Abstracts

Rationale: The vagus nerve may exert its recently discovered prominent role in the immune system through widespread connections in the brain. The hypothalamus may be a crucial structure involved and for this reason we investigated the acute and chronic VNS-induced effects on the HPA-axis in patients with refractory epilepsy.Methods: Before VNS initiation, serum ACTH and cortisol levels were investigated in patient blood samples gathered between 8.00 and 9.00 am. Similar samples were gathered one day following VNS initiation at 0.25 mA and again 6 months later. No AED changes were made during the study. CRP was determined to detect inflammation. Results: 11 patients (7F/4M) with a mean age of 30 years (range 19-51) were included. Before VNS initiation, mean serum cortisol was 17 μg/dL (range 8-23; SEM 4 μg/dL), mean serum ACTH was 25 pg/mL (range 13-48; SEM 10 pg/mL). After one day of VNS, mean serum cortisol was 17 μg/dL (range 8-34; SEM 5 μg/dL), mean serum ACTH was 25 pg/mL (range 13-40; SEM 8 pg/mL). After 6 months of VNS, mean serum cortisol was 17 μg/dL (range 6-26; SEM 4 μg/dL) and mean serum ACTH was 22 pg/mL (range 12-38; SEM 7 pg/mL). Mean CRP levels throughout the study remained low (0,8 mg/dL). Conclusions: Acute and chronic VNS does not affect serum cortisol and ACTH levels in patients with refractory epilepsy. These results indicate that the mechanism of action of VNS is not mediated by immediate effects on the HPA-axis. V. De Herdt is supported by a grant (‘aspirant’) from the FWO-Flanders.