Suggest Treatment For Swelling And Numbness After Playing Guitar

My husband plays in a band and plays the Guitar 3 nights a week for appro 4 hours. He has not played for 1 week now and on monday he woke up with his hand swelled and numbness up to his cheek. He said that his erbow was very cold and it was warm. He took 2 aleve/twice on tuesday and applied a heating pad on his back. The numbness was coming and going. Now today(wed) he woke up and he said that his arm feels like he's been lifting waits and is very weak.