Anomalous Palmaris Longus Muscle Producing Carpal Tunnel-like Compression-K. M. Baekhouse and D. Churehill-Davidson
ANOMALOUS PALMARIS LONGUS MUSCLE PRODUCING CARPAL TUNNEL-LIKE COMPRESSION K. M. B A C K H O U S E and D. C H U R C H I L L - D A V I D S O N , London During the past two years, three cases have been seen in which each patient presented with swelling of the anterior part of the wrist and lower forearm, suggestive of tenosynovitis affecting the digital flexor tendons and evidence of carpal tunnel compression. The first two cases were seen and treated individually and the third was examined and operated upon by both of us together. CASE REPORTS
The cases all had a common general appearance and presentation. They were all women under forty years of age who had quickly developed the characteristics of a carpal tunnel syndrome, though relatively mild and without marked thenar muscle loss. They all had pain in the lower forearm to wrist region and had noticed a swelling in the area. On examination, each had a swelling in the distal forearm proximal to the flexor retinaculum in much the same place and with the appearance of the thicker type of tenosynovitis seen in rheumatoid disease. The swellings showed slight bluish character in each case and moved with digital flexion. In one case a diagnosis of haemangioma was considered when considerable investigation showed no evidence of rheumatoid disease. All the cases were subjected to rheumatoid disease investigations in view of the site and character of the swelling and the nerve compression. The various rheumatoid tests being negative, the diagnosis was then considered most likely to be a non-specific tenosynovitis. In view of the median nerve compression and the pain, the patient was, in each case, subjected to surgery for decompression
Fig. 1. An excised distal belly of palmaris longus showing the proximal tendon and the broad attachment to the flexor retinaculum (transverse carpal ligament). 22
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Anomalous Pahnaris Longus Muscle Producing Carpal Tunnel-like Compression-K. M. Backhouse and D. Churehill-Davidson
and possible synovectomy. The swellings were found to be due to distal bellies of palmaris longus muscle (Fig. 1) overlying the median nerve, which was compressed between muscle belly and underlying tendons. The carpal tunnel itself showed no evidence of tightness in any of the patients. In one case there was considerable evidence of the compression effect on the nerve trunk where it lay between muscle belly and underlying tendons and there was a lack of continuity of the superficial chain of blood vessels. Removal of the muscle belly corrected the nerve compression. DISCUSSION
Carpal tunnel compression is a common condition for which a large number of causes have been described. In our experience and that of others (Backhouse, 1969; Phalen, 1966) rheumatoid or non-specific tenosynovial thickening is by far the most usual cause of the mechanical compression of the median nerve. We are so conscious of this relationship that we invariably look for other general manifestations of synovial disease in cases of carpal tunnel compression unless another cause appears obvious. Median nerve compression due to various anomalous muscles around the carpal tunnel have been described. Butler and Bigley (1971) reported a case of a long or aberrant lumbrical muscle within the tunnel and this we have seen ourselves on a number of occasions. In each of our cases where there was median nerve compression however, there was also a marked tenosynovial thickening and hence it would be difficult to make the lumbrical muscle a prime cause of the carpal tunnel syndrome. Gardner (1970) described a pseudo carpal tunnel syndrome due to a low flexor sublimis belly as had Bunnell (1948). Jackson and Harkins (1972) reported an aberrant belly of abductor digiti quinti arising from the tendon of palmaris longus and Walton and Cutler (1971) an unspecified abnormal muscle in the tunnel and closely bound to the median nerve by fibrous tissue. There appears to be no previous report of a distal palmaris longus muscle belly inducing median nerve compression. Palmaris longus is an extremely variable muscle. Reimann (1944) in an extensive study of 1,600 arms, showed it to be absent in 12.9% and showing a large variety of other morphological variations in 9.0% of cases, including some with a distal belly, or even more rarely (0.2%) a digastric muscle with proximal and distal bellies. In each of our three cases a large distal belly was present gaining an extensive, broad attachment into the flexor retinaculum. This gave the impression of the thickening of synovium over the flexor superficialis tendons in view of its extending over towards the ulnar side of the distal forearm where the usual tenosynovial swelling is apparent clinically. The interesting feature was that once a tourniquet had been applied at operation, the colour of the muscle became much more apparent against the pale exsanguinated skin, so making the diagnosis obvious even before the skin incision was made. SUMMARY
Three cases are recorded of a distal belly of palmaris longus muscle compressing the median nerve between itself and the underlying tendons, so producing an apparent carpal tunnel syndrome which initially was thought to be due to flexor tenosynovitis. The H a n d - - V o l . 7
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Anomalous Palmaris Longus Muscle Producing Carpal Tunnel-like Compression-K. M. Backhouse and D. Churchill-Davidson REFERENCES
BACKHOUSE, K. M. and KAY, A. (1969) Carpal Tunnel Syndrome. Lancet 1: 1150-1151. PHALEN, G. S. (1966) The Carpal-Tunnel Syndrome: Journal of Bone and Joint Surgery, 48A: 211-228. BUTLER, B. and BIGLEY, E. C. Jr. (1971) Aberrant Index (First) Lumbrical Tendinous Origin Associated with Carpal-Tunnel Syndrome. Journal of Bone and Joint Surgery, 53A: 160-162. GARDNER, R. C. (1970) Brief Recordings. Confirmed Case and Diagnosis of PseudocarpalTunnel (Sublimis) Syndrome. New England Medical Journal, 282: 858. BUNNELL, S. (1948) Surgery of the Hand. 2rid Edn. Philadelphia. J. B. Lippincott Company. p. 340. JACKSON, D. W. and HARKINS, P. D. (1972) An Aberrant Muscle Belly of the Abductor Digiti Quinti Associated with Median Nerve Paresthesias. Bulletin of the Hospital for Joint Diseases, 33: 111-115. WALTON, Col. S. and CUTLER, C. R. (1971) Carpal Tunnel Syndrome, Case Report of Unusual Etiology. Orthopaedics and Related Research, 74: 138-140. REIMANN, A. F., DASELER, E. H., ANSON, B. J., and BEATON, L. E. (1944) The Palmaris Longus Muscle and Tendon. A Study of 1,600 Extremities. Anatomical Record, 89: 495-505.
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ANOMALOUS PALMARIS LONGUS MUSCLE PRODUCING CARPAL TUNNEL-LIKE COMPRESSION K. M. B A C K H O U S E and D. C H U R C H I L L - D A V I D S O N , London During the past two years, three cases have been seen in which each patient presented with swelling of the anterior part of the wrist and lower forearm, suggestive of tenosynovitis affecting the digital flexor tendons and evidence of carpal tunnel compression. The first two cases were seen and treated individually and the third was examined and operated upon by both of us together. CASE REPORTS
The cases all had a common general appearance and presentation. They were all women under forty years of age who had quickly developed the characteristics of a carpal tunnel syndrome, though relatively mild and without marked thenar muscle loss. They all had pain in the lower forearm to wrist region and had noticed a swelling in the area. On examination, each had a swelling in the distal forearm proximal to the flexor retinaculum in much the same place and with the appearance of the thicker type of tenosynovitis seen in rheumatoid disease. The swellings showed slight bluish character in each case and moved with digital flexion. In one case a diagnosis of haemangioma was considered when considerable investigation showed no evidence of rheumatoid disease. All the cases were subjected to rheumatoid disease investigations in view of the site and character of the swelling and the nerve compression. The various rheumatoid tests being negative, the diagnosis was then considered most likely to be a non-specific tenosynovitis. In view of the median nerve compression and the pain, the patient was, in each case, subjected to surgery for decompression
Fig. 1. An excised distal belly of palmaris longus showing the proximal tendon and the broad attachment to the flexor retinaculum (transverse carpal ligament). 22
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Anomalous Pahnaris Longus Muscle Producing Carpal Tunnel-like Compression-K. M. Backhouse and D. Churehill-Davidson
and possible synovectomy. The swellings were found to be due to distal bellies of palmaris longus muscle (Fig. 1) overlying the median nerve, which was compressed between muscle belly and underlying tendons. The carpal tunnel itself showed no evidence of tightness in any of the patients. In one case there was considerable evidence of the compression effect on the nerve trunk where it lay between muscle belly and underlying tendons and there was a lack of continuity of the superficial chain of blood vessels. Removal of the muscle belly corrected the nerve compression. DISCUSSION
Carpal tunnel compression is a common condition for which a large number of causes have been described. In our experience and that of others (Backhouse, 1969; Phalen, 1966) rheumatoid or non-specific tenosynovial thickening is by far the most usual cause of the mechanical compression of the median nerve. We are so conscious of this relationship that we invariably look for other general manifestations of synovial disease in cases of carpal tunnel compression unless another cause appears obvious. Median nerve compression due to various anomalous muscles around the carpal tunnel have been described. Butler and Bigley (1971) reported a case of a long or aberrant lumbrical muscle within the tunnel and this we have seen ourselves on a number of occasions. In each of our cases where there was median nerve compression however, there was also a marked tenosynovial thickening and hence it would be difficult to make the lumbrical muscle a prime cause of the carpal tunnel syndrome. Gardner (1970) described a pseudo carpal tunnel syndrome due to a low flexor sublimis belly as had Bunnell (1948). Jackson and Harkins (1972) reported an aberrant belly of abductor digiti quinti arising from the tendon of palmaris longus and Walton and Cutler (1971) an unspecified abnormal muscle in the tunnel and closely bound to the median nerve by fibrous tissue. There appears to be no previous report of a distal palmaris longus muscle belly inducing median nerve compression. Palmaris longus is an extremely variable muscle. Reimann (1944) in an extensive study of 1,600 arms, showed it to be absent in 12.9% and showing a large variety of other morphological variations in 9.0% of cases, including some with a distal belly, or even more rarely (0.2%) a digastric muscle with proximal and distal bellies. In each of our three cases a large distal belly was present gaining an extensive, broad attachment into the flexor retinaculum. This gave the impression of the thickening of synovium over the flexor superficialis tendons in view of its extending over towards the ulnar side of the distal forearm where the usual tenosynovial swelling is apparent clinically. The interesting feature was that once a tourniquet had been applied at operation, the colour of the muscle became much more apparent against the pale exsanguinated skin, so making the diagnosis obvious even before the skin incision was made. SUMMARY
Three cases are recorded of a distal belly of palmaris longus muscle compressing the median nerve between itself and the underlying tendons, so producing an apparent carpal tunnel syndrome which initially was thought to be due to flexor tenosynovitis. The H a n d - - V o l . 7
No. 1
1975
23
Anomalous Palmaris Longus Muscle Producing Carpal Tunnel-like Compression-K. M. Backhouse and D. Churchill-Davidson REFERENCES
BACKHOUSE, K. M. and KAY, A. (1969) Carpal Tunnel Syndrome. Lancet 1: 1150-1151. PHALEN, G. S. (1966) The Carpal-Tunnel Syndrome: Journal of Bone and Joint Surgery, 48A: 211-228. BUTLER, B. and BIGLEY, E. C. Jr. (1971) Aberrant Index (First) Lumbrical Tendinous Origin Associated with Carpal-Tunnel Syndrome. Journal of Bone and Joint Surgery, 53A: 160-162. GARDNER, R. C. (1970) Brief Recordings. Confirmed Case and Diagnosis of PseudocarpalTunnel (Sublimis) Syndrome. New England Medical Journal, 282: 858. BUNNELL, S. (1948) Surgery of the Hand. 2rid Edn. Philadelphia. J. B. Lippincott Company. p. 340. JACKSON, D. W. and HARKINS, P. D. (1972) An Aberrant Muscle Belly of the Abductor Digiti Quinti Associated with Median Nerve Paresthesias. Bulletin of the Hospital for Joint Diseases, 33: 111-115. WALTON, Col. S. and CUTLER, C. R. (1971) Carpal Tunnel Syndrome, Case Report of Unusual Etiology. Orthopaedics and Related Research, 74: 138-140. REIMANN, A. F., DASELER, E. H., ANSON, B. J., and BEATON, L. E. (1944) The Palmaris Longus Muscle and Tendon. A Study of 1,600 Extremities. Anatomical Record, 89: 495-505.
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