This looks like a new trial? There's been one ongoing in France for a couple of years, university of Grenoble, not sure how that is going but there's a single case study here that looks promising
www.brainstimjrnl.com/article/S1935-861X%2814%2900270-8/abstract"Long Term Effects of Low Frequency (10 Hz) Vagus Nerve Stimulation on EEG and Heart Rate Variability in Crohn's Disease: A Case Report"