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.
1. SPASTIC DYSARTHRIA: Due to bilateral lesions of corticobulbar tracts
- Harsh, strained voice quality
- Pitch breaks
- Imprecise articulation
- Slow rate of speech
- Reduced breath support and/or control
- Reduced or mono-loudness
- Short phrases, reduced stress
- Hypertonicity (excess muscle tone)
- Bilateral spasticity
- Restricted range of motion (jaw)
- Reduced speed of movement
- Bilateral hyperreflexia
- Sucking and jaw jerk reflexes
- Cortical disinhibition
2. ATAXIC DYSARTHRIA: Due to bilateral or generalized lesions of the cerebellum
- Vocal tremor
- Irregular articulation breakdown
- Dysrhythmic rapid alternating movements of the tongue, lips, and mandible
- Excess and equal stress (scanning speech)
- Excess and variable loudness
- Prolonged phonemes and intervals
- Intention tremor: head, trunk, arms, hands
- Broad-based, ataxic gait
- Nystagmus and irregular eye movements
- Balance or equilibrium problems
- Hypertonicity (excess muscle tone)
- Overshooting: slow, voluntary movements
3. MIXED DYSARTHRIA: Due to bilateral, generalized lesions of multiple areas in the cerebral white matter, brainstem, cerebellum, and/or spinal cord
- Impaired loudness control (reduced, monoloudness, or excess and variable)
- Harsh or hypernasal voice quality
- Impaired articulation (imprecise, distorted, prolonged, or irregular breakdowns)
- Impaired emphasis (slow, prolonged intervals or sounds, reduced, or excess and equal stress)
- Impaired pitch control (monopitch or pitch breaks, too low or too high)
Differential diagnosis of the type of dysarthria has important implications for treatment planning by the speech/language pathologist, as well as decision-making by the physician regarding pharmacologic management.
Dysarthria and dysphonia in MS may be accompanied by the underlying symptoms of spasticity, weakness, tremor and ataxia; and complicated by fatigue. Therefore, evaluation of medication trials to treat these symptoms, and ongoing communication with the patient and physician about the impact on speech and voice, is recommended during therapy.
Clinical decision-making in treatment planning is individualized according to the person’s specific problems and communication needs. Improving speech intelligibility and naturalness should be the ultimate goal of therapy.
Traditional dysarthric compensations taught to MS speakers include:
- Improving breath support and control;
- Reducing the rate of speech;
- Using strategic pauses within and between words;
- Exaggerating articulation; and
- Actively self-monitoring/self-correcting speech.
Selection of appropriate treatment approaches, and where to begin therapy, depend on which deviant speech dimension(s) are most disabling in these two areas. Work on one target behavior can have overlapping, indirect effects on other physiological and acoustic variables. Measuring impact on participation and quality of life are recommended, to assess functional outcomes of dysarthria therapy.
Assessment protocols and treatment procedures for dysarthria in MS have shown recent advances. Trends have included the refinement of perceptual and acoustic analyses, and incorporation of the World Health Organization’s international classification of function, disability and health, which aids functional goal-setting. Specific treatments are being studied with the MS population and controls, to add evidence-based research to the expert opinion of clinicians.
Dysarthria in Multiple Sclerosis by Pamela H. Miller, MA, CCC-SLP. Clinical Bulletin / Information for Health Professionals. © 2008 National Multiple Sclerosis Society
For Further Information:
Polman CH, Thompson AJ, Murray TJ, Bowling AC, and Noseworthy JH. Multiple Sclerosis: the Guide to Treatment and Management, 6th edition. New York: Demos Medical Publishing, 2006. (updated online, 2008).
The Neuroscience on the Web Series: Neuropathologies of Swallowing and Speech by Patrick McCaffrey, Ph.D. Unit 14. Dysarthria: Characteristics, Prognosis, Remediation