A novel case of ulnar nerve compression neuropathy with co-existing accessory flexor carpi ulnaris and accessory abductor digiti minimi

There are numerous cases reported of the accessory muscles of the hand and wrist in surgical, cadaveric, and imaging-based studies. Anatomical muscle variations in the flexor compartment of the wrist and forearm can present as a pseudo mass or space-occupying lesion causing external compression on the traversing nerves. Guyon’s canal is a compact space with a high potential for nerve entrapment. Common etiologies include ganglion cysts, osteophytes, or soft tissue masses. This rare case illustrates the combined existence of two accessory muscles, an accessory flexor carpi ulnaris, and an accessory abductor digiti minimi, causing ulnar nerve compression in Guyon’s canal with imaging correlation. One can raise the suspicion of an anomalous muscle when symptoms concern a patient of a younger age group in the absence of common etiologies. Furthermore, detailed anatomical knowledge of muscles around Guyon’s canal is essential in making a diagnosis and aiding treatment.