Novel Variants of the Sternal Muscle in an Adult and an Anencephalic Infant: Embryological Insights and Clinical Implications

Background The sternal muscle is a supernumerary variant of the thoracic muscles found in 3–8% of the population. When present, it can be unilateral or bilateral, which can produce confusions during surgeries and imagenological examinations. Methods We report the finding of the sternalis muscle in two human cadavers, one adult and one anencephalic infant. The muscles were dissected from the fixed bodies and their morphometry analysed. Results In the case of the adult, we observed two sternal muscles connected in the superior portion by a central tendon. In the case of the anencephalic infant, we found a bilateral sternal muscle, in which the bellies came from the contralateral pectoralis major muscles. The two sternalis muscle variants found here were impossible to categorise according to the current classifications. Conclusions The sternalis muscle displays variants that are still not classified, as observed in the case of the adult and the infant, in which its presence was correlated with anencephaly. We discuss about this muscular variation in the clinical, imagenological and surgical context and propose a developmental link with the occurrence of neural tube closure defects.

A Cadaveric study on Rectus Sternalis muscle and its clinical significance in Western part of Tamilnadu state (Kongunadu region)

Background: Rectus sternalis is considered as an unusual accessory or supernumerary muscle which appears either unilateral or bilateral in the anterior thoracic wall of human beings. It varies in length, breadth, thickness and incidence among different races and in both sexes. Regarding its origin and insertion still a clear conclusion has not been reached because some authors says it originates and ascends for insertion while some of them opines it originates and descends for insertion. Clinically, its presence also leads to false diagnosis such as Breast tumours, lipoma etc. Aim of the study: To find out the presence of Rectus sternalis muscle in the anterior chest wall during routine dissection. Materials and Methods: 37 well embalmed and preserved cadavers of both sexes which is used for routine dissection to Phase-I MBBS students were taken into condideration. The pectoral region on either side of sternum was dissected in layers and visualised for the presence of Rectus sternalis. Results: Among 37 cadavers dissected, Rectus sternalis was found in the pectoral region of a male and a female cadaver. In male it appeared bilateral, whereas in female it is unilateral. In both the cases it lie superficial to pectoralis major. Conclusion: The incidence of Rectus sternalis reported from our study was 5.4%. In the earlier days it lead to misdiagnosis and made great challenge to radiologists and surgeons, but now-a days with advancement in imaging techniques its presence can be detected clearly thus avoiding unnecessary expenditure and invitro techniques. Clinically it is also used as pedicle flap in breast reconstructive surgeries. KEY WORDS: Cadaver, Dissection, Pectoral region, Rectus sternalis, sternocleidomastoid.

A Comparative Analysis of Rare Sternalis Muscles: A Case Report

The sternalis muscle is a rare variant in the anterior chest wall located anterior to the vertical muscle. It was found in two cadavers during routine cadaveric dissection of 20 bodies. This finding provided an opportunity to perform a comparative anatomical analysis between a unilateral sternalis muscle on a female versus a bilateral sternalis muscle on a male. Having a better understanding of the anatomical variants can be extremely useful, precisely to avoid misdiagnosing tumors and to assist in landmark identification during surgeries.