An anatomic investigation of the serratus posterior superior and serratus posterior inferior muscles

Consideration of the thoracic phenotype of cerebro-costo-mandibular syndrome

Cerebro-costo-mandibular syndrome (CCMS) is a congenital condition with skeletal and orofacial abnormalities that often results in respiratory distress in neonates. The three main phenotypes in the thorax are posterior rib gaps, abnormal costovertebral articulation and absent ribs. Although the condition can be lethal, accurate diagnosis, and subsequent management help improve the survival rate. Mutations in the causative gene SNRPB have been identified, however, the mechanism whereby the skeletal phenotypes affect respiratory function is not well-studied due to the multiple skeletal phenotypes, lack of anatomy-based studies into the condition and rarity of CCMS cases. This review aims to clarify the extent to which the three main skeletal phenotypes in the thorax contribute to respiratory distress in neonates with CCMS. Despite the posterior rib gaps being unique to this condition and visually striking on radiographic images, anatomical consideration, and meta-analyses suggested that they might not be the significant factor in causing respiratory distress in neonates. Rather, the increase in chest wall compliance due to the rib gaps and the decrease in compliance at the costovertebral complex was considered to result in an equilibrium, minimizing the impact of these abnormalities. The absence of floating ribs is likely insignificant as seen in the general population; however, a further absence of ribs or vestigial rib formation is associated with respiratory distress and increased lethality. Based on these, we propose to evaluate the number of absent or vestigial ribs as a priority indicator to develop a personalized treatment plan based on the phenotypes exhibited.

The unilateral muscular slip of the two-bellied Serratus Posterior Inferior muscle: a case report and a review of literature

PURPOSE

The two-bellied serratus posterior inferior (SPI) muscle with a muscular slip is a rare variation of the back region, which can cause significant discomfort to patients. Patients typically present with symptoms of chronic pain syndrome, radiating back pain, myofascial pain, or lower back pain. This report describes a case of a female cadaver with a two-headed SPI muscle and a right muscular slip, along with a literature review.

METHODS

A case of an unusual back muscle was observed in a female cadaver during advanced cadaver dissection of the back region. The SPI muscle was found deep to the latissimus dorsi muscle and superficial to the erector spinae and thoracolumbar fascia. Its oblique arrangement and insertion onto the 8th-11th costae were consistent with its known anatomy, but the presence of two separate fibrotendinous heads and an uncommon variance between the erector spinae and latissimus dorsi muscles was observed.

RESULTS

The SPI muscle fibers were found to be attached to the 8th costa on the right side and displayed two heads on both sides. In our study, the presence of muscular and tendinous digitations towards the twelfth rib was not detected, which aligns with the characteristics described for types D and E. However, we observed a separation between the digitations. Therefore, it is appropriate to classify our findings as type E according to the established categorization. Simultaneously, an anomalous muscular slip, which did not conform to any of the aforementioned classifications, was identified as extending towards the 8th rib.

CONCLUSION

The underlying cause of unilateral oblique muscular fiber extension is thought to result from aberrant muscle migration during embryonic development or alterations in tendon attachment sites. Differential diagnosis of unidentified lower back pain should consider the various types and alterations of the SPI muscle.

An Unusual Back Muscle Identified Bilaterally: Case Report

Most muscular structures in the human body are named based on their function, origin/insertion, or shape. During routine dissection of the back, an unusual muscle was found deep to the rhomboid muscles. The details of this case and a review of the extant literature are provided.