My Husband Suddenly Started Feeling A "restless Leg" Feeling In

My husband suddenly started feeling a "restless leg" feeling in his upper body, shoulders and arms, that was 3 days ago and it's never gone away. now it's spreading down his back. It's a feeling that makes him not be able to sit still, he wants to throw his body on the ground and it is like constant torture. I'm not sure anymore if it's just "restless leg", or something more serious. It doesn't stop.

Thank you!