Asian Journal of Research in Surgery

Aims: To report a rare case of ulnar nerve compression at Guyon’s canal caused by an extraneural lipoma and to emphasize the role of MRI and surgical management.

Presentation of Case: A 52-year-old man presented with a painless, slowly enlarging mass on the ulnar side of the right wrist evolving over two years, associated with numbness of the ring and little fingers for three months. Clinically, the mass measured approximately 3 cm, while imaging revealed a larger lesion. Examination showed decreased sensation in the ulnar nerve distribution and a positive Tinel’s sign without motor deficit. Nerve conduction studies confirmed severe ulnar compressive neuropathy at the wrist. MRI demonstrated a well-defined lipomatous mass extending into Guyon’s canal and displacing the ulnar nerve. Surgical excision was performed, and histopathology confirmed a lipoma. Recovery was uneventful with full sensory improvement and no recurrence.

Discussion: Guyon’s canal syndrome is uncommon and most frequently caused by ganglion cysts, whereas lipomas represent a rare etiology. Symptoms vary depending to the level of nerve involvement and may be subtle despite significant compression. MRI is essential to identify the underlying cause and its anatomical relationships. Surgical decompression with lesion excision is the treatment of choice and generally provides excellent outcomes.

Conclusion: Lipoma should be considered among the differential diagnoses of Guyon’s canal syndrome. MRI allows accurate diagnosis and surgical planning, and complete excision leads to favorable functional recovery.