What Is It, Causes, Signs and More
Author: Lily Guo
Editors: Alyssa Haag, Ian Mannarino, MD, MBA, Kelsey LaFayette, DNP, RN
Illustrator: Jessica Reynolds, MS
Copyeditor: Sadia Zaman, MBBS, BSc
What is dysarthria?
Dysarthria refers to a disorder in which the muscles used for speech are weakened, thereby resulting in slurred and slow speech that may be incomprehensible. People with dysarthria may be unable to control the muscles that are used for articulation, speed, and pitch of speech. Dysarthria is a common sign in nervous system disorders and can be divided into subtypes, such as hypokinetic, flaccid, and mixed dysarthria. Hypokinetic dysarthria is characterized by difficulty starting sentences and stuttered or slurred speech; flaccid dysarthria is marked by difficulty pronouncing consonants; and mixed dysarthria is a combination of various types.
What causes dysarthria?
Common causes of dysarthria include nervous system disorders and conditions that can cause facial paralysis, tongue or throat muscle weakness. An example of a nervous system disorder that typically causes dysarthria is amyotrophic lateral sclerosis (ALS), also referred to as Lou Gehrig disease. ALS is a progressive neurodegenerative disorder that attacks the motor neurons in the brain and spinal cord. It causes dysarthria because the bulbar (i.e., cranial) neurons are affected. Bulbar neurons are the nerve cells responsible for bringing messages from the lower parts of the brainstem (i.e., bulbar region) to the muscles that move the lips, tongue, soft palate, jaw, and vocal folds. Other nervous system disorders that cause dysarthria include Parkinson disease, Guillain-Barre syndrome, myasthenia gravis, Lambert Eaton syndrome, multiple sclerosis, cerebral palsy, Huntington disease, and muscular dystrophy. Parkinson disease is characterized by hypokinetic dysarthria, which can present with a soft tone and short rushes of speech. Guillain-Barre syndrome, Lambert Eaton syndrome and myasthenia gravis, all of which are autoimmune conditions that may attack the bulbar muscles, present with flaccid dysarthria. Similarly, a group of genetic conditions referred to as muscular dystrophies, may lead to the progressive loss of muscle mass and coordination, resulting in flaccid dysarthria. Multiple sclerosis is a demyelinating disease affecting the conduction rate of the nervous system and may result in mixed dysarthria. Cerebral palsy is a congenital disorder that results in difficulty with movement, posture, and coordination, and can affect the muscles used for speech. Huntington disease is an inherited disease that causes the degeneration of nerve cells in the brain and can lead to loss of coordination in speech producing muscles. Both cerebral palsy and Huntington disease may result in varying presentations of dysarthria.
Finally, other causes of dysarthria include strokes, brain injury or trauma, surgery to structures of speech, which include the vocal cords, lips, tongue and oropharynx, and medications used for sedation (e.g., barbiturates, benzodiazepines) and seizures (e.g., carbamazepine, phenytoin).
What are the signs and symptoms of dysarthria?
The signs and symptoms of dysarthria include slurred and slowed speech; inconsistencies in volume of speech (e.g., talking too quietly or too loudly); rapid or unusual speech rhythm that is difficult to understand; a sudden onset of a high pitched nasal voice; monotone speech; and difficulty moving the tongue or facial muscles. Hypokinetic dysarthria presents with reduced vocal volume, a monotone voice, reduced frequency range of speech, imprecise consonant and vowel pronunciation, breathiness when speaking, and short rushes of speech with irregular pauses. Flaccid dysarthria results in problems with breathing, phonation, and articulation, and leads to a nasal speech pattern that is difficult to understand. Mixed dysarthria is defined by impaired loudness control, harsh or hypernasal voice quality, impaired articulation, impaired emphasis, and impaired pitch control.
How is dysarthria diagnosed?
Dysarthria is typically diagnosed upon physical examination and after obtaining a medical history by a licensed clinician, such as a speech-language pathologist or a neurologist. They may order various tests to pinpoint the underlying cause of the speech disorder. This includes imaging the brain, head and neck with investigations such as magnetic resonance imaging (MRI) or computerized tomography (CT) scans. A brain and nerve study, such as an electroencephalogram (EEG), can be used to measure electrical activity in the brain; blood and urine tests can help determine if there is an underlying infectious or inflammatory disease; and a brain biopsy may assess for malignancy if a brain tumor is suspected in a person with dysarthria.
How is dysarthria treated?
Treatment for dysarthria depends on the cause, severity of symptoms, and the type of dysarthria. Nonetheless, speech therapy can help a patient regain normal speech and improve communication. The speech-language pathologist will typically work with the individual to adjust speech rate, strengthen the muscles of speech, increase breath support, improve articulation, and help family members and friends better understand the individual to improve communication. If speech and language therapy is not effective, the therapist may offer training in other communication methods, such as visual cues (e.g., sign language), gestures, an alphabet board, and other computer-based technologies.If the dysarthria is caused by prescription medications, the clinician may change or stop the causative medications. If dysarthria is caused by Parkinson disease, the clinician may try to manage the disease with medications, such as levodopa or dopamine agonists (e.g., pramipexole, ropinirole). Multiple sclerosis can be managed with medications that suppress the immune system such as glucocorticoids, while individuals with ALS may be prescribed the drug riluzole, which may slow progression of the disease. Guillain-Barre may be treated with plasmapheresis (i.e., the removal, treatment, and re-injection of blood) followed by intravenous injections of immunoglobulin G (IVIG). As Guillain-Barre syndrome occurs due to the production of harmful antibodies that act against one’s immune system, IVIG is able to replace the harmful antibodies with healthy ones. Finally, myasthenia gravis can be treated with medications such as cholinesterase inhibitors (e.g., pyridostigmine), which enhances communication between nerves and muscles.
Can dysarthria be cured?
Dysarthria may be able to be cured depending on the cause. In most cases of nervous system disorders, the symptoms can be degenerative and will continue to worsen. In such cases, dysarthria cannot be cured. However, in cases of medication-induced dysarthria, discontinuing the medication should improve the symptoms. Dysarthria caused by a stroke or brain injury will typically not worsen, and may improve over time. Lastly, dysarthria after surgery to the anatomical structures relevant in speech should not worsen, and may improve with appropriate therapy.
What are the most important facts to know about dysarthria?
Dysarthria refers to the weakening of the muscles used for speech, thereby resulting in abnormalities in the articulation, speed, and pitch of speech. Nervous system disorders that cause dysarthria include ALS, Parkinson disease, Guillain-Barre syndrome, Lambert-Eaton syndrome, myasthenia gravis, and multiple sclerosis. Medications, strokes, and brain damage can also cause dysarthria. The diagnosis of dysarthria relies on physical examination and distinguishing the underlying cause. This can include use of imaging and laboratory testing. Treating the symptoms depends on the cause, but nonetheless may include supportive speech therapy. Dysarthria can sometimes be cured depending on the cause, however, in other cases, may require long-term management with supportive measures (e.g., using alphabet boards and computer technology) to improve the quality of life.
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Resources for research and reference
ALS Association. (2020, June 10). FYI: Suggestions and information about Speech Changes & Augmentative Alternative Communication (AAC). In The ALS Association. Retrieved February 21, 2022, from https://www.als.org/navigating-als/resources/fyi-suggestions-and-information-about-speech-changes#:~:text=ALS%20leads%20to%20speech%20problems,vocal%20folds%20(voice%20box).
American Speech-Language-Hearing Association. (2022). Dysarthria. In American Speech-Language-Hearing Association. Retrieved February 21, 2022, from https://www.asha.org/public/speech/disorders/dysarthria/
Figueiredo, M. (2020, December 1). Dysarthria in MG Linked to Changes in Breathing, Other Motor Bases of Speech. In Myaesthenia Gravis News. Retrieved February 21, 2022, from https://myastheniagravisnews.com/news-posts/2020/12/01/dysarthria-in-mg-linked-changes-in-breathing-other-motor-bases-of-speech-study-shows/#:~:text=In%20people%20with%20myasthenia%20gravis,a%20small%20study%20from%20Brazil.
Miller, P. H. (2018). A Resource for Healthcare Professionals Dysarthria in Multiple Sclerosis. In National MS Society. Retrieved February 21, 2022, from https://www.nationalmssociety.org/NationalMSSociety/media/MSNationalFiles/Brochures/Clinical_Bulletin_Dysarthria-in-MS.pdfTomik, B., Guiloff, R. J. (2010). Dysarthria in amyotrophic lateral sclerosis: A review. Amyotrophic lateral sclerosis: official publication of the World Federation of Neurology Research Group on Motor Neuron Diseases, 11(1-2): 4-15. DOI:10.3109/17482960802379004