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Chapter 11
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Apraxia of Speech
Definition of Apraxia of Speech
Neurologic Basis of Apraxia of
Speech
The Motor Speech Programmer
Causes of Apraxia of Speech
Speech Characteristics of Apraxia
of Speech
Articulation
Prosody
Respiration
Resonance
Phonation
Assessment of Apraxia of Speech
Differential Diagnosis of Apraxia of
Speech
Diagnostic Characteristics of
Apraxia of Speech
Primary Clinical Characteristics
Nondiscriminative Clinical
Characteristics
Clinical Characteristics Usually
Found in Other Disorders
Clinical Characteristics Ruling Out
Apraxia of Speech
Additional Diagnostic
Considerations
Differentiating Between Apraxia of
Speech and Aphasia
Differentiating Between Apraxia of
Speech and Dysarthria
Treatment of Apraxia of Speech
General Principles of Treating
Apraxia of Speech
Specific Treatments
The Eight-Step Continuum
Treatment
Sound Production Treatment
Darley, Aronson, and Brown’s
Procedure
Melodic Intonation Therapy
PROMPT
Summary of Apraxia of Speech
Study Questions
295
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Definition of Apraxia of Speech
The following denition of apraxia of speech by McNeil et al.
(2009) is perhaps the most detailed and complete at the current
time. It includes characteristics of this disorder that have been
understood for a number of years, as well as a few that are fairly
new. The well-known components include traits such as prosodic
errors, slow rate of speech, and awkward timing and placement
of articulatory movements. It also mentions that listeners might
perceive these awkward movements as being phoneme substitutions. In addition, it states that pure apraxia of speech (without a
co-occurring aphasia or dysarthria) is rare. Each of these has been
a recognized characteristic of apraxia for some time. This denition also contains at least one assertion that could be surprising—
that the apraxic speech errors are relatively consistent for both
type and location during repeated productions of the same word
or phrase.
Apraxia of Speech is a phonetic-motoric disorder of speech production. It is caused by inefciencies in the translation of well-formed
and lled phonologic frames into previously learned kinematic
information used for carrying out intended movements. These inefciencies result in intra- and interarticulator temporal and spatial
segmental and prosodic distortions. It is characterized by distortions of segment and intersegment transitionalization and coarticulation resulting in extended durations of consonants; vowels; and
time between sounds, syllables and words. These distortions are
often perceived as sound substitutions and as the misassignment of
stress and other phrasal and sentence-level prosodic abnormalities.
Errors are relatively consistent in location within the utterance and
invariable in type. It is not attributable to decits of muscle tone
or reexes, nor to primary decits in the processing of sensory
(auditory, tactile, kinesthetic, proprioceptive), or language information. In its extremely infrequently occurring isolated form, it is not
accompanied by the above listed decits of basic motor physiology,
perception, or language. (McNeil et al., 2009, p. 264)
helpful to review and paraphrase its key points in a simple list.
1. When our cognitive system selects a word for speech
Because this denition is detailed and complex, it might be
production, the word’s phonological representations are
combined to form a phonological word “frame.” These
frames contain the necessary movement patterns needed to
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accurately produce the sequence of phonemes in words and
sentences.
2. However, these frames need to be transformed into a
neural-motor code that can be carried out by the speech
musculature. In cases of apraxia of speech, correct phonological frames are poorly transformed into movement
patterns for speech.
3. This results in speech that has both timing and movement
errors for sounds, syllables, and words.
4. The timing problem causes speech that is slow, with length-
ened productions of vowels, consonants, or both.
5. In addition, the timing problem causes pauses between
phonemes, syllables, words, and phrases.
6. The movement problem causes distorted productions of
vowels and consonants.
7. These distortions can sometimes sound like phoneme substi-
tutions, but they actually are distortions of the correct target
sound. (However, real substitutions can occur in apraxia of
speech.)
8. These timing and movement problems contribute signi-
cantly to prosody errors in connected speech.
9. On repeated utterances, articulation errors in apraxia of
speech are generally consistent for type of error (distortion,
substitution, omission) and for location.
10. Apraxia of speech errors are not caused by muscle, sensory,
or language decits.
apraxic speech errors are variable from trial to trial. For example,
Miller (1986) wrote that, “[Individuals with apraxia of speech] can
be said to have difculty in consistently realizing speech sounds.
Sometimes they say a sound or word correctly, and other times
they do not” (p. 99). Recent research has suggested that this traditional concept might not be correct. A number of studies have
reported that inconsistent articulation errors are more characteristic
of patients with phonemic paraphasias than of those with apraxia
of speech (McNeil et al., 1995; Shuster & Wambaugh, 2003; Wambaugh et al., 2004). This change to a key traditional characteristic
of apraxia of speech has sparked research and discussions (Haley
et al., 2018; Haley et al., 2021; Haley et al., 2013; Ziegler et al.,
2012). Certainly more studies are needed to examine this and other
questions. Until these types of issues are settled, apraxia will remain
a rich area of research.
Many earlier denitions of apraxia of speech mentioned that
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Overview of the Apraxias
Like the dysarthrias, apraxia of speech is a neurologic decit in
the production of speech sounds. However, unlike the dysarthrias,
the errors in apraxia of speech are not caused by muscle weakness,
abnormal muscle tone, reduced range of movement, or decreased
muscle steadiness. Rather, the errors in this disorder are caused
by a decit in the ability to accurately sequence the movements
needed to produce speech sounds.
As was mentioned in Chapter 1, the term apraxia comes from
the Greek word praxis, which refers to performance of an action.
Apraxia literally means without action. In fact, it probably is more
accurate to describe this disorder as dyspraxia (which means disordered action) because, strictly speaking, individuals with apraxia
of speech are not without movement; they can move their tongue,
lips, velum, and other parts of the speech mechanism. Their problem is with the selecting and sequencing of movements needed
to produce speech. Because apraxia has become such a common
word for describing this disorder, though, it is the one that is used
in this chapter.
There are several types of apraxia, of which apraxia of speech
is only one subcategory. The two main types of apraxia are ideational apraxia and ideomotor apraxia. Ideational apraxia is the
inability to make use of an object or gesture because the individual
has lost the knowledge (or idea) of the object’s or gesture’s function. In other words, individuals with ideational apraxia cannot
make proper use of an object or gesture because they no longer
know its purpose. A patient of Luria’s (1972) who had a head injury
gave a good example of ideational apraxia when describing an
event that occurred in a hospital:
I was lying in bed and needed a nurse. How was I to get her to come
over? All of a sudden I remembered you can beckon to someone and
so I tried to beckon to the nurse—that is, move my left hand lightly
back and forth. But she walked right on by and paid no attention to
my gesturing. I realized then that I’d completely forgotten how to
beckon to someone. It appeared I’d even forgotten how to gesture
with my hands so that someone could understand what I meant.
(p. 45)
from damage to the left parietal lobe. It often goes undetected
because its symptoms can be masked so easily by an accompany-
Ideational apraxia is an uncommon disorder that can result
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ing disorder such as aphasia. It also is difcult to detect because it
often resolves quickly when caused by a stroke (Miller, 1986). This
disorder has been noted in advanced cases of Alzheimer’s disease
as well (Cassidy, 2016; Vakkila & Jehkonen, 2023).
The second main type of apraxia is ideomotor apraxia. In
contrast to ideational apraxia, which is a disturbance in the conception of an object or gesture, ideomotor apraxia is a disturbance in
the performance of the movements needed to use an object, make a
gesture, or complete a sequence of individual movements; apraxia
of speech is one of the ideomotor apraxias. Individuals with ideomotor apraxia have not lost their knowledge of an object’s or gesture’s function; instead, they have a decit in the ability to carry out
the motor plan needed to use an object or make a gesture. When
asked to use a common object such as a toothbrush, an individual
with ideomotor apraxia may demonstrate the general pattern of
movements required to brush the teeth, indicating that he or she
understands the purpose of the toothbrush; for instance, the individual will hold the toothbrush properly and move it toward the
mouth. However, the separate movements needed to actually brush
the teeth might be out of sequence. Perhaps the up-and-down
motion of brushing the front teeth becomes the back-and-forth
movement of brushing the molars or vice versa. The individual’s
attempts to revise and correct these out-of-sequence movements
result in tooth brushing that is halting, slow, and awkward.
Ideomotor apraxia has been studied extensively since it was
rst described in the 1900s, and numerous characteristics of this
disorder have been noted. The following is a list of the more wellknown symptoms of ideomotor apraxia. It should be noted, however, that these symptoms are likely to be present in cases of pure
ideomotor apraxia. When additional motor, language, or cognitive
decits accompany the apraxia, these symptoms might be masked
by these other problems and will not necessarily be as evident as
these descriptions might suggest.
n Ideomotor apraxia typically affects voluntary movements more
often than spontaneous or automatic movements. For example,
if asked to wave goodbye on command, an individual with
ideomotor apraxia might not be able to successfully sequence
the movements needed to accurately complete the action.
Even if the action is complete, the overall movements could
be effortful and clumsy. However, if the individual were actually leaving a social situation, a goodbye hand wave would be
smooth and effortless. Another example of this might involve
a movement such as a smile. An individual with ideomotor
apraxia might not be able to smile promptly when asked to
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do so, but a moment later a spontaneous smile might appear
without difculty.
n Movement sequencing is easier when actually manipulating
a real object as compared with only pantomiming its use. For
example, an individual with ideomotor apraxia will probably
be more successful in showing how to drink from a cup when
actually given a cup, as compared with only pretending to
have one.
n Completing a movement sequence is easier when given a
gestural command (imitation), as compared with being given
a verbal command. In other words, individuals with ideomotor
apraxia might not be able to round their lips when they are
asked to do so, but they might be successful when a clinician
demonstrates the movement.
n The movement sequencing errors in ideomotor apraxia can
sometimes be inconsistent on repeated attempts of the same
action. An example of this occurred when one of the author’s
patients was asked to make the gesture for hitchhiking. Her
rst attempt resulted in the slow, clumsy formation of a st.
With additional effort, she was slowly able to protrude her
thumb to complete the gesture. When asked immediately to
do it again, her initial movement was to bring her ngertips
together in a pincer-like action, and it again took much effort
for her to move her hand into the correct “thumbs up” position.
There are at least three subcategories of ideomotor apraxia.
The rst is limb apraxia. This is the inability to sequence the movements of the arms, legs, hands, or feet during a voluntary action,
although the concept behind the action and the general motor
plan appears to be accurate. The earlier toothbrush example is an
illustration of this type of apraxia. Limb apraxia is most often the
result of left hemisphere damage. In a majority of cases, it affects
both the right and left limbs, although hemiplegia might hide its
effects on one side of the body. This disorder is usually assessed
by having the individual pantomime a variety of well-known movements, such as hammering a nail, shaving, putting a key in a lock,
and combing hair.
A second subcategory of ideomotor apraxia is nonverbal oral
apraxia. This type of apraxia is also known as buccofacial apraxia,
facial apraxia, orofacial apraxia, or lingual apraxia. As its name
implies, nonverbal oral apraxia is a decit in the ability to sequence
nonverbal, voluntary movements of the tongue, lips, jaw, and other
associated oral structures. The orofacial movements affected by this
disorder might include protruding the tongue, whistling, biting the
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lower lip, and pufng out the cheeks. When asked to perform tasks
such as these, an individual with this type of apraxia might grope
for the correct position of the mouth, delay performing the action,
only partially complete the movement, or perform the movement
slowly and awkwardly. Occasionally, some individuals with nonverbal oral apraxia have trouble performing voluntary movements that
are only partially associated with the oral mechanism. For example,
they might have trouble taking a deep breath when asked to do so,
or they might be unable to swallow on command.
Nonverbal oral apraxia is commonly seen in individuals with
left hemisphere damage, and it can often co-occur with aphasia.
Although this disorder can be puzzling and even distressing to
the patient, it does not affect spontaneous or reexive orofacial
movements, meaning that the individual will still be able swallow
while eating, breathe deeply when out of breath, smile at a joke,
and make other spontaneous movements of the oral mechanism.
Because individuals with this disorder usually are able to perform these important automatic oral movements without difculty,
nonverbal oral apraxia is usually thought to have little clinical
signicance (Wertz et al., 1991). For the speech-language pathologist, this type of apraxia is of interest primarily because it can
co-occur with the third subcategory of ideomotor apraxia, apraxia
of speech.
Apraxia of speech is a decit in the ability to select and timesequence the motor commands needed to correctly position the
articulators during the voluntary production of phonemes. Because
most speech is a voluntary motor task, apraxia of speech can have
serious effects on a patient’s ability to communicate verbally.
Apraxia of speech is a disorder specic to the movements needed
to produce phonemes, and it can co-occur with limb or nonverbal
oral apraxia. The distinction between nonverbal oral apraxia and
apraxia of speech is evident in the names of these two disorders.
Nonverbal oral apraxia is a disturbance in the sequencing of oral
movements that are unrelated to speech production, such as licking
the lips, blowing out a match, and moving the tongue from side to
side. Apraxia of speech, as already stated, is a timing and movement disturbance in the oral-pharyngeal muscles during speech
production. Although it is common for an individual to have a cooccurrence of these two apraxias, both can appear more or less
separately. For example, some individuals might have apraxia of
speech but not have obvious symptoms of nonverbal oral apraxia,
and other individuals could have nonverbal oral apraxia but not
obvious symptoms of apraxia of speech.
Apraxia of speech is usually caused by damage to the left
frontal lobe, especially when the damage occurs near Broca’s area.
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Because apraxia of speech is so often associated with damage to
the left hemisphere, cases of pure apraxia of speech are actually
quite rare. In the majority of cases, apraxia of speech co-occurs
with aphasia, usually Broca’s aphasia. Ziegler et al. (2022) found
that 44% of patients with chronic aphasia also had some degree
of apraxia of speech. In addition, it is common for it to co-occur
with unilateral upper motor neuron dysarthria (Duffy, 2020). The
simultaneous occurrence of these disorders can make it difcult for
a beginning clinician to separate the motor speech errors of apraxia
from the language and articulation errors of a co-occurring aphasia
and dysarthria. The remainder of this chapter is designed to make
it easier for the inexperienced clinician to identify the symptoms
of apraxia of speech and treat them appropriately.
Neurologic Basis of Apraxia of Speech
As with so many of the functions of the CNS, the method by which
motor commands are sequenced for speech is not well understood.
This lack of understanding is a reection of how complex the task
of motor speech programming is. For instance, sequencing the
motor commands of speech production requires input from many
different areas of the brain. The language centers provide the linguistic information that is to be spoken, including the phonemes
that need to be sequenced correctly. The basal ganglia, cerebellum,
and thalamus provide motor and sensory input about the planned
speech movements. The limbic system and right hemisphere provide information about the emotional context of the intended utterance. All of this information needs to be integrated and processed
so that an intended message can be transformed into a sequence
of neural impulses that will contract the appropriate muscles at
the correct times. The enormity of this task was illustrated by Darley et al. (1975), who calculated that for every second a person is
talking, a total of 140,000 neuromuscular contractions and relaxations occur in the speech production muscles. The neurologic
“mechanism” thought to control this remarkable process is called
the motor speech programmer.
The Motor Speech Programmer
The motor speech programmer is a neural network in the brain
that sequences the motor movements needed to produce speech
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Perisylvian area of
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accurately. It is thought to accomplish this by rst analyzing the
linguistic, motor, sensory, and emotional information of a planned
speech act. It obtains this information through its many neural connections with the cognitive, language, emotional, and motor planning areas of the brain and then sequences that information into
a neural code that represents the muscular contractions needed to
produce the phonemes, words, and phrases in the intended utterance. If that neural code is sequenced correctly and is received
intact at the neuromuscular junction, the muscles will contract in the
proper sequence, and the resulting speech will be produced uently.
Included in this neural code are the stress and intonational patterns
that are used to convey the communicative intent of the speaker.
Through the sensory information received by the motor speech programmer, the code also reects the immediate circumstances of the
oral-motor structures. For example, if the speaker is chewing gum,
the neural code must be modied accordingly to ensure clear articulation of the utterance despite the material in the mouth.
Although numerous writers have described the models of the
motor speech programmer (Darley et al., 1975; Duffy, 2020; Guenther, 2016; McNeil et al., 2009), it is actually a rather nebulous
cerebral structure. Unlike Broca’s and Wernicke’s areas, the motor
speech programmer has not been precisely localized in the brain.
Research has indicated that it resides near the perisylvian area
of the left hemisphere (Figure 11–1), where it has close associations with the language and motor centers of the brain. The motor
FIGURE 11–1. The perisylvian area of the left hemisphere. Damage to this
area (particularly the anterior portion of it) is often associated with apraxia
of speech.
the left hemisphere
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