GUYON'S CANAL SYNDROME AFTER CUBITAL TUNNEL RELEASE: A CASE REPORT

Background:Compression of the ulnar nerve typically occurs at the cubital tunnel and less commonly at Guyon's canal. The cubital tunnel is located between the olecranon and the medial epicondyle. A known risk factor for developing cubital tunnel syndrome is repetitive motions at the elbow, commonly found in tennis players and smokers. Guyon's canal is located at the medial wrist between the hook of hamate and pisiform. Compression at Guyon's canal is rare and most commonly occurs in cyclists. In this case, Guyon's canal compression was found after an ulnar nerve decompression and cubital tunnel syndrome in the contralateral extremity. Case Presentation:The patient is a 74-year-old female that presented to the physiatry clinic for bilateral weakness, numbness and tingling in the fourth and fifth fingers. Symptoms in the right hand began approximately eight years ago. She had a right ulnar nerve decompression with persistent numbness since then. Symptoms on the left hand began three months prior to presentation. Social history was significant for an 80-pack year smoking history. Physical exam revealed positive Formant's sign bilaterally and positive Tinel's sign at the right wrist, right elbow, and left wrist. Electrodiagnostic findings were consistent with left sided cubital tunnel syndrome and right sided compression at Guyon's canal. Conclusions:The use of EMG and NCS studies are helpful in diagnosing ulnar nerve lesions. However, if a cubital tunnel syndrome is found, a distal Guyon's canal compression may be masked. In this case, an undiagnosed Guyon's canal compression may have been hidden in the initial EMG study. Additionally, proximal compression of a nerve may contribute to the disruption neurofilament structure, resulting in the distal nerve to be more sensitive to compression.In patients with persistent symptoms of ulnar nerve compression after surgical cubital tunnel release, repeat EMG studies to screen for Guyon's canal compression should be considered.