Teenager with weaker pulses in the left arm when compared to the right arm

MRA of arterial thoracic outlet syndrome
MRA with contrast of the chest performed via a right forearm injection with the arms in a neutral (adducted) position (above) shows a normal appearance to the subclavian arteries. MRA was then performed with the arms in a raised (abducted) position (below) which shows development of a moderate stenosis in the proximal left subclavian artery.

The diagnosis was left arterial thoracic outlet syndrome.