Background: Although modified radical neck dissection type III preserves the spinal accessory nerve, the internal jugular vein, and the sternocleidomastoid muscle, the authors believe there is a significant morbidity to retained structures after neck dissection. Although the effects on accessory nerve function and internal jugular vein patency have been documented, there is little information about sternocleidomastoid morphology and function following modified dissection.
Methods: Using a SonoSite ultrasound machine, the authors assessed sternocleidomastoid muscle morphology, at rest and during contraction, in a cohort of 45 patients who underwent modified radical neck dissection type III with no radiotherapy. All patients had head and neck cancers and received unilateral neck dissection as part of their primary treatment. Static and dynamic measurements were performed at three different levels of the muscle, with the neck in the neutral position. The contralateral neck of the same patient was used as a control. Local muscle asymmetry patterns were calculated using the Absolute Asymmetry Index.
Results: Significant sternocleidomastoid atrophy was noted on the side of modified radical neck dissection type III (p < 0.05). The atrophy was particularly marked in the caudal and middle portions of the sternocleidomastoid muscle and was likely related to damage to the segmental blood supply in the caudal and middle portions of the muscle as well as injury to the innervation.
Conclusion: Despite evidence of significant atrophy, the muscle still underwent morphological changes during contraction that were comparable to those on the normal control side.