It sounds like something out of a nightmare. You’re lying back in a reclining chair, when someone in a white coat comes toward you wielding a syringe. The person plunges the needle into your neck and wiggles it around until it strikes a muscle deep in your throat. Then, the intruder hits the plunger and releases a deadening agent. The syringe is removed and you take a deep breath. You survived. That nightmare scenario is a reality for people with spasmodic dysphonia, or SD, a rare vocal disorder.