Accessory Flexor Muscle of Forearm - A Rare Variant - Embryological and Clinical Prospect.

Several muscle variations have been observed in flexor aspect of forearm which can hamper normal functioning of hand or may remain silent. One such unreported variation has been described in this report. An accessory muscle in the left forearm was found involving flexor carpi ulnaris (FCU) and palmaris longus (PL). This muscle was originating from the distal part of both FCU and PL through a slip from each tendon. After merging, it passed above the ulnar nerve and artery in the roof of Guyon's canal. This type of variation can cause neurovascular compression and can also mimic soft tissue mass, tumour or neuroma and can be misdiagnosed. Knowledge about this type of variation is important in cases of neurovascular decompression, forearm, and hand surgeries and these can be utilized in tendon transfer or free muscle flap for reconstruction purposes.