A 43-year-old female patient developed spasmodic torticollis, also

called "cervical dystonia", about five months ago. Dystonia is a form

of unusual movement that you can't control. Spasmodic torticollis affects the

muscles of the neck. Initially, this patient experienced a twisting of the head

towards the right shoulder during speech or driving. Over time, her head began

to turn virtually only toward that side and now her head is permanently tilted

toward her right shoulder. As the condition is slightly worsening and the cause

has not been identified, she has decided to undergo treatment with botulinum

toxin. Botulinum toxin is injected directly into the affected muscle. The main

mechanism of action is to block the release of acetylcholine from the nerve

endings into the synaptic cleft, thereby temporarily inhibiting muscle work in

the muscle. Where does the acetylcholine in these nerve endings come from?