Accessory Nerve Injury Clinical Presentation

Updated: Jan 24, 2022
  • Author: Rohan R Walvekar, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Cardinal symptoms associated with SAN injury

These include the following:

  • Pain over the muscle
  • Heaviness of the arm
  • Depressed motor functions that consist of an inability to lift the shoulder girdle and abduct the arm [14]
  • Late sequelae - Shoulder syndrome that consists of shoulder droop, atrophic trapezius, loss of abduction, paresthesias, and adhesive capsulitis resulting in a frozen shoulder

Physical Examination

Clinical signs associated with SAN injury

Pain around the shoulder and neck can be assessed on a 10-point visual analogue scale (VAS). The mean intensity associated with SAN-related shoulder syndrome can average around 7 (range, 6-9). [36]

The affected shoulder is depressed, with inferior rotation of the lateral angle of the scapula.

Scapular “winging” can be accentuated by abduction of the arm.

Wasting of the trapezius may be evident in the upper part of the neck. [20]

Range of motion (ROM) can be restricted, as follows:

  • Active abduction (30°-140° range)
  • Active forward flexion (50°-180° range) [38]

Serial clinical examinations and electromyographic studies that fail to show an improvement in function are a clinical sign associated with SAN injury.


Pitfalls in Diagnosis

A dual or contributing nerve supply from the cervical plexus to the trapezius muscle that results in some retained motor function after SAN injury can make the diagnosis of an SAN injury difficult.

Subjective symptoms that result from trapezial dysfunction secondary to myofascial pain syndromes, contralateral paresthesias, and radiculitis can make diagnosis difficult.

Variations in presentations can also be attributed to the anatomic level of SAN injury, amount of collateral tissue damage, and subjective pain thresholds. [14]