What is dysarthric speech?

What Dysarthric Speech Means

Dysarthric speech is a motor speech disorder caused by weakness, paralysis, or incoordination of the muscles used for speaking, resulting in slurred, slow, or imprecise articulation that reduces speech intelligibility while language comprehension and formulation remain intact. 1, 2

Core Definition and Characteristics

Dysarthria fundamentally differs from language disorders like aphasia because the underlying speech motor system is impaired, not the ability to formulate or understand language. 1 Patients with dysarthria can construct phrases correctly, have preserved vocabulary and grammatical structure, and maintain normal reading comprehension, writing ability, and understanding of others' speech. 3

Primary Speech Features

The hallmark characteristics include:

• Imprecise articulation of consonants - the most frequently observed feature in dysarthric patients 4
• Slurred speech with "swallowing" of sounds and unintelligible articulation 3
• Slow articulatory movements with patients describing sensations of a "thick tongue" or "porridge in the mouth" 3
• Harsh voice quality and audible inspiration during speech 4
• Reduced speech intelligibility despite preserved language content 2

Clinical Severity Spectrum

Dysarthria severity ranges across a continuum:

• Mild to moderate dysarthria presents as noticeable slurring but speech remains intelligible to listeners, with thickened or imprecise quality while meaning is preserved 5
• Severe dysarthria renders speech completely unintelligible or the patient may be mute 5
• On the NIH Stroke Scale, mild-to-moderate dysarthria (score of 1) indicates slurred but comprehensible speech when reading standardized word lists 5

Affected Speech Subsystems

Dysarthria results from disturbances across multiple physiological systems required for speech production:

• Respiration - impaired breath support for speech 2, 6
• Phonation - abnormal voice production at the larynx 2, 6
• Resonance - altered nasal/oral airflow balance 2, 6
• Articulation - imprecise movement of tongue, lips, and jaw 2, 6
• Prosody - disrupted rhythm, stress, and intonation patterns 2, 6

Neurological Classification

Six major types exist based on underlying neuropathology:

• Flaccid dysarthria - from lower motor neuron damage 2
• Spastic dysarthria - from upper motor neuron damage to cerebral cortex motor areas 2
• Ataxic dysarthria - primarily from cerebellar dysfunction 2
• Hypokinetic dysarthria - from extrapyramidal system disorders (e.g., Parkinson's disease) 2
• Hyperkinetic dysarthria - from extrapyramidal system disorders with excessive movements 2
• Mixed dysarthria - from damage to multiple areas producing combined features 2

Unilateral upper motor neuron (UUMN) dysarthria is the dominant type following acute ischemic stroke, present in 52% of post-stroke dysarthria cases. 4

Common Neurological Causes

Dysarthria should immediately raise concern for:

• Stroke - particularly with bulbar involvement affecting cranial nerves IX, X, and XII 7
• Parkinson's disease - the leading cause of hypophonia and slowed speech 7, 6
• Motor neuron disease (ALS) - causes progressive bulbar palsy with speech impairment 7
• Multiple sclerosis - can produce various dysarthria types 6, 7
• Cerebellar disorders - produce ataxic dysarthria 2
• Wilson's disease - manifests with dysarthria that can be cerebellar or extrapyramidal, potentially leading to aphonia 6

Associated Clinical Features

Dysarthria frequently occurs alongside:

• Drooling - from impaired swallowing and reduced oral motor control, particularly in Parkinson's disease and bulbar palsy 7, 6
• Dysphagia - swallowing difficulties from shared neuromuscular impairment 6
• Facial grimacing, open jaw, and lip retraction - characteristic in conditions like Wilson's disease 6

Functional Impact

The psychosocial consequences are disproportionate to the severity of physiological impairment:

• Communication difficulties profoundly affect social participation and quality of life 6, 1
• Speech changes and drooling are often early neurologic symptoms that signal underlying disease 6
• Patients may become progressively unable to communicate despite remaining alert and cognitively intact 6

Recovery Patterns

In acute ischemic stroke:

• Approximately 44-46% of patients develop dysarthria in the acute phase 4
• Half of stroke patients with dysarthria show complete recovery within one week following symptom onset 4
• The majority of post-stroke dysarthria cases are mild in severity 4