Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures or both. Dystonic movements are typically patterned, twisting and may be tremulous. Dystonia is often initiated or worsened by voluntary action and associated with muscle overflow activity (Fung et al., Movement Disorders, 2013).

Patients with dystonia may have superimposed movements that are slow (athetosis), or rapid (myoclonic), or rhythmic (tremor). It is the sustained twisted postures that are the key to diagnosis. There is a tendency for the movements to be absent at rest and be triggered by movement (action). The movements follow a similar pattern, and these repetitive postures support the diagnosis (unlike chorea which is random).

Dystonia is often is often better first thing in the morning. Frequently patients often have “sensory tricks” (putting slight pressure close to the dystonic muscles inhibits the dystonia). Dystonia may be very task specific (e.g. musicians dystonia, writer’s cramp). Several unusual properties (e.g.: leg dystonia improving when walking backwards) make this condition hard for family doctors to recognize as a real medical problem. It is not unusual to see several physicians prior to the diagnosis being made. Blepharospasm (eyelid spasms), and cervical dystonia  (neck twisting) are the two most common types of focal dystonia.

Dystonia Classification System

(adapted from Fung et al., Movement Disorders, 2013)

Axis I: Clinical Characteristics

a) By age of onset

Infancy (Birth to 2 years), Childhood (3-12 years), Adolescence (13-20 years), Early Adulthood (21-40), Late Adulthood (>40 years)

When dystonia starts in childhood it is usually secondary, and unfortunately is commonly either generalized at onset, or becomes generalized over time. Usually when dystonia starts in adulthood it is primary and tends to remain focal.

b) By body distribution (body part or parts affected)

Focal – if only one body part is affect. The main example are:

  • eyes ……………………………….. Blepharospasm
  • eyes and face …………….. Miege syndrome
  • jaw ………………………………….. Oromandibular dystonia (can be jaw opening or closing)
  • neck ……………………………….. Cervical dystonia
  • vocal cords ………………….. Spasmodic dysphonia (can be adductor or abductor dystonia)
  • trunk ………………………………. Axial dystonia
  • arm/hand ……………………… Writer’s cramp
  • leg/foot …………………………. Runner’s dystonia

Segmental – if only one segment of the body is affected, the dystonia is called “segmental” (e.g. one arm and the neck, or both legs).

Generalized – if one segment of the body and at least one other additional body part is affected, dystonia is called “generalized”.

Hemidystonia – if one side of the body is affected. This type is secondary to a brain problem on the opposite side from the dystonia and should be investigated with imaging of the brain.

c) By temporal pattern

  • Time course: static or progressive
  • Variability: persistent, action-specific, diurnal, paroxysmal

d) Associated features

  • Isolated
  • Combined with other movement disorders
  • Other co-occurring or systemic manifestations

Axis II: Cause

a) Nervous system pathology (based on MRI, family history and genetic testing)

  • Normal
  • Gegenerative
  • Structural lesion
  • Inherited

b) Acquired (secondary)

  • Perinatal (birth) injury
  • Infection
  • Drug-induced (extrapyramidal syndrome – EPS)
  • Toxic
  • Vascular
  • Neoplastic
  • Traumatic
  • Functional

c) Idiopathic (no known cause)

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