Dysarthria is a motor speech disorder. The muscles used to produce coherent language are weakened, or there is a lack of control over them. As a result, an individual with dysarthria has difficulty moving and controlling the muscles of their mouth, lips, tongue, face, and/or upper respiratory tracts involved in speech production. Dysarthria should not be confused with apraxia of speech, in which the muscles are intact and fully developed.
Dysarthria is a motor language disorder affecting the muscles needed for speech production.
Dysarthria can affect children and adults.
The primary treatment for dysarthria is speech therapy.
Additional ways of communicating are important for living with dysarthria.
Types and causes of dysarthria
As with other motor disorders of speech, dysarthria can be developmental or acquired.
Developmental dysarthria is a motor speech pathology in infants or children. In this case, the condition is caused by the following:
Disease, for example, cerebral palsy, affects all muscles in the body, including those required for speech production.
Brain damage is caused either in the womb or at birth.
Acquired dysarthria is a motor speech pathology in adults. In this case, the weakening or loss of muscles control required for speech is caused by the following:
Brain damage, pathology. For example, tumors, stroke, or trauma.
Note: Dysarthria is a side effect of some medications, for example, lithium, trifluoperazine, and onabotulinum toxin A.
Dysarthria is further subcategorized based on the affected parts of the nervous system:
Peripheral dysarthria is diagnosed when damage occurs to the muscles needed for speech, for example, the tongue, surrounding facial, neck muscles, and parts of the respiratory system (e.g., larynx).
Central dysarthria is caused by damage in the central nervous system — the brain. Depending on the site of damage the following categories of dysarthria are defined:
- Flaccid — the lower motor neurons
- Spactic — the upper motor neurons
- Mixed — upper and lower motor neurons
- Hypokinetic — the extrapyramidal tract and substantia nigra
- Hyperkinetic — the extrapyramidal tract and basal ganglia
- Ataxic damage to cerebellar
There isn’t much data on the prevalence of dysarthria, with most studies focusing on particular clinical groups. Dysarthria most commonly occurs in patients with motor diseases such as ALS, with the estimate being as high as 90%. In individuals who suffer from Parkinson’s disease (PD, link to relevant article), the prevalence of dysarthria is between 50% and 90% depending on disease progression. Dysarthria is also common in patients with cerebral palsy, with approximately 40% of them developing this motor speech pathology. And finally, stroke patients, with approximately 20% prevalence.
Studies show that most patients with progressive neurological diseases — where the disease worsens over time — will acquire a motor speech disorder, most commonly dysarthria. In these cases, dysarthria presents as a secondary illness caused by the effects of the primary disorder leading to respiratory difficulties or motor degeneration.
In the case of developmental dysarthria, the estimated prevalence in the general population is 1 in 1000 children. However, scientists lack consensus on the onset, criteria, and prevalence counts of dysarthria in children.
Dysarthria affects both genders equally.
Dysarthria has multiple causes; therefore, symptomatology varies from individual to individual. Furthermore, symptoms vary in type and severity. An individual with dysarthria will exhibit several of the following characteristics.
- Inability to control speech volume (whispering or talking too loudly)
- Slurred speech
- Inability to control speech tempo (talking very rapidly, very slowly, or involuntarily alternating tempo)
- Difficulty with intonation (e.g., monotone speech)
Other related symptoms:
- Difficulty swallowing
- Difficulty moving tongue
- Partial paralysis of facial muscles
- Difficulty controlling facial muscles
In dysarthria, the individual has trouble controlling speech-related muscles to produce coherent words and sentences. This results in language that may be difficult for others to understand. It is common for individuals with dysarthria to have difficulties in social, occupational, and educational settings because of a lack of ability to communicate coherently.
The primary treatment for childhood and acquired dysarthria is speech and language therapy. Given that this speech pathology results from many causes, a dedicated speech pathologist will offer the best, tailored treatment plan. In essence, therapy encourages the patient to use their speech and helps them to (re)learn how to use it more effectively. For example, therapists show patients how to increase or decrease tempo or tone. Successful therapy widens the range of sounds an individual with dysarthria can produce.
In severe cases, in addition to spoken language, the therapist may suggest introducing augmentative and alternative communication (ACC). ACC’s primary aim is to increase the communicativeness of an individual. This is achieved by using additional “ways” of expressing oneself correctly. In the most simplistic cases, they can be line drawings or printed words. Nowadays, electronic devices and manual communication boards are available — these are especially useful for more severe cases of dysarthria. Studies have shown ACC to be extremely helpful for individuals who have a desire to communicate but have difficulty with language production.
With successful treatment and support, many individuals with dysarthria find ways to communicate and interact with others. If you have a child or a close one with dysarthria, discuss treatment options with your speech pathologist. They can provide you with exercises to do at home as well as demonstrate some creative ways of communicating without speech.
It has been noted that without support and treatment, individuals with dysarthria may experience social isolation. In severe cases, social isolation results in depression. If you have a close one who suffers from dysarthria, they need your support. Attempting to communicate and understand them can be very helpful in easing their feeling of loneliness.
- Clinical Linguistics & Phonetics. Estimates of the prevalence of motor speech disorders in children with idiopathic speech delay.
- Handbook of Clinical Neurology. Disorders of communication: dysarthria.
- Clinician's Guide to Assistive Technology. Augmentative and Alternative Communication.