An unusual case of hypothenar hammer syndrome in the non-dominant hand.

A 60-year-old male patient was referred to the vascular clinic with a 2-week history of a 1.5 cm pulsatile tender swelling in the left hypothenar eminence. He worked as a gas fitter and sustained this swelling following an injury at work. Interestingly, unlike many cases reported, his left, non-dominant hand was only used passively while his dominant right hand was using the hammer. Duplex ultrasonography confirmed the presence of a true aneurysm of the left ulnar artery, measuring 11 mm in diameter, as it approached the palmar arch. The ulnar nerve was revealed to be ectatic and tortuous and was found to cork-screw in the palm. The aneurysm was removed surgically and histological specimens revealed an intraluminal organizing thrombus. The literature reveals that, in a true aneurysm, it is rare to present with symptoms of this syndrome in the non-dominant, passive hand.