Early-onset response is a predictor of better longterm outcome of vagus nerve stimulation therapy

ABSTRACT

Background & Objective: It is well established that the effectiveness of vagus nerve stimulation (VNS) therapy increases over 2-3 years. When increasing the dose of VNS, some patients were noted to respond even at low-dose stimulation in the first few months. The purpose of this study was to evaluate the relationship between an initial response to VNS and long-term response in a retrospective study of patients with intractable epilepsy. Method: We retrospectively analysed 56 patients who had VNS implantation in our centre. All patients had undergone complete presurgical evaluation. After implantation, the patients were examined at regular intervals of one month for 6-9 months and then followed up regularly for more than 2 years. Their seizure frequency and intensity were documented in their seizure logs. Results: Six patients achieved Engel class I (11%) seizure outcome, 16 achieved Engel class II (28%), and 19 achieved Engel class III (34%). Of the 22 patients with Engel I and II, the 19 in Engel class I (100%) and II (81%) showed an initial response within 6 months, an earlyonset response of VNS implantation. Conclusions: Early-onset response could be an independent predictor for achievement of Engel class I and II in long-term follow-up. Keyword Background & Objective: It is well established that the effectiveness of vagus nerve stimulation (VNS) therapy increases over 2-3 years. When increasing the dose of VNS, some patients were noted to respond even at low-dose stimulation in the first few months. The purpose of this study was to evaluate the relationship between an initial response to VNS and long-term response in a retrospective study of patients with intractable epilepsy. Method: We retrospectively analysed 56 patients who had VNS implantation in our centre. All patients had undergone complete presurgical evaluation. After implantation, the patients were examined at regular intervals of one month for 6-9 months and then followed up regularly for more than 2 years. Their seizure frequency and intensity were documented in their seizure logs. Results: Six patients achieved Engel class I (11%) seizure outcome, 16 achieved Engel class II (28%), and 19 achieved Engel class III (34%). Of the 22 patients with Engel I and II, the 19 in Engel class I (100%) and II (81%) showed an initial response within 6 months, an earlyonset response of VNS implantation. Conclusions: Early-onset response could be an independent predictor for achievement of Engel class I and II in long-term follow-up. Keyword Vagus nerve stimulation, long term outcome, early onset response, predictor, epilepsy