gms | German Medical Science

Objective: Vagus nerve (VN) stimulation in the cervical region is a hopeful neuromodulation procedure with indications in epilepsy, depression and in chronic heart failure. The implantation is considered to be secure. Nevertheless, the VN appears to have plenty of anatomical variations in the cervical region according to our own experiences. In contrast, existing historical and present anatomical and surgical studies on the VN describe a regular course of this nerve with only very few variations. The aim of our study was to examine cervical VN anatomy and to detect existing branches as a possible explanation of stimulation side effects.

Method: In 35 body donors the VNs were investigated macroscopically with focus on their location in the neurovascular sheath and on nerve branching. Anatomical dissection was conducted in a similar approach as done when performing surgical implantation of the electrodes for VN stimulation. In cases of atypical branches additional histological investigations served to confirm the diagnosis of neural tissue. Radiographs projected the occurring branches onto the cervical vertebrae.

Results: The regular course of the VN, being located dorsally in the neurovascular sheath between the carotid artery and the internal jugular vein, was only detected in only 42%. In the remaining majority, eight different locations were observed for the VN. Cervical VN branches were detected in 12 cases and documented radiologically. In all but one case neural tissue was found histologically. Additionally vascular abnormalities were observed.

Conclusions: Our study gives new insights into the cervical VN anatomy, proving that anatomical variations and branching of the VN is much more common than described previously. These findings should be taken into account when planning and realizing reliable and consistent VN stimulation and might explain potential stimulation side effects or fluctuations in therapeutical reliability.