Vagus nerve stimulation of patients with medically intractable epilepsy – long term results

Objective: The vagus nerve stimulation (VNS) for medically intractable epilepsy has already become a widely accepted treatment option for this clinical entity. Nevertheless, long term efficiency still remains controversial. We analyzed 21 patients with a follow up period up to 6 years.

Methods: Since 1998 the VNS has been established at our institutions. From this time we operated on more than 40 patients with refractory epilepsy. The implantation of VN-stimulators (Cyberonics VNS) was done via the standard approach. The presented data include 21 patients (10 female, 11 male; average age 37.5 years) with a minimum follow up of 24 months ranging from 27 to 71 months (mean 52.1). Patients with a history of medically intractable partial seizures who would not benefit from resective surgery or Lennox-Gastaut syndrome, and patients in whom previous epileptic surgery had failed were included. Seizure reduction, side effects, administration of antiepileptic drugs and surgical complications were analyzed.

Results: Clinically significant seizure reduction was defined as >=50% reduction of seizures (responders). 48% of the patients were non-responders. An overall seizure reduction of 70.5% was noticed in the responder group (n=11). Nine patients reported a reduction of seizure frequency between 50 and 87%. Two responders with a symptomatic focal epilepsy have been seizure free. After implantation of the VN-stimulator, 3 patients developed a transient laryngeal nerve paresis with hoarseness and another 3 patients reported breathing difficulties. After changing the stimulation parameters these symptoms improved. In one patient, an infection occurred. The stimulator was explanted and re-implantation was done after 3 months. A battery and stimulator change in 3 patients of the responder group was necessary after 55 to 65 months. Despite a seizure reduction in the responder group, the administration of combined antiepileptic drugs did increase from 2.4 to 3.1. In the non-responder group, 3 stimulators were explanted and 2 turned off as a result of failed therapy.

Conclusions: Our long term results show that a subgroup of patients (52%) with medically intractable epilepsy achieved a seizure reduction of 50% and more over a long period. This effect means a higher quality of life for these patients and their relatives. However, the patients must realize that this therapeutic option is not a substitute for medication.