Dysarthria refers to a speech disorder, caused by neuromuscular impairment, which results in disturbances in motor control of the speech mechanism. The demyelinating lesions caused by multiple sclerosis may result in spasticity, weakness, slowness, and/or ataxic incoordination of the lips, tongue, mandible, soft palate, vocal cords, and diaphragm. Therefore, articulation, speaking rate, intelligibility, and natural flow of speech in conversation are the areas most likely to be affected in those with multiple sclerosis. Intelligibility varies greatly depending on the extent of neurological damage.
Dysarthria is considered the most common communication disorder in those with MS. It is typically mild, with severity of dysarthria symptoms related to neurological involvement. Dysarthria evaluation in MS has traditionally included both informal and formal measures of a variety of oral-motor, speech, and voice functions, with comparison to referenced norms.
Dysphonia, which refers to a voice disorder, often accompanies dysarthria because the same muscles, structures, and neural pathways are used for both speech and voice production. Therefore, voice quality, nasal resonance, pitch control, loudness, and emphasis may also be affected in those with MS.
There are three types of dysarthria associated with MS: spastic, ataxic or mixed. Differential diagnosis depends on the extent and location of MS lesions, and the specific speech, voice, and accompanying physical signs that result. Mixed dysarthria is most common in MS, because multiple neurological systems are typically involved.
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How to Manage MS-Related Dyarthria (Speech Dysfunction)