Cervical vagus nerve morphometry and vascularity in the context of nerve stimulation - A cadaveric study

Vagus nerve stimulation (VNS) has become a well-established therapy for epilepsy and depression, and is emerging to treat inflammatory disease, with the cervical vagus nerve (CVN) as major stimulation site. CVN morphometries are missing for VNS, considering its variability. Morphometric data were obtained from CVNs in 27 cadavers, including branching patterns and histology. Cross-sectional area, greater and lesser diameters averaged 7.2 +/- 3.1 mm(2), 5.1 +/- 1.5 and 4.1 +/- 1.3 mm, and were <= 11.0 mm(2), <= 7.0 and <= 5.8 mm in 90% of the specimens, respectively. Midline distance (position lateral to the laryngeal eminence) and skin distance (anterior-posterior from skin) averaged 34.5 +/- 6.2 and 36.2 +/- 9.4 mm, <= 49.0 and <= 41.0 mm in 90%, respectively. Nerve dimensions and surface topography correlated closely, but without gender-, side- or branching-dependent differences. The nerve fascicle number averaged 5.2 +/- 3.5. Vagal arteries were observed in 49% of the cases. Negative correlations were found for age and cross-sectional area, as well as subperineural vessel count. Detailed anatomical data on the CVN and its vascularity are given, forming the morphometric basis for VNS refinement, filling an evident gap in light of the CVN being a structure with variable positions and branching. A 35 x 35-mm rule may apply for the CVN position, irrespective of branching or positional variation.