Introduction High frequency, low energy gastric neurostimulation (Enterra^TM) is indicated for compassionate treatment of patients with refractory gastroparesis. Symptom improvement is reported in 50–60% of patients but not accompanied by improved gastric emptying. It is likely that gastric neurostimulation affects the gut-brain axis influencing autonomic afferents.¹GammaCore (electroCore, LLC) is a non-invasive, afferent selective vagus nerve stimulator (nVNS) used for the treatment of migraine and cluster headache.²We report the first use of gammaCore (gC) in patients with refractory gastroparesis.

Method 35 consecutive patients with intractable gastroparesis were invited to undergo a course of gC whilst awaiting funding for Enterra. The gC device delivers its stimulus to afferent vagus fibres as they cross the neck adjacent to the carotid arteries and it is programmed to deliver doses of 120 s. Patients were trained to deliver 2 doses (240 secs) to the left and right vagus nerve respectively. This dosing regimen was self-administered 8 hly (12 doses/day) for 2 weeks, increasing in week 3 to 3 doses 8 hly (18 doses/day). Patients were asked to grade their symptoms daily using the 9 item Gastroparesis Cardinal Symptom Index (GCSI) with a 5 point Likert scale. The GCSI was completed for 2 weeks prior and throughout the treatment period. At the end of the treatment period, the mean aggregated GSCI score at baseline was compared with the score of the final week of treatment. Clinically meaningful improvement was defined as a GCSI Likert scale reduction of ≥1.

Results Twenty-three of the 35 patients (65.7%) used the gC as instructed and completed the diary. At 3 weeks, 8 patients (35%) had a ≥1 reduction in the aggregated GSCI score. Two patients who continued stimulation for more than three weeks had a delayed response, giving a total response rate of 43%. The response was evident within 1 week of commencing treatment in 8/10 responders (80%) and there was symptom recurrence within a week of stopping treatment in all the responders. There were no significant adverse events.

Conclusion In this group of patients with treatment refractory gastroparesis, 1/3 failed to engage with short term nVNS. In compliant patients,43% recorded a fall of ≥1 in their aggregated GCSI score. As gC stimulates afferent vagus fibres, it is likely that the response is mediated at the level of the gut-brain axis. In refractory gastroparesis, gC might offer a new approach to symptom control. The dosing and duration of nVNS required to obtain an optimal response deserves further consideration.

Disclosure of interest None Declared.

References

1. McCallum RW, et al. Neurogastroenterol Motil. 2010;22(2):161–7

2. Goadsby P, et al. Cephalgia 2014;34(12):986–93