Dysarthria is characterized by impaired muscle control over the speech mechanism as a result of central or peripheral nervous system damage. Unlike apraxia, dysarthria involves paralysis, weakness, decreased tone, or incoordination of the speech musculature. These muscles can be impaired with respect to range, strength, speed and timing and can affect respiration, phonation, resonance, articulation and prosody.
The major causes of dysarthria include stroke, brain tumors, head trauma, toxins and neuromuscular diseases, many of which are degenerative (e.g., Parkinson Disease, Multiple Sclerosis, etc.). The degree of impairment secondary to dysarthria can range in severity from quite mild to profoundly reduced speech intelligibility. The overall goal of dysarthria therapy is to improve speech intelligibility and speech motor control.