VNS) is an established therapy for medically refractory epilepsies, but its role in various forms of genetically determined epilepsies has not been well characterized.Methods: A retrospective chart review was performed for all patients who received a VNS at Children’s National Medical Center from April 1998 through January 2015. Patients with epilepsy due to a single gene disorder or chromosomal abnormality were identified and information regarding diagnosis, age of onset, and response to VNS were collected. As quantitative measures regarding seizure response to VNS were not routinely recorded, the response was assigned categorically.Results: 72 patients had VNS placed during this period, and 11 had epilepsy due to a single gene disorder or chromosomal abnormality. Mean time to surgery after seizure onset was 8 years (range 1-14 years). Seizure improvement was noted in 7 of these patients (64%): two with Dravet syndrome due to SCN1A mutation, two with tuberous sclerosis, and one each with Angelman syndrome, isodicentric chromosome 15, and ring chromosome 14. Four had no improvement after VNS: one each with Unverricht-Lundborg disease due to compound heterozygous CSTB mutation, Dravet syndrome due to SCN1A mutation, Dravet syndrome due to PCDH19 mutation, and chromosome 2p11 deletion. No patients worsened. All patients except those with clinically diagnosed tuberous sclerosis had confirmatory genetic testing. Six of the 22 patients with a VNS placed in December 2010 or later had a genetic diagnosis.Conclusions: VNS therapy has a role in various forms of medically refractory, genetically determined epilepsies. As genetic testing is becoming more clinically available, finding a specific genetic diagnosis will be possible in a larger proportion of patients with medically refractory epilepsies not referable to a structural cause. More research is indicated into examining the response of specific genetic epilepsies to VNS therapy and other forms of epilepsy treatment.