Hypertrophied reverse palmaris longus muscle: a rare cause of carpal tunnel syndrome
Keywords:Carpal tunnel syndrome, Rare, Reverse palmaris longus
Carpal tunnel syndrome (CTS) is usually secondary to compression or irritation of the median nerve in the fibro-osseous canal formed by the flexor retinaculum (transverse carpal ligament) and the carpal bones. The prevalence of CTS in the general population is about 7 to 19%. Several causes both local and systemic have been described, but CTS due to aberrant musculature are rare. Here we report a case of a middle-aged female with paresthesia of the hand and a positive Phalen’s test with nerve conduction study of the median nerve showing sensorimotor neuropathy. The patient underwent surgery for open CTS release where we found a hypertrophied reverse palmaris longus muscle attached to the palmar aponeurosis which was excised along with its proximal tendon. On post-operative follow up all the symptoms of CTS were completely resolved. Muscle abnormalities concern three muscles: the palmaris longus, the flexor digitorum superficialis of index, and the lumbricals. These muscles can be hypertrophied, bifid, duplicated, digastric, inverted or have an abnormal insertion, thus creating a mechanical restriction of the carpal tunnel. Surgical resection of abnormal muscle provides excellent functional recovery.
Padua L, Coraci D, Erra C, Pazzaglia C, Paolasso I, Loreti C, et al. Carpal tunnel syndrome: clinical features, diagnosis, and management. Lancet Neurol. 2016;15(12):1273-84.
von Schroeder HP, Botte MJ. Carpal tunnel syndrome. Hand Clin. 1996;12(4):643-55.
Newington L, Ferry S, Pritchard T, Keenan J, Croft P, Silman AJ. Estimating the prevalence of delayed median nerve conduction in the general population. Br J Rheumatol. 1998;37(6):630-5.
Michelsen H, Posner MA. Medical history of carpal tunnel syndrome. Hand Clin. 2002;18(2):257-68.
Palmer KT. Carpal tunnel syndrome: the role of occupational factors. Best Pract Res Clin Rheumatol. 2011 ;25(1):15-29.
Samson P. Le syndrome du canal carpien. Chir Main. déc 2004;23(Suppl 1):S165- 77.
Lozano-Calderón S, Anthony S, Ring D. The quality and strength of evidence for etiology: example of carpal tunnel syndrome. J Hand Surg. 2008;33(4):525-38.
Giersiepen K, Spallek M. Carpal tunnel syndrome as an occupational disease. Dtsch Arzteblatt Int. 2011;108(14):238-42.
Niver GE, Ilyas AM. Carpal tunnel syndrome after distal radius fracture. Orthop Clin North Am. 2012;43(4):521-7.
Suginaka H, Hara A, Kudo T. An unusual case of common digital nerve compression caused by a lipoma arising from the flexor tenosynovium. Hand Surg. 2013;18(03):435-7.
Saraf SK, Tuli SM. Anomalous m. palmaris longus producing carpal tunnel-like syndrome. Arch Orthop Trauma Surg. 1991;110(3):173-4.
Depuydt KH, Schuurman AH, Kon M. Reversed palmaris longus muscle causing effort-related median nerve compression. J Hand Surg Edinb Scotl. 1998;23(1):117-9.
Smith RJ. Anomalous muscle belly of the flexor digitorum superficialis causing carpal-tunnel syndrome. Report of a case. J Bone Joint Surg Am. 1971;53(6):1215-6.
Eriksen J. A case of carpal tunnel syndrome on the basis of an abnormally long lumbrical muscle. Acta Orthop Scand. 1973;44(3):275-7.
Weissenborn W, Sabri W. Muscle anomalies as a cause of carpal tunnel syndrome. Handchir Mikrochir Plast Chir. 1987;19(3):153-5.
Pardal-Fernandez JM. Carpal tunnel syndrome. The contribution of ultrasonography. Rev Neurol. 2014;59(10):459-69.
Zeiss J, Jakab E. MR demonstration of an anomalous muscle in a patient with coexistent carpal and ulnar tunnel syndrome. Case report and literature summary. Clin Imaging. 1995;19(2):102-5.
Barkáts N. Hypertrophy of palmaris longus muscle, a rare anatomic aberration. Folia Morphol. 2015;74:262–4.
Ioannis D, Anastasios K, Konstantinos N, Lazaros K, Georgios N. Palmaris longus muscle’s prevalence in different nations and interesting anatomical variations: review of the literature. J Clin Med Res. 2015;7:825–30.
Mathew AJ, Sukumaran TT, Joseph S. Versatile but temperamental: a morphological study of palmaris longus in the cadaver. J Clin Diagn Res JCDR. 2015;9:AC01-A3.
Olewnik Ł, Wysiadecki G, Polguj M, Podgórski M, Jezierski H, Topol M. Anatomical variations of the palmaris longus muscle including its relation to the median nerve—a proposal for a new classification. BMC Musculoskelet Disord. 2017;18:539.
Bergman RA, Afifi AK, Miyauchi R, Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles; 2015.
Albay SA, Astamoni YAK, Akalli BÜŞRAS, Unali ST. Anatomy and variations of palmaris longus in fetuses. Rom J Morphol Embryol. 2013;54:85-9.
Bernardes A, Melo C, Pinheiro S. A combined variation of Palmaris longus and Flexor digitorum superficialis: case report and review of literature. Morphologie. 2016;100:245-9.
Iqbal S, Iqbal R, Iqbal F. A bitendinous palmaris longus: aberrant insertions and its clinical impact—a case report. J Clin Diagn Res. 2015;9:AD03–A5.
Kumar N, Patil J, Swamy RS, Shetty SD, Abhinitha P, Rao MK, et al. Presence of multiple tendinous insertions of palmaris longus: a unique variation of a retrogressive muscle. Ethiop J Health Sci. 2014;24:175–8.
Marpalli S, Bhat ALS, Gadahad MRK. A case of reverse palmaris longus muscle—an additional muscle in the anterior compartment of the forearm. J Clin Diagn Res. 2016;10:AD03-A4.
Murabit A, Gnarra M, Mohamed A. Reversed palmaris longus muscle: anatomical variant—case report and literature review. Can J Plast Surg. 2013;21:55–6.
Sarkar M, Mukherjee P, Roy H, Sengupta SK, Sarkar AN. An unusual branch of celiac trunk feeding suprarenal gland—a case report. J Clin Diagn Res. 2014;8:AD03-4.