Dysarthria is a group of speech disorders caused by disturbance of control of the muscles, usually resulting from damage to the central or peripheral nervous system, and associated with certain neurodegenerative diseases like Parkinson's disease, Huntington's disease, cerebral palsy, brain tumors, stroke, or brain injury. In children dysarthria, a disorder of output, needs to be differentiated from verbal apraxia, a disorder of central nervous system processing (Bates, 2000). These two disorders are often poorly understood and differentiated by physicians and even speech therapists. Verbal apraxia is characterized by a child's inability to plan an execute voluntary movements of speech. Verbal output is decreased in these children: they don't say much. With dysarthria, there is disordered output: the children can plan, but because of a problem with the actual motor control centers, the child is unable to carry out the plan. Children with dysarthria often have very unusual characteristics to their voices. The may have abnormal speech patterns and make many mistakes. They may have slurred speech which varies in pitch and in volume. However, they will speak words in the correct order. Children with dysarthria may substitute consonants in their speech. These children will exhibit some evidence of neuromuscular difficulties other than in their speech and language development. For instance, they may have problems with swallowing and feeding, and may drool. Underlying neurological impairment such as cerebral palsy, traumatic brain injury, neuromuscular disorder or central nervous system hypotonia usually accompanies dysarthria in children.
A group of 10 women with amyotrophic lateral sclerosis (ALS) were studied for their speech intelligibility and its phonetic and acoustic correlates, and the results compared to those of a group of normal geriatric adults as controls (Kent et al, 1992, 723-733). A word-identification test ...