Chronic vagus nerve stimulation for drug-resistant epilepsy may influence fasting blood glucose concentration

Cervical vagus nerve stimulation (VNS) has been widely accepted as adjunctive therapy for drug-resistant epilepsy and major depression. Its effects on glycemic control in humans were however poorly understood. The aim of our study was to investigate the potential effects of VNS on fasting blood glucose (FBG) in patients with drug-resistant epilepsy.

Patients with drug-resistant epilepsy who had received VNS implants at the same hospital were retrospectively studied. Effects on FBG, weight, body mass index and blood pressure were evaluated at 4, 8 and 12 months of follow-up.

32 subjects (11 females/21 males, 19 ± 9 years, body mass index 22.2 ± 4.0 kg/m²) completed 12-month follow-up. At the 4 months, there were no significant changes in FBG concentrations from baseline to follow-up in both Sham-VNS (4.89 ± 0.54 vs. 4.56 ± 0.54 mmol/L, N = 13, p = 0.101) and VNS (4.80 ± 0.54 vs. 4.50 ± 0.56 mmol/L, N = 19, p = 0.117) groups. However, after 8 (4.90 ± 0.42 mmol/L, N = 32, p = 0.001) and 12 (4.86 ± 0.40 mmol/L, N = 32, p = 0.002) months of VNS, FBG levels significantly increased compared to baseline values (4.52 ± 0.54 mmol/L, N = 32). Changes in FBG concentrations at both 8 (R² = 0.502, N = 32, p < 0.001) and 12 (R² = 0.572, N = 32, p < 0.001) months were negatively correlated with baseline FBG levels.

Our study suggests that chronic cervical VNS elevates FBG levels with commonly used stimulation parameters in patients with epilepsy. Trial registration VNSRE, NCT02378792. Registered 4 March 2015-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02378792.