[A Case of Guyon's Canal Syndrome Associated with Cubital Tunnel Syndrome].

A 51-year-old man had a 1-year history of numbness on the ulnar side of the 4th finger, the 5th finger, and the ulnar side of the forearm, and weakness of the right hand. The Spurling sign was negative, and cervical radiography and magnetic resonance imaging revealed no abnormality. The Tinel-like signs at the Guyon's canal and cubital tunnel were positive. The diagnosis upon electrophysiological examination was cubital tunnel syndrome and Guyon's canal syndrome, but the possibility of Guyon's canal syndrome was high. Based on the presence of numbness in the forearm, the Tinel-like sign at the cubital tunnel, and the high incidence rate of cubital tunnel syndrome, an operation for cubital tunnel syndrome was performed. After the first operation, the numbness in the forearm was improved, but numbness in the 4th and 5th fingers, and weakness of the right hand remained, and the Tinel-like sign at the Guyon's canal also remained positive. The second operation for Guyon's canal syndrome was performed a month after the first operation for cubital tunnel syndrome. After the second operation, the residual symptoms improved gradually. Guyon's canal syndrome is a rare condition, but it may be considered a causative factor in patients with ulnar neuropathy.