What is the role of electrodiagnostic test 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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Electrodiagnostic tests are most sensitive for the detection of nerve conduction impairment. [2]

Nerve conduction studies reveal prolonged latencies in nerve injury, while electromyography (EMG) may reveal signs of denervation or reinnervation, depending on the timing of the study. [20]

Electrophysiologic integrity of the SAN does not correlate well with the clinical symptoms and outcome measures for shoulder dysfunction. [3]

However, EMG has shown a positive correlation with range-of-motion (ROM) tests, particularly active shoulder abduction with contralateral head rotation as a test of strength. Consequently, this physical examination maneuver serves as a reliable and cost-effective tool for evaluating the degree of upper trapezius denervation.

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