Dysarthria · What Is It, Causes, Signs, and More

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).

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.