Transcutaneous Sonography for Detection of the Cervical Vagus Nerve.

Cervical vagus nerve is not identified by computed tomography or magnetic resonance imaging. Transcutaneous sonography may be the best imaging study to evaluate the cervical vagus nerve. A 7 to 18 MHz linear array transducer was placed transversely on the lateral neck focusing on the carotid sheath from the clavicle level upward to the digastric muscle level bilaterally. The gray-scale technique was used, with the scan setting for the thyroid gland. Between January 2015 and March 2016, 314 patients with 628 cervical vagus nerves were enrolled, including 104 men and 210 women. Their ages ranged from 14 to 84 years. Transcutaneous sonography identified the entire trunk of bilateral cervical vagus nerves in 254 (80.9%) patients and did not identify 1 or both cervical vagus nerves in the other 60 (19.1%) patients. Among 628 cervical vagus nerves, transcutaneous sonography identified 626 (99.6%) lower cervical vagus nerves and 551 (87.7%) upper cervical vagus nerves. Among 551 visible upper cervical vagus nerves, 495 (89.8%) nerves were located laterally, 17 (3%) nerves were located medially, 9 (1.6%) nerves were located anteriorly, and 30 (5.4%) nerves were located posterior to the internal carotid artery. Man and left-side nerve were the factors associated with the anatomical variation in the upper cervical vagus nerve. Transcutaneous sonography can be the best imaging study to show the cervical vagus nerve and may be helpful to evaluate the nerve before neck operation.