What is the role of imaging studies in the diagnosis of 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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High-resolution ultrasonography (HRUS) allows visualization of the normal SAN, as well as changes after accessory nerve injury. The SAN appears as a singular small (approximately 1 cm in diameter on ultrasound), hypoechoic tubular structure in the transverse plane and as a hypoechoic linear structure in the longitudinal plane. It is best identified in the posterior cervical triangle. In addition, HRUS is able to demonstrate hyperechoic and atrophic changes in the trapezius muscle, granuloma formation, and scar entrapment of the SAN in the region of the injury and the normal course of the nerve beyond. However, the actual transection of the SAN is not readily visualized by HRUS. [9]

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