My Husband Has Been Having Problems With His Left Side

My husband has been having problems with his left side now for a couple of years. He's stiff and has a loss of dexterity in his left hand that makes it difficult for him to button his left sleeve on his dress shirts. He has little or no pain except for some pain in his left hip some days that cause him to limp. We've been to three doctors now who've checked him for stroke and Parkinson's but he doesn't really fit the symptoms. The last doctor we went to sent him for an MRI for his neck but it showed nothing conclusive. He feels better with excersise...especially weight bearing. He's 61 and otherwise in excellent health. His blood pressure and cholesterol is excellent. He has been under constant stress for several years and has only recently started to address it.