What are dystonic movements?

Dystonic Movements: Definition and Clinical Characteristics

Dystonic movements are involuntary, sustained muscle contractions that produce twisting or squeezing movements and abnormal postures, which can vary from rapid to slow in speed and may result in fixed postures when contractions are sustained. 1, 2

Key Characteristics of Dystonic Movements

• Phenomenology:

  • Involuntary sustained or intermittent muscle contractions
  • Produce twisting movements, repetitive movements, or abnormal postures
  • May involve opposing muscle groups simultaneously
  • Can be stereotyped and repetitive
  • Speed varies from rapid to slow
  • May result in fixed postures with sustained contractions 2

• Modifying Factors:

  • Typically worsen with anxiety, heightened emotions, and fatigue
  • Decrease with relaxation
  • Disappear during sleep
  • Often show diurnal fluctuations (minimal in morning, worse in afternoon/evening)
  • May be reduced by sensory tricks ("gestes antagonistes") 2

• Relationship to Activity:

  • May occur in relation to specific voluntary actions (action-specific dystonia)
  • Can occur in one body segment with movement of another (overflow dystonia)
  • With progression, often becomes present at rest 2

Types of Dystonia

Dystonia can be classified based on:

1. Distribution:

   • Focal (affecting one body region)
   • Segmental (affecting adjacent body regions)
   • Multifocal (affecting non-adjacent body regions)
   • Generalized (affecting multiple body regions) 1

2. Etiology:

   • Primary/Isolated (dystonia is the only neurological feature)
   • Combined (dystonia with additional neurological signs)
   • Secondary (due to identifiable causes like medications, stroke, etc.) 1, 3

3. Age of onset:

   • Early-onset (typically generalized)
   • Adult-onset (typically focal) 3

Common Forms of Dystonia

• Cranial dystonia: Includes blepharospasm, oromandibular dystonia, lingual dystonia, and spasmodic dysphonia
• Cervical dystonia: Also known as spasmodic torticollis
• Limb dystonia: Including writer's cramp and other task-specific dystonias
• Paroxysmal dyskinesias: Brief episodes of dystonic movements triggered by specific factors 4, 1

Paroxysmal Kinesigenic Dyskinesia (PKD)

PKD is a specific form of dystonia characterized by:

• Brief episodes triggered by sudden voluntary movements
• Attacks typically last less than 1 minute
• Often preceded by an aura (numbness, tingling, weakness) in 78-82% of patients
• Preserved consciousness during attacks
• Good response to anticonvulsant medications 4, 1

Causes of Dystonia

1. Genetic factors:

   • Multiple genes identified (TOR1A, THAP1, GCH1, KMT2B, PRRT2, etc.)
   • Often autosomal dominant inheritance with incomplete penetrance 1, 3

2. Secondary causes:

   • Medications (particularly antipsychotics and antiemetics)
   • Cerebrovascular diseases
   • Demyelinating disorders
   • Traumatic brain injury
   • Metabolic disorders (including hypocalcemia from hypoparathyroidism)
   • Lesions involving the basal ganglia, thalamus, or internal capsule 4, 1

Pathophysiology

The pathophysiology of dystonia involves:

• Abnormalities in transcriptional regulation
• Striatal dopaminergic signaling dysfunction
• Altered synaptic plasticity
• Loss of inhibition in neuronal circuits
• Basal ganglia dysfunction 1, 3

Diagnostic Considerations

Red flags suggesting secondary dystonia include:

• Onset after age 20
• Abnormal brain imaging
• Poor response to appropriate medications
• Abnormal neurological examination between episodes
• Attack duration longer than expected for the specific dystonia type 1

Understanding dystonic movements is crucial for proper diagnosis and management of affected patients, as appropriate treatment can significantly improve quality of life and reduce disability.