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54 MOTOR SPEECH DISORDERS: DIAGNOSIS AND TREATMENT
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5. How are the functions of the primary cortex different from
the functions of the association cortex?
6. What roles do the basal ganglia and cerebellum play in the
creation of a movement?
7. How is it known that movements do not originate in the
primary motor cortex?
8. What is the difference between the pyramidal and extra-
pyramidal tracts?
9. Describe the anatomical distinction between lower and
upper motor neurons.
10. What happens at the neuromuscular junction?
Chapter 3
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Evaluation of Motor Speech Disorders
Goals of a Motor Speech
Evaluation
Speech Production Components
and Disorders
Respiration
Phonation
Resonance
Articulation
Prosody
Standardized Tests for Dysarthria
Standardized Tests for Apraxia of
Speech
Conducting a Motor Speech
Evaluation
Muscle Strength
Speed of Movement
Range of Movement
Accuracy of Movement
Motor Steadiness
Muscle Tone
Instructions for the Motor Speech
Evaluation
Background Information and
Medical History
Face and Jaw Muscles at Rest and
During Movement
Explanation of Specific Tasks
Tongue at Rest and During
Movement
Explanation of Specific Tasks
Velum and Pharynx at Rest and
During Movement
Explanation of Specific Tasks
Laryngeal Function
Explanation of Specific Tasks
Auditory-Perceptual Evaluations
of the Motor Speech
Mechanism
Phonatory-Respiratory System
Explanation of Specific Tasks
Resonation System
Explanation of Specific Tasks
Combined Systems (Phonation,
Respiration, Resonation, and
Articulation)
Explanation of Specific Task
Stress Testing of the Motor Speech
Mechanism
Testing for Nonverbal Oral Apraxia
Explanation of Specific Task
Testing for Apraxia of Speech
Explanation of Specific Tasks
Analysis of Connected Speech
Summary of the Evaluation of
Motor Speech Disorders
Study Questions
Appendix 3–1: Motor Speech
Examination
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ost beginning clinicians find evaluating and diagnosing
motor speech disorders to be a challenging task for
several reasons. First, it can be dif
M
among the dysarthrias because many of the speech
characteristics of one dysarthria will be present in one
or more of the other dysarthrias. For example, imprecise
consonants and harsh vocal quality are characteristics of
every one of the dysarthrias. Second, an accurate diagnosis requires clinicians to listen very carefully to determine
which of their patients’ speech errors are most characteristic of a suspected motor speech disorder. Clinicians
usually develop this skill with experience, which beginning
clinicians will not have yet acquired. Finally, a detailed knowledge of the human motor system is an invaluable asset in
determining which speech errors are most important in
making a correct diagnosis.
It takes a concerted effort to learn about the motor
system because it is such a complex organization of nerve
cells and nervous system structures. However, when a clinician learns the parts and functions of the motor system,
the many symptoms of motor speech disorders become
less confusing. In short, the successful evaluation of motor
speech disorders requires clinicians to match what they
hear in a patient’s speech with what they know about the
functioning of the human motor system.
For beginning clinicians, the primary challenge is to
become familiar with how speech varies from one motor
speech disorder to another. Inexperienced clinicians need
to learn what makes flaccid dysarthria different from spastic dysarthria, what makes ataxic dysarthria different from
hypokinetic dysarthria, and so forth. Fortunately, the evaluation and diagnosis of motor speech disorders can be
accurate if beginning clinicians learn the characteristics of
motor speech disorders, become familiar with the neuromuscular bases of these disorders, and acquire hands-on
practice in a clinical practicum.
There are two basic methods of evaluating motor
speech disorders: instrumental and perceptual analysis.
Instrumental analysis uses sophisticated devices to
objectively measure the components of speech production.
ficult to distinguish
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For example, nasal and oral airflow during speech can be
measured precisely by computerized instruments. Other
instruments can accurately detect changes in voice onset
time, atypical formant frequencies in vowels, subtle loudness variations, and many additional aspects of speech
production. In contrast, in the perceptual analysis method
of assessment, the examiner uses his or her ears to detect
motor speech disorders. The value of the perceptual analysis method is that the ear is the ultimate judge of whether
there is problem with an individual’s speech. If a motor
speech disorder cannot be detected by ear, is there actually a disorder that needs to be treated?
This textbook concentrates on the perceptual analysis
method of evaluating motor speech disorders for several
reasons. Although the importance of instrumental assessment of these disorders is without question, most practicing
clinicians do not have access to such devices, and they must
rely primarily on what their ears tell them. Furthermore,
instrumental assessment is described in great detail in other
sources. Readers wishing to learn more about instrumentation in the assessment and treatment of motor speech
disorders should refer to a text such as Clinical Manage-
ment of Sensorimotor Speech Disorders, Second Edition
(McNeil, 2009).
Goals of a Motor Speech Evaluation
In many ways, the goals of a motor speech evaluation are no different from the goals of any speech-language evaluation. Haynes and
Pindzola (2011) said that a speech-language evaluation is done to
understand a patient’s problem and to establish the beginning level
of treatment. This certainly applies to a motor speech evaluation.
During a motor speech evaluation, the clinician collects relevant
background information about a patient and then asks the patient
to perform numerous tasks to assess the function of his or her
motor speech system. Once this information is collected, the clinician
should have a good description and understanding of the patient’s
speech abilities. With this knowledge, the clinician also has a baseline against which to compare the effects of any treatment.
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Duffy (2020), Swigert (2010), and others have suggested specic questions that clinicians should ask themselves during a motor
speech evaluation. This list of questions is designed to lead clinicians to a correct diagnosis (Duffy, 2020). In fact, it is not an
exaggeration to say that the primary purpose of a motor speech
evaluation is to obtain the information necessary to answer these
questions. If a clinician can answer each of the following questions
with a detailed, informed, and accurate response, the evaluation
will be nearly complete:
1. Is there a problem with the patient’s speech?
2. If there is a problem, what is the best way to describe it?
3. Does the problem seem to be the result of a neurologic
disorder?
4. If it seems to be neurologic in origin, did it appear suddenly
or slowly?
5. Is the problem related strictly to speech production, or is it
more of a problem with language, such as aphasia?
6. If it is a problem of speech production, do most of the
problems seem to be related to the sequencing of phonemes
(i.e., apraxia of speech)?
7. If there are no phoneme sequencing errors, what are the
characteristics of the patient’s speech errors and any associ-
ated motor problems?
The last two questions lead to the nal steps in a motor speech
evaluation. Question 6 asks whether the patient’s speech disorder
is dysarthria or apraxia of speech. Question 7 asks which type of
dysarthria might be present. If clinicians are able answer these
seven questions with condence, they will likely make an accurate
diagnosis.
Speech Production Components and Disorders
Speech does not just happen. It is dependent on the coordinated
interactions of ve components (or processes) that are essential
for normal speech production—respiration, phonation, resonance,
articulation, and prosody. These ve components must work
together and be combined smoothly for speech to be produced
normally. When one or any combination of the ve is affected by a
neuromotor disturbance, the result will be a motor speech disorder,
either dysarthria or apraxia of speech.
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Dysarthria is a speech production decit that results from
neuromotor damage to the PNS or CNS. This damage could affect
any of the ve components of speech production. Dysarthria is
not a language disorder, like aphasia, or a cognitive disorder, like
dementia. Likewise, dysarthria is not a result of an abnormal anatomical structure (e.g., cleft palate), a sensory loss (e.g., deafness),
or a psychological disturbance. It is strictly a speech production
disorder caused by neuromotor damage. There are actually a number of different types of dysarthria, with each having its own characteristics. Table 3–1 lists the causes and some of the more obvious
characteristics of the various dysarthrias.
Apraxia of speech also is a motor speech disorder. It is a
decit in the ability to create accurate phoneme sequences that
have the correct timing and placement of articulatory movements. It
often results in distorted articulation and prosody. Although it is the
result of CNS damage, the movement problem in apraxia of speech
is not caused by muscle weakness or slowness. As with dysarthria,
apraxia of speech is neither a language or cognitive disorder, nor
the result of an anatomical, sensory, or psychological disorder. It
is a disorder in the ability to time-sequence the motor commands
needed to move the articulators smoothly and accurately from one
position to another during the production of voluntary speech.
As already mentioned, when any of the ve components of
speech production are affected by a neuromotor disorder, dysarthria or apraxia of speech will result. (Whether it is one or the
other depends on where the disorder occurs in the nervous system.
Apraxia of speech is nearly always associated with damage to the
left hemisphere of the brain. Dysarthria, in contrast, can be caused
by damage to many parts of the nervous system.) Because the ve
components of speech production play such important roles in
motor speech disorders, each is discussed separately.
Respiration
The primary function of respiration is to exchange oxygen from
the atmosphere for carbon dioxide from cells in the body. By
exchanging these gases, respiration maintains life. Respiration also
is essential for speech production. It provides the subglottic air
pressure that is needed to set the vocal folds into vibration. Speech
production depends on a full, steady supply of air—especially for
connected speech. If the air supply is not full or steady, speech
production is affected. For example, if the nerves that innervate the
respiratory muscles are damaged, those muscles will be weak and
might not be able to move as much air into and out of the lungs
TABLE 3–1
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Type of Dysarthria Caused By Primary Characteristics
1. Flaccid Damage to the cranial
2. Spastic Bilateral damage to the
3.
Unilateral
Upper Motor
Neuron
4. Ataxic Damage to the
5. Hypokinetic A reduction of dopamine
6. Hyperkinetic Often associated with
7. Mixed Neurological damage
The Primary Etiologies and Characteristics of the
Various Dysarthrias
Muscle weakness that
nerves, spinal nerves,
or the neuromuscular
junction.
upper motor neurons
of the pyramidal and
extrapyramidal systems;
often caused by
brainstem strokes.
Unilateral damage to
upper motor neurons.
cerebellum or the neural
tracts that connect the
cerebellum to the rest
of the central nervous
system.
in part of the basal
ganglia. Parkinsonism is
the most common cause
of this dysarthria.
damage to the basal
ganglia, but in some
conditions the cause is
unknown.
that extends to more
than one portion of the
motor system.
can result in imprecise
consonants, breathy phonation,
hypernasality, shallow breath
support, and abnormal
prosody.
Spasticity and weakness in
the speech musculature that
results in harsh or strained-
strangled phonation, imprecise
consonants, hypernasality, and
abnormal prosody.
Imprecise consonants are the
most common characteristic.
There may be irregular
articulatory breakdowns or
harsh vocal quality in some
patients.
Problems controlling the
timing and force of speech
movements, resulting in
speech that often has a
“drunken” quality. Imprecise
consonants, distorted
vowels, irregular articulatory
breakdowns, and abnormal
prosody.
A reduction in the range and
speed of speech movements.
Harsh or breathy phonation,
imprecise consonants, and
abnormal prosody. In some
patients, there is an increased
rate of speech.
Involuntary movements that
interfere with normal speech
production. Unexpected
inhalations and exhalations,
irregular articulatory
breakdowns, and abnormal
prosody.
Any combination of the
characteristics of the six pure
dysarthrias. For example, a
patient with parkinsonism could
have a brainstem stroke that
might result in a hypokinetic-
spastic mixed dysarthria.
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as they normally would. Therefore, nerve damage means less air
for speech production, which limits the affected individual’s ability to speak in anything but short phrases. In addition, respiratory
decits that reduce the amount of air available for speech can also
cause reduced loudness and breathy voice quality.
Phonation
Phonation is the production of voiced phonemes through vocalfold vibrations in the larynx. Normal phonation is dependent on
the complete adduction of the vocal folds and enough subglottic
air pressure to set the vocal folds to vibrating. Just the right amount
of tension needs to be present during the adduction of the vocal
folds to produce a clear phonation. Neuromotor damage to the
nerves that innervate the vocal-fold adductor muscles can have
several effects on speech production. In conditions such as accid
dysarthria, the damage could cause weak or incomplete adduction.
This weakness results in phonations that have a breathy or harsh
quality. In conditions such as spastic dysarthria, the damage can
cause the adduction to be too tight, which results in the phonation having a strained-strangled quality. Neuromotor damage to the
laryngeal muscles also might reduce the ability to change pitch or
loudness during phonation.
Resonance
Resonance is the proper placement of oral or nasal tonality onto
phonemes during speech. This is accomplished by the raising and
lowering of the velum. Oral resonance is produced when the velum
is raised and closes off the nasal cavity from the vocal air stream,
which sends the sounds through the oral cavity. Nasal resonance
is produced when the velum is lowered and the oral cavity is
blocked by the lips or tongue, thereby directing the entire air
stream out through the nose. The key factor in this process is the
movement of the velum. The muscles in the velum need to respond
quickly to the different resonance requirements of the phonemes
being produced during speech. When the nerves innervating these
velar muscles are damaged, the muscles could be weakened or
their movements slowed. Weak or slow velar muscles cannot raise
the velum completely to separate the nasal cavity from the vocal
air stream during the production of nonnasal speech phonemes.
The resulting speech will have a hypernasal quality because nasal
62 MOTOR SPEECH DISORDERS: DIAGNOSIS AND TREATMENT
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resonance is being applied to phonemes that ordinarily have only
oral resonance.
Articulation
Articulation is the shaping of the vocal air stream into phonemes.
This shaping is accomplished in different ways. The air stream may
be blocked for stop and affricate phonemes, tightly restricted for
fricative phonemes, slightly restricted for semivowels, or relatively
unrestricted for vowels. The shaping of the air stream happens
at various points along the vocal tract. It also is accomplished by
different structures within the vocal tract, known as articulators.
Correct articulation requires the articulators to perform movements
that have the appropriate timing, direction, force, speed, and placement for any given phoneme. By any measure, accurate articulation
is the result of a very complex series of movements.
Unfortunately, neuromotor damage often affects the articulators. When this damage affects the muscles of the lips, tongue, jaw,
velum, or vocal folds, articulation is impaired. The degree of impairment depends on the severity of the damage and on which articulators are affected most severely. The articulation errors that can
be heard after neuromotor damage include imprecise consonants,
distorted vowels, inappropriate silences, and irregular articulatory
breakdowns.
Prosody
Prosody is the melody of speech. In most instances, prosody uses
stress and intonation to convey meaning. Stress is accomplished
by changing the pitch, loudness, and duration of syllables within
words to give those words added importance or to clarify meaning. Intonation is the use of pitch changes and stress to communicate, for example, whether an utterance is a question, assertion,
or exclamation. Adding prosody to an utterance is not a simple
task. Accurate and clear prosodic features of a message require the
coordinated participation of phonation, respiration, resonance, and
articulation. For example, to increase the loudness of a syllable or
word, an increased exhalation of air from the lungs is coordinated
with a simultaneous tensing of the vocal folds. To change pitch,
the vocal folds lengthen or shorten, which is accomplished by the
simultaneous actions of several laryngeal muscles. To increase the
duration of a syllable, the articulators are held in their position for
a moment longer than usual in coordination with a prolongation
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of phonation. The interactions of all of these vocal tract structures
must be precise or prosody will sound abnormal.
Given that prosody is so dependent on the complex interaction of the other components of speech production, it should be
easy to understand that neuromotor damage can affect prosody
in a number of ways. For example, if the damage causes weakness or slowness in the muscles of respiration and phonation, the
strength of these muscles and the timing of their contractions will
be impaired. The resulting speech could have a monopitch and
monoloud quality. If the damage causes involuntary movements
of the vocal-tract muscles, the involuntary movements will interfere with voluntary speech movements. The resulting speech might
have irregular pitch variations, sudden increases or decreases in
loudness, and prolonged intervals between syllables or words.
Standardized Tests for Dysarthria
Compared to other adult communication disorders (e.g., aphasia),
there are relatively few published standardized tests for dysarthria
(Hegde & Freed, 2022). One potential reason for this is the wide
availability of detailed, informal dysarthria assessment tools inside
a number of textbooks. Duffy (2020), Hegde and Freed (2022),
and Yorkston et al. (2010) each include complete assessment tools
for dysarthria in their chapters on assessment of motor speech
disorders. Nevertheless, the stand-alone standardized tests that are
available do provide a few special features that are not found in
the textbook-based assessments.
n Frenchay Dysarthria Assessment-2 (Enderby & Palmer,
2008)—First published in 1983, the Frenchay Dysarthria
Assessment-2 is unique in that it is the only published test
that aids in the differential diagnosis of the various dysarthrias
and provides information on intelligibility. Moreover, this test
also suggests which elements of the client’s speech most affect
intelligibility, something that can assist in developing treatment
goals. The client’s performance on a variety of tasks (reexes,
respiration, lips and tongue at rest and during movement,
velopharyngeal closure, laryngeal function, and intelligibility
for words, sentences, and conversation) is rated on a 9-point
scale. The administration time is reasonably short. The authors
report good intra- and interrater reliability and validity. Normative data are provided for ages 12 to 97 and for clients with
specic types of dysarthria.
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