Background: The sternocleidomastoideus muscle is the most prominent landmarks of the surface anatomy of the neck, separates the anterior part of the neck (anterior triangle) from the posterior part of the neck (posterior triangle). An accessory head of sternocleidomastoideus muscle may cause complications while trying to access vital neurovascular structures that are located in the minor and major supraclavicular fossa. The purpose of this study is to describe an anatomical variation of the sternocleidomastoideus muscle and clinical impact.
Methods and Findings: The anatomical variations described were found during routine dissection conducted in the laboratory of Morphology of the University of Pamplona in two male cadavers of 47 and 75 years respectively. Measurements were taken using a Vernier caliper. Topographic details of the variations were examined, recorded and photographed. The morphological variations in the number of heads (three and four) of origin of sternocleidomastoideus muscle was found in two male subjects in right and left neck, bilaterally. The posterior cervical triangle was diminished. The bilateral narrowing of the minor and major supraclavicular fossa minimizing space needed for potential surgical access. The branching patterns of the spinal accessory nerve and arterial patterns were normal.
Conclusions: The Knowledge of the presence of additional heads of sternocleidomastoideus muscle it might cause difficulties in subclavian or external jugular vein catheterization, and in surgical interventions involving structures lying under the sternocleidomastoideus muscle. These variations must be kept in mind while approaching the region to avoid complications as the classical anatomical landmarks might be misinterpreted and confuse.
from International Archives of Medicine