Anatomical Structure and Location of the Phrenic Nerve

Description

Arising from the anterior rami of C3 to C5 at the lateral border of the anterior scalene, the phrenic nerve descends vertically through the lower neck toward the superior thoracic aperture, deep to the sternocleidomastoid and anterior to the scalenus medius. Along its course it lies in close relationship to the prevertebral fascia, then crosses the first part of the subclavian artery and runs with the pericardiacophrenic vessels, remaining anterior to the root of the lung as it continues into the thorax. The clavicle and scapular elements frame the cervicothoracic junction, while the trapezius and strap musculature define the posterior and anterior boundaries around the nerve’s superficial-to-deep transitions. Orientation matters. Tracking the phrenic nerve in a single continuous field is clinically practical because many iatrogenic and compressive injuries occur where it is tethered against fixed structures, classically on the anterior scalene and at the thoracic inlet. Central venous catheter placement in the internal jugular or subclavian region, supraclavicular brachial plexus block, and cervical spine or thyroid surgery all place the nerve at risk, and postoperative hemidiaphragmatic paralysis can follow even minor traction. This view also supports teaching the C3,4,5 contribution to diaphragmatic motor supply and why referred pain can reach the shoulder via overlapping cervical dermatomes. Use this artwork for head and neck anatomy courses, anesthesia and critical care teaching files covering phrenic palsy after regional blocks, and surgical atlases discussing cervicothoracic approaches and thoracic inlet anatomy. It also fits radiology and ultrasound education where the expected nerve position relative to the anterior scalene and pericardiacophrenic bundle guides probe placement and interpretation. Anatomical accuracy verified by SciePro's Medical Advisory Board.