by the cause (etiology)
by how old the child was when it appeared (age of onset)
by where and how much dystonia affects the body (somatic distribution)
Primary dystonia is caused by an underlying genetic mutation. Idiopathic generalized dystonia and dopa-responsive dystonia (DRD or Segawa's disease), are two types of primary dystonia.
Secondary dystonia has environmental causes. This means the brain has been injured by exposure to a toxin or drug, a stroke, infection, or other trauma.
Age of child when symptoms first appear
childhood onset: younger than 12 years old
adolescent onset: between 13 and 20 years old
adult onset: older than 20 years
Where and how much of the body is affected
Focal: Only one part of the body, such as the leg, is affected.
Segmental: Two adjacent parts of the body are affected, such as the head and neck.
Hemi-dystonia: Different parts on the same side of the body are affected, such as the left hand and left foot.
Multi-focal: Two non-adjacent areas are affected, such as the left leg and right arm.
Generalized: Multiple parts of the body are affected, such as both arms and one leg.