guyon's tunnel syndrome during pregnancy with concomitant anomalous arch of the ulnar nerve: a case report.

numerous causes are reported for ulnar nerve compression at the wrist, known as guyon's tunnel syndrome. in the present article, a patient with guyon's tunnel syndrome during pregnancy concomitant with an anomaly of ulnar nerve is described. a 29-year-old iranian woman presented with clinical features of guyon's tunnel syndrome (pain and paresthesia in the fifth finger of the left hand and atrophy of the first dorsal interosseus muscle). symptoms of the patient appeared during the third trimester of pregnancy. electro diagnostic studies confirmed guyon's tunnel syndrome. surgical exploration revealed an anomalous arch of the ulnar nerve passing through the flexor carpi ulnaris (fcu) tendon. the anomalous arch of the ulnar nerve was released by resection of the segment of fcu tendon passing through the ulnar nerve arch. therefore, in patients with guyon's tunnel syndrome, the ulnar nerve anomaly should be kept in mind as a cause. moreover, pregnancy may have a provocative effect on guyon's tunnel syndrome similar to carpal tunnel syndrome (cts).