Comparing neurostimulation technologies in refractory focal-onset epilepsy

Abstract

For patients with pharmacoresistant focal epilepsy in whom surgical resection of the epileptogenic focus fails or was not feasible in the first place, there were few therapeutic options. Increasingly, neurostimulation provides an alternative treatment strategy for these patients. Vagal nerve stimulation (VNS) is well established. Deep brain stimulation (DBS) and cortical responsive stimulation (CRS) are newer neurostimulation therapies with recently published long-term efficacy and safety data. In this literature review, we introduce these therapies to a non-specialist audience. Furthermore, we compare and contrast long-term (5-year) outcomes of newer neurostimulation techniques with the more established VNS. A search to identify all studies reporting long-term efficacy (>5 years) of VNS, CRS and DBS in patients with refractory focal/partial epilepsy was conducted using PubMed and Cochrane databases. The outcomes compared were responder rate, percentage seizure frequency reduction, seizure freedom, adverse events, neuropsychological outcome and quality of life. We identified 1 study for DBS, 1 study for CRS and 4 studies for VNS. All neurostimulation technologies showed long-term efficacy, with progressively better seizure control over time. Sustained improvement in quality of life measures was demonstrated in all modalities. Intracranial neurostimulation had a greater side effect profile compared with extracranial stimulation, though all forms of stimulation are safe. Methodological differences between the studies mean that direct comparisons are not straightforward. We have synthesised the findings of this review into a pragmatic decision tree, to guide the further management of the individual patient with pharmacoresistant focal-onset epilepsy.

Predicting success of vagus nerve stimulation (VNS) from EEG symmetry

“…In our study, nearly all patients (85%) experienced some, mostly mild, side-effects. This percentage is higher than described by others, however, the type of reported side-effects is similar [13,14].…”

“…Low pdBSI values represent symmetric EEG activity, whereas higher pdBSI values indicate higher asymmetry of the EEG. For each patient, pdBSI values were determined for four different frequency bands: delta (0.5-4 Hz), theta (4-8 Hz), alpha (8)(9)(10)(11)(12) and beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). EEG symmetry, defined by pdBSI, was tested for relation with effect of VNS therapy after one year.…”

Effect of neurostimulation on cognition and mood in refractory epilepsy

“…For these patients, an alternative treatment is neurostimulation, which includes vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS), as well as recent, less‐invasive therapies including trigeminal nerve stimulation (TNS), transcranial direct current stimulation (tDCS), and transcranial magnetic stimulation (TMS). These therapies vary in their efficacy for seizure reduction and are associated with different side‐effect profiles …”

A Comparison of Vagal Nerve Stimulation and Responsive Neurostimulation for the Treatment of Medically Refractory Complex Partial Epilepsy

“…A total of 884 subjects in each arm would be needed to show a 5% difference in mean seizure frequency reduction. Only 57 patients in each arm are needed to show a 25% difference in mean seizure frequency reduction; however, based on the current literature, this magnitude of difference is unlikely [4-9, 12-14]. …”