A Case of Guyon Canal Syndrome Following Ulnar Nerve Transposition

Case Diagnosis: Delayed-Onset Guyon Canal Syndrome following Ulnar Nerve Transposition

Case Description or Program Description: A 71-year-old female presented with left-sided numbness and tingling involving the fourth and fifth digits, with symptoms radiating distally from the left elbow. Her medical history included ulnar nerve transposition at the left elbow performed two years prior and cervical fusion at C4/5 and C5/6 six years prior. She reported complete resolution of symptoms post-transposition until three months ago, when numbness and tingling reappeared in the left fourth and fifth digits. She denied weakness, neck pain, or inciting events. Physical examination revealed a positive Tinel’s sign at the left elbow and diminished sensation in the affected digits.

Setting: Outpatient physiatry clinic

Assessment/Results: Electrodiagnostic studies confirmed left-sided ulnar neuropathy across the wrist, consistent with Guyon Canal Syndrome due to sparing of the dorsal ulnar cutaneous (DUC) nerve.

Discussion (relevance): The incidence of Guyon Canal Syndrome is not well documented and its temporary resolution followed by recurrence of symptoms after ulnar nerve transposition has not been previously reported, to our knowledge. The sparing of the DUC in wrist compression is an important diagnostic clue, as the DUC branches off proximal to the ulnar nerve entering Guyon’s canal. Its preservation suggests that compression is occurring at the wrist, rather than the elbow. The presence of a cervical fusion further obscured the diagnosis, as adjacent segment disease can mimic ulnar neuropathy by affecting the C8/T1 nerve roots.

Conclusions: This case highlights an atypical presentation of Guyon’s Canal Syndrome, the diagnostic significance of DUC sparing, and the challenge of managing patients with overlapping peripheral pathologies. Electrodiagnostic findings, particularly DUC nerve sparing, are critical for accurate localization of ulnar neuropathies. Thorough evaluation of both peripheral and central causes is essential in patients with complex presentations and overlapping pathologies.