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Dysarthria is the term for a medical condition that is characterized by impaired speech, the origin of which is considered to be a disorder of the nervous system. As such, the condition is usually accompanied by poor control of muscles in the face and neck due to dysfunction of various cranial and facial nerves. Dysarthria may also involve a number of secondary systems related to speech and articulation, such as the respiratory system. The effects of these disturbances typically produce speech that is labored and lacking in normal pitch and intonation.
There are many factors that can cause dysarthria to occur. Traumatic brain injury, stroke, or brain tumors often damages motor neurons, which are responsible for coordinating signals from various parts of the brain and brain stem to precisely execute muscle movements. Dysarthria may also result from various neurodegenerative disorders, such as Huntington’s disease, cerebral palsy, multiple sclerosis, or Parkinson’s disease. Since this is the case, any sudden onset of impaired speech should be investigated without delay.
Dysarthria assessment is made according to the symptoms observed, which enables the clinician to categorize the condition. The general speech qualities examined are articulation, resonance, phonation, and prosody (rhythm and meter), with each area being impacted differently depending on the location and extent of neuron damage. For example, spastic dysarthria is related to nerve damage along the pyramidal tract, while ataxic dysarthria is caused by cerebellar dysfunction. Flaccid dysarthria is associated with damage to cranial nerves, and hyperkinetic dysarthria is associated with the formation of lesions of the basal ganglia. Hypokinetic dysarthria, on the other hand, is the result of lesions along the substantia nigra, a consequence specific to Parkinson's disease.
Dysarthria treatment is primarily administered by a speech pathologist, who will engage the patient in a variety of exercises to help improve pronunciation and voice inflection. One of the key goals is to slow down the rate of speech in order to be better understood. Pacing speech may be practiced with the aid of a metronome, which cues the patient to pronounce one syllable at a time in sync with instrument’s ticking noise. Some speech therapists employ pacing boards or graduating sticks, which require the patient to tap or touch a designated target each time a syllable is spoken.
A number of compensation techniques may also be explored. For instance, patients who have difficulty making a hard “t” or “d” sound may be encouraged to produce the sound by bringing the flat blade of the tongue to meet the teeth rather that the tip. Some patients may need to overstress the pronunciation of consonants, while others may need to become more aware of the tendency to suddenly erupt into loud speech. Additional therapeutic techniques involve role playing drills and mirroring exercises, followed by the therapist provoking the same response but without any visual or auditory cues.
Speech therapy usually improves overall speech for most patients. However, severe cases may necessitate the use of alternative communication methods, such as sign language. In some cases, surgical intervention may help, such as modification to the pharyngeal flap. In addition, prosthetic devices are available, including obturator and speech bulb implants, or non-invasive devices that either synthesize or digitize speech.