**Department of Orthopaedic and Trauma Surgery, Mayday University Hospital, London. United Kingdom.

Correspondence to:
Mr. Richard Goddard
4 Longdown Road,
Epsom,
Surrey.
KT17 3PT.
United Kingdom.
e-mail: richardgoddard@postmaster.co.uk 


ABSTRACT.
Carpal tunnel syndrome is a common peripheral nerve entrapment syndrome. It occurs most frequently in patients between 30 and 60 years old and is five times more common in women than in men. It is most commonly attributed to external compression of the median nerve secondary to a variety of causes. We describe an unusual case of median nerve compression due to a rare association of congenital macrodactyly and median nerve neuroma. Macrodactyly associated nerve tumours are discussed. 

KEY WORDS.
Carpal Tunnel Syndrome, Macrodactyly, Neuroma.



CASE REPORT
A twenty nine year old man presented to the orthopaedic clinic with a history of paraesthesia in the fingers of his left hand in the median nerve distribution. There was no history of trauma or neck pathology. On examination, there was evidence of congenital macrodactyly of his left index finger together with proximal soft tissue enlargement over the palmar and thenar area. He had a positive median nerve provocative test at the wrist and subsequent nerve conduction studies confirmed a left sided carpal tunnel syndrome with a left median nerve motor latency of 5.4ms compared to 2.8ms on the right. 
At exploration of the left carpal tunnel there was an hour glass constriction of an abnormally enlarged median nerve (Fig. 1.). The nerve was compressed anteriorly by a 2cm by 2cm fibrolipoma superficial to the flexor retinaculum, also by a 1cm by 2cm tumour arising from the surface of the nerve and posteriorly by an enlarged and thickened flexor tendon sheath. Excision of the tumour and tenosynovectomy achieved a complete decompression and restoration of the vascular supply to the compressed nerve. The excised tumour arising from the nerve had the histological appearance of a benign neuroma. 

Figure 1. Intra-operative photograph showing congenital macrodactyly of the index finger together with a grossly enlarged median nerve with an hour glass constriction.


DISCUSSION

This case presents an uncommon cause of carpel tunnel syndrome secondary to macrodactyly. Macrodactyly is a rare, nonhereditary, congenital abnormality in which there is enlargement of the bone and soft tissues of a digit. It represents 0.9% of all congenital anomalies of the upper limb [1]. In the literature, the overall reported sex ratio in macrodactyly, suggests a small predominance in males [2]. The index finger, as in this case, is the most commonly involved site [3], but any digit of the hand or foot may be involved. The predominant pathology of the digital tissue is a hamartomatous enlargement of the fibrofatty tissue and bone [4]. 
In the palm however, the metacarpal bone is not typically involved but nerve territory soft tissue overgrowth has been described. This may take the form of an enlargement of the median nerve, which has in a small number of cases resulted in median nerve compression. [1]. The nature of the nerve overgrowth is most commonly a hamartomatous enlargement, but in our case it was a benign neuroma. We believe that our patient had a number of unusual aetiological factors leading to carpal tunnel syndrome. Firstly, a benign neuroma of the median nerve and a thickened flexor tendon sheath within the carpal tunnel and secondly a fibrolipoma superficial to the flexor retinaculum, all of which resulted in an increase in carpal tunnel pressure and nerve compression. This multifactorial origin of carpal tunnel syndrome in patients with macrodactyly has to be taken in consideration when undertaking decompressive surgery.


REFERENCES.
1. Kotwal PP, Farooque (1998) Macrodactyly J Bone Joint Surg [Am] 80-B: 651-653
2. Kalen V, Burwell DS, Omer GE. (1988) Macrodactyly of the hands and feet. J Pediatr Orthop 8: 311-315
3. Frykman GK, Wood VE (1978) Peripheral nerve hamartoma with macrodactyly in the hand: Report of three cases and review of the literature. J Hand Surg [Am] 3: 307-312
4. Krengel S, Fustes-Morales A, Carrasco D, Vázquez M, Durán-McKinster C, Ruiz-Maldonado R (2000) Macrodactyly: Report of eight cases and review of the literature, Pediatr Dermatol 17: 270-276.

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