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 apraxia of speech.
AOS frequently co-occurs with dysarthria and/or aphasia and sometimes with limb apraxia, oral apraxia, apraxia of gait, and apraxia of swallowing. AOS does not involve muscle weakness, paralysis, spasticity, or involuntary movements typically associated with dysarthria, or language comprehension or production deficits that characterize aphasia.
There are no reliable data on the incidence and prevalence of AOS in adults. The collection of these data is hindered by challenges associated with the common co-occurrence of AOS with aphasia and dysarthria (Duffy, 2006; Duffy, Strand, & Josephs, 2014) and the difficulty distinguishing among those disorders—particularly in distinguishing between AOS characteristics and phonological errors that can occur in aphasia (McNeil, Pratt, & Fossett, 2004).
McNeil, Robin, and Schmidt (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).
The salient features of AOS that have gained broad consensus for differential diagnosis (Ballard, Tourville, & Robin, 2014; Duffy, 2013; McNeil et al., 2009) include
These features are consistent with deficits in the planning and programming of movements for speech and are noted to increase with greater syllable length and motoric complexity.
AOS can improve over time (e.g., in acute stages of stroke recovery, in response to therapy), remain stable, or worsen (e.g., primary progressive apraxia of speech).
The following other speech characteristics may not be unique to AOS and can also occur with co-existing dysarthria or aphasia.
Rate and Prosody
Linguistic and nonspeech/non-oromotor features that are observed during clinical presentation typically depend on the site of lesion and comorbid conditions. These include the following:
Acquired 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. The term primary progressive AOS (PPAOS) is used in such cases (Duffy, 2006; Duffy & McNeil, 2008; Duffy, Peach, & Strand, 2007). Premotor and supplementary motor areas are implicated in progressive forms of AOS (e.g., Josephs et al., 2012).
Speech-language pathologists (SLPs) play a central role in the screening, assessment, diagnosis, and treatment of persons with 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 (ASHA, 2016).
The following roles are appropriate for SLPs:
As indicated in the Code of Ethics (ASHA, 2010r), SLPs who serve this population should be specifically educated and appropriately trained to do so. SLPs who diagnose and treat AOS must possess skills in differential diagnosis of motor speech disorders and co-morbid language disorders; have specialized knowledge in phonological encoding disorders and motor learning theory; and have experience with appropriate intervention techniques.
Screening may be conducted by the SLP prior to more comprehensive evaluations, when AOS is suspected secondary to a neurological insult (e.g., stroke).
Screening does not provide a diagnosis or a detailed description of the severity and characteristics of speech deficits associated with AOS but, rather, identifies the need for further assessment. It can be completed using nonstandardized procedures, considering there are no AOS-specific standardized screening tools available to date.
During screening, SLPs also look for signs of co-morbid 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.
Screening may result in recommendations for
Results of screening procedures are interpreted within the context of the individual's cognitive–linguistic and sensory deficits.
A comprehensive assessment is conducted for individuals suspected of having AOS using 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 (ICF) framework (ASHA, 2007; 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 ICF.
Comprehensive Assessment for Acquired AOS: Typical Components
Medical status and history, education, occupation, and cultural and linguistic backgrounds
Self-reported areas of concern
Evaluate functional communication success and the psychosocial impact of the condition on the patient and caregiver, and identify meaningful functional goals for the individual and caregiver(s)
Communication difficulties, contexts of concern (e.g., social interactions, work activities), language(s) used in those contexts, and the individual's goals and preferences
Sensory and motor status
Relevant in identifying nonspeech communication methods for individuals presenting with greater severity
Factors that influence performance on speech assessment tasks
Integrity of speech subsystems
Respiration, phonation, resonance, oral articulatory system (lips, tongue)
Oral–motor mechanisms and nonspeech oral praxis
Used to differentiate AOS from dysarthria and oral apraxia
Strength, speed, and range of movement of components of the oral–motor system
Steadiness, tone, and accuracy of movements for speech and nonspeech tasks (Darley, Aronson, & Brown, 1969)
Perceptual speech characteristics
To identify salient features of the individual's speech that aid in differential diagnosis (e.g., AOS vs. dysarthria, aphasia, and nonaphasic cognitive deficits affecting communication)
Uses standardized and nonstandardized assessments and includes analysis of natural communication samples gathered in different modalities (speaking and reading) and contexts (social, educational, or vocational)
Examines influence of stress and/or fatigue on verbal communication (e.g., influence of physiologic and contextual factors that impact communication success)
Motor speech planning (Duffy, 2013) focused on identifying the threshold of breakdown on a continuum of motor planning demands using a variety of tasks and stimuli
Vowel prolongation (to examine respiratory–phonatory coordination)
Alternating motion rates (AMRs; also called diadochokinetic rates; to judge speed and regularity of movement of articulators)
Sequential motion rates (SMRs; to evaluate ability to move quickly and sequentially from one articulatory posture to another, an impairment that is particularly characteristic of AOS)
Intelligibility (the degree to which the acoustic signal produced by the individual is understood)
Comprehensibility (the degree to which a listener understands the individual based on the acoustic signal plus other linguistic and nonspeech cues)
Efficiency (the rate at which an intelligible or comprehensible utterance is communicated; critical to setting meaningful functional targets in treatment planning)
Acoustic and physiologic assessments using instrumental procedures to quantify abnormalities in voice onset time, rate, prosody and stress, articulation, and trial-to-trial variability
Voice and resonance
Helps differentiate AOS from dysarthria
Abnormal features of voice and resonance (e.g., harsh, breathy, weak voice; hypernasality, hyponasality)
Helps differentiate AOS from aphasia
Expressive and receptive skills
Identification of contextual barriers and facilitators
To determine potential for effective use of compensatory techniques and strategies, including the use of augmentative and alternative communication (AAC)
Facilitators (e.g., ability and willingness to use AAC systems; family support; motivation to return to prior level of function)
Barriers (e.g., reduced confidence in verbal communication; cognitive deficits; visual and motor impairments)
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. Differential diagnosis between these conditions and AOS is, therefore, an essential part of comprehensive assessment.
The dysarthria subtypes that are most difficult to distinguish from AOS are ataxic and unilateral upper motor neuron dysarthria (Duffy, 2013).
Examination of speech subsystems using both speech and sometimes nonspeech tasks is crucial to distinguish between AOS and dysarthria. Differences between AOS and dysarthria include those listed below.
AOS is sometimes difficult to differentiate from aphasia in its clinical presentation, given the frequent co-occurrence of these two conditions. In addition, aphasia may be so severe that AOS may be masked during the assessment.
Although the speech sound errors noted on assessment arise from different processing impairments (motor planning deficits in AOS vs. linguistic breakdown in aphasia), the error patterns are often similar, particularly in very mild or very severe presentations. Temporal acoustic characteristics of speech help distinguish between AOS and aphasia better than perceptual characteristics alone (Haley, Jacks, de Riesthal, Abou-Khalil, & Roth, 2012).
The following characteristics can help distinguish between AOS and aphasia (Duffy, 2013):
Periodic reassessment of individuals with AOS is important because neurological recovery can occur for several months or longer, especially in the early phases of recovery. 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 PPAOS require periodic reassessment to ensure that the individual is communicating at maximal levels of independence and to plan ahead 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).
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. Scores from standardized tests should be interpreted and reported with caution in these cases.
Consistent with the WHO's ICF framework (WHO, 2001), the goal of intervention is to help the individual achieve the highest level of independent function for participation in daily living. Intervention is designed to
For individuals with 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 ICF.
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 counseling; providing resources and information; coordinating services; advocating for practices that incorporate family preferences and address family priorities; and teaching specific skills to family members and other significant communication partners. See family-centered practice.
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 co-existing aphasia)|
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).
Approaches aimed at improving speech production and intelligibility focus on re-establishing motor plans/programs and improving the ability to select and activate them and set program parameters (e.g., speed) in specific situations (Knock, Ballard, Robin, & Schmidt, 2000). These treatment approaches include articulatory–kinematic approaches, sensory cueing, rate and/or rhythm control, and various combinations thereof.
Augmentative and alternative communication (AAC) approaches are used to provide functional communication options, while at the same time, supporting, enhancing, and potentially improving speech production (Lasker, Stierwalt, Hageman, & LaPointe, 2008; Yorkston, Beukelman, Strand, & Hakel, 2010).
From the perspective of the WHO's ICF framework (WHO, 2001), approaches aimed at improving speech production and intelligibility focus on "body functions/structures" within the ICF framework, whereas AAC approaches are directed at "activities/participation."
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. See Ballard et al. (2015) and Wambaugh, Duffy, McNeil, Robin, and Rogers (2006) 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, the presence of limb apraxia may preclude using manual signs to support functional communication. The presence of oral apraxia may support the need for more aggressive or alternative approaches to the use of phonetic placement cues in speech treatment.
Articulatory–kinematic approaches are based on principles of motor programming/planning. They
See Bislick, Weir, Spencer, Kendall, and Yorkston, 2012 and Maas et al. (2008) for discussions of motor learning principles as they apply to the treatment of motor speech disorders.
MIPT is appropriate for individuals with severe apraxia of speech. 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).
Script training is a functional approach to treating neurogenic communication disorders (Holland, Milman, Munoz, & Bays, 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 (Youmans, Youmans, & Hancock, 2011).
SPT is used 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, Kalinyak-Fliszar, West, & Doyle, 1998; Wambaugh & Mauszycki, 2010).
The SML treatment approach addresses the underlying inability to plan and program the production of speech motor targets (SMTs) 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 he or she cannot benefit from, or does not receive, sufficient intrinsic sensory feedback.
IS is part of many treatment approaches. It is a method for practicing movement gestures for speech production that involves imitation and emphasizes multiple sensory models (e.g., auditory, visual, tactile). 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, Square, Schlosser, & van Lieshout, 2001; Chumpelik, 1984; Freed, Marshall, & Frazier, 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" as to the 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, such as acoustic/spectrographic feedback displays.
EPG 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). EPG 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.
EMA uses miniature receiver coils placed on and in the mouth (e.g., tongue dorsum, corners of mouth, or velar margin) to record and provide a visual display of tongue, mouth, palate, and jaw movements during treatment. AOS treatment research involving EMA has focused on tongue placement (see, e.g., Katz, Bharadwaj, & Carstens, 1999; Katz, McNeil, & Garst, 2010).
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 have also resulted 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, Kubitz, & Maher, 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, LaPointe, & Rosenbek, 1984).
MIT is a prosodic facilitation approach that 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. MIT was first designed for individuals with nonfluent aphasia, many of whom have co-occurring apraxia of speech (Sparks, Helm, & Albert, 1974; Sparks & Holland, 1976; Zumbansen, Peretz, & Hébert, 2014).
MPT is a type of pacing technique that uses rhythmical sequences of tones that provide metrical templates to guide production of target utterances. Individuals are asked to produce the target utterances in synchrony with the 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 the 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, Abkarian, & Johns, 1988; Mauszycki & Wambaugh, 2008).
tDCS is an experimental procedure in which transcranial direct current is delivered to the left inferior frontal gyrus (IFG) 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 speech or writing with aided symbols (e.g., picture communication, line drawings, speech-generating devices, and tangible objects) or unaided symbols (e.g., manual signs, gestures, and finger spelling). 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.
Not all individuals with AOS are candidates for treatment. For example, the language impairments associated with aphasia can affect both comprehension and expression so severely that functional communication (verbal or alternative/augmentative) is not possible. In such cases, clinicians might first focus on improving basic language and cognitive abilities to support functional communication. If language and cognitive abilities do not improve sufficiently, AOS treatment would not be appropriate (Freed, 2012).
Treatment for individuals with 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, Duffy, & Josephs, 2013).
Some adults were diagnosed with CAS as children, but, despite having had treatment, their speech difficulties persist. Others have had long-standing speech difficulties that are only now being diagnosed as apraxia. Adults with previously or newly diagnosed CAS often seek services because their speech difficulties are having an impact on communication in school, work, or social settings. The treatment principles and at least some of the options described above may be appropriate for these individuals. Goals focus on the individual's specific communication needs (e.g., in the classroom, at work, or in social situations). See childhood apraxia of speech for more detailed information about CAS.
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 treatment of co-morbid 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). Given the need for repetitive production practice in motor speech disorders like AOS, intensive and individualized treatment is often stressed. See Ballard et al., 2015, for a discussion of average dosage.
Timing refers to the timing 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. Treatment can be effective for individuals in the chronic phase of AOS, based on data from AOS treatment studies and supporting data from stroke literature suggesting that recovery of stroke-related deficits can occur during this phase (Wheaton, 2015).
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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The recommended citation for this Practice Portal page is:
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/.