Predictors of seizure reduction outcome after vagus nerve stimulation in drug-resistant epilepsy

Abstract

A B S T R A C TPurpose: To evaluate the predictors of seizure reduction outcome after vagus nerve stimulation (VNS) in patients with drug-resistant epilepsy (DRE). Methods: A meta-analysis was performed using relevant research from databases such as PubMed, Embase, Cochrane Online Library, and Clinicaltrials.gov. Studies were selected according to predefined inclusion and exclusion criteria. The quality of studies was evaluated by using the Newcastle-Ottawa Scale (NOS) scale. All data was pooled by STATA 12.0 software for meta-analysis. Results: The review considered 1281 articles, and 16 articles with NOS score ≥6 were included in the analysis. The meta-analysis showed that at 6 m, 1, 2, 3, 4, 6 and 12 years after implantation, 33.99, 43.42, 46.50, 63.31, 52.71, 54.64, 70.37 and 82.90% of patients exhibited > 50% reduction of seizure frequency after VNS. The duration of epilepsy showed a significant difference between the good responders and poor responders (p = 0.038), whereas age at VNS implantation (p = 0.305), age at seizure onset (p = 0.530), seizure type (p = 0.11), etiology (p = 0.187), and history of previous epilepsy surgery (p = 0.075) were not predictors of seizure reduction outcome after VNS. Several features about the electroencephalogram (EEG) feature and heart rhythm complexity (HRV) have not been analyzed by a sufficient number of studies. Conclusions: DRE patients with shorter duration of epilepsy may be better candidates for VNS rather than those who are younger at onset and implantation. Several EEG or HRV features may have predictive value but more research is needed.

Biomarkers of seizure response to vagus nerve stimulation: A scoping review

“…3 However, other investigations into the same clinical markers reported conflicting results. 8 A recent principal component analysis of 31 clinical variables coupled with support vector machine learning revealed these markers to be no better than chance alone at predicting VNS response. 9 Moreover, the statistical methods used by the majority of studies examining clinical covariates compare responders to nonresponders using aggregate group-average statistics, which cannot be readily extrapolated to individual patients.…”

Health Technology Assessment Report on Vagus Nerve Stimulation in Drug-Resistant Epilepsy

“…The efficacy of VNS on epilepsy at a younger age is still a matter of discussion [ 40 , 45 , 46 , 48 , 60 , 61 , 62 , 63 ]. Shorter history of epilepsy as a positive factor, reported by Kavcic, Wang and some other authors [ 48 , 64 , 65 , 66 ], is not accepted by all [ 61 , 63 , 67 ]. VNS appeared to have a role in malformation of cortical development, tuberous sclerosis, and post-traumatic and post-stroke epilepsies [ 46 , 68 ].…”

Frequency of Automatic Stimulations in Responsive Vagal Nerve Stimulation in Patients With Refractory Epilepsy

“…Indirect anti‐excitatory modulation of neural circuitries is achieved after a longer duration of the therapy. The response to VNS therapy is progressively improving over time (5‐6), supposedly due to the indirect effects of VNS. It has been hypothesized that the shift from constant cyclic stimulation to more variant stimulation patterns would lead to better responses.…”

“…Neuromodulation therapies offer an alternative treatment option for this group of patients including vagal nerve stimulation (VNS), deep brain stimulation (DBS), and intracranial responsive neurostimulation (RNS). VNS has been available for more than 25 years with proven efficacy; at least 50% of the patients experience a 50–60% reduction in seizure frequency (4), and long‐term outcomes (efficacy and safety) tend to improve with time (5‐6).…”