Anomalous Flexor Digitorum Superficialis Muscle Belly Associated with Carpal Tunnel Syndrome

Anomalous muscle bellies in the forearm generally are asymptomatic and appreciated an academic sense during cadaveric dissections. Few prior anatomic variations have been described with symptoms, associated even more rarely carpal tunnel syndrome (CTS). We discuss evaluation management of a case CTS belly flexor digitorum superficialis to index within tunnel. Carpal (CTS) is most frequent compressive estimated prevalence 4% 5%.1Chammas M. Boretto J. Burmann L.M. et al.Carpal - part I (anatomy, physiology, etiology diagnosis).Rev Bras Ortop. 2014; 49: 429-436Crossref PubMed Scopus (80) Google Scholar can be thought as 3 pathogenetic branches: increase structures occupying volume, reduction systemic disease. Aberrant musculature leading increased content volume for CTS, at roughly 1.3% patients presenting CTS.2Lindley S.G. Kleinert J.M. Prevalence encountered elective release.J Hand Surg Am. 2003; 28: 849-855Abstract Full Text PDF (98) While not required diagnosis, electromyography and/or neuromuscular ultrasound may aid diagnosis or surgical planning. Open release has preferred treatment excellent success rates historically. A 27-year-old right hand dominant male presented orthopedic clinic after feeling “pop” volar aspect his wrist followed by significant radially-based pain months before evaluation. He noted paresthesias stiffness gripping. In clinic, he had decreased sensation long fingers positive Tinel’s Durkan’s compression tests. The patient magnetic resonance image, ordered referring physician, that did note abnormality. later underwent study (NMUS), which extrinsic lesion contiguous (FDS) tendon (Fig. 1). Under monitored anesthesia care, open was performed. median nerve compressed deviated ulnarly anomalous FDS 2). To safely navigate address aberrant anatomy, approximately 4 cm proximal extension incision thorough neurolysis tenosynovectomy performed, without excision belly. Postoperatively, improvement sensory findings 2 week follow-up. Written informed consent obtained from publication this report accompanying images. Vichare3Vichare N.A. superficialis. Report case.J Bone Joint Br. 1970; 52: 757-759Crossref first symptomatic finger who aching palmar mass, but no 1970. reported association Smith 1971.4Smith R.J. causing carpal-tunnel syndrome. 1971; 53: 1215-1216Crossref (69) case, classic symptoms intraoperatively observed arising compressing against transverse ligament (TCL).4Smith Since then, 5 other reports caused described.5Ametewee K. Harris A. Samuel Acute produced indicis muscle.J 1985; 10: 83-84Crossref (28) Scholar, 6Gleason T.F. Abraham E. Bilateral unilateral duplication muscle: report.Hand. 1982; 14: 48-50Crossref (4) 7Hutton P. Kernohan Birch R. An syndrome.Hand. 1981; 13: 85-86Crossref (24) 8Javed S. Woodruff secondary accessory belly: review literature.Hand (N Y). 9: 554-555Crossref (18) 9Schön Kraus Boller O. al.Anomalous syndrome: report.Neurosurgery. 1992; 31: 969-971Crossref (32) Ametewee al5Ametewee Javed Woodruff8Javed only cases retention TCL division, our now third successful excision. Five 7 anatomy their 20s, uncommon demographic development CTS. Historically, conduction studies were gold standard further workup CTS; however, recently shown validated tool comparable sensitivity specificity.10Zaki H.A. Shaban Salem W. al.A comparative analysis between electromyographic diagnosing (CTS): systematic meta-analysis.Cureus. 2022; 14e30476Google NMUS unique use identifying underlying pathology