What is Dysarthria?
Dysarthria is a motor speech disorder caused by impaired speech production due to muscle weakness, abnormal tone, and/or incoordination affecting articulation, phonation, resonance, prosody, and/or respiration. 1
Core Definition and Mechanism
Dysarthria results from neurological injury that reduces speech intelligibility through weak, imprecise, slow, and/or uncoordinated muscle control of the speech production system. 2 Unlike aphasia (which is a language disorder affecting the ability to formulate or understand language), dysarthria affects the motor execution of speech while the underlying language system remains intact. 3
Clinical Characteristics
The speech disturbances in dysarthria manifest through several observable features:
- Imprecise articulation with slurred speech quality 1
- Slow speech rate and excessive pausing 1
- Breathy or harsh voice quality 1, 4
- Hypernasality due to resonance problems 1
- Monopitch and monotonous loudness 1, 4
- Reduced stress patterns in speech 4
The severity ranges from mild slurring where speech remains intelligible, to severe dysarthria where speech becomes unintelligible or the patient is mute. 5
Underlying Pathophysiology
Dysarthria arises from damage to the motor speech system affecting multiple physiological components:
- Respiration deficits impacting breath support for speech 1, 6
- Phonation problems affecting voice production at the larynx 1, 6
- Resonance abnormalities from velopharyngeal dysfunction 1, 6
- Articulation impairment due to weakness or incoordination of tongue, lips, and jaw 1, 6
- Prosody disturbances affecting rhythm, stress, and intonation patterns 1, 6
Types of Dysarthria
Six major types exist based on neurological localization: flaccid (lower motor neuron), spastic (upper motor neuron), ataxic (cerebellar), hyperkinetic and hypokinetic (extrapyramidal), and mixed dysarthria (multiple sites). 6 Each type has distinctive speech characteristics that assist with neurological diagnosis. 6
Clinical Impact
The psychosocial impact of dysarthria is disproportionate to the severity of the physiological impairment, profoundly affecting quality of life, social participation, and psychosocial well-being. 1, 5, 3 Approximately 20% of stroke patients present with dysarthria. 7 The communication difficulties extend beyond the speech impairment itself, affecting social relationships and the ability to express personality. 6
Distinction from Aphasia
A critical clinical distinction: dysarthria is a motor speech disorder with intact language comprehension and formulation, whereas aphasia is a language disorder affecting the ability to understand or produce language content. 3 A patient with severe dysarthria may have completely normal language function but cannot physically articulate words clearly. 7