Is dysarthria a sign of Parkinson's disease (PD)?

From the Guidelines

Dysarthria is a common sign of Parkinson's disease, though not everyone with Parkinson's will develop it. Dysarthria in Parkinson's typically manifests as hypokinetic dysarthria, characterized by soft, monotone speech, rapid speech patterns, and sometimes slurring. This speech disorder occurs because Parkinson's affects the motor control of muscles used for speaking, including those in the face, mouth, respiratory system, and larynx. The underlying cause is the depletion of dopamine in the brain, which impairs the coordination and strength of these muscles. Some key points to consider about dysarthria in Parkinson's disease include:

• Dysarthria can affect any of the subsystems underlying speech production, including the respiratory, laryngeal, velopharyngeal, and oral-articulatory subsystems 1.
• Speech therapy is the primary treatment for dysarthria in Parkinson's patients, with techniques like the Lee Silverman Voice Treatment (LSVT LOUD) showing particular effectiveness 1.
• While medications like levodopa that treat other Parkinson's symptoms may sometimes improve speech, their effect on dysarthria is often limited.
• Dysarthria typically appears after other classic Parkinson's symptoms like tremor, rigidity, and bradykinesia, so it's usually not the first sign of the disease.
• Voice therapy, as discussed in the 2018 clinical practice guideline on hoarseness (dysphonia), is effective for dysphonia across the life span, including in patients with Parkinson's disease–related dysphonia 1.

From the Research

Dysarthria as a Sign of Parkinson's Disease

• Dysarthria is a collective name for a group of neurologic motor speech disorders, resulting from central and/or peripheral nervous system abnormalities 2.
• In Parkinson's disease, dysarthria is characterized by hypokinetic dysarthria, which presents with prosodic insufficiency, related to a monotony of pitch and intensity, a reduction of accentuation, variable speech rate, and possible phoneme imprecision 2, 3.
• The symptoms of dysarthria in Parkinson's disease can affect both voice and speech quality, as well as prosody and intelligibility, leading to communication difficulties in daily living activities 2, 3.

Prevalence and Progression of Dysarthria in Parkinson's Disease

• Dysarthria is a common manifestation of Parkinson's disease, increasing in frequency and intensity with the progress of the disease 4.
• Hypokinetic dysarthria can appear at any stage of the disease, usually worsening as the disease progresses 5.
• Up to 20% of Parkinsonian patients are referred for speech and language therapy, aiming to improve the intelligibility of the patient's speech 4.

Treatment and Management of Dysarthria in Parkinson's Disease

• Traditional speech therapy can lead to improvement of dysarthria, with intensive programs having substantial beneficial effects on vocal loudness 3, 5.
• The use of levodopa to replenish dopamine concentrations in the striatum seems to improve articulation, voice quality, and pitch variation, although some studies show no change in phonatory parameters 3.
• Deep-brain stimulation procedures, such as stimulation of the subthalamic nucleus, can improve some motor components of speech, although intelligibility may decrease after surgery 3.
• A comprehensive speech therapy treatment, targeting the five subsystems of speech production, can result in significant improvements in tongue and lip strength, phonatory duration, intensity, and vocal quality 5.