The effects of vagus nerve stimulation on tryptophan metabolites in children with intractable epilepsy

S. Klinkenberg, C.J.H. van den Borne, M.W. Aalbers, P. Verschuure, A.G. Kessels, L. Leenen, K. Rijkers, A.P. Aldenkamp, J.S.H. Vles, H.J.M. Majoie

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background: The mechanism of action of vagus nerve stimulation (VNS) in intractable epilepsy is not entirely clarified. It is believed that VNS causes alterations in cytokines, which can lead to rebalancing the release of neurotoxic and neuroprotective tryptophan metabolites. We aimed to evaluate VNS effects on tryptophan metabolites and on epileptic seizures and investigated whether the antiepileptic effectiveness correlated with changes in tryptophan metabolism.

Methods: Forty-one children with intractable epilepsy were included in a randomized, active-controlled, doubleblind study. After a baseline period of 12 weeks, all children underwent implantation of a vagus nerve stimulator and entered a blinded active-controlled phase of 20 weeks. Half of the children received high-output (therapeutic) stimulation (n = 21), while the other half received low-output (active control) stimulation (n = 20). Subsequently, all children received high-output stimulation for another 19 weeks (add-on phase). Tryptophan metabolites were assessed in plasma and cerebrospinal fluid (CSF) by use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and compared between high- and low-output groups and between the end of both study phases and baseline. Seizure frequency was recorded using seizure diaries. Mood was assessed using Profile of Mood States (POMS) questionnaires.

Results: Regarding tryptophan metabolites, anthranilic acid (AA) levels were significantly higher at the end of the add-on phase compared with baseline (p = 0.002) and correlated significantly with improvement of mood (tau = 039, p = 0.037) and seizure frequency reduction (tau = 0.33, p

Conclusion: Vagus nerve stimulation induces a consistent increase in AA, a neuroprotective and anticonvulsant tryptophan metabolite. Moreover, increased AA levels are associated with improvement in mood and reduction of seizure frequency. 

Original languageEnglish
Pages (from-to)133-138
Number of pages6
JournalEpilepsy & Behavior
Volume37
DOIs
Publication statusPublished - Aug 2014

Keywords

  • VNS
  • Pediatric
  • Therapy-resistant seizures
  • Tryptophan metabolic pathway
  • Kynurenine
  • Anthranilic acid
  • RANDOMIZED CONTROLLED-TRIAL
  • CEREBROSPINAL-FLUID
  • OXIDATIVE STRESS
  • RESISTANT EPILEPSY
  • PARTIAL SEIZURES
  • QUINOLINIC ACID
  • KYNURENIC ACID
  • PATHWAY
  • 3-HYDROXYKYNURENINE
  • INFLAMMATION

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