Hunt, 1 in 1908 described the first clinical case of ulnar compression within Guyon’s canal resulting from chronic occupational trauma. Since then, numerous causes have been cited in the etiology of ulnar nerve compression in Guyon’s canal. 2–9 We report two cases of subfascial lipoma of the hypothenar region that were responsible for a sensory disturbance resulting from the compression of the superficial branch of the ulnar nerve at Guyon’s canal.
A 61-year-old woman presented with a slowly enlarging, painless mass that she had had in her right palm for 2 years (Fig). She experienced numbness along the ulnar side of the hand. A clinical examination revealed a 6 × 4-cm painless, soft mass located in the hypothenar region of her palm. Digital range of motion was normal, but light touch and two-point discrimination tests disclosed decreased sensibility along the palmar surface of the small finger and the ulnar half of the ring finger, in comparison with her left hand. Electromyography showed a reduction in amplitude of sensory antidromic action potential in the ulnar nerve of the right hand. With the patient under general anesthesia, surgical exploration was performed through an incision centered over Guyon’s canal. After the skin and the volar carpal ligament were incised, a yellowish mass (5 × 4 × 2 cm) was found, which was compressing the sensory branch of the ulnar nerve. The mass was removed, and histological examination showed mature adipose tissue consistent with the diagnosis of lipoma. Healing was uneventful. Four months later the patient had full digital motion, and a normal sensation and motor examination.
A 49-year-old woman presented with a painful mass in her right palm that had been present for approximately 6 years. Eight years previously the patient had undergone an operation to release the transverse carpal ligament in the same hand. Examination revealed a 5 × 2-cm soft mass over the right hypothenar eminence. Sensory testing (light touch and two-point discrimination) showed decreased sensibility in the superficial branch of the ulnar nerve distribution compared with the left side. The interosseus muscles, the adductor pollicis muscle, the abductor digiti minimi, and the lumbricals were normal. Phalen’s test and Tinel’s sign were both negative. Electromyography showed an increase in distal sensory latency of the ulnar and median nerves of the right hand. Surgical exploration was performed through an incision centered over the old scar, which extended both proximally and distally. After releasing the median nerve, which presented adhesions, a lobulated mass was found in the hypothenar region and was removed. The mass was submuscular and had been pressing against the sensory branch of the ulnar nerve. Histological examination confirmed the diagnosis of lipoma. The postoperative course was uneventful. Follow-up showed that sensory symptoms had disappeared.
Lipomas in Guyon’s canal are rare tumors that can be responsible for compression neuropathy depending on their size. 2–4 Guyon’s canal is a semirigid triangular space, with the apex pointing outward radially. Its osseus boundaries are formed ulnarly by the pisiform and the hook of the hamate, and dorsally by the triquetrum and hamate bones. The roof consists of the volar carpal ligament, which is blended with the tendinous insertion of the flexor carpi ulnaris into the pisiform bone. Inside this canal, the ulnar nerve divides into the superficial and deep branches. The superficial branch passes distally to the fat pad in the canal; the deep branch, together with the branch of the ulnar artery, passes distally and deeply between the origin of the abductor digiti quinti and flexor digiti quinti brevis to innervate the deeper interosseus muscle. Compression neuropathy of the ulnar nerve at Guyon’s canal may present different signs according to whether the ulnar nerve itself or the superficial or deep branch is compressed.
Shea and McClain 5 classified ulnar syndromes at the wrist, on the basis of the site of involvement, into three types: type I, a combined sensory and motor deficit if the location of the compression is in Guyon’s canal before the division of the ulnar nerve into superficial and deep branches; type II, motor deficit only; and type, III sensory deficit only as in our patients.
The differential diagnosis of ulnar tunnel syndrome in Guyon’s canal includes ganglion, accessory muscles, ulnar artery thrombosis, anomaly of the hamate, and giant cell tumor. 5–9 Treatment of lipomas in Guyon’s canal consists of the excision of the lipoma, and identification and release of the vital structures compressed or displaced by the tumor. Careful surgery avoids complications.
Mariarosaria Galeano, MD*
Michele Colonna, MD*
Giovanni Risitano, MD†
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