What is the prevalence of 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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Iatrogenic SAN injury most commonly occurs following diagnostic lymph node biopsies of the posterior triangle of the neck. Injury rates from these procedures are reportedly 3-8%. Severe functional deficits of the upper extremity have been reported in up to 60-80% of patients who undergo radical neck dissections. [15] A large retrospective series reported clinical evidence of SAN injury in 1.68% of patients who underwent modified radical neck dissection. [16]

Clinical evidence of SAN injury has been reported to be as high as 30% in selective neck dissections that included cervical zones II-IV and V. This percentage is significantly lower if zones II-IV are dissected but zone V is spared. [2]

Reported injury rates vary, however. A retrospective study by Popovski et al found that in radical, selective, and modified neck dissections, postoperative morbidity rates for the SAN were 46.7%, 42.5%, and 25%, respectively. [17]

The dissection of level IIB is also a topic of controversy. It was previously presumed that preservation of zone IIB and consequently reduced manipulation of the SAN in a lateral neck dissection would result in less postoperative shoulder dysfunction. However, reports do not support this assumption. Other, less frequent causes of SAN injury are listed below (see Etiology).

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