Case History: Case X

A 25-year-old man came to his doctor's appointment complaining that he was having a lot of trouble with text messaging with his left hand. He had several burns and scratches on his fingers. Physical examination showed decreased pain and temperature sensation in both hands, more severe in the thumb and first two fingers of both hands, as well as adjacent regions in the lateral hands and forearms. Vibration and proprioception were normal. What is the most likely diagnosis?