See the Assessment section of the Apraxia of Speech (Adults) Evidence Map for pertinent scientific evidence, expert opinion, and client/caregiver perspective.
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
- comprehensive assessments; and/or
- referral for other examinations or services.
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
- impairments in body structure and function, including underlying strengths and weaknesses in speech sound production and verbal/nonverbal communication;
- co-morbid deficits such as other types of apraxia, aphasia, and dysarthria;
- the individual's limitations in activity and participation, including functional status in communication, interpersonal interactions, self-care, and learning;
- contextual (environmental and personal) factors that serve as barriers to, or facilitators of, successful communication and life participation; and
- the impact of communication impairments on quality of life and functional limitations relative to premorbid social roles and abilities for the individual and the impact on his or her community.
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
- Production of stimuli of increasing linguistic complexity—phonemes, syllables, mono/multisyllabic words, and sentences that place varying demands on the speech motor system
- oral/nasal vs. voiced distinction
- consonant clusters across syllables vs. within syllables
- stressed vs. unstressed syllables and words
- automatic/reactive vs. volitional/propositional speech
- imitation vs. self-generated responses
- Contextual speech—to assess integrated functioning of all the speech subsystems
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:
- Diagnosis of AOS.
- Clinical description of the characteristics and severity of the disorder.
- Statement of prognosis and recommendations for intervention that relate to overall communication adequacy, including augmentative or alternative communication (AAC) measures as needed. See ASHA's Practice Portal page on Augmentative and Alternative Communication.
- Identification of relevant follow-up services for appropriate intervention and support for individuals with AOS.
- Referral to other professionals as needed, including, for example, the following professionals:
- Occupational therapist—for nonspeech, sensory–motor, or fine motor issues.
- Physical therapist—if gross motor skills or overall muscle tone are of concern.
- Neurologist—if the causal diagnosis is uncertain or if other neurological signs or symptoms are identified that require further investigation or management.
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.
Distinguishing AOS From Dysarthria
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 can present without muscle weakness, which is often a sign of several dysarthria types.
- AOS is marked by articulatory and prosodic deficits, unlike dysarthria, in which several speech subsystems can be affected.
- In contrast to AOS, dysarthric speech may present with more consistent error patterns and is generally not influenced by automaticity of speech production, stimulus modality, and linguistic variables (Duffy, 2013).
- Other apraxic speech characteristics, such as a larger variety of articulatory errors and groping for articulatory postures, are typically not seen in dysarthria.
- Poorer performance on SMRs than on AMRs in AOS may distinguish it from ataxic dysarthria (Duffy, 2013).
Distinguishing AOS From Aphasia
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):
- Prosodic abnormalities that characterize AOS are typically absent in aphasia.
- Multimodal language processing deficits that are typically seen in aphasia are absent in AOS alone.
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.