Presentation on theme: "Children with Developmental Apraxia of Speech Communication Profiles and Interventions Laura J. Ball, Ph. D. Munroe-Meyer Institute for Genetics and."— Presentation transcript:
1Children with Developmental Apraxia of Speech Communication Profiles and Interventions Laura J. Ball, Ph. D.Munroe-Meyer Institute for Genetics and RehabilitationUniversity of Nebraska Medical Center, Omaha
2Demographics Onset Course Gender Prevalence Aggregation Onset: From birth, see impairments in development of movements for speech production.Course: Often long, arduous treatments. Question if because slp’s didn’t know appropriate interventions, or if just difficult to treat.Gender: Male to female: 3 to 1 For dissertation, had 19% female (or approximately 5 to 1)Prevalence: Generally one in one thousand, not really known.Aggregation: Genetic studies show some familial transmission with certain disorders (Renpenning syndrome, Soto’s syndrome? etc.)
3Research Classifications Unitary Entity: isolate one characteristic that differentiates DAS from other childhood speech problems.Syndrome does not require one “necessary and sufficient” dx criterion.Subtypes:behavioral characteristics are associated with dx criteria for each of 2+ subtypes of the disorder.
4Theoretical Perspective Shriberg et.al., (1997a, 97b, 97c) present a schema for speech production in DAS with linguistic processing stages.1. Input processes (auditory-temporal, perceptual)2. Organizational processes ( representational, transformational)3. Output processes (selection-retrieval, pre-articulatory sequencing)4. Articulatory execution.
5DAS: Deficit in Input Processes? Auditory-Temporal & Perceptual input processes are usually proposed from 2 general perspectives. Children with DAS have:1. Across-the-board deficits in language processes.2. Specific deficits in either formulation or transformation of appropriate phonological representations.
6Robin et.al., (1993) noted that children had disordered prosody, suggesting that “impaired temporal perception could impact ability to gain information about durational aspects of prosody and add to the observed prosodic difficulties.”
7DAS: Deficit in Organizational Processes? Representational & Perceptual OrganizationVelleman & Strand (1994) implicate representational processing. They suggest that children with DAS “could be seen as impaired in their ability to generate & utilize frames, which would otherwise provide the mechanisms for analyzing, organizing, & utilizing information from their motor, sensory, & linguistic systems for the production of spoken language.”
8Maassen, Thoonen, & Gabreels (1993): Children with DAS demonstrate a “phonological encoding disorder.”
9Snow, Marquardt, & Davis (1992): Children with DAS “demonstrate an apparent breakdown in the ability to perceive ‘syllableness’ and access & compare syllable representations with regard to position & structure.”
10Groenen, Crul, Maassen, & Thoonen (1993): “weaker auditory memory traces” suggest perceptual discrimination tasks have diagnostic value. “The degree of dysfunction in speech production is related to the degree of dysfunction in speech perception.”
11Transformational Organization Morphophonemic, allophonic & sociolinguistic rules appear to be intact.
12DAS: Deficit in Output Processes? Pre-articulatory Sequencing(most prevalent) attributes the variability observed in speech output to deficits in pre-articulatory sequencing of the spatio-temporal movements for speech sounds.
13Selection-RetrievalPhonetic variability involves a lower-level deficit in motor programming, rather than retrieval of phonemic units.Walton & Pollack (1991) “motor theory”: “Although one could argue that there is a phonemic confusion in the speech of these children, one could also argue that their ability to demonstrate these contrasts is lost when their motor systems are taxed or challenged.”
14DAS is a disorder of movement Lack consistent error production seen with developmental delay. Not result of immature sound productions, but actual motoric impairment.Dysarthria will also exhibit consistent errors, with some physical signs of weakness, paralysis, etc.DAS is a disorder of movement.
15Diagnostic Features Speech Errors: Differ from errors of children with developmental delay, phonological processes.Resemble errors of adult acquired apraxia (contrast between voluntary and involuntary performance, variability of errors).Differ from dysarthria, which has errors in phonation, resonance, articulation & prosody.
16DAS impacts all aspects of communication Researchers have defined DAS solely as sound production error patterns because of a need to eliminate any “outliers” in their research projects. In terms of finding a genetic determinant, a case of “pure DAS” yields a much nicer result. More recently, researchers are indicating more consensus that DAS is actually a disorder of movement and not sound production per se. As clinicians, we all know that these children exhibit a range of communication disorders that happen to include articulation errors. The articulation is frequently not consistently in error: they may produce one sound in error in a particular word one time and a completely different sound in error in that same word the next time. In addition, they may produce completely different sounds each time. It is important to note also that these children may be the ones you hear people saying “she can say it, I heard her do it once, she just doesn’t want to,” “she’s being stubborn!”, etc. Children with DAS have a disorder of movement and sequencing of the oral structures for production of sounds.
17Why do we Communicate?Light (1988) identified four purposes of social communication:1. expression of wants or needs,2. transfer of information,3. social closeness, and4. social etiquette.
18Important Aspects 1. DAS as a disorder of movement 2. DAS as a disorder impacting all aspects of communication
19DAS DefinedTypically defined in terms of sound production error patterns, actually a disorder of movement.Difficulty is noted with purposeful voluntary movements for speech, creating an inability to sequence speech movements in the absence of paralysis.The articulation aspect of DAS is motor in nature. It is a disorder of MOVEMENT, not in actual sound production. So as SLP’s it may be a difficult concept. We are very used to thinking in terms of individual sound production. With these children, we need to focus on the process of movements required. The reason there is so much irregularity in the child’s speech is that they don’t get the sound sequences. Look at production of similar movements with lots of drill.
20DAS is a disorder of movement Lack consistent error production seen with developmental delay. Not result of immature sound productions, but actual motoric impairment.Dysarthria will also exhibit consistent errors, with some physical signs of weakness, paralysis, etc.DAS is a disorder of movement.
21Survey of SLPs Participants regional SLP’s treating DAS Profiles children actually in treatmentPerspectiveclinical awareness vs. “pure” research versionWhen going through the process of reviewing the literature and identification of these aspects of communication, it occurred to me that some of the controversy regarding (Clare Waldron) DAS may be due to the varied characteristics of the children being seen in clinical practice and those being chosen for research subjects. With different goals in mind: one of the “researcher” looking for necessary and sufficient definitional characteristics and the other of “clinician” looking for the most efficaceous treatment strategy. So, we collected data from groups of SLP’s attending regional conferences on DAS and from clinicians treating children with DAS in their caseloads. At this point, we have collected information from ~ N = 50 SLP’s.
22ProfilesResults of the survey showed three general profiles of children with DAS being seen for treatment. We examined: articulation/motor speech/phonologicalintelligibility of speechreceptive/expressive languagesocial interactionbehavioral communicationacademic communication skills.In 100% of the children described, there were communication difficulties noted in addition to the speech articulation.
23DAS & Communication: Characteristics Decreased intelligibilityDisordered languageSocial withdrawalBehavioral aggressionAcademic failureThese characteristics have been commonly cited in the research literature and within the books directed at DAS.
24Important Aspects… gee, notice a pattern here? 1. DAS as a disorder of movement2. DAS as a disorder impacting all aspects of communicationSo to summarize to this point, the two overriding aspects found in the research reveal that….
25Screening for DASAddress increase in referrals & diagnoses of DAS among preschool populationShort administration timeOrganize, streamline assessment processIncrease assessment efficiencyMorehouse & Linderman, 2000
26Screening for Developmental Apraxia of Speech (SDAS) Oral Motor MovementsPhoneme StimulabilityIntelligibilityChecklist of DAS CharacteristicsIncreasing Word LengthMultisyllabic Words Across TrialsInterpretation & RecommendationsMorehouse & Linderman, 2000
27Assessment of DAS (Strand, 1998) NeuromuscularMuscle strength, tone, & coordinationReflexesSensory functionStructural FunctionStructures, tissue characteristics, & sensationRange of motion, strength, coordination, speed, & ability to vary muscle tension.Assessment involves gathering large quantities of data and then sifting through the results to eliminate definite causative factors.Neuromuscular:Overall gait, muscle strength, tone, coordination, reflexes, and sensory function.Oral structural/functional: any limits of function?
28Motor Speech Production Simple to complex phonetic sequencing:CV, VC, CVC (vary the vowel)monosyllabic wordsmultisyllabic wordsphrasessentences of increasing lengthExamine ability to sequence phonetic segments in various contexts. Follow simple to complex hierarchy. Might try sequence of cueing also: simultaneous presentation, immediate repetition, delayed repetition, delayed consecutive repetition. (E. Strand)Sample variety of vowels.Word repetition, words of increasing length: me meat meetingSentence repetition, increasing length and varying phonetic complexity.Automatic vs. controlled contexts: count to 10, name particular numbers, familiar/unfamiliar phrases,Connected speech: conversation, picture description, narrativePhysiological parameters:pitch: level, breaks, variation, tremorloudness: mono-, excess, decay, alternatingvoice quality: harsh, hoarse, breathy, strained, nasality, nasal emissionrespiration: forced inspiration/expiration, audible, grunt at end of expirationprosody: rate, phrasing, increase in rate with speech, variable rate, stress, short rushes of speech
29Assess at Level of Breakdown Examine any vowels NOT heard in spontaneous speechExamine CV/VC combinations, also omitting those heard in spontaneous speechExamine CVC productions, omitting those heard in spontaneous speechsame 1st & last phonemedifferent 1st & last phoneme
30Examine Words of Increasing Length simultaneous production with examinerdirect imitationdelayed imitation
31Examine Multisyllabic Words simultaneous production with examinerdirect imitationdelayed imitation
32Physiological functioning for speech production RespirationLaryngeal functionResonance: Large numberhyper- nasalhypo- nasalmixed nasality
33Articulation & Phonology What evaluation procedures would be most appropriate to address the needs of children with DAS?What evaluation procedures would be most appropriate to address the needs of children with motor-based speech disorders?
34Intelligibility & Comprehensibility What are the most appropriate means of assessing intelligibility in young children?How might you get a measure of a child’s comprehensibility vs. intelligibility?
35Intelligibility/Comprehensibility Index of Augmented Speech Comprehensibility in Children (I-ASCC) (Dowden, 1997)A non-standardized clinical measure to assess comprehensibility.
36I-ASCC HierarchyPresent a picture with a verbal cue such as “What is this?”Present a picture and provide contextual cues such as “It’s a food you might eat. What is it?”Present a picture plus an embedded model such as “It’s pizza. Now you say it.”* Show Pizza overheadWith the IASCC, you proceed through a hierarchy of cueing to obtain a response from the child. In addition, you provide the transcriber with a hierarchy of cues during transcription. Initially, they are presented intelligibility cues of the speech sound signal on audiotape only. After initial transcription, they are asked to play back the tape and transcribe the utterance when provided with some contextual information “It is something that children like to eat for dinner.” for a measure of comprehensibility. For example, I may show the child a picture/icon of pizza, the child names it and it is recorded. The transcriber listens once to the word & writes it, then again after reading the cue for that word.*show list of cues
38IntelligibilityJudge listens to taped utterances without contextual cues and transcribes.
39ComprehensibilityAfter listening to & judging the entire set of utterances without contextual cues, the listener rewinds the tape, reads a contextual cue and transcribes again.
40Contextual Cues Something children eat at snack time. Something children use during craft time.Something children eat for lunch.Clothing young girls wear outside.What you see children doing with a book.
41LanguageWhat current methods exist to measure expressive language in unintelligible children?What are the most appropriate assessment procedures for assessing both receptive and expressive language in children with DAS?
42Clinically, consider of ALL of the following: Movement skillsReceptive & expressive language skillsPhysical structures and functionsComprehensibilityCommunication repertoires in useDo the response errors appear to have a motor planning basis?Do the response errors appear to have a phonological or linguistic basis?Do the response errors appear to have a structural basis (e.g., dysarthria)?Does the child have reduced intelligibility? (e.g.,artic, respiration, phonation, & compensatory strategies.)Does the child have reduced comprehensibility? (e.g.,environment, semantic/syntactic context, familiarity & patience of listener.)Does the child communicate appropriate social interactions?Does the child communicate appropriate behavioral interactions?Does the child communicate appropriately for academic interactions, skills?Degree of motor planning vs. physical impairmentSeverityIntelligibilityDegree DAS speech affects overall communication
43Differential Diagnosis Determine which characteristics are most readily apparent. Are there dominant speech characteristics?Dysarthria vs. DASFluency disorder vs. DASPhonological disorder vs. DASDevelopmental articulation vs. DAS
44Research QuestionsWhat attributes of overall communication disabilities are found in children with DAS?Do clusters based on communication disabilities exist for children with DAS?
45Methods N=36 children with DAS Screening: DAS Screening Instrument (Blakeley, 1980)Child Social Interaction Scales (Adapted from Booth-Butterfield and Gould, 1986; Duran, 1992; Wiemann, 1977; Canary and Spitzberg, 1987; McCrosky, 1982; Christophel, 1990; and Burgoon, 1976.)
46Criteria for Inclusion Committee of 3 DAS experts rated “degree of DAS”A mean score 3, considered DAS
47Articulation and Phonology Do children with DAS use phonological processes? Examine consistency of productions.Khan-Lewis Phonological AnalysisArticulation & prosodyGoldman-Fristoe Test of ArticulationConsider impact on language skills & reading development
48Language Language sample if intelligibility allows Comprehensive receptive & expressiveMorphology & syntaxTest of Auditory Comprehension ofLanguage (III) (1998)Peabody Picture Vocabulary Test (IIIA/B)For your personal information, you may wish to videotape record and complete analysis for nonverbal/gestural interactions used by the child.
49Communication Social communication skills Behavioral communication repertoiresAcademic communication skillsSocial Skills Rating System (Gresham and Elliott, 1990)
50Assessment Procedures Contributing to DAS Profile Identification
51Profile Communication Aspects Intelligibility & ComprehensibilityLanguage (receptive & expressive)SocialBehavioralAcademicIn general:Determine approach appropriate to the level of motor impairmentMethods address strengths and deficitsConsider stimuli length, phonetic complexity, number, type of utterancesMotor learning theory:Need motivation, focused attention, and prepractice.Repetitive motor drill: enough trials to create automatic processing, reinforcements that don’t take time, facilitate repeated opportunities for production. Mass practice: quick development, poor generalization ( if need child to have quick success) Distributed practice: takes longer to develop but get better generalizationKnowledge of results: give info about movement performance, not too specific (lose the anatomy cues!)
52Cluster AnalysisMeasure used to examine large data set and determine if there are patterns of similarity among the variables.Results in “dendrogram” (see diagram) which depicts the total data set and each stage of grouping the most similar data points (or in this case, children with DAS) into clusters.
53Cluster AnalysisConfirmatory measure of profiles previously obtained (Ball & Beukelman, 1998).Classifies sample into smaller number of mutually exclusive groups based on similarity.Variables analyzed simultaneously to discover underlying structure.
55Profile Identification Procedures Discriminant Function Structure WeightsArticulation-oriented Function 1 ArticulationDASIntelligibilityMLUPCCLanguage-oriented Function 2Parent/behaviorLanguage comprehension .434Receptive VocabularyPhonological skills
56Cluster One, n = 12 high # articulation errors high social skill ratingshigh DAS scores (very DAS)few consistent phonological processeslow intelligibilitylow vocabulary scoreshigh disruptive behaviorslow receptive language scoressmall MLUlow PCC
57Cluster Two, n = 12 high # articulation errors high social skills ratingsless DASmany consistent phonological processeslow intelligibilityhigh vocabularyscoresfew disruptive behaviorshigh receptive language scoreshigh MLUhigh PCC
58Cluster Three, n = 1 high # articulation errors many consistent phonological processesmore DASlow intelligibilitylow vocabulary scoresless socially interactivemany behavioral disruptionslow receptive language skillslow MLUlow PCC
59Cluster Four, n = 11 low # articulation errors few consistent phonological processesless DAShigh intelligibilityhigh vocabulary scoresless socially interactivefew behavioral disruptionshigh receptive language scoreshigh MLUhigh PCC
60Cluster Status on Significant Variables I II IVHigh Articulation Err; Low Language X XLow Articulation Err; High Language XHigh Behavior Probs.; Low Language X XLow Behavior Probs.; High Language X
63Motor Learning TheoryMotor learning occurs as a result of experience & practiceRelevant factors:Precursors to Motor LearningConditions of PracticeKnowledge of ResultsEffects of Rate
64Motor Learning: Prepractice The prepractice portion of a therapy session involves:Motivationmake the tasks seem importantset goals with the child with standard to achievenot just “do the best you can”Focused Attention
65General Idea of Task understand task clearly ways they will learn keep instructions simple; focus on 1-2 important aspects of movement.DO NOT OVERINSTRUCT
66Observational Learning modeling & demonstration with pictures, videotapes, and live demosshow the child the movements a few times covering all stimuli being targeted in the sessionbe wary of verbal instructions
67Establish Reference of Correctness auditory feedbacki.e., for /pa/, may have lip closure as correct to begin, then later move to correct articulation
68Motor Learning: Practice Knowledge of PerformanceKnowledge of ResultssummaryimmediateRepetitive Practicemassdistributed
69Knowledge of Performance (KP) Feedback about the correctness of a particular movement pattern re: accuracy of production.e.g., “I heard you say ….”
70Knowledge of Results (KR) Feedback about the outcome of a movement pattern re: environmental goal.e.g., “Yes, you got it!” “No, that’s not quite it.”
71Avoid extraneous activity (speaking, movements by clinician/child) during the period between the response & when you deliver KR, also after KR
72Summary KR is better than immediate KR, better to wait until several (easier wait 15, difficult wait 3-5) responses are obtained
73Conditions of Motor Speech Practice (DAS) Repetitive Practiceneed enough trials/session to allow motor learning to occur & become habituated to automaticuse reinforcements that don’t take timedevelop activities that facilitate repeated opportunities for production of target movement patterns
74Mass vs. Distributed Practice decision depends on severity and typemass yields quick development of accurate productiondistributed requires longer time, but get better generalizationdirect imitationdelayed imitation
75Examine Sentences of Increasing Length direct imitationwith repeated attempts
76Speech Practice for DAS Intensive treatment is requiredLarge number of movement repetitions required (no fewer than 20)Come to neutral position between attempts (rest), do NOT divide into component partsProgress through hierarchy of task difficultyTreat rhythm, stress & intonation to coincide with articulation drills
77Augmentative and Alternative Communication Children with DAS
78Integrating AAC and Natural Speech Extent of AAC use depends upon the communication load that can be carried by natural speech.Extent of AAC use will vary from child to child.Extent of AAC use will vary for a child depending on the communication goal.
79Lindblom Model of Mutuality RichInformationfrom theacoustic signal(Intelligibility)PoorPoor Signal-Independent RichHigher ComprehensibilityLower Comprehensibility
81AAC Use & Intelligibility of Children with DAS N = 36 children confirmed with DASM = 6 years, 1 month ageM = 44% intelligibilityRange of intelligibility from 0 to 97%N = 1 child using AAC at time of evaluation for DAS
82Use of AAC systems by Children with DAS (Cumley, 1997) Participants were children with severe phonological disorder and/or DASN = 16 Children3 yrs, 5 months to 7 yrs, 5 months
83ProceduresDAS children with a range of intelligibility were taught to use an AAC techniqueChildren engaged in play situationsInteractions were video recorded and analyzed
84Research Design ABA Design: 1. No AAC Board Present 2. Treatment Condition with AAC Board Present3. Post-treatment Condition with AAC Board Present
85Results Increase comprehensible messages Increased successful communication repairsChildren with most severe speech disorders used AAC most frequently
86AAC use did not decrease the number of speech attempts!!! AAC use reduced the number of gestures.AAC was used primarily to resolve communication breakdowns.
88Multimodal Considerations Communicative contextsCommunicative goalsIntent of communication situationImmediate & future communication needsSupport development of skillsAAC multimodalities: help with multiple disabilities encountered with DAS.Children with more severe intelligibility were more likely to use AAC (Cumley, 1998)Limb apraxia: sign language may be a problemCo-occurring language disorders: traditional orthography may be a problemSocial/behavioral disorders: may be due to communication frustrationModality options:natural speechgesturessign languagelow tech symbol boards-- remnant books, communication dictionaries, community based notebooks, symbol communication boards.high tech voice output communication device--Wolf, Macaw, Voice in the Box, AlphaTalker, etc. Sharp memo writer, etc.“The use of aided or unaided techniques that successfully support natural speech attempts and facilitate the access and participation in communication interactions.” (Cumley & Swanson, 1992)Need easy access, portability, support communication intent & natural speech.
89Focus on Communicative Competence Theme-specific boardsPicture/symbol dictionaryRemnant booksVoice output communication aidsCollaborate roles & responsibilities for each partnerEstablish initiation & repair of breakdowns)
91AAC Evaluation Why children with DAS are difficult to augment typically ambulatoryhave developed alternative, often unique communication strategiesmay have intact cognitive skillslanguage development ongoingmay have poor literacy skills
92AAC Device Specifications PortabilityComprehensive systemhigh techlow techCover extensive vocabulary demandsMinimize sequencing demandsTeach sequencing skillsAllow & facilitate language development
93Family Concerns re: DAS Qualitative Research ProjectGarn-Nunn & Katz, 2000Obtained postings daily from APRAXIA-KIDS listserveApparent ThemesDiagnosisTreatmentSecuring TreatmentPersonal
94Family Diagnostic Concerns 26% of postingsVarying descriptive termsNature of problemConcomitant problemsImportance of Early DiagnosisSLP crucial to successGarn-Nunn & Katz, 2000
95Family Treatment Concerns 28% of postingsImportance of speech motor practiceSign language, AAC facilitate speech earlyParents intensively involved with treatmentChanging nature of treatmentEducational concernsGarn-Nunn & Katz, 2000
96Family Concerns: Securing Treatment Services 22% of postingsIntensive treatment, long period of timeSecure different sources of treatmentIEP procedures, goals, availability of servicesPrivate insurance issuesParent advocacy training, IDEAGarn-Nunn & Katz, 2000
97Family Personal 17% of postings Success stories, thanks, encouragement Failures, ventingExplaining DAS to others & to childLocal support groupsGarn-Nunn & Katz, 2000
98Case Study Walt, 10 year 6 month old male Regular 4th grade classroom Intelligibility <50% to unfamiliar listenerDiagnosed with DAS in 19988 years of traditional articulation-oriented speech therapyPast evaluation, recommendations
99Assessment Results Language TACL-3 PPVT-III Receptive subtests from CELF-RMLU
100Articulation/Phonology GFTAKLPAScreening Test for Developmental Apraxia of Speech (Blakeley, 1980)Percent of Consonants CorrectMotor Speech Tasks
101Intelligibility/Comprehensibility Social CommunicationSocial Skills Rating System(Gresham & Elliott, 1990) (AGS)Child Social Interaction ScaleIntelligibility/ComprehensibilityI-ASCC
102AAC Assessment for Walt Examine current communication and communication needsparent & child interviewspeech evaluation resultscommunication abilitiesunderstands symbols for communicationemerging literacy skills
103Physical Status ambulatory, active good fine motor control hearing and vision WNL
104Walt’s Communication Device Lightweight & portableDurableExtensive vocabularySupport emerging literacy skillsSupport developing languageAllow for novel message generationGood quality voice output for communication in a variety of contexts
105Walt’s Communication System DynaMyte (DynaVox Systems, Inc)Topic BoardsLetter BoardRemnant bookNatural speech
106Classroom Recommendations Provide multiple avenues of communicationComputer supported literacy optionsPhonetic based word generation (Intellikeys)Story reading (Living Books, Intellikeys)Story writing (Write:Outloud, CoWriter)Organizational software (Inspiration)
108ReferencesBradford & Dodd (1996). Do all speech-disordered children have motor deficits? Clinical Linguistics and Phonetics, 10(2),Davis, B. (1998a). Differential diagnosis of developmental apraxia. Newsletter: ASHA Special Interest Division 1: Language Learning and Education, 5(2), 4-7.Hayden, D.(1994). Differential diagnosis of motor speech dysfunction in children. Clinics in Communication Disorders, 4(2),Hayden & Square (1999). Verbal Motor Production Assessment for Children (VMPAC). The Psychological Corporation: A Harcourt Assessment Company
109More ReferencesCumley, G. (1997). Introduction of an augmentative and alternative modality: Effects on the quality and quantity of communication interactions of children with severe phonological disorders. Unpublished Doctoral Dissertation, University of Nebraska-Lincoln.Davis, B., Jakielski, K., & Marquardt, T. (1998). Developmental apraxia of speech: Determiners of differential diagnosis. Clinical Linguistics and Phonetics, 12(1),Dowden, P. (1997). Augmentative and Alternative Communication Decision Making for Children with Severely Unintelligible Speech. AAC, 13(1),
110More ReferencesHall, P., Jordan, L., & Robin, D. (1993). Developmental apraxia of speech: Theory and clinical practice. Austin, TX: Pro-ed.McNeil, M., Robin, D., & Schmidt, R. (1997). Apraxia of Speech: Definition, differentiation, and treatment. In M. McNeil (Ed.), Clinical management of sensorimotor speech disorders (p. 394). New York: Thieme.Shriberg, L., Austin, D., Lewis, B., McSweeny, J., & Wilson, D. (1997a). The Percentage of Consonants Correct (PCC) metric: Extensions and reliability data. JSLHR, 40(4),
111More ReferencesShriberg, L., Aram, D., & Kwiatkowski, J. (1997a). Developmental apraxia of speech I: Descriptive and theoretical perspectives. JSLHR, 40(2),Shriberg, L., Aram, D., & Kwiatkowski, J. (1997b). Developmental apraxia of speech II: Toward a diagnostic marker. JSLHR, 40(2),Shriberg, L., Aram, D., & Kwiatkowski, J. (1997c). Developmental apraxia of speech III: A subtype marked by inappropriate stress. JSLHR, 40(2),Strand, E. (1998). Treatment of developmental and acquired apraxia of speech. In D. Beukelman & K. Yorkston (Eds.), Motor speech disorders. Baltimore: Brookes.
112More ReferencesStrand, E. A. (1995). Treatment of motor speech disorders in children. Seminars in Speech and Language, 16(2),Shriberg, L., Austin, D., Lewis, B., McSweeny, J., & Wilson, D. (1997b). The Speech Disorders Classification System (SDCS): Extensions and lifespan reference data. JSLHR, 40(4),Caruso & Strand (1999). Clinical Management of Motor Speech Disorders in Children. NY: Thieme.Beukelman, D., & Mirenda, P. (1998). Augmentative and Alternative Communication. (2nd ed.). Baltimore: Brookes.