What is a spinal accessory nerve (SAN) injury?

Updated: Mar 04, 2020
  • Author: Rohan R Walvekar, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Cranial nerve XI, the spinal accessory nerve (SAN), is vulnerable to injury, owing to its long and superficial course in the posterior cervical neck. [1] An important landmark in the neck, the SAN is considered to contribute most motor innervation to the trapezius muscle. Injury to the SAN results in varying degrees of shoulder dysfunction. This article reviews the important surgical landmarks and anatomic variations of the SAN, etiologies of SAN injury, and outcomes of surgical repair. Early identification of SAN injury and appropriate treatment can have a significant impact on overall shoulder function and, consequently, quality of life. (See the image below.)

Course of the spinal accessory nerve (SAN) in the Course of the spinal accessory nerve (SAN) in the posterior cervical triangle. DG = posterior belly of digastric muscle; T = trapezius; LS = levator scapulae; IJV = internal jugular vein; black arrow = SAN.

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