What is Dysarthria
Dysarthria is a collective term for a group of motor speech disorders that result from paralysis, weakness, or incoordination of the speech musculature after neurological damage 1.
Core Definition and Pathophysiology
Dysarthria fundamentally differs from language disorders (like aphasia) or motor planning disorders (like apraxia of speech). It is specifically a motor execution problem affecting the physical production of speech sounds. The disorder arises from damage to the nervous system that controls the muscles used for speaking 2.
Affected Speech Subsystems
Dysarthria can impair any combination of the five subsystems underlying speech production 1:
- Respiratory system - breath support and control for speech
- Laryngeal system - voice production and phonation
- Velopharyngeal system - resonance and nasal airflow regulation
- Oral-articulatory system - tongue, lips, and jaw movements for sound formation
- Prosodic system - rhythm, stress patterns, pitch variation, and speech rate
Clinical Presentation and Impact
Prevalence
Approximately 20% of stroke patients present with dysarthria, though the specific type and severity vary based on lesion location and extent 1.
Observable Characteristics
The speech disturbances manifest as problems with 3:
- Intelligibility - how well listeners understand the patient's speech
- Articulation precision - clarity of individual speech sounds
- Voice quality - may include breathiness, strain, or hoarseness
- Resonance - often hypernasality from velopharyngeal dysfunction
- Prosody - abnormal rhythm, stress patterns, rate, pitch, and loudness variations
Quality of Life Impact
The psychosocial impact of dysarthria is disproportionate to the severity of the physiological impairment 1. Motor speech disorders negatively affect:
- Social participation and community engagement
- Psychosocial well-being
- Overall quality of life
- Communication effectiveness in daily activities
Types of Dysarthria
Six major types exist based on neurological localization 2:
- Flaccid dysarthria - lower motor neuron damage
- Spastic dysarthria - upper motor neuron damage to cerebral cortex motor areas
- Ataxic dysarthria - cerebellar dysfunction affecting coordination 4
- Hypokinetic dysarthria - extrapyramidal system disorders (e.g., Parkinson's disease)
- Hyperkinetic dysarthria - extrapyramidal system with excessive movements
- Mixed dysarthria - damage to multiple areas producing combined features
Distinction from Related Disorders
Dysarthria vs. Apraxia of Speech
Apraxia of speech is a motor planning/programming disorder, not a weakness or coordination problem like dysarthria 1. Apraxia involves difficulty volitionally producing correct speech sounds despite intact muscle strength. It typically co-occurs with nonfluent aphasia.
Dysarthria vs. Aphasia
Aphasia is a language disorder affecting comprehension and expression, while dysarthria is purely a motor speech execution problem 5. Patients with dysarthria have intact language abilities but cannot physically produce speech normally due to muscle dysfunction.
Clinical Recognition
Key Warning Signs
The most relevant markers of dysarthria include 6:
- Conspicuous rhythm and stress pattern abnormalities
- Hypernasality
- Strained-strangled voice quality
- Reduced articulatory precision
Common Pitfall
In hospitalized patients, postprocedural dysarthria may be incorrectly attributed to anesthetic agents rather than recognized as a new neurological deficit 7. This can delay appropriate evaluation and treatment.
Assessment Requirements
Motor speech evaluation should systematically assess 3:
- Respiration (breath support and control)
- Phonation (voice production)
- Resonance (degree of hypernasality)
- Articulation precision
- Prosody (emphatic stress, intonation contours)
- Overall intelligibility with familiar and unfamiliar listeners
Evaluation uses auditory-perceptual, acoustic, and physiological measures across contexts ranging from isolated sounds to conversational speech 3.