Anatomical Variation of the Splenius Capitis Muscle

Background: This study involves the post-mortem dissection of a unique orientation of muscle fibers branching from the splenius capitis. The splenius capitis muscle is part of the superficial back, which functions bilaterally to extend the head and unilaterally to flex and rotate to the ipsilateral side. The splenius capitis originates on the spinous processes in the cervical region and inserts into the mastoid process of the temporal bone and lateral one-third of the superior nuchal line of the occiput. Case Information: The muscle variant arose from the medial border of the along the superior nuchal line, traveled lateral to the primary muscle body for 6.1 cm, and inserted into the fascial layer below the mastoid process. Careful attention was paid to accompanying variations in neurovasculature and musculoskeletal function during the dissection. However, no additional structures were found to be travelling along the novel fibers. Due to the small size of the fiber and the insertion into the superficial fascia, no change in function was proposed to be caused by the variant. Conclusions: Due to the variability in musculoskeletal formation in the muscles of the back, care must be taken during surgical procedures in which anatomical variants could alter or impede surgical technique. In addition, variations in musculature of the back must be considered in patients undergoing long-term tension headaches. Careful dissections should be performed in the future to identify anatomical variations.