Neurosurgery notes/Functional/Movement disorders/Dystonia

Dystonia

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Movement disorders
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Torticollis

Definition

  • A movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both.

Numbers

  • 1% of population

Aetiology

  • Primary dystonias are either sporadic mutations or heritable.
    • Inherited - a dystonia caused by mutations in a specific gene
    • Idiopathic (aka sporadic/familial)
      • Dystonia is the sole neurologic sign (with exception of the tremor)
      • Other causes of dystonia such as acquired or neurodegenerative processes have been ruled out.
    • DYT1 dystonia
      • Aka:
        • DYT1 Early-Onset Isolated Dystonia
        • Oppenheim’s dystonia
      • Numbers
        • Presents in childhood or adolescence and only on occasion in adulthood.
        • Dystonic muscle contractions causing posturing or irregular tremor of a leg or arm are the most common presenting findings.
        • Most common cause of early-onset generalized dystonia
        • Common in Ashkenazi Jewish population (prevalence of 1 in 2000)
      • Genetic
        • Autosomal dominant
          • A penetrance of 30-40%.
      • Clinical features
        • Onset of symptoms
          • Late childhood/early adolescence,
        • Begin in one leg and later generalize.
    • Dystonia plus syndromes
      • General
        • = Dystonia + Parkinsonism, tremor, or myoclonus
      • Can be divided into
        • Dystonia-Parkinsonism (DYT3 and DYT12)
        • Dopa-responsive dystonia (DYT5)
          • Eg: Segawa’s disease
          • Is a childhood-onset levodopa-responsive dystonia.
          • Clinical features
            • The initial symptom is generally foot dystonia
              • With a marked diurnal fluctuation that attenuates with age.
            • A postural tremor typically develops in adulthood, followed later by bradykinesia.
            • Rest tremor is absent.
            • Response to levodopa is marked and sustained.
          • Genetics
            • Both autosomal dominant and autosomal recessive subtypes
        • Paroxysmal dystonia (DYT8, DYT9, and DYT10)
        • Myoclonus-dystonia (DYT11)
          • DYT11 has its onset in childhood or adolescence
          • Manifested as dystonia with alcohol-responsive proximal myoclonic jerks.
          • The dystonia is usually mild and present in 50% of patients.
          • Eg:
            • Cervical dystonia
            • Writer’s cramp
          • Many adults with myoclonus-dystonia syndrome report dramatic improvement in their symptoms with alcohol ingestion.
  • Acquired (secondary)
    • Drug reaction
      • Dopamine antagonist side effect: tardive dyskinesia
        • Stereotyped and repetitive movement of the face (e.g., tongue-thrusting and involuntary chewing movements is often accompanied by a feeling of restlessness). This akathisia may be localized and reported as a “burning” sensation, often of the genitals or mouth.
    • Brain injury
    • A symptom of another neurological or metabolic disorder
      • Wilson disease
      • Huntington’s disease,
      • Parkinson’s syndromes,
      • Lysosomal storage diseases.

Clinical features

  • Dystonic movements are typically Patterned, twisting, and may be tremulous.
  • Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation.
  • History
    • Ask about
      • Age of onset
        • Infancy: birth to 2
        • Childhood: 3 to 12
        • Adolescence: 13 to 20
        • Early adulthood: 21 to 40
        • Late adulthood: over 40
      • Body distribution
        • Focal: one body region
        • Segmental: two or more contiguous body regions
        • Multifocal: two or more non-contiguous body regions
        • Generalised: two or more contiguous regions plus trunk
        • Hemidystonia: one side of the body Temporal features
      • Disease course
        • Static ‐ Progressive
        • Variability
          • Persistent ‐ Diurnal ‐ Task specific ‐ Paroxysmal
      • Associated features
        • Isolated dystonia
        • Combined dystonia
          • Coexists with another movement disorder, or
          • Occurrence of other neurological or systemic manifestations
    • For example,
      • Dystonia that begins in childhood is more likely to have a discoverable acquired cause and is more likely to progress from focal to generalised.
      • Typical adult onset focal dystonia is likely to be a subtype of isolated dystonia and will rarely spread.
    • FMx
      • Genetic cause.
  • Ex
    • Ask if patients can alleviate their dystonia by lightly touching surrounding body areas (“sensory trick”), a phenomenon that illustrates the dynamic nature of dystonia and the importance of sensory influences.
    • Dystonia is often accentuated within a neurological examination that includes a range of postures and tasks.
    • A latent abnormal posture (eg, in the head and neck) can be revealed by asking the patient to close their eyes and let position drift to where it feels most comfortable.
    • If tremor accompanies dystonia it is usually jerky, variable in amplitude, and worsened by particular positions
      • How to differentiate dystonia tremor from ET
        • Dystonia rotatory shakes
        • ET Nods

Mechanism

  • Dysfunction of the basal ganglia
  • Neuro-functional disorder, i.e. a disorder characterized by abnormal connectivity that may occur in a structurally normal-appearing brain.

Types

  • Generalised dystonia
    • Affects most or all of the body.
    • May involve the trunk and the limbs
  • Focal dystonia
    • Affects one part of the body.
    • Neck (torticollis)
        • Most commonly affected site with a tendency for the head to turn to one side.
        Types of neck dystonia
        Types of neck dystonia
    • Eyelids (blepharospasm)
      • Involuntary closure of the eyelids that leads to excessive eye blinking, sometimes with persistent eye closure and functional blindness.
      • Meige syndrome
          • A form of focal dystonia characterized by blepharospasm, forceful jaw opening, lip retraction, neck contractions, and tongue thrusting.
          • Numbers
            • F>M,
            • Onset 60s
          • Aetiology
            • Idiopathic
            • Phenothiazine or butyrophenone use
          • Botulinum toxin injection has been more effective in treatment than any oral medication.
          Blepharospasm and oromandibular dystonia of Meige syndrome patient
          Blepharospasm and oromandibular dystonia of Meige syndrome patient
    • Mouth (oromandibular dystonia)
      • Involuntary contraction of muscles of the mouth, tongue, or face.
    • Hand (writer’s cramp).
  • Multifocal dystonia
    • Affects two or more unrelated parts of the body.
    • The classic example is head and neck dystonia
  • Segmental dystonia
    • Affects two or more adjacent parts of the body.
  • Hemidystonia
    • Is typically associated with deficits in the contralateral basal ganglia and also called unilateral dystonia.

Syndromes

  • Young onset generalised dystonia
    • DYTI etc
  • Adult onset focal dystonia
    • Cervical dystonia, blepharospasm, upper limb dystonia, task specific dystonia
  • Paroxysmal dyskinesias
    • Paroxysmal kinesigenic dystonia, GLUT-I transporter deficiency
  • Acquired / secondary dystonia
    • Tardive (dopamine antagonist drugs), dystonic cerebral palsy, vascular, post-encephalitic
  • Dystonia as part of wider neurodegenerative syndrome
    • Parkinson’s disease, PSP, CBD, Huntington’s disease
  • Functional dystonia
  • Dopa-responsive dystonia / myoclonus dystonia

Management of dystonia

  • Drugs for dystonia
    • General
      • Poor evidence base, limited effectiveness
    • Options
      • Tetrabenazine
        • Mech
          • VMAT (vesicular monoamine transporter) inhibitor → depletion of monoamine neurotransmitters like NA, DA, 5HT
        • Used also for Huntington's
        • Useful in tardive dystonia
      • Anticholinergics
        • Eg: Trihexyphenidyl
        • Useful in generalized dystonia
      • Baclofen
        • Useful in segmental / generalized / oromandibular dystonia
      • Benzodiazepine
        • Useful in myoclonus dystonia
      • Carbamazepine
        • Useful in paroxysmal and secondary dystonias
      • L-Dopa:
        • Effective in dopa-responsive dystonia
  • Injections
    • Botulinum toxin
      • Mechanism chemodenervation and local paralysis
    • Primarily used in focal dystonia
    • Type A — Botox, Dysport, Xeomin
    • Type B — Neurobloc
    • Challenges
      • Immunoresistance
      • Expense
      • Treatment cycle
  • Surgery