Thoracic outlet syndrome happens when nerves or blood vessels get pinched between the collar-bone and first rib. Symptoms shoot into the arm or hand, not the chest, so many people think the problem is elsewhere.

Arm pain is the headline. It starts in the shoulder or armpit and runs down the outer arm, worse when you raise the arm or carry a bag.

Numbness and tingling follow. Fingers feel “asleep,” especially the ring and little fingers, or the whole hand when you sleep with your arm overhead.

Weak grip shows up next. You drop coffee cups, have trouble opening jars, or your handwriting gets sloppy.

Color changes pop up. The hand turns pale or blotchy when you lift it overhead and flushes red when you drop it.

Pulse can fade. Feeling the wrist pulse while raising your arm may show a weaker beat.

Late signs include constant numbness, muscle wasting in the hand, or arm swelling—an alarm that the nerve or vein is badly compressed.