What are the different types of dysarthria?

Types of Dysarthria

Dysarthria is classified into six major types based on underlying neuropathology: flaccid, spastic, ataxic, hypokinetic, hyperkinetic, and mixed dysarthria. 1

Major Types of Dysarthria and Their Neuroanatomical Basis

• Flaccid Dysarthria

  • Associated with lower motor neuron impairment
  • Affects muscles of speech production due to damage to cranial nerves or neuromuscular junction
  • Characterized by weak articulation, hypernasality, and breathy voice quality

• Spastic Dysarthria

  • Associated with upper motor neuron damage linked to motor areas of cerebral cortex
  • Features strained, harsh voice quality, slow speech rate, and imprecise consonants
  • Often seen in conditions affecting bilateral corticobulbar tracts

• Ataxic Dysarthria

  • Primarily caused by cerebellar dysfunction
  • Characterized by irregular articulatory breakdowns, distorted vowels, and excess and equal stress
  • Common in cerebellar disorders and multiple system atrophy 2

• Hypokinetic Dysarthria

  • Related to extrapyramidal system disorders, particularly basal ganglia
  • Features reduced loudness, monopitch, monoloudness, and rushed speech
  • Typically associated with Parkinson's disease and related disorders

• Hyperkinetic Dysarthria

  • Related to extrapyramidal system disorders
  • Two subtypes:
    • Choreatic: characterized by irregular, unpredictable movements
    • Dystonic: characterized by sustained abnormal postures affecting speech production

• Mixed Dysarthria

  • Associated with damage in multiple neurological areas
  • Presents with characteristics of at least two dysarthria types
  • Common in progressive neurological diseases like multiple system atrophy 2

Clinical Presentation and Diagnosis

The accurate classification of dysarthria types is challenging based on perceptual analysis alone. Studies have shown that the accuracy of classification based solely on listening to speech samples is poor (approximately 35%), with low inter-observer agreement 3. This highlights the importance of comprehensive assessment by speech-language pathologists using standardized tools 4.

Multiple system atrophy (MSA) provides an excellent example of mixed dysarthria. In a study of 46 MSA patients, 32 had all three components (hypokinetic, ataxic, and spastic), 13 had two components, and only 1 had a single component 2. The predominant dysarthria type often corresponds to the clinical subtype of MSA.

Management Approaches

Speech and language therapy is the primary intervention for dysarthria, targeting specific speech subsystems affected in each type:

• For flaccid dysarthria: Exercises to strengthen weak muscles
• For spastic dysarthria: Techniques to reduce muscle tone and improve coordination
• For ataxic dysarthria: Strategies to control speech rate and rhythm
• For hypokinetic dysarthria: Techniques to increase vocal intensity and speech rate control
• For hyperkinetic dysarthria: Methods to control involuntary movements affecting speech

Communication partner training has proven effective in improving communication activities 4. As dysarthria progresses, particularly in neurodegenerative conditions, augmentative and alternative communication approaches may become necessary 4.

Common Pitfalls in Diagnosis

1. Confusing dysarthria with aphasia (language disorder vs. motor speech disorder)
2. Relying solely on perceptual analysis for classification
3. Failing to recognize mixed dysarthria patterns
4. Not considering the broader neurological context when evaluating speech disorders

Advanced technologies like artificial intelligence models have shown promise in differentiating between dysarthria types, particularly ataxic and hypokinetic dysarthria, with higher accuracy than human clinicians 5.