Palmaris profundus causing carpal tunnel syndrome: a rare anatomical variant
Tam Quinn MBBS BMedSci,1 Dean White MBBS FRACS2
Box Hill Hospital
Epworth Eastern Hospital
Name: Tam Quinn
Address: Department of Plastic and Reconstructive Surgery
Box Hill Hospital
8 Arnold Street
Box Hill Victoria 3128
Phone: +61 (0) 3 9895 3353
Citation: Quinn T, White D. Palmaris profundus causing carpal tunnel syndrome: a rare anatomical variant. Aust J Plast Surg. 2019;2(2):71–73. https://doi.org/ 10.34239/ajops.v2n2.105
Accepted for publication: 13 February 2019
Copyright © 2019. Authors retain their copyright in the article. This is an open access article distributed under the Creative Commons Attribution Licence which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.
Palmaris profundus is an anatomical variation, usually found incidentally during carpal tunnel release. Its location deep to the transverse carpal ligament can cause compression of the median nerve. This unusual cause of carpal tunnel syndrome can persist, despite adequate release, and may require resection of the palmaris profundus.
Keywords: carpal tunnel syndrome, anatomical variation, median nerve, hand, wrist
A 79-year-old, right-handed man presented with a 12-month history of bilateral paraesthesia and pain in both hands. He experienced pain particularly when driving and at night, when it woke him from sleep. The left hand was more symptomatic than the right. On examination he had paraesthesia in the median nerve sensory distribution and Phalen’s test was positive. His past history was significant for ischaemic heart disease, prostate cancer and renal impairment.
A nerve conduction study was requested by his general practitioner and this showed decreased sensory latency of the median nerve bilaterally, in keeping with moderate to severe carpal tunnel syndrome.
A right open carpal tunnel release was performed The skin incision and transverse carpal ligament (TCL) were divided in the usual fashion under direct vision. The median nerve was identified and pro-tected. Unusually, an additional tendinous structure was identified deep to the TCL (Figure 1). This structure was radial and volar to the median nerve and appeared to be contained within the same fascial sheath. It then dispersed and became continuous with the deep aspect of the palmar aponeurosis of the hand. Traction on this tendon did not cause either excursion or relaxation of the palmaris longus (PL) tendon and was thus determined to be a separate structure. A more proximal dissection was not clini-cally indicated and thus not performed.
His left carpal tunnel release was performed some months prior to the right by the same surgeon. He was noted to have normal anatomy on the left. Postoperatively, his carpal tunnel symptoms resolved completely.
Fig 1. Arrow indicating tendinous structure located deep to the transverse carpal ligament (TCL)
The palmaris profundus (PP) tendon was described by Frohse and Fränkel in 1908.1 . While numerous case reports and anatomical dissections have been described, there has been no comprehensive ac-count of its incidence. Reimann and colleagues found one cadaver with bilateral PP in a dissection of 1600 extremities.2 Although this suggests an incidence of 1 in 800, given the relative paucity of reports, it would appear that it is even less common.
A review of the literature found several case reports, of which approximately a quarter were anatomical studies. As was the case with our patient, most cases of PP were found incidentally during carpal tun-nel release. Four cases of bilateral PP were reported.2-4 Of the remainder, the majority were found to be on the right side. With the data available, this would seem to indicate that PP has a right side prepon-derance of 6:1.
Three subtypes of PP were described by Pirola and colleagues based on its origin:5 type I arising from the radius, type II arising from the flexor digitorum superficialis fascia and type III arising from the ulna. Other origins have been described, including the common flexor origin, the epimysium of the flexor pollicis longus and the PL. In every case where the insertion was reported, the PP attached into the deep aspect of the palmar aponeurosis. PL was noted to be absent in some cases.4-6
Palmaris profundus has been described as ‘musculus comitans nervi mediani’ due to the fact that the tendon of PP ap-peared to be within the same fascial sheath as the median nerve.7 While almost always volar to the me-dian nerve, PP was usually found on the radial side of the nerve, though in one case it was reported as crossing the nerve from the radial to the ulnar side.6
In two cases, PP was observed and left in situ at the primary operation.8,9 When symptoms did not re-solve or recurred, the patients underwent a revision where PP was excised. Both authors reported that each patient’s symptoms resolved following resection of the PP tendon. It is well known that any in-crease in the volume of the carpal tunnel—be it synovitis, oedema or aberrant structures—causes car-pal tunnel syndrome. McClelland and colleagues found that PP impeded endoscopic carpal tunnel release, requiring conversion to an open procedure.10
Palmaris profundus is a rare anatomical variation that can cause carpal tunnel syndrome. It is usually unilateral with a right side preponderance. The origin of the muscle can be variable while its insertion is reliably the deep aspect of the palmar aponeurosis. It is usually found incidentally at the time of carpal tunnel release and may be a cause of failed endoscopic carpal tunnel release. Excision of the aberrant tendon can lead to resolution of the symptoms, whereas leaving it may cause to the patient to require revision surgery.
The authors have no financial or commercial conflicts of interest to disclose.
- Frohse F, Fränkel M Muskeln des Menschlichen Armes. In: Handbuch der Anatomie des Menschen, 1908. pp 115–18.
- Reimann AF, Daseler EH, Anson BJ, Beaton LE. The palmaris longus muscle and tendon. A study of 1600 extremities. Anat Rec. 1944; 89(4):495–505. https://doi.org/10.1002/ar.1090890408
- Floyd T, Burger RS, Sciaroni CA. Bilateral palmaris profundus causing bilateral carpal tunnel syndrome. J Hand Surg. 1990;15(2):364–66. https://doi.org/10.1016/0363-5023(90)90125-B
- Bayliss J, Cope JM. A problematic variation of the palmaris profundus. Int J Anat Var. 2016;9:73–75.
- Pirola E, Hervert-Blouin MN, Amador N, Amrami KK, Spinner RJ. Palmaris profundus: one name, several subtypes, and a shared potential for nerve compression. Clin Anat. 2009;22(6):642–48. https://doi.org/10.1002/ca.20848 PMid:19644968
- Elbardouni A, Elyaacoubi M. Carpal tunnel syndrome caused by a palmaris profundus muscle. J Orthop. 2011;8(3):e4.
- Sahinoglu K, Cassell MD, Miyauchi R, Bergman RA. Musculus comitans nervi mediani (M. palmaris profundus). Ann Anat. 1994;176(3):229–32. https://doi.org/10.1016/S0940-9602(11)80483-8
- Lange H. Carpal tunnel syndrome caused by the palmaris profundus muscle: case report. Scand J Plast Recon. 1999;33(2):251–52. https://doi.org/10.1080/02844319950159532 PMid:10450585
- Christos L, Konstatinos N, Evagelos P. Revision of carpal tunnel release due to palmaris longus profundus. Case Rep Orthop. 2015;2015. Article ID 616051: 4 pages. https://doi.org/10.1155/2015/616051 PMid:26075127 PMCid:PMC4446466
- McClelland WB, Means KR. Palmaris profundus tendon prohibiting endoscopic carpal tunnel release: case report. J Hand Surg. 2012;37(4):695–98. https://doi.org/10.1016/j.jhsa.2012.01.006 PMid:22397841