How to Manage MS-Related Dysarthria (Speech Dysfunction)

DYSARTHRIA in multiple sclerosis ranges in prevalence from 41% to 51% according to studies.  Speech and voice problems may be identified by the person with MS, a family member, or a healthcare professional.  Common complaints include difficulty with precision of articulation (causing the slurring of speech), speech intelligibility, ease of conversational flow, speaking rate, loudness, and voice quality.  In very severe cases, vowels may also be distorted.  When these problems interfere with a person’s quality of life—particularly the ability to communicate daily needs—a referral for evaluation and treatment by a speech/language pathologist is recommended.

The normal processes of speech and voice production are overlapping and require the following five processes to work together smoothly and rapidly:

• Respiration:  Using the diaphragm to quickly fill the lungs fully, followed by slow, controlled exhalation for speech.

• Phonation:  Using the vocal cords and air flow to produce voice of varying pitch, loudness, and quality.

• Resonance:  Raising and lowering the soft palate to direct the voice to resonate in the oral and/or nasal cavities to further affect voice quality.

• Articulation:  Coordinating quick, precise movements of the lips, tongue, mandible, and soft palate for clarity of speech.

• Prosody:  Combining all elements for a natural flow of conversational speech, with adequate loudness, emphasis, and melodic line to enhance meaning.

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.