In dysarthria, there are inherent problems in converting the mentally formulated word patterns into understandable speech. Many structures are involved in this basically complex process. A stream of air must pass through the vocal cords into the oral cavity. Here it is further modified by movements of the palate, tongue and lips, to issue forth as understandable words. Disorders of this system are referred to as dysarthria.
In simple dysarthria there is no abnormality of the brain centers. The patient is able to understand perfectly what is heard and, if literate, can read and write without difficulty, even though the person is unable to articulate a single intelligible word.
The whole process depends on a smooth, uninterrupted flow of impulses via the nervous system to the parts involved. If there is any reduction in this flow, then normal speech is impeded. A large number of nervous-system disorders may give rise to defects in the normal flow of impulses.
Generalized damage to the blood vessels is common. This may be due to various degrees of atherosclerosis in which the vessel walls thicken and prevent the normal supply of oxygen and nutritive elements to the affected parts.
Hemiplegic degenerative lesions of the nerve tracts such as disseminated sclerosis, or tumors of the brain may all be responsible. In motor neuron disease, and myasthenia gravis, it may have a more local effect on essential structures involved in the production of speech.
Sometimes, chronic intoxication and drug poisoning may cause similar symptoms. Treatment and outlook for this defect depend entirely on the underlying cause and the prospects for assisting this.