Radial artery aneurysm secondary to dynamic entrapment by extensor pollicis longus tendon: a case of snapping thumb.

Aneurysms of the distal radial artery at the level of the wrist are rare. Most reported cases are posttraumatic, either from iatrogenic arterial puncture for radial arterial access or from a penetrating injury. Other causes include infection and connective tissue disorders. Early diagnosis is important to avoid the potential complications of thrombus formation, distal digital ischemia, and rupture. Evaluation of the radial artery is typically performed using non-invasive modalities like ultrasonography, computed tomographic angiography (CTA), and magnetic resonance angiography (MRA). Invasive angiography can also be performed, particularly if minimally invasive treatment options are being considered. We report a case of a 35-year-old male mechanic who presented with pain at the base of the left thumb dorsally, with reproducible painful snapping on dynamic exam. Ultrasound demonstrated a fusiform aneurysm of the radial artery. At the level of the aneurysm, there was dynamic entrapment of the artery between the extensor pollicis longus (EPL) tendon and the underlying trapezium. The patient's symptoms improved with conservative management and avoidance of the snapping-producing maneuvers. To our knowledge, this is the first published case of snapping at the base of the thumb resulting in repetitive entrapment of the radial artery by the EPL tendon captured on dynamic ultrasound examination.