I'm concerned about my brother. He's in his early 60's and in good physical shape as he has an active lifestyle and job. However, he has started to drag his left foot. He literally has to lift his leg up, move the leg forward, and set the leg back down. The foot hangs unnaturally down, as if the ankle or muscles are just non-existent in the foot. He says no doctors will take his health insurance. I believe he is in denial about what could be happening. My question is, what are the possible causes of this?