Participants will provide a medical history, as well as occupational and social information. They will have a standard neurological examination, including a test of cognitive (thinking) abilities, muscular function, reflexes and sensory examination. The latter involves testing with a pin placed on the surface of the skin. Participants will also have routine blood tests and will fill out questionnaires on their daily functioning and psychological well being. Additional procedures may include magnetic resonance imaging (MRI) scans and possible referral to a psychiatrist for evaluation of depression or emotional difficulties.