Differential Diagnosis ofSevere Speech Impairment

in Young Children

Severe speech inipairment may resull froma variety ot etiologies and may representlinguistic impairment, motor speech impair-ment, or both. Differential diagnosis typi-cally refers to the process of determining

the appropriate classiñcation or label for the speechsound disorder, such as phonolojiic impairment, child-hood apraxia of speech, or dysarthria. More importantthan the label, however, is the determination of therelative contribution of cognitive versus linguisticversus motor impairment, because children withspeech .sound disorders frequently exhibit impairmentin more than one area. Determining the degree towhich the child is struggling to learn the rule-governed system of phonology, compared with havingproblems with planning and programming movementgestures for speech, directly affects appropriatetreatment planning.

This article offers a look at the clinicaldecision-making processes used in differentialdiagnosis for children suspected of speech sounddisorders. Because the focus will be on children withsevere impairments, it deals with territory in whichclinicians may feel uncertain or at least less confident.

1 0 AUGUST 12. 2008

by Edythe A. Strand and Rebecca J. McCauley

Terms, Labels, and CategoriesBefore beginning a discussit)n of differential diag-

nosis, it is important to delineate the different termsused frequently to denote levels of impairment. Theterm "'phonological disorders" often is used to referto the entire range of developmental communicationdisorders in which sound production is principallyaffected. More recently, however, the broad rangeof disorders involving speech sound production isreferred to as "speech sound disorders." This usagealso reserves the term "phonological disorders" torefer to a linguistic level of impairment.

Another subset of speech sound disorders is"childhood apraxia of speech" (CAS). Most defini-tions of CAS focus on the child's difficulty planningand/or programming purposeful voluntary movementsfor speech in the absence of weakness or paralysis

LEADER

of the speech musculature. Until recently there hasbeen controversy regarding (he specific behavioralmarkers that should be used to identify this level ofimpairment. The ASHA position statement on CASnow provides a definition ot the disorder and a list ofbehavioral characteristics associated with it (ASHA,2()07). That document defines CAS as:

"a neurological childhood (pédiatrie) speechsound disorder, in which the precision andconsistency of movements underlying speechare impaired in the absence of neuromusculardeficits (e.g., abnormal reflexes, abnormal tone).CAS may occur as a result of known neurologicalimpairment, in association with complex neu-robehavioral disorders of known or unknownorigin, or as an idtopathic neurogenic speechsound disorder The core impairment in planning

and/or programming spatio-temporal parametersof movement sequences results in ermrs in speechsound production and prosody." (p. 6)

"Dysarthria" is a collective term for a group ofrelated tiiotor speech disorders resulting fromdisturbed muscular control of ihe speech mechanismdue to damage (o the central or peripheral nervoussystetn. Dysarthria manifests as disrupted or distortedoral communication due tt> paralysis, weakness, abnor-mal tone, or incoordination of the muscles used inspeech. Processes of phonation, respiration, resonance,articulation, and prosody are affected. Movementsmay be impaired in force, timing, endurance, direc-tion, anti range of molii)n. In some types of dysarthria..

involuntary movements (dyskinesias) occur, disruptingarticulatory output. Symptoms may include slurredspeech, weak or imprecise arliculatory contacts, weakrespiratory support, low volume, incoordination of therespiratory stream, and hypernasality. Table I showsphonologic impairment. CAS. and dysarthria in rela-tion to a very basic model of speech production.

Another term frequently u.sed in diagnostic reportsis "oral-motor deficits." The use of this term can beproblematic because it can mean different things.Clinicians sometimes use this term to indicate prob-lems with speech production and other times to meandeficits in nonspeech oral movement. A child who

Table 1. Relationship between specific functions and possible communication disorders.

Function (^^IfNeural Process ^B|h)ssible Communicative DisorderCommunicative idea

Word retrievalPhotiologic delay/impairmentSyntactic/grammatical ordering

Specifying range of motion,direction, speed and force ofmovement

Execution of movementresulting in acoustic output

Cognitive

Linguistic

Motor planning andprogramming

Motor execution

Pragmatic language deficit(difficulty demonstrating communicative intent)

Language delay/impairmentPhonological mapping

Childhood apraxia of speech (CAS)

Dysarthria

has nonverbal oral-motor problems because ol" actualweakness or paralysis will also have associated prob-lems in speech production, for which we use the termdysarthria. Alternatively, a child may have nonverbaloral-motor problems because of difficulty with praxis,which is defined as the ahility to conceptualize, plan,and program skilled volitional movement. Childrenmay have difficulty with praxis for volitional non-speech oral movement (e.g., blowing, kissing), whichis called nonverbal oral apraxia. If the child has difh-culty with praxis for the intentional action of move-ment toward a speech goal, we use the term CAS forthe type of communicative disorder. Nonverbal oralapraxia sometimes, but not always, occurs in combina-tion with CAS (see Figure I. p. 12).

Differentiation between movement plaiming versusmovement execution can be conceptually and practi-cally difficult and is often at the heart of differentialdiagnosis of severe speech impairment. Our assess-ment procedures and interpretation of assessment datahelp in that challenge.

Assessment ProceduresDifferential diagnosis results from a full battery

of assessment tasks and standardized tests, includingcomplete language testing. This discussion, however,focuses on those aspects of the assessment that relateto differentiating the relative contribution of phono-logic impairment versus CAS versus dysarthria inchildren with severe speech sound impairment.

See Diagnosis page 12

A S H A

LEADER AUGUST 12.2008 1 1

Diagnosis from page 11

Differential diagnosis is difficult and

it is not always possible to be "sure."

It is important to think in terms of

relative contribution of phonologic,

motor planning, and motor

execution problems, and

plan treatment accordingly.

HistoryAs we obtain inforniatioti abottt the course of

speech development and identify suspected etiologicalfactors and co-existing problems, certain observationscan provide supportive evidence toward diagnosis.Table 2 (p. 13) shows comparative findings acrosschildren with different speech-sound disorder clas-sifications. Note that findings often overlap, and theseobservations alone are not sufficient for decisionsregarding diagnosis.

Sound System AssessmentThe description of the sound system may involve

describing phonetic and phonemic inventories(independent analysis) as well as standardized tests{McCauley & Strand, 2008) in which the child'sphonologic performance is compared to a normativesample (relational analysis). Observations of processesseen in normal development (e.g., assimilation, front-ing, clu.ster simplification, stopping) are noted, alongwith those that are nondevelopmental (e.g., use offavorite sound, glottal replacement, initial consonant

Figure 1. Specific terms related to "oral-motor" problems.

Oral-Motor Problems\

IExecution

(weakness: irange of motion; (strength; ispeed)

Nonverbal Verbal

Dysarthria

Nonverbal

Nonverbaloral apraxia

deletion, idiosyncratic cluster reduction). Observationsregarding syllable and word shapes used by the childcan aid in differential diagnosis. For example, childrenwith phonologic impairment and children with CASboth may exhibit reduced phonetic and phonemicinventories, but children with CAS will often showrelatively fewer vowels and less vowel differentiation.Children with CAS will also show more inconsistencyover repeated trials and more nondevelopmentai typesof errors.

Oral Structural-Functional ExaminationAn oral structural-functional exam will determine

or rule out the presence of nonverbal oral apraxia anddysarthria. This task is appropriate for these purposesbecause interpretation of movement is made in a non-speech context. Observations of the size and relativeposition of each structure allow the clinician to formu-late hypotheses regarding possible structural deficitsrelated to sound-production disorders. Interpretation ofthe function (range of motion, strength, speed, coordi-

nation, and the abilityto vary muscular ten-sion) of each move-able structure of thespeech mechanismduring nonspeechtasks allows theclinician to detenninewhether neuromuscu-lar deficits contributeand/or if there arepraxis problems fornonspeech oralmovements.

Typically, chil-dren with phonologic

Praxis(plantiitig/programming movement)

IVerbal

CAS

impairment and children with CAS exhibit normalperformance for range of motion, strength, speed,coordination, and the ability to vary tiiuscular tension,and children with dysarthria will exhibit itnpairment.Oral nonverbal apraxia is more likely to be seen inchildren with CAS than in children with dysarthria orphonologic impairment, but many children with CASexhibit normal oral praxis.

Clinical reports sent to us commonly note theobservation of "weakness." We see this descriptioneven for children who come in with good bilabial orlingual alveolar plosing during vocal play or bab-bling. One must be careful in judgments of weakness.For example, even children with low tone can havenormal strength. Tone relates to the state of the musclecontraction at rest. Strength relates to the degreethe child can recruit motor units to contract musclefibers to move a structure. A child who can produce aplosive sound with good clarity and volume likely hasadequate strength for speech.

The structural-functional examination includestesting each of the five parameters {range of motion,speed, strength, the ability to vary muscular tension,and coordination) for each structure in isolation. Themotor-speech examination includes observations aboutinteraction of movement among structures (Strand &McCauley. 1999). These observations are importantbecause during connected speech, the relative sever-ity of impairment across structures and across the fiveparameters may be difficult to detennine. Consider, forexample, that a child with weak tongue movement canuse the jaw to compensate during speech.

It is also important to remember that childrenexhibit a large range of variability in their responses tothese tasks. For example, it would be a mistake to saythat a delay in talking is due to "weakness" or "incoor-dination" when the child really just didn't understand

1 2 AUGUST 12. 2008A S H A

LEADER

the task or was unwilling to perform it. The results ofthe structural-functional exam should be interpreted inconjunction with all other assessment observations.Motor-Speech Examination (MSE)

The MSE is an essential tool for clinicians facedwith the challenge of differential diagnosis of severespeech-sound disorders. In this task the child is askedto imitate utterances of increasing length and phoneticcomplexity. The purpose of the MSE is to examine thechild's ability to sequence phonetic segments imita-tively in various contexts. This examination allowsthe clinician to make observations of those behaviorsfrequently associated with deficits in speech praxis,including vowel and consonant distortions, timingerrors, dysprosody, and inconsistency across hierarchi-cally organized stimuli. These observations allow theclinician to determine the degree to which motor-planning deficits may contribute to the child's dif-ficulty with speech acquisition. By adding dynamicassessment strategies (e.g., observing the child'sresponses to hierarchical cueing such as slowing themovement, providing tactile and gestural cues) to theMSE, decisions regarding severity and prognosis canalso be made. The MSE also helps with decisionsregarding the phonetic content and syllable shapesappropriate for the initial stimuli.

Children with phonologic impairment and CASwill perform differently on motor-speech examina-tions, although performance will vary with severity.In general, children with CAS will exhibit relativelymore vowel distortions, occasional groping for articu-latory positions for utterances they have not previ-ously produced, inconsistency over repeated trials,inconsistent voicing errors, lexical stress errors, andsegmentation of multisyllabic words.

From Diagnosis to TreatmentDifferential diagnosis for children with severe

speech-sound disorders is critically importantbecause correct diagnosis leads to the appropri-ate treatment. Different treatment approaches andtechniques are indicated for deficits in motor execu-tion (dysarthria), the planning required for skilledmovements of speech (CAS), or the child's underly-ing knowledge of the sound structure of the language(phonologic impairment). The clinician must alsodifferentiate speech delay that reflects deficits in andtherefore dictates treatment of the language fromcognitive bases for communication, such as thosefound in many children with more severe mentalretardation or autism spectrum disorders.

Differential diagnosis of severe speech-sounddisorders is difficult and it is not always possibleto be "sure." It is important to think in terms of therelative contribution of phonologic, motor planning,and motor execution problems, and plan treatmentaccordingly. To do the best we can for children,clinicians need to consider all the assessment dataand avoid placing too much importance on any oneobservation. It is important to be careful in the use ofterminology such as "oral-motor deficits," to he pre-cise in denoting problems with praxis for nonspeechmovement versus speech, and to denote speechpraxis problems versus problems with executionof movement.

Finally, we need to remember that classificationsor labels may change over time with neural matura-tion and appropriate treatment. For example, chil-dren with CAS often progress to the point at whichspeech characteristics are more appropriately labeledphonologic impairment or residual articulation errors.Assessment does not end with the initial differential

Table 2. Comparison of typical findings across children with phonological disorders only versus CASversus dysarthria.

Phonological Disorder Only CAS Dysarthria : ^ ^ ^Delays in intelligible speech

Frequent family history ofcommunication disorders, oftensimilar to the child's

Frequent reports of otitis media

Usually no problem with babbling

Usually no neurologic signs

Delays in intelligible speech

Frequent family history ofcommunication disorders, oftensimilar to the child's

Some reports of feeding problemsand oral-motor concerns

Reduced quantity of vocalization/babbling in early history; frequentreport of few babbled consonantsand lack of vowel differentiation

Reports of soft neurologic signs(e.g. gross- and fine-motor delays)

Delays in intelligible speech

Possibly no family history

Frequent reports of feedingproblems and oral-motor concerns

Ability varies depending on the typeand severity of the dysatthria

Reports of frank neurologic signs

diagnosis; it continues as we measure the effects oftreatment. Differential diagnosis also continues aschildren exhibit changing speech production character-istics as a result of our intervention. w

Edythe Strand is a consultant in iheDivision of Speech Pathology, Depart-ment of Neurology, at the Mayo Clinic(Rochester. Minn.) and an a.ssociateprofessor in the Mayo Medical School.Her primary clinical and researchintere.sts include assessment and treat-

ment of children and adults with neurologic speech,language, and voice disorders. Contad her atstrand.edythe@mayo.edu.

Rebecca McCauley, a profes.wr incommunication sciences at theUniversity of Vermont, will soon join! he facility of the Department of Speechund Hearing Science al Ohio StateUniversity. She has served on ASHAcommittees related to the effects of oral

motor exercises on speech and swallowing andchildhood apraxia of speech (ASHA, 2007). Contacther at rebecca.mccauley@uvm.edu.

Photos by Ben Sledge of the Language-Learning EarlyAdvantage Program at the University of Maryland (UM),College Park. Pictured are UM students Jessica Bauman,Lauren Graham, and Lauren Polovoy.

Additional references for this article can be found atThe Leader Online. Search on the title of the article.

Selected ReferencesAmerican Speech-Language-HearingAssociation. (2007). Childhood apraxia ofspeech: Nomenclature, definition, roles andresponsibilities, and a call for action [positionstatement]. Rockville, MD: Author.McCauiey, R. J., & Strand, E. A. (2008). Areview of standardized tests of nonverbal oral andspeech motor performance in children. AmericanJournal of Speeoh-Language Pathology, 77(1).1-11.Strand, E. A., & McCauley, R. (1999) Assess-ment procedures for children with phonologic andmotcr speech disorders. In A. Caruso andE. A. Strand (Eds.), Clinical Management of MotorSpeech Disorders of Children. New York: Thieme.Strand, E. (2003). Childhood apraxia of speech:Suggested diagnostic markers for the youngerchild. In L D. Shriberg and T. F, Campbell (Eds.),Proceedings of the 2002 Childhood Apraxia ofSpeech Symposium. Carlsbad, CA: The HendrixFoundation.

T H E A S H A

LEADER AUGUST 12. 2008 1 3