Apraxia of speech (AOS) is a “neurologic speech disorder that reflects an impaired capacity to plan or program sensorimotor commands necessary for directing movements that result in phonetically and prosodically normal speech” (Duffy, 2013, p. 4). AOS has also been referred to in the clinical literature as verbal apraxia or dyspraxia. For the purpose of this page, AOS will refer to acquired AOS; most information, especially that regarding assessment and diagnosis, also applies to progressive AOS.
The incidence of apraxia of speech (AOS) refers to the number of new cases identified in a specific time period. The prevalence of AOS refers to the number of individuals who are living with AOS in a given time period.
There are no reliable data on the incidence and prevalence AOS in adults due to challenges associated with the common co-occurrence of AOS with aphasia and dysarthria (Duffy, 2006; Duffy et al., 2014). Collection of data is also challenging due to difficulty distinguishing among those disorders—particularly in distinguishing between AOS characteristics and phonological errors that can occur in aphasia (McNeil et al., 2004).
McNeil et al. (2009) suggest that isolated AOS (i.e., AOS in the absence of dysarthria or aphasia) is very uncommon. Duffy (2013) observed that AOS was documented as the primary, but not necessarily the only, communication disorder for 6.9% of all motor speech disorders in the Mayo Clinic Speech Pathology practice. This percentage would undoubtedly increase drastically if the data included cases in which AOS was a secondary communication disorder (e.g., less severe than aphasia or dysarthria; Duffy, 2013; pp. 269–270).
The salient features of apraxia of speech (AOS) that have gained broad consensus for differential diagnosis (Allison et al., 2020; Ballard et al., 2014; Duffy, 2013; McNeil et al., 2009) include
The above features are consistent with deficits in planning and programming movements for speech and may increase with greater syllable length and motoric complexity. AOS can improve, remain stable, or worsen depending on specific diagnosis and time elapsed since onset (e.g., primary progressive AOS vs. acute stroke recovery).
The following speech characteristics may not be unique to AOS and can occur in the presence or absence of coexisting dysarthria or aphasia.
Rate and Prosody
Linguistic and nonspeech/non-oromotor deficits may be comorbid to AOS and typically depend on the site of the lesion. These include the following:
Acquired apraxia of speech (AOS) is caused by any process or condition that compromises the structures and pathways of the brain responsible for planning and programming motor movements for speech. Causes most often include
Occasionally, AOS is the first, only, or most prominent symptom in degenerative conditions (e.g., corticobasal degeneration, progressive supranuclear palsy). The term primary progressive AOS is used in such cases (Duffy, 2006; Duffy & McNeil, 2008; Duffy et al., 2007, 2020).
Speech-language pathologists (SLPs) play a central role in screening, assessment, diagnosis, and treatment of persons with apraxia of speech (AOS). The professional roles and activities in speech-language pathology include clinical services (diagnosis, assessment, planning, and treatment); prevention and advocacy; and education, administration, and research. See ASHA’s Scope of Practice in Speech-Language Pathology (American Speech-Language-Hearing Association [ASHA], 2016b).
The following roles are appropriate for SLPs when treating persons with AOS:
As indicated in the ASHA Code of Ethics (ASHA, 2016a), SLPs who serve this population should be appropriately trained to do so. SLPs who diagnose and treat AOS must possess skills in differential diagnosis of motor speech disorders and comorbid language disorders, have specialized knowledge in phonological encoding disorders and motor learning theory, and have experience with appropriate intervention techniques.
Screening identifies the need for further assessment and may be completed prior to a comprehensive evaluation. Screening can be completed using nonstandardized procedures. There are no apraxia of speech (AOS)–specific standardized screening tools available to date.
During screening, SLPs also look for signs of comorbid language, cognitive-communication, and swallowing deficits associated with the neurological insult.
It is best practice to complete a hearing screening to rule out hearing loss that might affect testing. If the individual wears hearing aids, the devices need to be inspected to ensure that they are in working order, and they need to be worn during screening.
Results of screening procedures are interpreted within the context of the individual’s cognitive–linguistic and sensory deficits. Screenings are ideally conducted in the language(s) used by the person, with sensitivity to cultural and linguistic diversity.
Screening may result in recommendations for
A comprehensive assessment is conducted for individuals suspected of having AOS and uses both standardized and nonstandardized measures (see assessment tools, techniques, and data sources).
Consistent with the World Health Organization’s (WHO) International Classification of Functioning, Disability and Health framework (ASHA, 2016b; WHO, 2001), comprehensive assessment of individuals with AOS is conducted to identify and describe
See Person-Centered Focus on Function: Acquired Apraxia of Speech [PDF] for an example of assessment data consistent with the International Classification of Functioning, Disability and Health framework.
Comprehensive assessment focuses on functional aspects of speech generation:
Comprehensive assessment typically includes the following features:
This includes a review of current medical status, medical history, surgical history, prior level of function, education, occupation, and cultural and linguistic background. A case history may address activity/participation, contextual, and quality-of-life issues.
An SLP may evaluate functional communication status and the psychosocial impact of a given medical condition on the patient and caregiver(s) and identify meaningful functional goals for the individual and caregiver(s). An SLP may also identify communication difficulties, contexts of concern (e.g., social interactions, work activities), language(s) used in those contexts, and the individual’s goals and preferences.
The identification of such barriers and facilitators assists the SLP in determining the potential for effective use of compensatory techniques and strategies, including the use of AAC.
A person’s sensory and motor status may affect their ability to access nonspeech communication methods (e.g., writing, using gestures). Therefore, these factors may influence performance on speech assessment tasks. Consultation with members of the interdisciplinary team (e.g., occupational therapy) may be valuable.
This pertains to the integrity of the structure and function of the respiratory, phonatory, resonatory, and articulatory (lips, tongue, velum, hard palate, dentition) systems. Oral–motor mechanisms and nonspeech oral praxis includes the strength, speed, and range of movement of the components of the oral–motor system. It also refers to steadiness, tone, accuracy, and coordination of movements for speech and nonspeech tasks. Assessment of these systems is useful in differentiating AOS from dysarthria and oral apraxia.
This pertains to salient features of speech that aid in differential diagnosis (see the Differential Diagnosis section below). This includes analysis of the perceptual correlates of the respiratory, phonatory, resonatory, and articulatory subsystems. Analysis of such characteristics may use standardized and/or nonstandardized assessment and may include analysis of natural communication samples gathered in different modalities (i.e., speaking or reading) and contexts (i.e., social, educational, or vocational), as well as more structured tasks (e.g., imitative speech tasks, multiple repetitions of multisyllabic words). The SLP may also examine the influence of stress and/or fatigue on verbal communication (e.g., influence of physiologic and contextual factors that impact communication success).
Abnormal features of voice and resonance (e.g., harsh, breathy, weak voice; hypernasality, hyponasality) are typically absent in isolated AOS. Analysis of voice may help differentiate AOS from dysarthria. See the Differential Diagnosis section below.
Language assessment consists of expressive and receptive language. Analysis of language may help differentiate AOS from aphasia. See the Differential Diagnosis section below.
AOS results from an impaired ability to plan commands that direct the correct movements for speech (Duffy, 2013). Assessment of motor speech planning includes the production of stimuli of differing motoric complexity—phonemes, syllables, monosyllabic/multisyllabic words, and sentences that place varying demands on the speech motor system. Motor speech planning assessment contrasts the following items:
Assessment of motor speech planning also examines the following:
Assessment may result in the following outcomes:
AOS often co-occurs with or presents similarly to other neurogenic communication disorders such as dysarthria and aphasia. AOS does not involve muscle weakness, paralysis, spasticity, or involuntary movements typically associated with dysarthria or language comprehension or production deficits that characterize aphasia.
Differential diagnosis between these conditions and AOS is essential. The chart below provides a basic comparison between characteristics of these disorders.
|Language processing deficits||No||No||Yes|
|Consistent error patterns*||No||Yes||No|
|Groping for articulatory postures||Yes||No||No|
*See the “Distinguishing AOS From Aphasia” section below for further details.
Please note that the chart above does not capture all the nuances of differential diagnosis of AOS. Information below may further clarify this subject.
The dysarthria subtypes that are most difficult to distinguish from AOS are ataxic and unilateral upper motor neuron dysarthria, and the latter may often co-occur with AOS. Poorer performance on sequential motion rates (SMRs) than on alternating motion rates (AMRs) in AOS may distinguish it from ataxic dysarthria (Duffy, 2013). Examination of speech subsystems using speech—and, sometimes, nonspeech—tasks is crucial in distinguishing AOS from dysarthria. AOS is primarily marked by articulatory and prosodic deficits, unlike dysarthria in which other speech subsystems can be affected—most notably, resonance. Unlike AOS, dysarthria is generally not influenced by automaticity of speech production, stimulus modality, and linguistic variables (Duffy, 2013).
AOS may be difficult to differentiate from aphasia in its clinical presentation, and the conditions frequently co-occur. Duffy (2013) notes distinctions between AOS and aphasia (e.g., prosodic errors, language processing deficits) reflected in the comparison chart above.
Aphasia may be so severe that AOS may be masked during assessment. Although speech sound errors are thought to arise from different processing impairments (motor planning deficits in AOS vs. linguistic breakdowns in aphasia), error patterns are often similar, particularly in very mild or very severe presentations. Temporal acoustic characteristics of speech help distinguish AOS from aphasia better than perceptual characteristics alone (Haley et al., 2012). Nevertheless, many people with speech sound errors following a neurological injury may not be easily classifiable, with borderline presentations possible similar to both AOS and aphasia with phonemic paraphasia (Haley et al., 2017). Speech error patterns have, at various times, been described as consistent or inconsistent in speakers with AOS and considered as a potential diagnostic feature (see, e.g., McNeil et al., 2009; Wertz et al., 1984). However, recent evidence concludes that error consistency is often present both in people with AOS and in people with aphasia without AOS and is therefore not useful for differential diagnosis (Haley et al., 2020).
Periodic reassessment of individuals with AOS is important because neurological recovery can occur for several months or longer in the context of acquired AOS. Ongoing assessment can also be used to examine an individual’s responses to rehabilitation and to life adaptations after the injury. Progressive conditions such as primary progressive AOS require periodic reassessment to ensure that the individual is communicating at maximal levels of independence and to plan for additional communication adaptations that may become necessary with disease progression.
The SLP considers the influence of cultural and linguistic factors on the individual’s communication style and the potential impact of impairment on function when selecting screening and assessment tests. The assessment is conducted in the language(s) used by the person with AOS, with the use of interpretation services as necessary (see collaborating with interpreters, transliterators, and translators).
Although the impact of AOS on speech changes is the same across languages (i.e., disrupted articulation and prosody), the impact on communication is different. For example, speakers of tonal languages may require special consideration when working with AOS, as AOS may contain prosodic deficits. Prosodic deficits in tonal languages may have the capacity to change the meaning of a given word.
Appropriate accommodations and modifications can be made to the testing process to reconcile cultural and linguistic variations. Comprehensive documentation includes descriptions of these accommodations and modifications. If a standardized test is modified or if accommodations are provided that are not allowed for in the assessment, standardized scores are invalid and inappropriate to report.
The goal of intervention is to help the individual achieve the highest level of independent function for participation in daily living (WHO, 2001). Intervention is designed to
For individuals with apraxia of speech (AOS), treatment goals focus on facilitating the efficiency, effectiveness, and naturalness of communication by
Barriers to successful communication and participation can be minimized for individuals with AOS by
See Person-Centered Focus on Function: Acquired Apraxia of Speech [PDF] for an example of functional goals consistent with the International Classification of Functioning, Disability and Health framework.
The goal of family-centered practice for individuals with AOS is to create a partnership so that family members fully participate in all aspects of the individual’s care. The range of services offered to families includes
When designing a treatment program for an individual with AOS, consider the following factors:
|Examples of Stimulus and Task Variables That Affect Responses*|
|Oral/nasal distinctions||Voiced distinctions|
|Bilabial and lingual/alveolar place of articulation||Other places of articulation|
|Consonant clusters that cross syllables||Consonant clusters within syllables|
|Shorter syllables||Longer syllables|
|High-frequency syllables and words||Low-frequency syllables and words|
|Stressed syllables and words||Unstressed syllables and words|
|Automatic/reactive speech||Volitional/propositional speech|
|Imitation of a model||Self-generation of response (especially in those with coexisting aphasia)|
|*Source: Duffy (2013).|
Treatment can be restorative (i.e., aimed at improving or restoring impaired function) and/or compensatory (i.e., aimed at compensating for deficits not amenable to retraining). In the case of progressive AOS, it may also help maintain speech functioning.
Approaches aimed at improving speech production and intelligibility focus on reestablishing motor plans/programs and improving the ability to select and activate them and set program parameters (e.g., speed) in specific situations (Knock et al., 2000). These treatment approaches include articulatory–kinematic approaches, sensory cueing, rate and/or rhythm control, and various combinations thereof.
Approaches used to compensate for AOS focus on teaching use of strategies or external aids and creating or personalizing those resources (e.g., using gestures, writing, or drawing to communicate).
Some approaches may be used in both restorative and compensatory capacities. For example, AAC is used to provide functional communication options while supporting, enhancing, and potentially improving speech production (Lasker et al., 2008; Yorkston et al., 2010).
Below are brief descriptions of treatment options for addressing AOS, grouped by approach. This list is not exhaustive, and the inclusion of any specific treatment does not imply endorsement from ASHA. Please see the Apraxia of Speech (Adults) Evidence Map for systematic reviews of AOS interventions.
Treatment selection depends on a number of factors, including severity of the disorder, communication needs of the individual, and presence and severity of co-occurring conditions (e.g., aphasia and associated language and cognitive deficits, dysarthria, or progressive neurological diseases).
Apraxia in other systems may play a role in treatment. For example, similar to limb weakness, the presence of limb apraxia may impact access to AAC.
Articulatory–kinematic approaches are based on principles of motor programming/planning. They
See Bislick et al. (2012) and Maas et al. (2008) for discussions of motor learning principles as they apply to the treatment of motor speech disorders.
Multiple input phoneme therapy is appropriate for individuals with severe AOS. The program proceeds through a hierarchy of steps that stress phoneme generalization using multiple input stimuli. The individual’s stereotypic utterances are used as initial stimuli; the clinician models these utterances while simultaneously providing a gestural/prosodic cue (e.g., tapping the individual’s arm). The clinician then fades the voice and mimes the movement while the individual continues to produce the target. New words use the initial phoneme of a stereotypic utterance (e.g., “one” to “win”). The number of targets and the length and phoneme complexity progressively increase. The individual initially repeats the stereotypic utterance in a nonvolitional manner and eventually regains volitional control and the ability to spontaneously express words and phrases (Stevens, 1989; Stevens & Glaser, 1983).
Sound production treatment is intended to improve production of consonants that are problematic for a particular speaker. It uses a treatment hierarchy that incorporates modeling and repetition of minimal-contrast word pairs. Auditory, visual, and tactile cues are used, along with articulatory placement cueing and graphemic cues (Wambaugh et al., 1998; Wambaugh & Mauszycki, 2010).
The speech motor learning treatment approach addresses the underlying inability to plan and program the production of speech motor targets in varying phonetic contexts and in utterances longer than single words or nonwords. Nonwords, constructed from a corpus of target consonants and vowels, are used as treatment stimuli. Treatment proceeds in steps, taking the individual from imitated blocked practice of each nonword to self-initiated production of a series of nonwords. Eventually, real words and phrases containing these words are identified and rehearsed until the criterion is met (van der Merwe, 2011).
Many treatments for AOS incorporate sensory input (e.g., visual, auditory, proprioceptive, and tactile cues) to teach the movement sequences for speech. Sensory cues can be used separately or in combination (i.e., multisensory approach). Feedback is an important aspect of motor learning. These external cues may facilitate speech production by providing additional feedback to the individual if they cannot benefit from, or do not receive, sufficient intrinsic sensory feedback.
Integral stimulation is a method for practicing movement gestures for speech production that involves imitation and emphasizes multiple sensory models (e.g., auditory, visual, tactile). This method is part of many treatment approaches. Treatment follows a “listen to me, watch me, do what I do” sequence, in which the individual hears and sees how the clinician produces a targeted sound sequence or word/phrase and then imitates (Rosenbek et al., 1973).
Tactile cueing methods of speech facilitation are those that provide direct tactile input for correct speech production. Using these methods, the SLP applies pressure or otherwise touches the individual’s face, neck, and head to provide a tactile cue for correct production or speech movement gesture.
PROMPT is a tactile method of treatment based on touch pressure, kinesthetic, and proprioceptive cues (Bose et al., 2001; Chumpelik, 1984; Freed et al., 1997). Using this approach, the clinician uses finger placements on the individual’s face and neck to cue various aspects of speech production (e.g., place and manner of articulation) and help the individual limit unnecessary movements. PROMPT requires specialized training.
Visual cueing methods provide visual cues for shape, placement, or movement of the articulators. Visual cues can be provided via low-tech methods (e.g., simple hand signs or visual feedback via a mirror) or more technologically advanced methods that utilize computer software and screen, ultrasound images, and other forms of biofeedback (e.g., acoustic/spectrographic feedback displays).
Electropalatography utilizes a palatal device with electrodes to record and visualize contact of the tongue on the palate while an individual makes different speech sounds (Howard & Varley, 1995). Electropalatography provides real-time visual feedback as well as a split-screen option so that the SLP can model the correct tongue placement while the patient observes.
Electromagnetic articulography uses miniature receiver coils placed on and in the mouth (e.g., tongue dorsum, corners of the mouth, or velar margin) to record and provide a visual display of tongue, mouth, palate, and jaw movements during treatment. AOS treatment research involving electromagnetic articulography has focused on tongue placement (see, e.g., Katz et al., 1999, 2010).
Script training is a functional approach to treating neurogenic communication disorders (Holland et al., 2002). It is used to facilitate verbal communication on specific topics selected by the individual. Script training helps the individual who wants to speak relatively normally on a few personally relevant topics. A number of phrases are practiced so that they become automatic and can be inserted into conversation relatively fluently (Henry et al., 2018; Youmans et al., 2011).
Rate and rhythm control approaches (also called prosodic facilitation approaches) use intonation patterns (melody, rhythm, and stress) to improve speech production. Although these approaches are aimed at improving prosody, they may also result in improved articulation for individuals with AOS (Mauszycki & Wambaugh, 2011). Using these patterns, the clinician guides the individual through a gradual progression of steps that increase the length of utterances, decrease dependence on the clinician, and decrease reliance on intonation (Martin et al., 2001).
Contrastive stress is used when speaking to highlight a particular word in a phrase or sentence; varying the stressed word also changes the meaning of the sentence. In treating AOS, contrastive stress can be used in target phrases or sentences to improve the individual’s ability to produce speech with varying intonation contours (Wertz et al., 1984).
Melodic intonation therapy uses melody, rhythm, and stress to facilitate speech production. The clinician provides models of intoned utterances of varying lengths. Reliance on intonation is gradually decreased over time. Melodic intonation therapy was first designed for individuals with nonfluent aphasia, many of whom have co-occurring AOS (Sparks et al., 1974; Sparks & Holland, 1976; Zumbansen et al., 2014).
Metrical pacing treatment is a pacing technique that uses rhythmical sequences of tones that provide metrical templates to guide the production of target utterances. Individuals are asked to produce target utterances at the same time as pacing signals. The synchronization pulse is generated by a computer and can be varied by rate (corresponding to speech rate) and metrical structure (syllable number and stress pattern) to simulate natural stress patterns of speech (Brendel & Ziegler, 2008).
Rhythmic pacing strategies use various rate control techniques to provide temporal cues that help pace speech production. Techniques include hand or finger tapping and use of a pacing board or metronome (Dworkin et al., 1988; Mauszycki & Wambaugh, 2008).
Transcranial direct current stimulation is an experimental procedure in which transcranial direct current is delivered to the left inferior frontal gyrus to modulate cortical activity. It has been used in conjunction with articulatory–kinematic treatment to improve the speech of individuals with AOS secondary to stroke. Speech targets consist of syllables and words that are presented auditorily and are repeated by the individual (Marangolo et al., 2011).
AAC involves supplementing or replacing natural spoken language with writing and/or aided (e.g., picture communication, line drawings, speech-generating devices, and tangible objects) or unaided (e.g., manual signs, gestures, and finger spelling) symbols. Whereas aided symbols require some type of transmission device, the production of unaided symbols requires only body movements. When selecting AAC systems or devices, it is important to determine the individual’s willingness to use them. See Lasker and Bedrosian (2001) for a discussion on promoting acceptance of AAC by adults with acquired communication disorders. See ASHA’s Practice Portal page on Augmentative and Alternative Communication for additional information.
Severity of co-occurring conditions may influence treatment decisions. For example, improving the functional communication of an individual with severe language and cognitive impairments following a stroke may take precedence over treatment of their AOS. Treatment for individuals with progressive AOS resulting from degenerative disease is often appropriate, particularly for those with no significant language or cognitive impairments. The goal of treatment is to maximize communication at each stage of the disease, not to reverse decline (Duffy, 2013). Goals in the early stages might begin with efforts to improve speech and maintain comprehensibility, followed by establishing the use of compensatory strategies, including AAC (Duffy & McNeil, 2008; Jung et al., 2013).
In addition to determining the optimal speech and language treatment for an individual with AOS, the clinician considers other service delivery variables that may have an impact on treatment outcomes, such as format, provider, dosage, timing, and setting.
Format refers to the structure of the treatment session (e.g., group and/or individual). The appropriateness of treatment format (individual vs. group vs. both) depends on the primary goal at a particular point in the treatment process. For example, initial treatment may involve intensive drills to improve speech production and/or practice in using AAC aids. However, once the individual has made progress on these goals, group treatment may be incorporated to provide opportunities for practice.
Provider refers to the person providing the treatment (e.g., SLP, trained volunteer, caregiver). SLPs treat the speech motor and communication aspects of AOS and train individuals in the use of AAC. It is important to involve family members, caregivers, and other communication partners in the treatment process to help them understand the individual’s communication needs and learn strategies to facilitate communication. Other professionals (e.g., physical therapist or occupational therapist) may be involved in the treatment of comorbid deficits. It is important for SLPs to collaborate with other professionals regarding treatment and to take advantage of opportunities for co-treatment.
Dosage refers to the frequency, intensity, and duration of service. Treatment dosage for AOS should be consistent with principles of motor learning (Maas et al., 2008; Rosenbek et al., 1973; Wambaugh et al., 2014). Intensive and individualized treatment is often stressed because of the need for repetitive production practice in motor speech disorders like AOS. See Ballard et al. (2015) for a discussion of average dosage.
Timing refers to the initiation of intervention relative to diagnosis. Generally speaking, treatment begins as early as possible post onset. Treatment can also be appropriate when an extended amount of time has elapsed since onset, particularly if an individual has not received any treatment for AOS during that time.
Setting refers to the location of treatment (e.g., home, community-based). A naturalistic treatment environment that incorporates a variety of communication partners may facilitate generalization and carryover of skills.
This list of resources is not exhaustive, and the inclusion of any specific resource does not imply endorsement from ASHA.
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American Speech-Language-Hearing Association. (n.d.). Acquired Apraxia of Speech. (Practice Portal). Retrieved month, day, year, from www.asha.org/practice-portal/clinical-topics/acquired-apraxia-of-speech/.