What Causes Pain In Shoulder And Arms?

My Dr is treating me for corpral tunnel after months of complaining about a on going pain in my shoulder and lower left arm it hurts even when my blanket lays on it and my arm swells from my elbow down to the top of my hand and my fingers hurt my wrist hurts sometimes but not always but my arm hurts constantly and now my dr is ordering me a brace that will cover my forearm and hand I feel like he is just humoring me