Cervical dystonia (CD) is an idiopathic focal dystonia characterized by abnormal head and neck posture caused by tonic involuntary contractions in a set of cervical muscles. Four subtypes, based on the principal direction of posture, consist of:

• - Torticollis: Rotation of the head left or right in the transverse plane.

• - Lateralcollis: Head tilt toward left or right shoulder, in the coronal plane.

• - Anterocollis: Head tilt forward, with neck flexion in the sagittal plane.

• - Retrocollis: Head tilt backward, with neck extension, in the sagittal plane.

The clinical spectrum of CD is extremely variable: the 54 muscles involved in head and neck posture may show complex mixtures of involvement, unilateral or bilateral, with contractions of tonic, tremulous or myoclonic character. Currently, the most effective, and now first-line treatment of CD, has become intramuscular injection of botulinum toxin.

This chapter enumerates the different muscles involved in major subtypes of CD, grouped by anatomical location, and their principal direction of action. Sets of muscles involved in different head postures are presented in tabular format for easy selection and targeting. Dose ranges for individual muscles are tabulated for each of the four commonly used botulinum neurotoxin preparations.