European Journal of Molecular & Clinical Medicine

Abstract

Sternocleidooccipitomastoid (SCOM) muscles of16 cadavers were dissected over a
period of eight years to study possible clinical significance. It was observed that fifteen
cadavers had the classical attachment and innervation as described in the standard
textbooks of anatomy. But SCOM in one male cadaver revealed bilateral anomalous
attachments. Both sides SCOM had supernumerary clavicular heads whereas the
sternal heads (LSH, RSH) had the usual attachments. On the right side there were three
clavicular heads (RCH1, RCH2, RCH3) out of which medial two heads (RCH1 &
RCH2) joined with RSH at the level of cricoid cartilage to get inserted on the mastoid
process extending up to the superior nuchal line. The RCH3 remained separate up to
the level of greater cornu of hyoid bone, where it gives a slip to the main belly before
inserting on the superior nuchal line, as two slips. On the left side also, there were three
clavicular heads (LCH1, LCH2, LCH3) which merged with LSH at the level of thyroid
prominence before attaching on the mastoid process and superior nuchal line. At the
level of greater cornu of hyoid bone, another supernumerary slip arising from deep
aspect of left main belly was noticed which inserted on the medial aspect of superior
nuchal line and external occipital protuberance. The left SCOM had an additional twig
from ansa cervicalis apart from accessory nerve whereas the right SCOM had the usual
nerve supply. During ablative and reconstructive surgeries of the face and oral cavity
surgeons should remember the variation in clavicular head and additional nerve supply
of SCOM.