Guyons canal syndrome due to accessory palmaris longus muscle: aetiological classification: a case report

Accessory muscles and anatomic variations are well described at the Guyon's canal. Though this case report is similar to variants published in previous reports, it differs from the rest due to rapidity of worsening of symptoms in few months following use of cane. We report a case of 69 year old man with ulnar nerve compression at Guyon's canal by accessory palmaris longus arose from distal third palmaris longus and from deep fascia of forearm. The hypertrophied muscular portion of accessory palmaris longus crosses over the ulnar nerve and artery at Guyon's canal becomes tendinous before merging with the hypothenar muscle. With co-existing anatomical variants, pressure in Guyon's canal might rapidly increase, might be causative factor and cause compression of deep branch of ulnar nerve following frequent dorsiflexion of wrist like in our case. Following division of accessory palmaris longus symptoms rapidly improved. In this article we discuss the aetiological classification, diagnostic criteria and treatment based on available evidence.