Neuromodulation of autism spectrum disorders using vagal nerve stimulation.

Influential theories propose an important role for the autonomic nervous system in social behaviour and emotion regulation. Difficulties with these capabilities occur in autism spectrum disorders (ASD). Vagus nerve stimulation (VNS) is a neuromodulation technique that stimulates autonomic pathways by means of an electrode implanted around the left vagus nerve in the neck. It is a licenced treatment for epilepsy and depression. This study searches the literature for evidence of VNS effects on behaviour in ASD. A literature search was conducted by two independent reviewers using Embase, Medline, PsycInfo and Cochrane using relevant search terms following the principals of the PRISMA guidance. The search strategy utilised a combination of text words and thesaurus terms to retrieve records relating to autism/pervasive developmental disorder and vagus nerve stimulation. No limits were applied. Supplementary searches were carried out on trials registers, and using backwards and forwards citation searching. A predesigned inclusion and exclusion criteria was administered to the identified results. From the 242 results identified search strategy 11 were found to satisfy the full search criteria and used to discuss the hypothesis. Eight studies were case series and three case reports. There is some evidence that VNS, when performed for epilepsy, may improve behaviour in people with ASD. There are indications that this occurs independently of its effects on seizure frequency and mood, although more rigorous studies are required.