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ICD 784.5

Article by:
Sarah Morales, BS
Children's Speech Care Center

Dysarthria (also called slurred speech) involves disturbances in control over speech muscles. Thus, dysarthria is grouped in the category of motor speech or speech motor disorders. Dysarthria occurs due to impairment or damage to the nervous system (brain, spinal cord, nerves in the body). The speech muscles themselves may be impaired, weak or paralyzed, or the areas of the brain responsible for coordinating their function may be affected or damaged. This disorder is more common in elderly persons, sometimes present as the result of a stroke. The disorder could also occur due to tumors in the nervous system or a traumatic head injury. Degenerative diseases (diseases that worsen over time) such as Parkinson’s disease, amyotrophic lateral sclerosis, dementia, Huntington’s chorea, syphilis, and other neurological diseases (diseases that destroy nervous system tissue over time) are other causes of dysarthria. Metabolic diseases such as sickle-cell anemia or toxin exposure (i.e. lead/mercury poisoning) are also potential causes of dysarthria. Although commonly seen in adults, dysarthria is also seen in children due to paralysis, weakness, altered muscle tone or incoordination of the muscles used in speaking. Conditions such as cerebral palsy can cause dysarthric speech.

There are several types of dysarthria based on the patient’s site of lesion (area of nervous system damage). Flaccid dysarthria involves muscle weakness and loss of muscle tone. This patient’s speech is breathy, weak, lacking in intonation (melody), and has imprecise consonants. Reflexes are absent. Spastic dysarthria involves excessive muscle tension and overly sensitive reflexes. This patient’s voice often sounds strained or strangled, and reflexes are so easily elicited that these extraneous movements interfere with speech production. Ataxic dysarthria involves difficulty in coordinating the rate, range, and force of speech movements. This patient may over- or undershoot the appropriate positions of the articulators (lips, tongue, jaw) in speech. Hyperkinetic dysarthria involves a loss of inhibitory (stopping, halting, slowing) control—thus, abnormal, involuntary movements interrupt speech. These may occur in the form of tremors (shaking), tics (sudden jerks), athetosis (writhing movements), or dystonia (movement to an extraneous posture and momentary freezing in that position). Hypokinetic dysarthria involves a lack of movement, usually caused by Parkinson’s disease. As one of my professors once described this disorder, “it puts you in a box”—in other words, it limits the patient’s amount, range, and force of movement.

Dysarthria may appear similar to another disorder called verbal dyspraxia. However, these two disorders are quite different. Dysarthria involves distortions of speech sounds (slurred sounds) and speech may be slow or effortful because of poor muscle control, whereas the person with verbal dyspraxia is more likely to have difficulties initiating and/or sequencing sounds for speech. They may show groping behaviors or omit, substitute or “mix up” sounds/syllables due do poor motor speech programming within the brain. The person with verbal dyspraxia has difficulty pronouncing sounds, syllables and words because they cannot consistently find the correct placement for the speech structures. Unlike dysarthria, nothing is wrong with the muscles themselves. The person with dysarthria is more likely to exhibit skill in copying another person’s example of speech. Apraxia is also a disorder that is highly resistant to treatment (responds poorly or slowly to treatment). The second link listed below offers more information on distinguishing these two disorders.

The diagnosis of dysarthria is usually made in a team approach. Speech-language pathologists work closely with many professionals (i.e. physician, neurologist, occupational or physical therapist) to diagnose and rehabilitate patients with dysarthria. In severe cases, augmentative and alternative communication (additions to/replacements for speech--i.e. sign language, computerized speech) may be necessary.

For more information, view the following links:



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