Reversed palmaris longus muscle: a report of two cases

Reversed Palmaris Longus: A Rare Anatomical Phenomenon Discovered

The palmaris longus (PL) muscle is considered by many to be a vestigial muscle due to it having little to no functional significance on the upper limb. This, however, made it highly valuable in surgical procedures, especially as a graft in plastic and reconstructive cases. Variations in the muscle's morphology were discussed in the literature, but some are more rare than others. Those variations may have clinical implications on different pathologies such as Guyon's syndrome or Carpal tunnel syndrome based on the nerves and vessels surrounding it, and thus demand a proper understanding of the variation's anatomy. Here, we report a case of one of the rarer variations, a unilaterally reversed palmaris longus muscle in the left forearm of a 55-year-old male cadaver, discovered in a routine teaching session. Throughout the case, we will discuss the normal anatomy, the variation, and the clinical implications this variation may have.

A Unique Three-Tendinous Head Reverse Palmaris Longus: A Case Report

The Palmaris longus (PL) is a fusiform muscle that is part of the superficial flexors on the anterior compartment of the forearm. It originates from the common flexor tendon at the medial epicondyle of the humerus and inserts at the flexor retinaculum. The Palmaris longus has been reported to present in multiple variations. Some of these variations include agenesis, reversal, and multiple bellies of the muscle. The Palmaris longus is clinically significant as a landmark for carpal tunnel syndrome steroid injection, hand anesthesia, and used as a surgical graft. Medical students at the University of Medicine and Health Sciences, St. Kitts and Nevis, encountered a unique variation of the PL during cadaver dissection. This article explores the exclusiveness of a three-tendinous head reverse PL and what makes it unique compared to similar findings in other reports.

Median Nerve Compression in the Distal Forearm by a Reversed Palmaris Longus Muscle in a Pediatric Patient: A Case Report

CASE

A 9-year-old girl presented with a 1-year history of volar wrist and hand pain accompanied by hand paresthesia. Magnetic resonance imaging described a superficial muscle belly in the distal forearm, compatible with a reversed palmaris longus (RPL). An initial trial of conservative treatment was unsuccessful, so the median nerve was explored in the distal forearm, with the release of the flexor retinaculum and resection of the RPL muscle belly. One year after surgery, the child had no symptoms.

CONCLUSION

To the best of our knowledge, there are only 12 reported cases of RPL, and none at such a young age or symptomatic in daily routine activities such as the case presented.

Persistent Median Artery With a Reversed Palmaris Longus and Volar Ganglion

Being aware of the variants of upper extremity anatomy is of utmost importance to a surgeon. This case report describes a patient who presented with two separate wrist masses. Operative exploration was planned, and both the structures were investigated. The distal mass was identified as a volar wrist ganglion, and the more proximal mass was identified as the muscle belly of a reversed palmaris longus muscle. Incidentally, it was noted that the patient had a patent, persistent median artery. Although many variants of the palmaris longus have been described, as have been cases of a persistent median artery, both have not been previously documented in a single patient. Although this is rare, having knowledge of possible anatomic variations is valuable for any surgeon operating on the upper extremity.

Reversed Palmaris Longus Muscle With Median Nerve Compression Symptoms: A Case Report and Review of the Literature

BACKGROUND

The palmaris longus (PL) is one of the most anatomically variable muscles in the body. Although these variations are often asymptomatic, symptoms related to nerve compression can sometimes be encountered. If treatment is indicated, correct diagnosis is important for successful management. In cases of upper extremity nerve compression, variations of the PL should be included in the differential diagnosis. We report a case of reversed PL (RPL) with symptoms of median nerve compression and review the literature, emphasizing the rare and challenging character of these lesions.

METHODS

The literature review was performed using Google Scholar and PubMed databases. Keywords were "reversed palmaris longus," "reversed palmaris longus median nerve compression," "anomolous palmaris longus muscle," and "symptomatic palmaris longus." Only clinical RPL muscle cases with at least one of the symptoms of paresthesia and pain in the median nerve sensory area or swelling on the wrist were included.

RESULTS

In the literature review, 21 publications including 30 patients, matched the search criteria between 1973 and 2018 and were evaluated.

CONCLUSION

In carpal tunnel syndrome, in cases with atypical presentation, RPL should be considered in the differential diagnosis.

Bilateral reversed palmaris longus muscle: a case report and systematic literature review

PURPOSE

We present a case of a bilateral reversed palmaris longus muscle and a systematic review of the literature on this anatomical variation.

METHODS

Routine dissection of a 90-year-old male cadaver revealed a rare bilateral reversed palmaris longus. This was documented photographically, and length and relation to anatomical landmarks were recorded. This finding stimulated a systematic review of the literature on the reversed palmaris longus variation, from which measurements were collated and statistical analysis performed to determine the prevalence, average length, relationship to side and sex, and to discuss its clinical and evolutionary implications.

RESULTS

The average length of the muscle belly and tendon of reversed palmaris longus was 135 mm and 126 mm, respectively. Statistical analysis revealed no disparity in presentation due to sex and side; however, bilateral reversed palmaris longus has only been reported in males. A high proportion (70.8%) of reversed palmaris longus were discovered in the right upper limb compared to the left.

CONCLUSION

Variations in palmaris longus are purported to be as a result of phylogenetic regression. Clinically, patients with this variant may present with pain or swelling of the distal forearm, often as a result of intense physical exertion related to occupation or sport. Clinicians should be aware of this muscle variant as its presence could lead to confusion during tendon allograft harvesting procedures in reconstructive and tendon grafting surgery.