Sirenomelia: An anatomical assessment and genetic sex determination of two cases.

The etiology of sirenomelia is currently unknown. Data are limited in comparing external and internal abnormalities using modern imaging technologies and molecular genetic analysis. The purpose of the current study was designed to compare external and internal anatomical defects in two cases of sirenomelia and Potter's sequence. Considered rare, Potter's sequence is a fetal disorder with characteristic features of bilateral renal agenesis, obstructive uropathy, atypical facial appearance, and limb malformations. The internal and external malformations of two term fetuses with sirenomelia and Potter's sequence were compared using assessment of external features, radiography and MRI on internal structures, and molecular genetic studies on sex determination. Data reveal that both fetuses were male and manifested with an overlapping but distinct spectrum of abnormalities. Principal differences were noted in the development of the ears, brain, urogenital system, lower limbs, pelvis, and vertebral column. Defects of the axial mesoderm are likely to underlie the abnormalities seen in both fetuses. The first one, which had only caudal defects, was found to have a spectrum of abnormalities most similar to those associated with more severe forms of the small pelvic outlet syndrome, although the structure and orientation of the sacrum and iliae were different from previously reported cases. The other had both caudal and cranial defects, and was most similar to those described in the axial mesodermal dysplasia syndrome. Defects associated with sirenomelia can be evaluated with standard gross anatomy examination, radiology, MRI, and modified PCR techniques to determine anatomical abnormalities and the sex of preserved specimens, respectively. Evidence indicated that sirenomelia could be developed via various etiologies.

Unilateral identification of a rare superficial brachioulnoradial artery contributing to the superficial palmar arch and brachial artery continuing as the interosseous artery: a case report.

The occurrence of variations in human arterial branching of the upper limb has been commonly reported in peer-reviewed literature. However, the variability of upper limb arterial patterns may be underappreciated in medical practice, which can result in clinical and surgical errors. Here we report a case of a rare, unilateral arterial variation of the left upper limb of a 76-year-old Caucasian male cadaver, discovered during a routine educational dissection. Observed characteristics of the variation include a high brachial artery bifurcation into a superficial brachioulnoradial artery and brachial artery continuing as the interosseous artery and then a bifurcation of the superficial brachioulnoradial artery into a superficial radial and a superficial ulnar artery, which eventually contribute to the formation of the superficial palmar arch. The anatomical characteristics, prevalence, embryological origin, and clinical significance of the variation are discussed.

Agenesis of the left hepatic lobe: a cadaveric case report.

Agenesis of the left hepatic lobe is a rare anomaly described as the absence of liver tissue on the left side of the gallbladder fossa or falciform ligament. Here we report a case of agenesis of the left hepatic lobe identified during educational dissection of an 84-year-old male formalin-fixed cadaver. The gross anatomical characteristics, embryological origin, and clinical relevance of this rare variation are described in this report.

A prevalence study of the atlantomastoid muscle.

PURPOSE: To contribute to the documentation and consideration of the prevalence of the atlantomastoid muscle in humans. METHODS: Sixty formalin-fixed cadaveric sides were dissected for the presence of the atlantomastoid muscle (2 sides per donor). Laterality, origin, insertion, and other observable characteristics of the variant were recorded along with donor sex for comparative analyses. RESULTS: The atlantomastoid muscle was observed in nine sides (15%): two left side only, three right side only, and 2 bilaterally. The origin of the muscle was consistent from the transverse process of the atlas, lateral to both the insertion of obliquus capitis inferior and the origin of obliquus capitis superior. In one instance, the origin of atlantomastoid was continuous with the most superior tendinous slip of levator scapulae. The insertion of each atlantomastoid variant was the mastoid process, however, the precise location was variable. CONCLUSION: The atlantomastoid muscle is a common accessory muscle of the suboccipital region; the muscle was present in 15% of the cadaveric sides dissected in this study. Despite the notable prevalence of atlantomastoid muscles, there is little current literature dedicated to its study. Here, we document the first new information related to the prevalence of atlantomastoid since 1964 and discuss the development and potential clinical significance of the muscle.

An unusual digital neural loop in a cadaver with bilateral high branching median nerves - case report.

Digital neural loops are present in the palms of most individuals. They can arise within the common palmar digital nerves (CPDNs) or proper palmar digital nerves (PPDNs). Typically, common palmar digital arteries (CPDAs) pass through digital neural loops, however there are reports of loops forming around the superficial palmar arch or proper palmar digital arteries (PPDAs). We describe an unusual digital neural loop that involved both a CPDN and a PPDN. To our knowledge, this is the first documented case of a digital neural loop of this type and therefore anatomists and surgeons may benefit from an awareness of its existence. A modification to a current classification system for digital neural loops is presented to include this novel loop. Interestingly, the cadaver documented in this report featured a high division of the median nerve in each forearm. On both sides, the ulnar component of the bifid median nerve followed an intramuscular course in which it pierced the flexor digitorum superficialis and then continued into the palm as the 3rd CPDN. A brief review of the literature is provided for both digital neural loops and the high division of the median nerve variant. Documented muscle associations noteworthy to the bifid median nerve are discussed. Developmental connections, if any, that exist between the unique digital neural loop and the high division of the median nerve are not speculated upon.

An online catalog of muscle variants: Student perceptions of a new opportunity for self-directed learning.

OBJECTIVE:: Muscle variants are common findings in dissection laboratories. These anomalous structures can be relevant in the diagnosis and management of certain conditions and therefore could be incorporated into anatomy curricula at chiropractic colleges. We aimed to create an online resource of muscle variants to facilitate student self-directed learning within this area of study. METHODS:: At the time of their discovery during routine educational dissection, muscle variants included in the catalog were documented and subsequent case reports written. All content created for this resource, including photographs and videos, was hosted on the institution's learning management system. Students enrolled in our doctor of chiropractic program were invited to view the catalog and encouraged to leave feedback by completing an online survey. RESULTS:: Student responses to Likert-style survey questions generally indicated high levels of satisfaction regarding the utility and features of the catalog. Open-ended and Likert-style survey questions were used to help guide the future directions of this developing resource. Concurrent anatomy students were not more likely to contribute to the catalog compared to students who had previously completed the university's anatomy course series ( p = .75, 2-tailed Fisher exact test). CONCLUSION:: An online supplement to graduate-level gross anatomy courses can aid in the instruction of muscle variants by providing an opportunity for student self-directed learning. This resource will be updated continually and will be expanded on to include neurovascular and visceral variants. Student participation will be sought in developing future content to be included in this catalog.

Bilateral Tensor Fasciae Suralis Muscles in a Cadaver with Unilateral Accessory Flexor Digitorum Longus Muscle.

Muscle variants are routinely encountered in the dissection laboratory and in clinical practice and therefore anatomists and clinicians need to be aware of their existence. Here we describe two different accessory muscles identified while performing educational dissection of a 51-year-old male cadaver. Tensor fasciae suralis, a rare muscle variant, was identified bilaterally and accessory flexor digitorum longus, a more common muscle variant, was present unilaterally. Tensor fasciae suralis and accessory flexor digitorum longus are clinically relevant muscle variants. To our knowledge, the coexistence of tensor fasciae suralis and accessory flexor digitorum longus in the same individual has not been reported in either cadaveric or imaging studies.