Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery

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An Unusual Cause of Carpal Tunnel Syndrome: Case Report Spyridon Sgouros & Mohammed Salman Ali To cite this article: Spyridon Sgouros & Mohammed Salman Ali (1992) An Unusual Cause of Carpal Tunnel Syndrome: Case Report, Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, 26:3, 335-337, DOI: 10.3109/02844319209015281 To link to this article:

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$cand .J Plast Reconstr Hand Surg 26: 335-337, 1992


Spyridon Sgouros and Mohammed Salman Ali From the Department of Orthopaedic Surgery, Russells Hall Hospital, Dudley, West Midlands, D YI 2HQ, United Kingdom

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(Submitted for publication December 2, 1991)

Abstract. A 38 year old woman with carpal tunnel syndrome of the right hand was treated with operative decompression, initially successfully. Subsequently, she developed a compartment syndrome after an injury. On re-exploration, an accessory palmaris longus muscle was encasing the median nerve at the distal forearm and passing through the flexor sheath. underneath the flexor retinaculum, inserted into the deep palmar fascia.

morning developed severe pain in the fingers and forearm. There was pronounced tenderness and swelling at the wrist and the distal forearm. Passive finger extension was painful, the radial pulse was palpable, and she had numbness and paraesthesiae in the median nerve distribution. A clinical diagnosis of compartment syndrome was made and the wrist was re-explored through the old incision, which was extended proximally. An accessory palmaris longus muscle was encasing the median nerve at the level of

Abnormal muscles of the forearm and hand are a well documented cause of carpal tunnel syndrome. We report an unusual case of an accessory palmaris longus muscle. Its implications on treatment are discussed. CASE REPORT A 38-year-old female nurse presented with a six month history of paraesthesiae in the distribution of the median nerve of the right hand. She reported several episodes of waking up in the early hours of the morning with pain over the hand, which would subside following light exercise. Her grip became progressively less powerful, and she developed altered sensation on the lateral three digits of the affected hand. She was overweight and hypothyroid, for which she was being treated with thyroxine. The conservative treatment was unsuccessful and therefore she was referred to the hospital. Examination on 9 October 1990 showed some wasting of the thenar eminence of the right hand. The abductor pollicis brevis muscle was slightly weak. There was no sensory deficit but forced palmar flexion of the wrist induced parasthesiae in the fingers innervated by the median nerve, confirming the diagnosis of carpal tunnel syndrome. This was decompressed on 7 November 1990, and the median nerve was released. N o other abnormality was found. She had immediate relief of her symptoms. Despite the recommendations, she returned to her nursing duties on the fifteenth postoperative day. On the nineteenth day she sustained a minor injury to the operated lower forearm and wrist, and the following

Fig. 1. Diagram of the anatomical relations of the abnormal muscle. Scand J Piust Reconstr Hund Surg 26


S. Sgouros and M. Sdnian Ali

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Fig. 2. The accessory palmaris longus muscle after excision.

the distal forearm, and there was oedema and secondary haemorrhage in the accessory muscle sheath around the median nerve. The muscle originated from the common flexor origin. Its tendon was traced into the hand under the flexor retinaculum and was inserted just distal to it into the third slip of the central part of the palmar aponeurosis ( 18) (Fig. I). The accessory muscle was dissected clear of the median nerve before excision (Fig. 2). and the deep fascia of the forearm was divided. The wound was closed by second intention five days later. After the second operation there was immediate improvement of the function of the hand, and a month later she had regained normal grip strength. On review at three months the function, sensation, and motor power of the hand were normal, and the patient found the scar aesthetically acceptable.

the hand. O n counting the tendons, it was obvious that there was one extra tendon within the flexor sheath. We could find no published reports of any similar cases, though one has been described after anatomical dissection ( 1 I ) . Unlike our case though, the muscle originated from the middle third of the radius, and the tendon was lateral t o the median nerve. Although we would not advocate routine exploration of the flexor sheath for fear of adhesions, we nevertheless suggest that it should be considered as an option when further re-exploration is needed on patients who have already had carpal tunnel decompression.



The presence of abnormal muscles in the forearm and wrist is a well documented cause of carpal tunnel syndrome. Cases of high origin of lumbrical muscles (4, 6, 8, 17), abnormal flexor digitorum superficialis ( 13, 15, 16) and flexor superficialis indicis (1, 12) have been reported, as have bitendinous palmaris longus with the median nerve emerging between the two tendons (n = I ) (S), hypertrophic palmaris longus (n = 2) (2, 7) and atypical distal belly of palmaris longus that looked like a tumour ( n = 1) (10). We found three reports of accessory palmaris muscles (3, 9, 14), but in all cases the tendon was superficial to the flexor retinaculum and therefore immediately identified at the first operation. At the second operation in this case wide exploration was necessary because of the compartment syndrome. It was only then that the abnormal muscle was seen in the forearm. The flexor sheath was opened and its tendon was seen passing underneath the remnants of the flexor retinaculum into Scimcl J Plust Rrconstr Hund Surg 26

I . Ametewee K, Harris A, Samuel M. Acute carpal tunnel syndrome produced by anomalous flexor digitorum superficialis indicis muscle. J Hand Surg (Br) 1985; l0:l: 83-84. 2. Ashby B. Hypertrophy of the palmaris longus muscle. J Bone Joint Surg 1964;468: 230-232. 3. Bang H, Kojima T. Tsuchida Y. A case of carpal tunnel syndrome caused by accessory palmaris longus muscle. Handchir Mikrochir Plast Chir 1988; 20:3: 141 -143. 4. Butler B. Bigley E. Aberrant index (first) lumbrical tendinous origin associated with carpal tunnel syndrome. J Bone Joint Surg 1971; 53A: 160- 162. 5. Dorin D,Mann R. Carpal tunnel syndrome associated with abnormal palmaris longus muscle. South Med J 1984; 77~9:1210-1211. 6. Eriksen J. A case of carpal tunnel syndrome on the basis of an abnormally long lumbrical muscle. Acta Orthop Scand 1973;M3:275-277. 7. Goulding R. Gross hypertrophy of the palmaris longus muscle simulating a tumour of the forearm. Br J Surg 1948; 36: 213-214. 8. Jabaley M. Personal observations o n the role of the lumbrical muscles in carpal tunnel syndrome. J Hand Surg ( A m ) 1978; 3:l:82-84.

An unusual cause of carpal tunnel syndrome

14. Spinner M, Freundlich B. An important variation of the palmaris longus. Bull Hosp Jt Dis 1967; 28: 126130. 15. Still J, Kleinhert H. Anomalous muscles and nerve entrapment in the wrist and hand. Plast Reconstr Surg 1973; 52: 394-400. 16. Tanzer R. The carpal tunnel syndrome. A clinical and anatomical study. J Bone Joint Surg (Am) 1959; 41A: 626-634. 17. Touborg-Jensen A. Carpal tunnel syndrome caused by an abnormal distribution of the lumbrical muscles. Scand J Plast Reconstr Surg 1970; 4: 72-74. 18. William P, Warwick R. Gray's Anatomy, 37th ed. Edinburgh: Churchill Livingstone, 1989: 627.

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9. King T, O'Rahilly R. Muscle palmaris accessories and duplication of muscle palmaris longus. Acta Anat 1950; 10: 327-331. 10. Mayer E. Abnormality of the palmaris longus muscle. Handchirurgie 1981; 13: 263-265. I I . Reimann A, Dase Ler E. Anson B. Beaton L. The palmaris longus muscle and tendon. A study of 1600 extremities. Anat Rec 1944; 89: 495-505. 12. Rudigier J. Bohl J. Median nerve compression syndrome caused by atypical palmar (muscle). Handchir Mikrochir Plast Chir 1985; l 7 : l : 27-30. 13. Smith R. Anomalous muscle belly of the flexor digitorum superficialis causing carpal tunnel syndrome. J Bone Joint Surg 1971; 53A: 1215-1216.


Scand J Plast Reconsrr Hand Surg 26

An unusual cause of carpal tunnel syndrome. Case report.

A 38 year old woman with carpal tunnel syndrome of the right hand was treated with operative decompression, initially successfully. Subsequently, she ...
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