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Section 6. Neurologic Disorders
Chapter 45. Speech and Language Disorders
Topics:    Introduction | Aphasia | Dysarthria

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Dysarthria

Dysarthria is impaired articulation due to neuromuscular deficits. When possible, the causative disorder is treated. Treatment may also include speech therapy.

Dysarthria is the most common speech disorder. The term dysarthria is sometimes used loosely to refer to any speech disorder. However, technically, dysarthria refers to impairment of articulation (the process by which word sounds are formed as the air stream from the vocal cords is altered by the pharynx, palate, tongue, jaw, teeth, lips, and face). Disorders of the brain (eg, stroke, multiple sclerosis, Parkinson's disease), motor neurons (eg, amyotrophic lateral sclerosis), cranial nerves (eg, Bell's palsy), neuromuscular junction (eg, myasthenia gravis), or muscles can cause incoordination or weakness of speech muscles resulting in dysarthria. Dysarthria does not affect reading and speech comprehension, spelling, and writing; however, these abilities can also be impaired in patients with brain lesions that cause dysarthria and aphasia.

Dysarthria may be ataxic, flaccid, hyperkinetic, hypokinetic, spastic, or mixed (see Table 45-3). The term speech apraxia is sometimes used to refer to impaired articulation caused by abnormal sequencing of the muscle movements required for producing speech sounds. Speech apraxia is characterized by inconsistent articulation errors. Speech apraxia and Broca's aphasia often coexist.

Dysarthria should be distinguished from impairment of speech due to other conditions, such as laryngeal and vocal cord disorders (eg, vocal cord tumor, arthritis, vocal cord inflammation due to gastroesophageal reflux disease), esophageal disorders, myxedema, and drugs that decrease salivation.

Differentiating among speech disorders is sometimes difficult because their features often overlap or coexist.

When possible, the disorder causing dysarthria (eg, Parkinson's disease, myasthenia gravis) is treated. If the disorder cannot be effectively treated or if dysarthria persists despite treatment, speech therapy is provided; patients are taught to control the rate of speech, to emphasize consonants, and to articulate. In a speech laboratory, various assessment methods (eg, visual and auditory feedback methods, quantitative acoustic assessment of vocal quality, analysis of speech parameters) may be used to help direct treatment. If speech remains incomprehensible, augmentative communication devices similar to those used for patients with aphasia can be used.

This topic was last updated March 2006.

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