Histopathological changes in tissues surrounding vagal nerve stimulation generators: A retrospective analysis of revision surgeries

Purpose Vagal nerve stimulation (VNS) is an effective treatment for patients with epilepsy, depression, and other neuropsychiatric conditions. Understanding the tissue changes associated with VNS devices is crucial for optimizing patient outcomes and device development. This study aimed to investigate the histopathological changes in the tissues surrounding the VNS generator and explore potential correlations with clinical factors and battery performance. Methods A total of 23 patients who underwent VNS generator revision surgery owing to battery depletion were included. Tissue samples from the areas surrounding the VNS generator were obtained and analyzed for histopathological changes. Demographic and device-related variables were also recorded. Results Capsule formation was observed in all patients. Acute inflammation were not detected in any case. Perivascular lymphocytic infiltration, foreign-body giant cell reaction (FBGCR), and calcification were observed in 8.7%, 26.1%, and 43.5% of patients, respectively. Crystalloid foreign body appearance was noted in 4 patients. The median output current of the generator was higher in patients with lymphocytic infiltration than in those without lymphocytic infiltration. The median off time was higher in patients with skin retraction than in those without skin retraction. Moreover, discomfort was associated with the presence of FBGCR. Conclusion Our study provides insights into the tissue changes associated with the VNS generator, with capsule formation being a common response. Crystalloid foreign body appearance was not reported previously. Further research is needed to understand the relationship between these tissue changes and VNS device performance, including the potential impact on battery life. These findings may contribute to VNS therapy optimization and device development.