Impact of Failed Intracranial Epilepsy Surgery on the Effectiveness of Subsequent Vagus Nerve Stimulation

BACKGROUND: Using the Cyberonics registry, Amar and colleagues reported poorer efficacy of vagus nerve stimulation (VNS) in patients who failed intracranial epilepsy surgery (IES). OBJECTIVE: To study the impact of failed IES and other surrogate marker of severe epilepsy on VNS effectiveness in a large cohort with treatment-resistant epilepsy (TRE). METHODS: We retrospectively reviewed 376 patients (188 female patients; 265 adults; mean age, 29.4 years at implantation) with TRE who underwent VNS implantation between 1997 and 2008 and had at least 1 year of follow-up. One hundred ten patients (29.3%) had failed >= 1 prior craniotomies for TRE, and 266 (70.7%) had no history of IES. RESULTS: The mean duration of VNS therapy was 5.1 years. Patients with prior IES were more commonly male and adult, had a greater number of seizure types, and more commonly had focal or multifocal vs generalized seizures (P < .05). There was no significant difference in the mean percentage seizure reduction between patients with and without a history of IES (59.1% vs 56.5%; P = .42). There was no correlation between type of failed IES (callosotomy vs resection) and seizure reduction with VNS therapy. CONCLUSION: Failed IES did not affect the response to VNS therapy. Unlike prior reports, patients with callosotomy did not respond better than those who had resective surgery. Nearly 50% of patients experienced at least 50% reduction in seizure frequency. For patients with TRE, including patients who failed cranial epilepsy surgeries, VNS should be considered a palliative treatment option.