An unusual variation creates interest among anatomists, but is a cause of concern among clinicians when it mimics a pathology. The sternalis muscle is one such variant of the anterior chest wall located subcutaneously over the pectoralis major, ranging from a few short fibers to a well-formed muscle. We observed a bilateral case, which was accompanied by an atypical presentation on the left side where a huge, bulky sternalis muscle was associated with the absence of the sternal fibers of the pectoralis major. The fibers arose as a lateral strip from the upper two-thirds of the body of the sternum and costal cartilages 2 through 6 with the intervening fascia and aponeurosis of the external oblique. The right sternalis was strap-like and was placed vertically over the sternal fibers of the pectoralis major, arising from the underlying fascia and aponeurosis of the external oblique. The sternalis muscles, on each side, converged into an aponeurosis over the manubrium that was continuous with the sternal heads of the right and left sternocleidomastoid muscle, respectively. This rare anomaly has puzzled radiologists and surgeons in confirming diagnosis, missing it all together or mistaking it for a tumor on mammography or CT scan. These findings prompted us to review its topography, development, and application in relation to the anterior chest wall.
Adult ; Human ; Male ; Muscle Fibers/pathology ; Muscle, Skeletal/*abnormalities/pathology ; *Thorax

Morphological variations of the sternocleidomastoid (SCM) muscle assume relevance during attempted surgical interventions in the cervical region. The present study reports bipartite clavicular attachment of the SCM in the neck of an adult male cadaver during performance of a routine anatomy demonstration. The anomaly was unilaterally observed on the left side of the neck. The clavicular head of the muscle exhibited two bellies, one medial and one lateral. While the medial belly was fused with the sternal head, the lateral belly appeared to blend with the medial. Cranially, the SCM attached to the mastoid process and superior nuchal line. We have attempted to elucidate the embryological basis of the above muscular variant. Additionally, we discuss its clinical relevance, highlighting the utility of the SCM in various reconstructive procedures. We assert that detailed anatomical knowledge of such SCM variants is of utility not only to the gross anatomist, but also for neck and orthopaedic surgeons and anaesthetists. Moreover, radiologists require familiarity with such aberrations to decipher magnetic resonance imaging scans of the cervical region.
Adult ; Anatomists ; Cadaver ; Head ; Humans ; Magnetic Resonance Imaging ; Male ; Mastoid ; Muscles ; Neck ; Recognition (Psychology)