What are dysarthria and dysphagia?

Dysarthria and Dysphagia: Definitions and Clinical Significance

Dysarthria is a motor speech disorder resulting from paralysis, weakness, or incoordination of the speech musculature after neurological damage, while dysphagia is a swallowing disorder involving difficulty in the oral, pharyngeal, or esophageal phases of swallowing. 1

Dysarthria

Dysarthria affects the physical production of speech sounds through impairment of the respiratory, laryngeal, velopharyngeal, and/or oral-articulatory subsystems that underlie speech production. 1 The disorder manifests as:

• Reduced speech intelligibility and naturalness due to muscle weakness or incoordination 1
• Impaired articulation, resonance, phonation, respiration, or prosody depending on which subsystem is affected 1
• Slurred or unclear speech that may negatively affect social participation, psychosocial well-being, and quality of life 1

Approximately 20% of stroke patients present with dysarthria, though the specific type and characteristics vary based on lesion site and severity. 1

Dysphagia

Dysphagia involves impaired swallowing that threatens both respiratory safety (through aspiration risk) and nutritional adequacy. 1 The disorder can affect multiple phases:

Oral Phase Problems

• Weakness of lip muscles causes poor lip seal with drooling and food particles trapped in the buccal sulcus 1
• Weakness of masticatory muscles leads to poor chewing and inability to form a normal food bolus 1
• Weakness of tongue muscles impairs the tongue's ability to propel the food bolus 1

Pharyngeal Phase Problems

• Reduced soft-palate closure leads to reflux of food and liquid into the nose 1
• Altered pharyngeal peristalsis creates high risk of aspiration during swallowing due to incomplete epiglottic closure 1

Clinical Consequences

Dysphagia leads to three major complications: aspiration pneumonia, malnutrition, and reduced quality of life with anxiety during meals for both patients and caregivers. 1 The disorder affects food intake by increasing meal time and causing fatigue during and after meals. 1

Critical Clinical Relationship

Dysarthria serves as a predictor of dysphagia, particularly in stroke patients, and is associated with oral stage swallowing problems. 2 The two conditions frequently co-occur:

• Dysarthria and dysphagia co-exist in approximately 45% of patients with neurological diseases 3
• In ALS patients with spinal onset, over 70% have both dysarthria and dysphagia, with statistically significant correlation between their severity levels 4
• The presence of dysarthria should prompt evaluation for dysphagia to identify aspiration risk early 2

Prevalence Across Neurological Conditions

Dysphagia occurs in at least 50% of stroke patients, with these patients having a three-fold increased risk of developing early aspiration pneumonia and significantly higher mortality than non-dysphagic stroke patients. 1 In parkinsonian disorders, dysarthria appears earlier than dysphagia: median dysarthria latency is 24 months in PSP and MSA versus 84 months in Parkinson's disease, while dysphagia latencies are longer across all conditions. 5

Impact on Mortality and Quality of Life

Survival time after onset of dysphagia is similarly poor (15-24 months) across parkinsonian disorders, regardless of the specific diagnosis. 5 The latency to dysphagia complaint is highly correlated with total survival time (correlation coefficient 0.88), making it a critical prognostic indicator. 5

Both disorders profoundly impact quality of life through reduced communication effectiveness, social withdrawal, fear of eating, and nutritional compromise. 1, 4 In ALS patients, the severity of both dysarthria and dysphagia directly correlates with decreased swallowing quality of life, particularly affecting symptom frequency, communication, and fear of eating domains. 4