Supernumerary heads of sternocleidomastoid muscle and its clinical significance: A cadaveric study

Background: Sternocleidomastoid muscle is main muscle of neck region which is attached proximally to mastoid process and lateral half of the superior nuchal line and distally to the sternum and clavicle. It is related to numerous important neurovascular structures. Avariation in its anatomy is clinically important especially for neck surgeries and catheterization of internal jugular vein. Aim and Objectives: To establish the incidence, number and variations of supernumerary head of ternocleidomastoid muscle in cadavers. Material and Methods: We studied the variations in the heads of the ternocleidomastoid muscle in the 84 cadavers (n=168, Right= 84; Left=84) which were used for undergraduate teaching in our college. Muscle was exposed by doing meticulous dissection. Proximal and distal attachments were carefully cleaned and number of supernumerary heads with their origin and insertion were noted. Results: Present study observed supernumerary heads of sternocleidomastoid muscle in 32.73% cadavers. In majority of cases the supernumerary heads (which may be 2, 3, 4) was found to be arising from superior surface of medial 2/3 clavicle. Conclusion: Detailed knowledge of this variation is crucial for head and neck surgeons, radiologist, anesthetists and clinicians dealing with this region