25A. Focal dystonias

From greek.doctor

A dystonia is a movement disorder with sustained or intermittent muscle contractions causing abnormal movements or postures. It can be focal, segmental, or generalised, it can be early-onset or late-onset, and it can be primary or secondary.

Etiology

Most dystonias are idiopathic, but some are familiar or secondary to CNS injury or neurodegeneration.

Classification

Dystonias are often classified according to etiology, age of onset, and distribution:

  • According to etiology
    • Primary (most common)
    • Secondary
      • CNS injury
      • Neurodegenerative disease
  • According to age of onset
    • Infantile
    • Childhood
    • Adolesence
    • Early adulthood
    • Late adulthood
  • Distribution
    • Focal
    • Segmental
    • Multifocal
    • Hemidystonia
    • Generalised

Most common types of focal dystonia

There are many types of focal dystonia, depending on the affected body part:

  • Cervical dystonia (= torticollis)
    • Sudden, painful contraction of sternocleidomastoid causing the head to turn, tilt, or flex
  • Hand dystonia (= writer’s cramp)
    • Non-painful contractions in the hand or arm which occur when writing
  • Eye dystonia (= blepharospasm)
    • Spasm of periocular muscles, causing involuntary twitching or blinking
  • Orofaciomandibular (OMD) dystonia
    • Spasm of muscles of mouth and jaw, causing chomping movements
  • Hemifacial spasm
    • Spasm of half the face

Treatment

The main treatment of focal dystonias is botulinum toxin injection into the affected muscle. This is very effective. In case botulinum toxin injection is insufficient, deep brain stimulation may be used.

The efficacy of oral drugs in focal dystonia is limited. Benzodiazepines, baclofen, and anticholinergics may be used.