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304 MOTOR SPEECH DISORDERS: DIAGNOSIS AND TREATMENT
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speech programmer has especially close ties to the ventral premotor cortex (which includes Broca’s area). This area seems to play
an important role in transforming the neural code into an accurate representation of the intended utterance. The motor speech
programmer is a remarkable entity. It gives humans the ability to
rapidly and accurately sequence speech movements, and when it
is damaged, apraxia of speech can be the result.
Causes of Apraxia of Speech
Disorders that damage the motor speech programmer have the
potential to cause apraxia of speech. In practical terms, this means
that apraxia of speech is the result of injury to the perisylvian area
of the left hemisphere of the brain. Although the left perisylvian
area is the most common site of a lesion in cases of apraxia of
speech, it is not the only one. Injuries to the insula and the basal
ganglia also have been associated with apraxia of speech. The specic conditions known to cause apraxia of speech include stroke,
degenerative disease, trauma, and tumor, with the most frequent
cause being stroke. In a retrospective study at the Mayo Clinic
of 155 quasi-randomly selected cases, Duffy (2005) reported that
strokes caused 49% of the cases of apraxia of speech. Most of these
strokes affected the perisylvian area of the left hemisphere, primarily the frontal and parietal lobes. Some cases of apraxia of speech
also involved damage to the temporal lobe, but in each of these
instances, frontal- or parietal-lobe damage was present as well.
The second most common cause of apraxia of speech in the
Mayo study (in 27% of the cases) was degenerative disease, including
Alzheimer’s disease, primary progressive aphasia, and CreutzfeldtJakob disease. Although diseases such as these are usually associated with diffuse brain damage, Duffy (2005) indicated that at least
in the early stages, their effects can be focal and result in apraxia
of speech or other disorders associated with distinct lesions.
Trauma was the third most frequent cause of this disorder
in the Mayo study, resulting in 14% of the cases. Surgical trauma
in the left frontal lobe was the most common type of trauma that
resulted in apraxia of speech. Aneurysm repair, removal of a tumor,
and hemorrhage evacuation were some of the surgical procedures
noted in the study. Although a few cases of closed head injury also
resulted in apraxia of speech, most were the result of the more focal
trauma of surgery. The remaining cases were caused by tumors in
the left frontal lobe, seizure disorder, undetermined etiology, or mul
tiple causes, such as a left hemisphere stroke and dementia. Duffy
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(2005) cautioned about generalizing the results of this retrospec-
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tive study to the overall population because it was not a scientic
sample of patients.
Speech Characteristics of Apraxia of Speech
Studies of apraxia of speech have revealed many speech production errors that are unique to this disorder. Most researchers agree
that apraxia of speech is a disorder primarily of articulation and
prosody, although instrument-based studies have revealed problems in other areas of speech production, such as respiration. In
general, individuals with this disorder are often described as having
speech that is slow, labored, and halting. They could demonstrate
instances of articulatory groping, which are trial-and-error attempts
at nding the correct articulatory positions for target phonemes.
Such groping might be especially noticeable at the beginning of
an utterance or word. Traditional denitions of apraxia of speech
indicate that these individuals frequently will be inconsistent in
their speech errors, perhaps making one error on a rst attempt
at a word and then making a different error on a second attempt.
However, as mentioned at the beginning of this chapter (McNeil
et al., 2009), some research suggests that the articulation errors in
apraxia of speech are fairly consistent for both location and type on
repeated trials. In severe cases of this disorder, affected individuals might be nearly mute because they cannot voluntarily produce
any sounds. Others with severe apraxia of speech might be able to
produce only a few “stock” (stereotypic) phrases.
The following sections present the specic characteristics of
apraxia of speech. Not all of these characteristics will be present
in the speech of each individual with this disorder. Several factors
inuence how many aspects will be present. For example, the
severity of the apraxia will inuence how many of these characteristics might actually appear in a patient’s speech (Miller, 1986).
Individuals at the most severe and mild ends of the disorder typically will demonstrate fewer examples of these characteristics than
persons in the moderate range of severity. A co-occurring disorder,
such as aphasia or dysarthria, also can affect how many of these
characteristics will be present because the additional condition
could mask the apraxic speech errors. An example of this could be
when a patient has severe Broca’s aphasia and moderate apraxia of
speech. The aphasia will restrict the patient’s verbal expression so
severely that few, if any, opportunities will arise for a demonstration of the apraxic speech errors. Watch the PluralPlus Apraxia of
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Speech Case 1 and 2 videos for examples of patients with moderate
www
and severe cases of this disorder.
Articulation
Articulation errors are the most common problem in apraxia of
speech. These errors arise from decits in the patient’s ability to
smoothly sequence the oral movements needed to produce uent
speech. The following list of articulation errors is a compilation of
those reported by Darley et al. (1975), Duffy (2020), and Wertz et al.
(1991) in individuals with apraxia of speech. It is not a complete
listing, but it concentrates on the errors most likely to be encountered by the typical clinician.
n Substitutions of one phoneme for another might appear to
be more common than distortions, omissions, additions, or
repetitions. However, instrumentation or narrow transcription
of these substitution errors often reveals that they actually are
distortions of the target phoneme.
n Placement errors are the most frequent type of substitution
error, followed in order of commonality by manner, voicing,
and oronasal errors.
n The substitution of a voiceless phoneme for a voiced phoneme
is more common than a substitution of a voiced phoneme for
a voiceless.
n Some substitution errors can be perseverative (Viking is pro-
nounced “Viving”).
n Fricatives and affricates generally are more often in error than
stops, nasals, semivowels, or vowels.
n Consonant clusters are more likely to be in error than single
consonants, and single consonants are more often in error
than vowels.
n The position of a phoneme within a word does not always
determine whether it will be in error. When it does, however,
phonemes in the initial position of a word are more likely to
be in error than those in the medial or nal position.
n Phonemes that appear infrequently in speech are more often
in error than frequently appearing phonemes.
n Articulation is more accurate on real words as compared with
nonsense words.
n Articulation errors are more common on multisyllabic words
than on single-syllable words.
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n The farther the distance between the points of articulatory
contact, the higher the rate of articulation errors. For example,
“puh-tuh-kuh” is typically more difcult than “puh-puh-puh.”
n The voluntary production of speech (e.g., describing a picture)
is more difcult than automatic speech (e.g., counting 1 to 20)
or reactive speech (e.g., swearing), although this might not
always be true for individuals with severe apraxia of speech.
As mentioned previously, these individuals could have apraxia
to such a signicant degree that they are nearly mute for all
types of speech.
n Sounds produced with the lips or with the tongue on the
alveolar ridge are often easier to produce than sounds produced elsewhere.
Prosody
The prosody of individuals with apraxia of speech is frequently
abnormal, but it is not exactly clear how apraxia affects prosody.
Wertz et al. (1991), Duffy (2020), and others have offered several
possibilities for how apraxia and prosody interact. One possibility
is that prosody is disrupted by the patients’ attempts to compensate
for the articulatory errors in their speech. For example, the slow
speech rate and equal syllable stress that are noted in apraxia of
speech could be the result of patients purposely trying to maintain
the best articulation possible while speaking. Another possibility
is that the many articulation decits of this disorder make normal
prosody extremely difcult. For instance, a patient who repeatedly
stops an utterance, revises the articulation of a target sound, and
then restarts the utterance will have great difculty maintaining
normal prosody. A nal possibility for the interaction of apraxia
and prosody is that prosodic errors are an integral part of apraxia
of speech, just as the articulatory errors are. In other words, the
prosodic errors in apraxia of speech are the direct result of a
patient’s motor sequencing decit and not merely a reaction to it.
Duffy (2020) indicated that instrumentation studies have provided
some evidence for this third possibility, although the other two
might be true as well. Wertz et al. (1991) concluded that, “prosodic
disturbances probably reect the effects of the primary motor decit as well as the effort to compensate” (p. 69). The following is a
list of the more obvious prosodic errors that might be present in
patients with apraxia of speech:
n The rate of connected speech is slower than normal.
n Equal stress is often placed on all syllables in an utterance.
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Silent pauses can occur at the initiation of a word, between
n
syllables, or between words. These pauses might be the result
of articulatory groping or because the syllables and words are
being produced individually, instead of being produced with
the normal uent blending of one syllable into another.
n The normal variations of pitch and loudness in utterances
might be reduced.
Respiration
Apraxia has been shown to affect respiration. As mentioned previously, some individuals with apraxia of speech might not be able
to take a deep breath on command. When attempting this task,
they will demonstrate the same halting, effortful movements seen
in their articulation. Instrumentation has revealed more subtle respiration decits in patients with apraxia. In a study of ve subjects with apraxia, Keatley and Pike (1976) found that the amount
of abnormal respiratory function was related to the severity of
the subjects’ apraxia of speech. The most severely affected subject
demonstrated abnormal performance on 10 of the 13 measures of
respiratory function. It is important to note, however, that these
were voluntary respiratory tasks and that reexive respiration is
not affected by apraxia.
Resonance
Hypernasality and hyponasality are seldom signicant problems
in apraxia of speech. Although little research into the velar movements of individuals with this disorder has been conducted, the
few studies that have been completed suggest that disturbed resonance in apraxia of speech seldom reaches the point at which it
is perceptible. For example, Itoh et al. (1979) found that although
velar movements can be inconsistent on repetitive movements, the
general movement pattern of the velum usually remains within normal limits. This might be why Haley et al. (2019) found that “nasal
ambiguity” made up only 5% of the distortion errors produced by
their patients with both aphasia and apraxia of speech.
Phonation
Individuals with mild or moderate apraxia of speech seldom demonstrate isolated decits of phonation. When they do have difculties with phonation, it is usually in conjunction with an articulation
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problem. For example, there might be a delay in initiating the
phonation of the rst phoneme in a word, but this delay is part
of the individual’s groping for the correct articulatory position for
that phoneme. In some cases of severe apraxia of speech, however,
patients will have signicant decits in their ability to phonate. For
instance, they might be unable to complete such a “simple” phonatory task as prolonging a vowel. In these instances, the patients’
motor speech sequencing is so disrupted that both voluntary and
spontaneous attempts at phonation are unsuccessful. Duffy (2020)
reported that such severe phonatory decits usually occur in the
rst 1 or 2 weeks after the onset of the apraxia. If they continue
beyond this period, such phonatory decits usually indicate the
presence of a co-occurring disorder, such as severe aphasia or aki
netic mutism.
It is rare for a patient with apraxia of speech to have phonatory decits that are more severe than accompanying articulatory
problems. Individuals with severe apraxia of speech who cannot
prolong a vowel very likely have co-occurring articulatory problems
that are just as severe as their phonatory decits. However, Marshall
et al. (1988) described a remarkable patient who was an exception.
Their patient had a left hemisphere stroke after the repair of a cerebral aneurysm. The patient’s resulting speech and language decits
did not resemble those of Broca’s aphasia, dysarthria, or apraxia
of speech. Rather, he demonstrated the omission of syllables and
words and had numerous stuttering-like dysuencies. For example,
when greeted by someone he had seen only once before, he said,
“Face mem [remember], not name mem [remember].” Eventually, it
was determined that the patient had a laryngeal apraxia that prevented the normal integration of phonation with the other components of speech production, especially articulation. The accuracy of
this diagnosis was conrmed when the patient was taught to use an
electrolarynx. With this device providing the voicing for his speech,
he communicated normally, using correct articulation, syntax, and
grammatical morphemes. Sieron et al. (1995) reported a similar
case of laryngeal apraxia in a 51-year-old patient who demonstrated
aphonia and disrupted respiration only while speaking. All other
respiratory, speech, and language abilities were intact.
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Assessment of Apraxia of Speech
Patients in whom apraxia of speech is suspected need to be thoroughly assessed with a motor speech evaluation such as that in
Appendix 3–1. All items on the evaluation should be administered, not just those related to apraxia of speech. However, while
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conducting the motor speech evaluation, clinicians will want to pay
particular attention to those tasks that provide especially useful
diagnostic information for this disorder, including the following:
n One common assessment procedure for apraxia of speech
is the sequential motion rate (SMR) task, especially as
compared with the patient’s performance on the alternating
motion rate (AMR) task. Many individuals with mild or moderate apraxia of speech can complete the AMR task accurately
because it involves only one movement sequence with only
one place of articulatory contact. However, they will be unable
to complete the SMR task as accurately because it requires the
sequencing of multiple articulatory positions in three different
locations within the mouth. A difference in their performance
on these two tasks might be evident.
n Conversational speech and reading aloud are particularly
useful tasks for determining the effects of the apraxia on
prosody, as well as for highlighting pauses and prolonged
transitions between words and phrases. Note also the intrusion
of a schwa during pauses in connected speech.
n Repeating words of increasing length (e.g., fan–fancy–fantastic)
can be especially difcult for some patients with apraxia of
speech.
n Reading or repeating low-frequency, multisyllabic words in
isolation or in sentences also can be difcult for these patients.
Differential Diagnosis of Apraxia of Speech
Once the assessment is completed, the clinician must analyze the
results to determine the kinds of errors that are present in the
patient’s speech. This is perhaps the most important part of diagnosing apraxia of speech. The analysis must be complete and correct because the patient’s speech errors need to be compared with
the errors that are most closely associated with apraxia. The diagnosis can be made only when it is determined that a signicant
number of the patient’s speech errors match those known to occur
in apraxia of speech.
Diagnostic Characteristics of Apraxia of Speech
In their review of apraxia of speech treatment studies, Wambaugh
et al. (2006a) developed four categories of behaviors to determine
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which participants in the studies had been correctly diagnosed.
By matching the written descriptions of the studies’ participants to
the behaviors listed in these categories, Wambaugh and colleagues
were able to estimate the accuracy of the diagnoses in the original
studies. Clinicians also can use these four categories to assist in
the diagnosis of their patients. The rst category, primary clinical characteristics, contains those behaviors that (as a whole) are
almost exclusively found in individuals with apraxia of speech. The
second category, nondiscriminative clinical characteristics, contains
those behaviors that often can be observed in apraxia of speech
but also are found in other disorders. The third category contains
behaviors that usually are found in disorders other than apraxia of
speech. The fourth category consists of behaviors that rule out the
presence of apraxia of speech.
Primary Clinical Characteristics
The following six behaviors are indicative of apraxia of speech
when, as a group, they are present in a patient’s speech:
n The patient demonstrates prosody abnormalities.
n The patient has a slow speech rate characterized by length-
ened productions of vowels, consonants, or both.
n The patient has a slow speech rate with pauses between
phrases, words, syllables, or phonemes. These pauses might
often be lled with a schwa.
n The patient produces consonants and vowels that are distorted.
n The patient has phoneme substitutions that are distorted.
n The patient demonstrates articulation errors during repeated
utterances that generally are consistent for type of error
(omission, distortion, substitution) and for location.
Nondiscriminative Clinical Characteristics
The following behaviors are only suggestive of apraxia of speech
when they are found in a patient’s speech because they also can
be found frequently in other disorders, such as uent aphasia. By
themselves, these behaviors should not be used to make the diagnosis of apraxia of speech.
n The patient has short periods of error-free speech.
n The patient’s automatic, overlearned speech (e.g., counting
1 to 10) is produced better than propositional speech (e.g.,
describing the prior day’s activities).
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n
The patient self-corrects errors and shows other signs of error
awareness.
n The patient has difculty initiating speech.
n The patient’s speech errors increase as word length increases.
n The patient has perseverative errors or movements.
n The patient demonstrates articulatory groping, either visually,
audibly, or both.
Clinical Characteristics Usually Found in Other Disorders
The following behaviors are more likely to be found in other disorders and therefore should not be used to make the diagnosis of
apraxia of speech.
n The patient demonstrates a difference between expressive and
receptive speech and language abilities.
n The patient has transposition errors on phonemes or syllables.
n The patient has anticipatory articulation errors.
n The presence of limb apraxia or nonverbal oral apraxia does
not necessarily indicate a diagnosis of apraxia of speech.
Clinical Characteristics Ruling Out Apraxia of Speech
These three behaviors are exclusionary characteristics; they do
not occur in the speech of patients with apraxia of speech. Their
presence in a patient’s utterances indicates that apraxia of speech
would not be the correct diagnosis.
n The patient demonstrates a fast rate of speech.
n The patient has a normal rate of speech.
n The patient demonstrates normal prosody.
Clinicians can use these four categories of behavioral characteristics to assist in the diagnosis of apraxia of speech. After carefully analyzing the patient’s speech characteristics through a motor
speech evaluation and comparing them with the items in these
four diagnostic categories, the following guidelines can be used to
determine whether apraxia of speech is the likely diagnosis.
n A patient demonstrating all six of the primary characteristics
has a high probability of having apraxia of speech.
n A patient primarily demonstrating the nondiscriminative
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characteristics and most of the primary characteristics has a
moderate probability of having apraxia of speech.
n A patient primarily demonstrating the four characteristics
associated with other disorders has a low probability of having
apraxia of speech.
n A patient demonstrating any of the “ruling out” characteristics
does not have apraxia of speech.
Additional Diagnostic Considerations
Before making the nal diagnosis of apraxia of speech, it is important to rule out other conditions that can cause movement difculties similar to those seen in apraxia. Brookshire (2015) discussed
four such conditions. The rst is muscle weakness, which can produce slow, labored movements in affected body parts. Such effortful
movements could sometimes resemble the movements of apraxia.
The rst step in making the differential diagnosis between weakness and apraxia is determining which movements are affected.
When muscle weakness is the cause of the movement difculty,
all movements of the affected body part will reect the weakness.
However, in cases of apraxia, the problem exists only with the
voluntary movements of the affected body part; automatic and
spontaneous movements usually will be performed normally. In a
case of true apraxia of speech, for example, the patient might be
able to spontaneously produce a very clear “hello” when greeting
a clinician at the beginning of a treatment session. But later, in the
middle of the treatment session, the patient’s voluntary attempts to
say “hello” might be lled with distorted or substituted phonemes,
revisions, or other apraxic errors. If the patient’s articulation errors
were the result of weakness, all attempts at saying hello would
show evidence of the imprecise articulation.
Sensory loss is the second condition that needs be examined
carefully before conrming a diagnosis of apraxia. Brookshire
(2015) noted that sensory loss does not necessarily cause a movement disorder, but it can contribute to slowed or clumsy movement
of an affected body part. For example, sensory loss in oral structures can contribute to imprecise articulation of speech sounds,
as anyone who has had local numbing for dental treatment can
attest. When there is sensory loss in suspected cases of apraxia, it
is important for the clinician to determine whether the movement
difculties are caused by the sensory loss or the apraxia. As in cases
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