While well established in the independent treatment of epilepsy and depression, findings published in Seizure: European Journal of Epilepsy indicate Vagus nerve stimulation (VNS) may also be effective in the treatment of pharmacoresistant epilepsy and comorbid depression.

This study investigated 59 adults (38 women and 21 men) with epilepsy and different types of depression symptoms. Among these adults, 18 had focal-frontal, 18 had focal-temporal, 5 had multifocal, 2 had idiopathic generalized, 7 had symptomatically generalized, and 9 had cryptogenic epilepsy. All participants had comorbid depression, specifically 33inidividuals had interictal dysphoric disorder, 12 had major depression, 10 had personality disorder cluster, and 20 had organic affective disorder. Eleven adults had 2 or more of these subtypes.

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Prior to VNS surgery, baseline diagnoses were established by an independent psychiatrist using Montgomery-Åsberg Depression Rating Scale (MADRS) and Beck-Depressions-Inventory (BDI). The need for VNS was determined by an interdisciplinary team of specialists based on the etiology and severity of epilepsy.

Severity of depression symptoms was re-evaluated using the same scales by the same psychiatrist 1 year after VNS surgery. Epilepsy response to VNS was measured by a neurologist independent of depression response.  Positive response was established by a seizure reduction of at least 50%.

After 6 months, 59% of the patients had a reduction of seizure frequency >50% or reported an improvement in quality of life due to a reduction in the severity of their seizures. The reduction in seizure frequency increased to 64% after 12 months and to 66% 2 years after VNS implantation. Improvement was seen across all types of epilepsy.

Two years after VNS, two-thirds of all cases had a reduction of their seizure frequency of more than 50%. Severity of symptoms of depression improved from a mean MADRS score of 29 to 18 (P <.001) and a mean BDI score of 24 to 14 (P <.001). All subtypes of depression also improved from VNS, with interictal dysphoric disorder and major depression showing the greatest effect.

The study authors indicated that retrospective analysis revealed a correlation between improvement in seizure frequency and reduction in symptoms of depression. They highlighted that proposing a causality from this finding may be limited by temporal factors, in that investigations for depression and seizure frequency were carried out at different time points. They further reported that determining whether improvement in depression symptoms is a direct or indirect effect of seizure reduction will require further investigation.

Despite these limitations the study authors stated, “VNS seems to be a very effective tool in the treatment of patients suffering from both diseases as a comorbidity and should receive more consideration in clinical standard and treatment.”

Reference

Spindler P, Bohlmann K, Straub HB, Vajkoczy P, Schneider UC. Effects of vagus nerve stimulation on symptoms of depression in patients with difficult-to-treat epilepsy [published online April 3, 2019]. Seizure: Eur J Epilep. doi: 10.1016/j.seizure.2019.04.001