What is dysarthria, its medical causes and types?

Dysarthria: Definition, Medical Causes, and Types

Dysarthria is a motor speech disorder resulting from neurological damage that affects the muscles used for speech production, causing impaired articulation, phonation, respiration, resonance, and/or prosody. 1 It significantly impacts communication, social participation, psychological well-being, and quality of life, potentially leading to social isolation, depression, anxiety, and lifestyle changes.

Definition and Characteristics

Dysarthria is characterized by:

• Weak, imprecise, slow and/or uncoordinated muscle control affecting speech 2
• Disturbances in respiration, laryngeal function, airflow direction, and articulation 3
• Reduced speech intelligibility and naturalness
• Preserved language function (unlike aphasia)

Medical Causes

Dysarthria results from damage to the central or peripheral nervous system affecting the motor control of speech muscles. Common causes include:

1. Stroke: Affects approximately 20% of stroke patients 1
2. Traumatic brain injury
3. Neurodegenerative disorders:
   • Parkinson's disease
   • Multiple system atrophy
   • Motor neuron disease (ALS)
4. Cerebellar disorders
5. Tumors
6. Infections
7. Surgical complications

Types of Dysarthria

There are six major types of dysarthria, each with distinctive speech characteristics that can assist with diagnosis 3:

1. Flaccid Dysarthria

   • Associated with lower motor neuron damage
   • Characteristics: breathy voice, hypernasality, imprecise consonants
   • Causes: cranial nerve damage, myasthenia gravis, Guillain-Barré syndrome

2. Spastic Dysarthria

   • Associated with upper motor neuron damage
   • Characteristics: strained-harsh voice quality, slow rate, imprecise articulation
   • Causes: bilateral stroke, cerebral palsy, multiple sclerosis

3. Ataxic Dysarthria

   • Associated with cerebellar dysfunction
   • Characteristics: irregular articulatory breakdowns, excess and equal stress, irregular pitch and loudness
   • Causes: cerebellar stroke, multiple sclerosis, cerebellar degeneration

4. Hypokinetic Dysarthria

   • Associated with basal ganglia dysfunction
   • Characteristics: monotone, reduced loudness, variable rate, short rushes of speech
   • Causes: Parkinson's disease 4

5. Hyperkinetic Dysarthria

   • Associated with basal ganglia dysfunction
   • Characteristics: excess loudness variations, prolonged intervals, distorted vowels
   • Causes: Huntington's disease, dystonia, chorea

6. Mixed Dysarthria

   • Associated with damage to multiple motor systems
   • Characteristics: features of two or more dysarthria types
   • Causes: multiple sclerosis, amyotrophic lateral sclerosis, multiple strokes

Assessment and Diagnosis

Accurate diagnosis requires:

• Formal assessment by speech-language pathologists using standardized tools 1
• Evaluation of all speech subsystems: respiration, phonation, resonance, articulation, and prosody 5
• Motor speech evaluations to establish the presence and severity of dysarthria 5
• Auditory-perceptual, acoustic, and physiological measures 5

Relying solely on perceptual analysis has poor accuracy (35%) and low inter-observer agreement 1.

Management Approaches

Management of dysarthria should be individually tailored and can include:

1. Behavioral techniques targeting:

   • Physiological support for speech (respiration, phonation, articulation, resonance)
   • Global aspects of speech production (loudness, rate, prosody) 5

2. Environmental modifications:

   • Listener education
   • Reducing noise levels 5
   • Communication partner training 1

3. Augmentative and alternative communication (AAC):

   • May be necessary as the condition progresses 1
   • Should supplement speech when needed 5

4. Telerehabilitation:

   • Useful when face-to-face treatment is impossible or impractical 5
   • Emerging evidence supports feasibility 5

5. Psychosocial support:

   • Activities to facilitate social participation
   • Promotion of psychosocial well-being 5

Common Pitfalls in Diagnosis and Management

• Confusing dysarthria with aphasia (dysarthria affects speech production, not language)
• Failing to distinguish between different types of dysarthria
• Relying solely on perceptual analysis without formal assessment
• Not recognizing mixed dysarthria patterns 1
• Overlooking the psychosocial impact, which can be disproportionate to the severity of the physiological impairment 5

Despite the prevalence and impact of dysarthria, there is limited high-quality evidence on the effectiveness of interventions. Current research indicates potential immediate beneficial effects at the impairment level, but more research is needed 2.