The Neuroscience on the Web Series:
CMSD 642 Neuropathologies of Swallowing and Speech

CSU, Chico, Patrick McCaffrey, Ph.D


Chapter 14. Dysarthria: Characteristics, Prognosis, Remediation


Characteristics Of Dysarthria in Communication

All types of dysarthria affect the articulation of consonants, causing the slurring of speech. In very severe cases, vowels may also be distorted. Intelligibility varies greatly depending on the extent of neurological damage. Hypernasality is frequently present as are problems with respiration, phonation and resonance.

Spastic Dysarthria

You will recall that it is due to damage to the pyramidal tract. This direct, mono-synaptic tract is predominantly facilitatory. That means its cell bodies send impulses that result in movement, along its axons. The principle result of damage is difficulty with fine motor movements. This is due to exaggerated stretch reflexes, resulting in increased muscle tone and incoordination. All of the cranial nerves except VII and XII are stimulated bilaterally by the cortico bulbar tracts. Bi-lateral lesions on those tracts result in a much more severe dysarthria than unilateral lesions. However, unilateral lesions on a cortico-bulbar tract will affect cranial nerves VII (facial movement) and XII (tongue protrusiont). Since the other cranial nerves recieve signals from both cortico-bulbar tracts, the muscles they innervate are barely affected. Thus, one would not expect problems with the lips, cheecks, throat, velum, or larynx. With bi-lateral cortico-bulbar lesions all of the above, and more, would be affected.

Phonation

Vocal quality is harsh. Sometimes the voice of a patient with spastic dysarthria is described as strained or strangled (Duffy, 1995). Pitch is low, with pitch breaks occurring in some cases.

Resonance

Hypernasality typically occurs, but is usually not severe enough to cause nasal emission.

Prosody

Bursts of loudness are sometimes noted in the speech of patients with spastic dysarthria.

Articulation

According to Duffy (1995) range of movement, tongue strength, speech rate and voice onset time for stops are reduced. There is an increase in phoneme to phoneme transitions, in syllable and word duration, and in voicing of voiceless stops.

Hyperkinetic Dysarthria

As described above, hyperkinetic dysarthria is usually thought to be due to lesions of the basal ganglia. Its predominant symptoms are associated with involuntary movement. There may be unilateral or bilateral damage.

Phonation

As with spastic dysarthria, vocal quality may be described as harsh, strained, or strangled. Voice stoppages may occur in dysarthria associated with dystonia.

Resonance

Hypernasality is common.

Speech

When voluntary speech movements are made there is often a super-imposition of involuntary movements. Speech can range from total lack of intelligability to a mild problem. There are many syndromes, several of which are described above, associated with this problem.

Hypokinetic Dysarthria

Associated mainly with Parkinson's disease, It is due to a lesion in the substantia nigra; however, it can also result from anti-psychotic medications, frequent blows to the head and other etiologies described above. According to Ferrand and Bloom, 1997, in order for normal muscle movement to occur dopaminergic and cholinergic (ACh) pathways must be in balance.

Phonation

Hoarseness is common in Parkinson's patients. Also, low volume frequently reduces intelligibility.

Resonance

Hypernasality may occur

Prosody

Monopitch and monoloudness may occur. Pallilalia, or the compulsive repetition of syllables, is sometimes present.

The sound production pattern of patients with Parkinson's disease is sometimes described as articulatory undershoot.

Articulation

Bradykinesia (reduced speed of muscles) associated with Parkinson's disease causes difficulty in the initiation of voluntary speech. This can result in delay in starting to talk as well as very slow speech. According to Duffy (1995), there may be freezing of movement during speech. Rigidity can also occur. Additionally, Parkinson's patients have reduced loudness, imprecise consonant production, reduced pitch variability and festinating speech. The latter can result in extremely fast speech together with short rushes of speech (Ferrand and Bloom, 1997).

Ataxic Dysarthria

This disorder is due to damage to the cerebellar control circuit. According to Duffy (1995), it can affect respiration, phonation, resonance and articulation, but its characteristics are most pronounced in articulation and prosody.

Phonation

Vocal quality may be harsh. As loudness may vary excessively, and increased effort is evident, ataxic speech is sometimes described as explosive speech.

Resonance

Hypernasality is not common, but may occur.

Prosody

Patients with ataxic dysarthria tend to place equal and excessive stress on all syllables spoken. The term scanning speech has been used in the past to describe this prosodic pattern. (The name was originally used by Charcot in reference to the speech of a patient who spoke very slowly and paused after each syllable). The label is no longer applied to ataxic dysarthria in order to avoid confusion as it has been used to describe a variety of different speech problems.

Articulation

All dysarthric speech could be described as slurred. However, due to the incoordination caused by cerebellar lesions, ataxic speech sounds especially slurred. Patients sound almost inebriated. Gait is affected in the same way. According to Duffy (1995), it is a breakdown in motor organization and control. The result is slowness and inaccuracy in range, force, timing, and direction of articulatory movements.

Flaccid Dysarthria

This results from damage to the lower motor neurons (cranial nerves) involved in speech.

Phonation

If CN X is damaged, voice will be affected as this nerve innervates the intrinsic musculature of the larynx. Occasionally, only one vocal fold is paralyzed. If the fold is paralyzed in an adducted position, the voice will sound harsh and have low volume. If the fold is paralyzed in the abducted position, this will cause breathiness along with a reduction in loudness. Bilateral vocal fold paralysis is more common than unilateral paralysis. When the folds are in an abducted position, the voice is breathy and inspiratory stridor may be noted. (Of course, paralysis of both vocal folds in a completely adducted position would constitute a medical emergency; the airway would be closed off).

Resonance

Hypernasality will occur if the muscles involved in velar elevation have been affected. Frequently, velar movement is reduced sufficiently to cause nasal emission.

Prosody

Monopitch and monoloudness may both result from vocal fold paralysis.

Associated Characteristics

Muscles affected by flaccid paralysis may begin to atrophy or lose mass over time. Also, lack of innervation may cause fasciculations or twitching of muscle fibers. These movements are especially visible in the tongue; its surface may dimple as if worms were moving beneath its skin.

Unilateral paralysis of the oral structures may be noted. The affected side of the mouth may sag, causing drooling, while it will be drawn to the unparylized side The jaw will deviate toward the weakened side while the tongue moves toward its stronger side.

Mixed Dysarthria

Characteristics will vary depending on whether the upper or lower motor neurons remain most intact. For example, if upper motor neurons are most damaged initially, the voice will sound harsh. However, if lower motor neurons are most affected, the voice will sound breathy.

          Prognosis

According to Netsell (1984, as cited in Halperen, 1986), a number of factors influence the prognosis of dysarthric patients. Among them are:

Neurological status and history

Dysarthrias caused by bilateral subcortical lesions, brain stem lesions or degenerative diseases like ALS have the poorest prognosis.

Age

In general, the younger the patient, the better the prognosis. Children are especially likely to have a good outcome, because of neural plasticity.

Treatment Effects

Patients who receive treatment, especially coordinated speech, medical, physical and behavioral treatment have a better outcome than those who do not.

Personality and Intelligence

Patients who were purposeful and optimistic before injury have a better prognosis than those who were not. Those who kept their minds "active" have a better prognosis than do those who did not.

Support Systems

Obviously, patients who receive support form family members and/or friends have a more favorable prognosis than those who don't.

Dysarthria is treated differently depending on its severity. Patients with a mild or moderate form of the disorder can be taught to use strategies that make their speech more intelligible. Before compensation is attempted every effort should be made to improve physiological support for articulation, resonance and respiration. Patients with mild to moderate dysarthria will be able to continue to use speech as their primary mode of communication. Patients whose dysarthria is more severe, however, may have to learn to use alternative forms of communication.

Remediation of Severe Dysarthria

Dworkin (1991 p.188) recommends the following sequence of treatments for spastic dysarthria that with some cautions may be used with other types such as hyperkinetic , hypokinetic and flaccid. For hyperkinetic and ataxic dysarthrias, Dworkin feels that in most cases muscular tone reduction and muscular strengthening exercises may not be necessary. For flaccid dysarthria muscular tone reduction would not be required :

Lingual, labial, and mandibular musculature tone reduction (relaxation techniques).

Lingual, labial, and mandibular musculature strengthening (exercises).

Lingual, labial, and mandibular force physiology training (isometric).

Phonetic stimulation in various contexts.

Remediation of Severe Dysarthria/Cerebral Palsy

Adaptation of the Bobath Method in Remediation of Dysarthria

Crickmay adapted the Bobath method of physical therapy for the remediation of dysarthria in children and adults with cerebral palsy. Since cerebral palsy results from upper neural lesion problem it can present with any of the dysarthrias mentioned above, except flaccid which is caused by lesions on the cell bodies or axons of cranial nerves. The methods Crickmay advocates make sense to me. It is as timely now as when it was first published. The Bobath method has three main stages. In the first stage the patient's abnormal and pathological reflexes are inhibited. In the second stage more developmentally mature movements are facilited. In the third stage movements are put under the voluntary control of the patient. It is a important that the speech therapist have guidance and assistance from a physical therapist before he/she initiates remediation.

In order to normalize muscle tone the patient is placed in a reflex inhibiting posture (RIP) which he/she has become accustomed to while in physical therapy. Two postures that tend to have normalizing effects are the prone (extended spine and flexed elbows-lying on your stomach while leaning on your elbows), and the supine (hips and knees extended, shoulders flexed -held by therapist, and head back-chin held. In inhibiting abnormal speech reflexes the therapist should go from gross to fine. Head control, the ability to lift and turn the head is a prerequisite for speech. Crickmay suggests that the individulal be in a supine position with legs and arms at his/her sides and hips and legs flexed. This is a good time to work on desensitize the face/articulators. Remember we are talking about desensitizing the speech mechanism because when you manipulate the tongue and lips the child may react with spasms. Crickmay suggests that you help the patient build up tolerance by holding him/her in the RIP while gently and carefully touching and moving the hypersensitive face. Since the mouth is the most sensitive he/she should start with facial areas furthest from the mouth and work in towards the mouth. The patient will resist and try to break out of the RIP. He/she should be held gently but firmly so that he/she can build up a tolerance and permit the speech pathologist to manipulate the speech mechanism. The time taken for this to happen is quite variable-from a few days to several weeks.

The patient learns to lie quietly in an RIP keeping the face free of abnormal movement. When facial grimacing occurs it can be usually controlled by the fingertips. Those with spasticity often have an open mouth, lips drawn back grin. Crickmay suggests flexing the head forward to inhibit the extensor spasm, and close the patients mouth.

To control drooling, Crickmay recommends teaching the patient to keep the teeth closed and the tongue tip up against the alvealor ridge as he/she swallows. The clinician then inhibits any extraneous movements of cheecks and lips.

To teach a normal mouth position, Crickmay suggests the following:

Help the patient close his/her teeth in a normal jaw position. Place one hand under the patient's chin and hold that position for him/her. Use the other hand to stroke the patients lips and cheecks forward in order to relax the face. Chin pressure must be released gradually in order to permit the patient to assume control and to experience a closed mouth. Help the patient gradually increase the time the mouth remains closed.

To reinforce the closed mouth position negative practice may be used. The clinician asks the patient to go back the original open mouth position and then to deliberately assume the new closed mouth one. Repeated practise will enable the patient to feel the difference between positions. Using a mirror during practise will provide visual reinforcement.

In order to inhibit the infantile sucking reflex, Crickmay recommends the following:

Put the patient in an RIP. Gently stimulate the lips by touching them with a straw or finger. Use the other hand to prevent them from moving into a sucking position. The clinician will have to control the patient's lips by keeping them in a relaxed position despite the stimulation. Finally the therapist should help the child assume control. This can be done by the clinician removing his/her hand occasionally-gradually increasing the length of time until the patient can inhibit the reflex without assistance.

To facilitate the chewing reflex (a normal reflex, which with sucking and swallowing is a prerequisite for speech) the clinician can give hard licorice or chocolate (absent dietary or swallowing restrictioins). It should be pressed against the hard palate in order to stimulate chewing. Rubbing the gums and teeth, front, back and sides, in a rotary motion with a finger will also help.

To facilitate independent tongue movement, Crickmay suggests holding the patient's jaws apart while having him/her raise the tongue to the alvealor ridge. Next, encourage him/her to produce /t/, /d/, /l/, and /n/ sounds. Make sure the jaw dosen't become fixed. It should be immobilized, but given some freedom of movement. Finally, permit the patient to take control.

Differentiation of lip movements may be necessary for many patients. The techniques described above can be used with patients who have difficulty differentiating lip, tongue, and jaw movements. That is they cannot make the /r/ sound without moving both lips and tongue or are unable to make /t/, /l/, or /n/ sounds without also moving the jaw.

 

Remediation of Mild to Moderate Dysarthria

Compensatory Strategies

According to Rosenbeck and La Pointe (1978), and McCaffrey et al (2001,) the goal of therapy for dysarthria is to help patients achieve compensated intelligibility. In other words, patients must learn techniques that help them to make good use of their remaining physiological capacity to produce understandable speech.

Because dysarthria can impair respiration, phonation, resonance and prosody, therapy will often include compensatory strategies which address these aspects of speech production as well as articulation.

  1. The most effective way for most dysarthrics to make themselves more intelligible is to reduce the rate of their speech and produce syllables one by one. Speaking this way will disrupt intonation patterns and may make the person sound "robot-like." However, it is the best way to maximize the clarity of dysarthric speech.

    Many patients have difficulty learning to speak slowly. A
    pacing board may be helpful for such patients. Pacing boards are divided into sections and the patient must tap one section every time he pronounces a syllable. As the fingers cannot move nearly as rapidly as the articulators, this should slow the rate of speech enough to improve intelligibility. After reduced rate has been established using the board, the client can begin to count syllables on his fingers. Eventually, he should be able to maintain the proper rate without counting syllables at all. A device called a graduated stick may be used instead of a pacing board. Graduated sticks have bumps on them at regular intervals and the client must touch one bump every time he says a syllable. Metronomes can also be used to slow speech rate. Patients are taught to pronounce one syllable per "tick" on the metronome.

    The use of a pacing board, graduated stick or metronome to slow rate may be referred to as intrasystemic reorganization. Intrasystemic reorganization for speech remediation is described by La Pointe and Rosenbeck as introducing a non speech function into the impaired act that is not normally used in the impaired act in order to facilitate speech. This new function is called an organizer. According to Duffy, 1995 using tongue protrusion to facilitate the production of interdental sounds is an example of using a lower level function for a higher level purpose.
  2. Dysarthric patients should also try to emphasize all syllables as they speak. This will reduce vowel distortion.
  3. Patients should also use greater excursion of the mandible, tongue and lips to improve production of both consonants and vowels. The exaggeration of jaw and tongue movements is the most crucial aspect of this strategy; it may be too difficult for some patients to increase the amplitude of their tongue movements.
  4. Consonant exaggeration is another compensatory strategy that improves the intelligibility of dysarthric speech. Teach the patient to over-articulate in order to emphasize the sounds that s/he is slighting. (Medial and final consonants are typically most slighted in running speech.)
  5. If a patient has difficulty with a particular type of phoneme, the clinician may have to teach him to use compensatory placement to produce those sounds. For example, it the patient has trouble with tongue tip sounds like /t/, /d/, /n/, /s/ and /z/, he/she could learn to make them with the blade rather than the tip of the tongue. If the patient can no longer put his lips together to make bilabials, he could learn to use his teeth to contact the lips.
  6. Monitoring techniques are often used to work with patients who have problems with either reduced or excessive loudness. For example, the visipitch could be used to help Parkinson's patients who speak too softly or patients with spastic dysarthria who have bursts of very loud speech.
  7. Reducing phrase length is another way to increase the loudness of a dysarthric's speech. When a patient with hypokinetic dysarthria stops to take a breath and rest for an instant between every few words, their vocal volume usually increases. (Slowing the rate of speech, which will be the main focus of therapy for dysarthria, may automatically reduce phrase length and improve the patient's loudness.)
  8. The yawn-sigh technique for easy onset of voice, the use of a breathy voice and Froeschel's chewing method of focusing energy in the oral cavity may all be used to reduce the strained-strangled vocal quality that occurs in spastic dysarthria. Patients with this kind of voice problem are often using hard glottal attack. In this case, any technique used to ameliorate this problem will help the patient.
  9. Some dysarthrics, especially those with the hypokinetic form of the disorder, may have an excessively breathy voice. Pushing exercises may help a patient who has this problem by facilitating glottal closure.
  10. .Many dysarthrics speak at an abnormally low pitch. If they continue to do so for a sufficient length of time, they may develop a functional voice disorder like nodules. For this reason, it may be necessary to address the patient's voice problem although there is usually a trade-off between improving pitch/intonation and improving intelligibility.

Prosthetic Devices

If a Parkinson's patient with hypokinetic dysarthria cannot learn to speak more loudly through the use of monitoring techniques or the use of short phrases, he or she might be provided with an electro-larynx or computer hardware/software as a way of increasing vocal volume.

Usually, therapy does not effectively reduce the hypernasality that accompanies most types of dysarthria. Patients can be given blowing exercises or exercises that contrast nasal sounds with oral sounds (eg., /n/ vs. /a/). Perceptual training, such as having the client listen to a tape recording of his voice, is also used. Froeshel's chewing method may help to some extent by concentrating energy in the oral cavity. But, if the velum is paralyzed, none of these techniques will do anything to alleviate the problem.

If hypernasality is severe, the patient should be referred to an ENT to explore the possibility of pharyngeal flap surgery or the use of an obturator and speech bulb prosthesis. (Although these were developed as treatments for cleft palate, they could also be used with a dysarthric patient.)

Isometric Exercises

Oral motor exercises may be used in therapy with dysarthric patients. Programs must also include speech exercises as the movements involved in speech are different from other types of oral-motor movements.

Feedback

In addition to the use of the visipitch to monitor loudness levels, other kinds of feedback are employed in therapy with dysarthric patients.

  1. Tactile and kinesthetic feedback can be used to teach compensatory articulation strategies.
  2. Electromyographic (EMG) feedback can be used to reduce the hypertonicity of muscles.
  3. Delayed auditory feedback (DAF) has been used successfully with Parkinson's patients.

Rosenbeck, et al. (1973), developed an eight step continuum for treating apraxia of speech. This can be modified for use with dysarthric patients. The principle modification would be to give dysarthrics several models of the desired production. With apraxics one model is given with several opportunities to match it) :

Step 1

Integral stimulation-the therapist asks the patient to look and listen AND imitate. (watch me and do the same).

Step 2

Same as 1 except the patient is asked to delay the response; then the therapists silently mimes the response while the patient is producing the target stimulus.Step 3

Integral stimulation followed by imitation WITHOUT cues-miming or otherwise.

Step 4

Integral stimulation with several successive productions without simultaneous cues or intervening stimuli

Step 5

Printed stimuli are presented by the therapist without auditory or visual cues followed by patients production while looking at the written stimuli.

Step 6

Written stimuli, with delayed production after removal of the written stimuli.

Step 7

The therapist elicits a response by asking a question.

Step 8.

Role playing is used to elicit responses.


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Other courses in the Neuroscience on the Web series:
CMSD 620 Neuroanatomy | CMSD 636, Neuropathologies of Language and Cognition

Copyright, 1998-2013. Patrick McCaffrey, Ph.D. .