Speech and language difficulties (2002)


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Speech and language difficulties (2002)

  1. 1. Child and AdolescentPsychiatryEditedbyMichael RutterCBE,MD, FRCP, FRCPsych, FMedSci FRS,Professorof Developmental PsychopathologySocial, Genetic and Developmental Psychiatry ResearchCentreInstitute of PsychiatryLondonEric TaylorMA, MB, FRCP, FRCPsych, FMedSciProfessorof Child and AdolescentPsychiatryDepartment of Child and AdolescentPsychiatryInstitute of PsychiatryLondonFOURTH EDITIONBlackwellScience
  2. 2. r9 -- Speechand LanguageDifficulties I,;) .-, Dorothy ~M. Bishop Introduction so that the bulk of phonology and syntax is acquired by around 4 years of age. There are, however, frequent exceptions, and The ability to communicate through language distinguishes theseare the topic of this chapter. humans from all other animals. Spoken language allows us to Delay in learning to talk is a common reason for a parent to convey information, expressour feelings and demonstrate so- seek advice from a .family doctor or paediatrician. Because cial affiliations. It also provides a vehicle for organizing our human communication is complex, assessment and diagnosis thoughts and memories,enabling us to construct complex lines of speechand languagedifficulties in children is a particularly of reasoning, and to contemplate past, future and hypothetical challenging problem that requires expertise in several differ- events,rather than remaining grounded in present reality. The ent areas, including linguistics, audiology, child development, developmentof written languageprovides evenmore dramatic neuropsychology, paediatric neurology and psychiatry. This releasefrom the here-and-now,making it possible to transcend chapter will usethe diagnostic flow chart shown in Fig. 39.1 to spaceand time. introduce a range of different conditions that can lead to speech All known human cultures have language,but there is huge and languagedifficulties in children. This depicts the sequence diversity in how languagesare structured, both in terms of the of decisions the clinician needsto make when first assessing a sounds used to expressmeaning (phonemes)and the ways in child who presentswith poor communication. However, recent which linguistic elementsare combined (syntax). For instance, researchsuggests that this diagnostic processshould not becon- Frenchhastwo different vowels that sound like 00 to a speaker fined to thosecases wherecommunicative impairment is the pre- of English, but which arephonemically distinct; they signal con- senting complaint, but should be extendedmuch more broadly trasts in meaning, so that rue and roux mean different things. to all children referred to psychiatric services. The reasonis sim- In English, on the other hand, we make a phonemic contrast be- pie: surveysof children attending psychiatric clinics revealthat a tween the sounds th and z (e.g. bathe vs. baize), which are high proportion of them have somekind of communicative im- not distinguished in French.In tone languages,such as Chinese pairment, and in many cases goesunrecognizedunlessa for- this Mandarin, the pitch at which a word is spoken signalsmeaning, mal assessment made. Cohen (1996) summarized findings is so that ba has four completely different meanings depending from a Canadian study in which 399 consecutivepsychiatric re- on whether the pitch is rising (to uproot), falling (a harrow), ferrals of children agedfrom 4 to 12 yearswere given a detailed changing from fall to rise (to hold) or at a level high pitch language assessment. Children with autistic disorder, general (eight)." developmentaldelay,neurolog.icaldamage,hearing impairment Moving to grammar; in English, relationships between enti- or a non-English-speakinghome background had beenexclud- ties are indicated by a mixture of word order and grammatical ed from this sample. Around one-quarter of the children had morphemes(e.g. inflectional endingssuch as -ing or -ed, and previously identified languageimpairments. Of the remainder, small function words such as by). Thus it is the boy who is none of whom was thought to be language-impaired,34% met doing the kissing in the boy kissesthe girl, but is the recipient of criteria for language impairment. There appeared to be two the kiss in the girl kissesthe boy or the boy is kissedby the girl. reasonswhy communicative difficulties had been overlookedIn somelanguages,suchasTurkish, word order generally obeys in thesechildren. First, they did not have such overt expressivethe sequencesubject-object-verb, and inflectional suffixes do language difficulties as children with previously identifiedall the work of expressingrelationships. Other languages,such problems, although their receptivelanguageskills were aspooras ChineseMandarin, havevirtually no inflections. Word order, as that group. Secondly,they were more likely to haveexternal-particles and prepositions are usedto indicate how the elements izing psychiatric disorders, which may have diverted attentionof a sentence interrelate. from communication. Cohen et al. (1998) suggested that Clearly, languageacquisition involves far more than learning languagefunction should be incorporated routinely into the as-labels for things. The child must work out which speechsound sessmentand treatment process for children with psychiatriccontrasts are meaningful in the ambient lang~age,and how to impairments. Somesuggestions how to implement this rec- forcombine words and grammatical morphemes to expressrela- ommendation are given below in the sectionon Assessment.tionships betweenthings and events.Most children master this In the next section, different diagnostic entities will be re-complex skill with no explicit instruction and with relative ease, viewed, with a main focus on specificdevelopmental language664 "~
  3. 3. ~ SPEECHAND lANGUAGE DIFFICULTIES START Islangu Does child h age . Yes produce Yes Refer to speech and language compre enslon . t , . Immature /d evlan t . th eraplst,. query expressive . age-approprla e. utterances? language disorder No No Isspeech unintelligible or Language impairmentsecondary Yes ~ens?r poorly to hearingloss earln articulated? 40 dB Yes Any indication of I . No neuro oglcaI or Referto speechand language ~tru~ural therapist, query developmental Referfor neurologicalopinion, Yes Any evi.denceof Impairment? phonological disorder acquiredepileptic aphasia re.9resslon or No query seizures? No Are speech Yes ~rrors. Yes No Inconsistent and worsewith longer Refert? speechand language .. utterances therapist, query developmental GobaI deveopmentaI deIay I I No well above ability Non-verbal .. verbaldyspraxia h . Dysarthria/anarthria compre enSlon level? Yes Detailedevaluationto consider Yes Impairmentsin Ischild m.ute Yes Selectivemutism autisticdisorder/ PDDNOS non-verbalsocial exceptwIth close communication/play? family/friends? No Isspeechfluent? Referto speechand language . No therapist, query developmental Assessexpressive language. fl d d t tt . , {, considermixed receptive- uency Isor er ,s u erlng, expressive languagedisorder Yes Is voice quality Refer to otolaryngology, query normal? No voice disorder Yes Does child say Consider Asperger syndrome. things that are Yes pragmatic language bizarre or impairment tangential? Fig.39.1Decision for diagnosing tree speech language and disorders children. in .. disorder.Assessment procedures will briefly be reviewed in a of this chapter, but it is worth noting here that assessment can later section. be difficult in children with major behavioural difficulties. It is tempting to assumethat the child can understand but is unco- operative, but it is at least as likely that the behavioural difficul- A decision tree for diagnosis ties stem from fear and frustration in a child who comprehends very little. If the child doesnot co-operatewith formal compre- In Fig. 39.1, the question of whether comprehension is age- hensiontesting, proceeddown the decision tree on the left-hand appropriate is placed at the top of the decision tree. There are side of the diagram. good reasonsfor this. First, whereasproblems with expressive As shown in Fig. 39.1, results from a comprehensionassess- speech languageare usually fairly easyto detecton the basis and ment are not sufficient for a diagnosis,but they determinewhich of informal observation, comprehensionis much harder to esti- diagnosesshould be considered, and also help the clinician to matethis way. Secondly,different diagnosesneedto be consid- adjust his or her languagelevel to the childs level of understand- ered for the child with comprehension problems than for one ing, for instance when conducting a psychiatric interview. whose problems are confined to speech output or sentence Where comprehension is unimpaired, we can exclude autistic formulation. disorder and mental handicap. It is also unlikely that hearing Methods for testing comprehensionare discussedat the end lossor acquired epileptic aphasiais implicated. 665
  4. 4. -- CHAPTER 39 Hearing loss loss. It is often cited as a cause of speech and language difficul- "" ties, but recent research suggests that the effect may have been ! The first diagnosis to consider in a child with comprehension dif- overestimated in the past by relying on clinical samples (Bishop ficulties is hearing loss. Note that in Fig. 39.1 evaluation of hear- & Edmundson 1986; Bishop 1988). Epidemiological studies ing comes before assessment of non-verbal ability. It is all too have found only weak influences, if any, on long-term speech, easy to assume that if a child has low IQ then the language im- language and literacy outcomes (Grievink et at. 1993; Peters et pairment has been explained. However, impaired hearing is a at. 1994). It is also important to be aware just how common common correlate of many syndromes that affect general ~ntelli- OME is. A Dutch epidemiological study of children screened at gence, and an audiological evaluation should always be under- 3-monthly intervals between 2 and 4 years of age found that .taken in a child with poor understanding, regardless ofIQ level 55% of children had at least one episode of bilateral OME Furthermore, one should beware of relying on hearing tests car- during this period (Zielhuis et at. 1990). ried out some years previously: some conditions lead to progres- For simplicity, progress through the flow chart is halted when sive hearing loss. It is salutary to note that on follow-up in a primary diagnosis (in italic type) is arrived at. However, it is, of adulthood, Mawhood et at. (2000) found bilateral hearing course, entirely possible that more than one pathology is pre-" losses exceeding 40 dB in three out of 23 children who had sent. The question the clinician needs to consider is whether the been identified as having severe receptive language disorder in primary diagnosis can adequately explain the childs commu- . childhood. nicative profile, or whether there are some features that are not A vexed question is what level of hearing loss is sufficient to accounted for. For instance, we would expect a child with a explain language impairment. The research literature suggests severe sensorineural hearing loss to be slow in acquiring spoken that most children with severe and profound hearing losses will language, but to make excellent progress in mastering a sign have major problems acquiring oral language and literacy skills, language, if exposure to this mode of communication was even if they are diagnosed early and given hearing aids and provided early in development (Petitto 2000). Even if no auditory training (Conrad 1979). Most of these children will signed input is available, we would expect to see good use of demonstrate normal communicative ability in the visuomotor non-verbal communication (gesture and facial communica- modality if exposed early to a sign language (Orlansky & tion). Thus, if a hearing-impaired child shows little sign of com- Bonvillian 1985), and there is no evidence that learning to sign municating non-verbally, this is an indication that the hearing interferes with acquisitionof spoken language (Bishop1983). lossis not the whole story,and further diagnoses needto be Recently, dramatic gains in spoken language acquisition have considered. been seen in some children who have received cochlear implants The flow chart in Fig. 39.1 explicitly recommends continuing early in life (Miyamoto et at. 1997; Tomblin et at. 1999) and it through the decision tree if a child has a conductive hearing loss seems likely that this intervention will become increasingly or a mild sensorineural loss (under 40dB). This does not mean widespread. Nevertheless, outcome can be very variable, and that mild or intermittent losses should be ignored, nor that they some children make disappointing progress. It is also worth not- are irrelevant in the aetiology of speech and language problems, ing that there is strong resistance to cochlear implants from but they are unlikely to be the whole explanation for a childs di f- some members of the deaf community, who maintain that if the ficulties. In so far as detrimental long-term effects of OME have child learns sign language, deafness need not be a handicap been reported, they tend to occur in samples with nther risk (Lane 1990). factors present, e.g. low birth weight and/or socioeconomic Much lessis known about the impact of mild and moderate disadvantage (Gravel etat. 1996). sensorineural hearing loss on language development. The hand- ful of studies that include children with mild or moderate hear- A . d .1 t . h . , " , 11 fi d 1 1 1 , d cqulre epl ep ICap asia mg Impairmenttyplca y n anguage eves mterme late . "an (l dau- KIeff nersyndrome) between those of normally hearIng and more severely heanng- impaired children (Brannon & Murry 1966). However, the Acquired epileptic aphasia (AEA) should be suspected when average results may mask substantial variation. A recent small language regresses after a period of normal development. Typi- studyof children with sensorineural hearing losses in the range cally, the child becomes increasingly unresponsive to spoken of 20-70dB HL, showed age-appropriate levels of language language, sometimes over a period of months but sometimes comprehension and expression in 78% of children (Norbury within a matter of days. Deterioration in expressive language et at., 2001). All of these were attending regular classrooms, typically follows. Deafness may be suspected, but normal hear- most had mild losses (20-40dB), and most wore hearing aids. ing thresholds are obtained. In classic Landau-Kleffner syn- None used sign language. This suggests that mild hearing loss drome, the clinical picture is one of severe and selective receptive can act as a risk factor for language impairment, but that, given aphasia, with the child retaining good non-verbal intelligence appropriate intervention, many children compensate well for (Landau & Kleffner 1957). This has also been described as an their hearing difficulties. auditory agnosia, which may extend to affect perception of Otitis media with effusion (OME) is a common childhood non-verbal as well as verbal sounds. complaint that is often associated with mild conductive hearing The epileptic basis of the disorder may be overlooked because 666
  5. 5. r - SPEECHAND lANGUAGE DIFFICULTIES over 50% of thesechildren do not presentwith frank seizures. no consistentcausehasbeendemonstrated.A pair of discordant However, abnormal electrical activity, usually involving the monozygotic twins has been reported, ruling out a purely temporal lobes, is evident on sleep electroencephalography geneticaetiology (Feekeryet al. 1993). (EEG),although this abnormality typically diesdown byadoles- Medical interventions typically involve use of anticonvul- cence,making retrospectivediagnosisdifficult. santsto control the epileptic activity, but although this is often The developmentalcourseof AEA is highly variable. In some effective in controlling seizures,it doesnot necessarilynormal- children, the diseasefollows a fluctuating course, with periods ize the underlying EEG abnormality and doesnot always lead to of improvements followed by regression. On average, the improvement in language.Someauthorities haverecommended younger the child at onset, the worse the outcome for language, aggressive treatment with corticosteroids (Lerman et al. 1991), but this generalization hides a great deal of variability (Bishop or neurosurgical intervention in caseswhere it is possible to 1985). Many children with onsetbefore5 yearsof agehaveseri- isolate the epileptic focus (Morrell et al. 1995). For both treat- ous and lifelong difficulties in understanding spoken language. ments, some casesof dramatic improvement have beenreport- Nevertheless, a long-term case study suggeststhat gradual ed, but suchsuccess not invariable, making it difficult to weigh is improvement of language skill can continue over many years the risks of adverseeffects against the possibility of recovery, (Van Dongen et al. 1989). Regarding seizures,the outcome is especiallyin a disorder that may, in any case,follow a fluctuat- much more favourable, with these usually disappearing by ing course. It is generally agreedthat an educational approach adolescence. that relies on developing visual forms of language (written or It is particularly important that child psychiatrists are aware signed)is more effectivethan attempting to overcomethe childs of this rare disorder, because appearanceof communicative the auditory impairment. difficulties in a previously normal child often prompts a psychi- There has been some debate in the liter~ture as to whether, attic referral, especiallyif there are associatedbehavioural dis- even after excluding those with Landau-Kleffner syndrome, turbances, as is not uncommonly the case (Appleton 1995). there is an unusually high rate of EEG abnormality in children Differentialdiagnosis from deafness shouldbeunproblematic if with languageimpairments(Echenne al. 1992; Parry- et proper audiological assessment carried out. AEA differs from is Fielder et al. 1997), and whether a similar pathophysiological selectivemutism in that languagecomprehensionis usually in- processmight be present in children with more typical forms tact in the latter condition, and the child can be observedto talk of developmental language disorder. For the present, this re- normally under certain restricted conditions. Neither is true for mains a speculation without firm evidence (Deonna 2000). AEA. As noted by Genton & Guerrini (1993), it is essentialto Where a child presents with language disorders and seizures conduct an EEG recording for one full sleepcycle in any child but does not have the clinical picture of AEA, it is recom- who develops an unexplained language disorder, as this will mended that the diagnostic process continues through the clearly demonstrate the underlying functional abnormality in decisiontree. the brain of the child with AEA. As with so many of the conditions reviewed in this chapter, the Global developmentaldelay boundaries of AEA are not clear-cut, and diagnosis of atypical casesposesparticular problems. Caseshave been described in It is customary to make a diagnostic distinction betweencases which only expressivelanguaseis disturbed. In other children, wherenon-verbal ability and ve,bal ability areequally impaired, the regressionaffectssocial.interaction and adaptive behaviour and those where poor verbal skills are discrepant with normal as well as language,making it difficult to draw a sharp line be- non-verbal ability. Terminology in this area is something of a tweenAEA and autistic regression(Deonna2000). minefield. Clinically, the term global developmental delay is The prevalenceof AEA is hard to determine as it is a rare dis- usedfrequently, although rather imprecisely,to refer to children order,which is often misdiagnosed either deafness selective as or who function well below agelevel in a rangeof domains, includ- mutism (seebelow). Appleton (1995) noted that over 200 cases ing verbal and non-verbal ability, adaptive skills and motor de- have been reported since the condition was first described in velopment. Terms such as mental handicap and intellectual 1957, and this number is increasing as the availability of new retardation are still used in some quarters to refer to children methods of brain imaging makes it possible to discover more with an overall IQ below 70 (2 SD below the mean), but these about the underlying abnormality (Morrell & Lewine 1994; labels have fallen out of favour because negativesocial con- of Guerreiro et al. 1996). Most clinicians, however,can expect to notations. In the UK, the preferred term in many clinical and see only one or two cases during a lifetime. educational contexts is learning difficulty or learning disabil- The aetiology of AEA remainsa mystery.No structural brain ity, but this has enormous potential for confusion, because lesion has beendemonsttated,and magneticresonanceimaging outside the UK people tend to restrict the use of theseterms to (MRI) and computed tomography (CT) scan are usually nor- children with normal intelligenceand a specificlearning disabil- mal, but metabolic abnormalities, predominantly in the tempo- ity in one domain, such as specific reading disability. The term rallobes, are apparent on functional imaging (Guerreiro et al. global developmentaldelay is usedhere,while recognizingit is 1996; Da Silva et al. 1997). A variety of diseases, ranging from far from ideal (especiallyas delay implies, unrealistically, that cerebralarteritis to subacuteencephalitis,have beenmooted but there may be subsequent catch-up). 667
  6. 6. - - CHAPTER39 Sadly,a diagnosis of global developmental delay is often the A core characteristic of autism is lack of social sensitivity. It is prelude to relative neglect of the childs language difficulties. sometimesthought that all autistic children live in a world of There is a tendencyto assume that the level of non-verbal ability their own, ignoring all other people.This is far too extremea pic- sets some kind of limit on the level of language that can be ture: many children with autism will enjoy cuddles and rough- achieved. There is evidence against this viewpoint from two and-tumble play, but they may neither seeknor offer comfort or sources.First, somesyndromesare associatedwith a phenotype affection. In older, verbal, high-functioning children, one may in which intelligence is impaired but languageis an area of rela- find a strong desire to interact with other people, but a severe tive strength.The most well-known caseis that of Williams syn- lack of understanding of how to do this. The concept of friend- drome. This is sometimes misleadingly described as though ship as a reciprocal emotionally supportive relationship is hard language is normal. and other skills imp~ired. The reality for for a child with autism to grasp. most children is that both verbal and non-verbal abilities are Diagnosis dependson historical information about early de- well below averagebut, nevertheless, skills suchas verbal mem- velopment as well as observation and assessment the childs of ory, vocabulary and syntax arefar better than thoseseen other in current behaviour and abilities. Specificinstruments developed children with different aetiologieswho have similar levelsof IQ for the diagnosis of autistic disorder include the Autism (Morris & Mervis 1999). Furthermore, there may be relative Diagnostic Interview-Revised (ADI-R), which is a parental in- sparing of aspectsof syntax and morphology that give especial terview, and the Autism Diagnostic Observation Schedule difficulty to children with developmental language disorders (ADOS-G), which hasfour modules,to cover the agerangefrom (Clahsen& Almazan 1998). The secondpoint is that interven- infancy to adulthood, each involving direct observation of the tion studies suggestthat in many caseschildren of low IQ can child or young person in situations designedto elicit autistic be- benefit from language intervention just as much as those of haviours (Lord et al. 1994, 2000). Autistic disorder is coveredaverageIQ(Feyetal.1994). thoroughly by Lord & Bailey (Chapter 38), so in this section I Although the flow chart shows global developmental delay shall focus just on areasof diagnostic difficulty.and autistic disorder as separateentities, these disorders com- Textbook casesof autistic disorder or developmental lan-monly co-occur, and so it is import~nt to evaluate social com- guagedisorder are easyenough to recognize,but many childrenmunication, play and repetitive behaviour in children with a presentwith a pattern of symptoms that doesnot fit unambigu-global developmentaldelay. ously in either category, while showing some features of both. Thus their difficulties extend beyond the highly selectiveimpair-Autistic disorder and related condtion S I ment of language structure seen in developmental language dis- order, but they do not have the full triad of autistic impairments Delayed language development and poor comprehension are in severeenough form to merit a diagnosisof autistic disorder. hallmarks of autistic disorder, and the issueof differential diag- OHare et al. (1998) carried out an audit of 103 children re- nosis between autistic disorder and specific developmental ferred to a speechclinic at Edinburgh Childrens Hospital, and language disorder frequently crops up in clinical settings. A found that eight of them met diagnostic criteria for autism, but a diagnosis of autistic disorder should be suspectedif the childs further 14 had autistic symptomatology that fell short of meet- comprehensiondifficulties are accompaniedby more pervasive ing diagnostic criteria, in most casesbecause only two elements difficulties affecting social interaction, non-verbal communica- of the triad of autistic impairments were present.All but one of tion and play, or if the child shows unusual repetitive or ritualis- thesechildren was rated as having abnormal receptivelanguage . tic behaviours, or restricted interests. The clinician needs to on a speech therapy assessment.Although the diagnosis of consider whether language development is merely delayed, or Asperger syndrome is sometimesusedin such cases,this is not whether thereare deviant featuresthat would not be regardedas appropriate if the childs languagemilestonesare delayed. normal at any age, such as repetitive use of stereotypedcatch- In the UK, the term autistic spectrum disorder is usedquitephrases,unusualand exaggeratedintonation, pronoun reversal, widely, although often without clear diagnostic criteria. In theand a frequent failure to respond when the parent attempts to USA, and increasingly elsewhere,the DSM-IV (American Psy-attract the childs attention. An intriguing observation in some chiatric Association 1994) term pervasive developmental dis-children with autism is that scoreson tests of expressivelan- order not otherwise specified (PDDNOS) is frequently applied.guage(suchas picture naming) may be higher than those on re- However, this is not very satisfactory,asthis was clearly intend-ceptive tests (suchas selectinga named picture). Whereasmost ed as a default category to be used in rare caseswhen a childchildren with communicative problems will use non-verbal showed autistic symptomatology but diagnostic criteria formeansof expression,children with autism often have difficulty autistic disorder were not met. Furthermore, it provides little in-in both interpreting and producing appropriate non-verbal formation about symptomatology and does not help decisionscommunication. Imaginative play doesnot developnormally in about educational placement. Bishop (2000) suggestedthatchildren with autism; instead there may be repetitive routines, thesedifficulties probably reflect the fact that diagnostic labelssuchasforming long lines of toy cars, or the child may be preoc- impose a categorical structure on what is in reality a multidi-cupied with everyday artefacts such as lights or switches, and mensionalspace, with children varying in terms of the severityofdisregardstoys that most children would find attractive. impairments in language,social interaction and range of inter~668
  7. 7. ~CHAPTER 39Researchhas shown that measures obtained from spontaneous (1994b) offered guidelinesthat still seemrelevant in the light ofspeech samples are useful in identifying children who are current research:children whose expressivevocabularies con-deemedlanguageimpaired but who do not meet conventional sist of lessthan 50 words at the ageof 24 months should becare-psychometric criteria (Dunn et al. 1996). Unfortunately, such fully monitored, but long-term problems are unlikely in thosemeasuresare time-consuming and not always practicable in with vocabularies of more than eight words who have goodclinical settings. Furthermore, adequate normative data are comprehension.often lacking. There are a number of longitudinal studies showing that the In the final analysis,the specificcriteria adopted for identify- child whose language is significantly impaired at 4-5 years ofing languageimpairment will dependpartly on onesgoalswhen age is at high risk of developing literacy problems (Bishop &making the diagnosis. Stringent criteria developed in research Adams 1990; Tallal et al. 1997; Stothard et al. 1998; Johnsoncontexts are not always appropriate in clinical settings, where et al. 1999). Although it is commonly believed that oral lan-the goal is to provide a diagnosis that ensures the child has guage problems disappear with age to be replaced by literacyaccess appropriate services. to Here, one wants to usemeasures problems, this is seldom seen.Rather, the oral languageprob-that haveecological validity-that have relevancefor function- lemsbecomelessobvious in casualinteractions, but can beread-ing in everyday communicative and social settings-and to ily demonstrated on formal testing. It would be wrong to giveidentify those children who will benefit from intervention. If the impression that all language-impaired4 year olds are des-one requires a large discrepancy between verbal and non- tined for academic failure: some children do show markedverbal ability before children can be considered for special improvement. However, these tend to be children with pre-educational services, then many children with poor verbal skills dominantly expressivedifficulties that have resolved by the ageare denied access,even though their linguistic problems may of 51/2years (Bishop & Edmundson 1987; Bishop & Adamsbe identical to those of other children who do meet diagnostic 1990).criteria. DLD is associatedwith increasedrisk for psychiatric as well as language and literacy problems. The underlying nature ofD I t I d this associationhas beenthe causeof much speculation (Rutter eveopmena course prognosIs an " . & Lor d 1987) Comor b1 lty cou ld reflect t he m fl uence 0 f .d. °A number of longitudinal studies have thrown light on the de- common aetiological risk factors, or the causal effect of onevelopmental course of DLD. There is general agreement that condition on the other (Beitchmanet al. 1996). For instance,forthe child with significantly impaired receptive language skills some children affective disorders and low self-esteem mayhasa poor prognosis,evenif this diagnosisis madeat a very early be a consequenceof growing awareness of communicativeage.Comprehensionproblems do not usually appear to resolve inadequacy.spontaneously.On the contrary, the range of impairments seenin a child with receptive language difficulties often increases .h d. "I d h. ° d. I PrevaencewIt age, exten mg to encompasssocIa an psyc IatriC Isor-der (Rutter & Mawhood 1991), and impairment on non-verbal Two recentepidemiological surveys,in the USA and Canada,es-as well as verbal measures(Stothard et al. 1998; Johnson et al. timated the prevalenceof specificlanguageimpairment (SLI) in1999). There is muc;h more debate about prognosis for pre- 5 year olds at around.7% (Tomblin et al. 1997; Johnson et al.school expressive languagedisorders,with someproposing that 1999). However, it should be noted that neither study adoptedoutcome is generallygood and intervention is seldomwarranted the stringent discrepancy criteria of DSM-IV and ICD-I0, but(Paul 2000), while others maintain that these children are at rather diagnosedSLI if the child scored below cut-off on stan-high risk for persistingdifficulties that may only becomeappar- dardized languagetests,but had a non-verbal IQ of 80 or aboveent on detailed testing (Scarborough& Dobrich 1990; Rescorla and no other exclusionary criteria. Furthermore, in the study byetal.1997). At leastsomeof this controversy arisesbecause dif- Tomblinetal., only 29% of thosediagnosedascases ofSLIwereferent studies have used different follow-up periods to assess already known by parents to have any speechor languagediffi-prognosis. In the longitudinal study conducted by Paul et at. culties. This estimateis likely therefore to be higher than would(1996), the initial impressiongiven by the first wavesof follow- be the caseif it were basedon a definition such as DSM-IV orup was that 2 year olds with expressivelanguagedelayswere at ICD-10, which requires both that there be a substantial dis-high risk of persisting communicative problems. However, the crepancy between verbal and non-verbal ability, and that thelonger the follow-up, the smallerthe proportion of children who language impairment interferes with everyday or academichad marked languageimpairment. It appearsthat the numbers functioning.of children with clinically significant language difficulties doshrink dramatically as children mature. It seemsreasonableto R kf t " d t I o . . . IS ac ors an ae 10ogyconclude that a good long-term prognosIs IS usually seen mchildren identified aslate talkers before the ageof 3 years,pro- The principal risk factors for DLD are:vided the problem is restricted to expressivelanguageand the. male gender-in clinical samples, sex ratio of affecteddelay is not too severe(Whitehurst & Fischel 1994). Bishop males:femalesisaround30r4:1 (Robinson 1991);670
  8. 8. ~ -, SPEECH AND lANGUAGE DIFFICULTIES . family history of DLD-around 30% of affected children should not lead us to conclude that environmental factors are have an affected first-degree relative, compared with 3% of the unimportant, or that nothing can be done to alleviate language general population (Stromswold 1998); and difficulties. Provisional evidence suggests genes may act as risk . being a later-born child in a large family (Bishop 1997a). factors that increase the probability that a child will have a Although much has been written about language outcomes of languag~ disorder, but the severity and persistence of language medical risk factors, such as otitis media and low birth weight, disorder can be highly variable, even within a pair of genetically thereisnostrongevidencethattheseactasmajorriskfactorsfor identical monozygotic twins. A study by Bishop et al. (1999) specific DLD, although they may act synergistically to cause im- suggested that environmental factors could impair the childs pairment in a child who is already at risk from other causes ability to process non-verbal auditory stimuli, with a subsequent (Bishop 1987). Although there is an association between low so- small knock-on effect on language development. In children cioeconomic status and DLD (Fundudis et al. 1979), this is not who were not at genetic risk, this negative effect was not of strong, and there is little support for the commonly held view clinical significance, but in those who were at genetic risk, that parents can cause their child to become language impaired for whom language learning was a more difficult task, the by inadequate verbal stimulation, except in the most extreme combination of environmental and genetic risk factors was suf- cases of abuse and neglect. ficient to lead to clinically important problems in language Over the past decade, there has been an explosion of research learning. concerned with the genetic basis of DLD (see Bishop, 2001 for a review). Three twin studies have obtained closely I t t o slml " " I ar fi n d mgs " 0 f h Ig h h enta " o b I l Ity o o f or t h IS d Isor d er o " (L ewls & o n erven Ion Thompson 1992; Bishop et al. 1995; Tomblin & Buckwalter Intervention is usually carried out by speech and language 1998). A molecular study of a three-generational family show- therapists, who use a wide range of techniques to stimulate lan- ing an autosomal dominant pattern of inheritance for severe guage learning. In the past, there was a vogue for drilling chil- speech and language disorder found clear evidence of linkage to dren in grammatical exercises, using imitation and elicitation a site on chromosome 7 (Fisher et al. 1998), although it is un- methods, in an attempt to have the child extract the salient clear how far these results will generalize to other cases of heri- grammatical regularities. Such methods fell into disuse when it table language disorder. became apparent that there was little generalization to everyday Currently, there is considerable interest in two aspects of lan- situations. Contemporary approaches to enhancing develop- guage functioning that have been postulated as behavioural ment of language structure are more likely to adopt milieu markers of heritable SU. The first is phonological short-term methods, in which the intervention is interwoven into natural memory, typically assessed by asking the child to repeat non- episodes of communication, and the therapist builds on the sense words of increasing length, such as hampent or blonter- childs utterances, rather than dictating what will be talked staping (Gathercoleetal.1994). Poor performance on this task about. In addition, there has been a move away from a focus characterizes many children with SU, even those who had early solely on grammar and phonology toward interventions that difficulties that appear to have resolved. Furthermore, deficient develop childrens social use of language, often working in performance on non-word repetition showed very high heri- small groups that may include normally developing as well as .tability in a twin study (Bishop et al. 1996). The second area in l~nguage-impaired peers (Gallagher 1996; Hayden & Pukonen which many children with DLD have disproportionate difficul- 1996). ties concerns certain aspects of grammar. Children with DLD Another way in which modern approaches to remediation dif- can have major problems in adding appropriate verb endings, fer from the past is that parents are more likely to be directly in- such as past tense -ed, when given an eliciting sentence frame volved, particularly with preschool-aged children (Girolametto (e.g. Q: Here the boy is raking the leaves. What has he just et al. 1996). Methods such as the Hanen approach" involve done? A: Raked the leaves) (Rice2000). Rice & Wexler (1996) videoing interactions between parent and child and then using have postulated an underlying impairl11ent of an innate system these when working with groups of parents in a constructive that has evolved to handle specific types of grammatical rule. way to help them facilitate communication. With the exception of non-word repetition, the measures used to A radically different approach has been developed by Tallal assess such hypotheses are not available as standardized tests, et al. (1996), who have devised a computer-based intervention, making them 1nsuitable for clinical use at present. Nevertheless, FastForword, that involves prolonged and intensive ttaining on the work is promising in suggesting that we may be able to specific components of language and auditory processing. The develop more selective language measures that will identify theory underlying this approach maintains that language diffi- homogeneous groups of children with a common aetiology. culties are caused by a failure to make fine-grained auditory That would be a considerable improvement on the current discriminations in the temporal dimension, and the training position, where the same child mayor may not receive a diag- materials are designed to sharpen perceptual acuity, in much the nosis of DLD depending on which tests are used to assess verbal ability. The fact that there is sttong genetic influence on DLD "See website at http://hanen.velocet.ca/programs_parentoshtml 671
  9. 9. CHAPTER39sameway as has been demonstratedin animal experiments. By phonological teststhat require no speechfrom the child. Someembeddingtraining in attractive computerized games,children children with phonological problems have difficulties in dis-can be persuadedto participate in thousands of training trials, criminating between similar speechsounds, such as pat vs.in a way that would simply not be possible with a standard cat, when asked,for instance,to selecta picture to match whattherapist-basedinteraction. they haveheard. However, the most common difficulty is not so For all thesetypes of intervention, there are few adequately much in telling soundsapart, asin recognizingthat different ex-contl;olled trials that allow one to assessclinical efficacy.In gen- emplars of the same sound are indeed the same sound. So iferal, one does not seemiracle cures, but this is not to say that asked to say whether bag or boat rhymes with rag, or togains are negligible (Bryne-Saricks 1987; Law et at. 1998). A judge whether soup or coat begins with the same sound asclinical trial assessing FastForword approach showed sig- the Sam, the child with phonological problems may perform atnificant gainsrelative to a control group (Merzenich et at. 1996), chancelevels (Bird et at. 1995). Suchobservations suggestthatbut questionsremain about the persistence and generalizability the difficulty is one of categorization of speech,rather than poorof theseeffects.Sincethe initial controlled trial, the authors have acuity for differencesbetweenspeech sounds.gathered a large amount of data on pre- and post-intervention The prognosis of pure phonological disorder is much betterlanguage test scoresof children enrolled in FastForword, but than that of languagedisorder (Bishop & Adams 1990;Johnsonthis is difficult to evaluate without controls for practice and et at. 1999), especiallyif the phonological difficulties resolvebyplacebo effects (TallaI2000). Furthermore, it is not possible to the time the child starts school (Bird et at. 1995). It is difficultknow which specific components of this complex intervention to estimate the prevalenceof phonological problems, becauseare most effective,or whether the whole gamut of different exer- studies typically do not discriminate betWeen different types ofcisesis essentialto achievetherapeutic benefits. speech problem; lisping and other deviations,specificphonolog- ical impairments, and speech problems accompanyinglanguageD I t I h I . I d. d impairment all tend to be included together. Furthermore, eve opmen a p ono oglca Isor er . prevalenceappearsstrongly age-dependent, with speechprob-It is customary to draw a distinction betWeen speech, physi- the lems declining sharply betWeen3 and 6 years of age (Morleycal act of articulating speechsounds, and language,the whole 1972). After excluding children with additional handicaps,complex system of combining elements of sound at different Johnsonetat. (1999) obtained a prevalence estimateof6.1 % forlevelsof complexity to expressmeaning. It is possibleto have a specific speech-onlyimpairments at 5 years of age.This figurelanguageimpairment with normal speech(e.g.in cases DLD of excludes the children from this sample who had comorbidwhere the child speaksclearly but doesnot comprehendor pro- speechand languageimpairment. Shriberg et at. (1999) report-ducecomplex syntactic constructions). The conversesituation is ed a prevalenceof speechdelay in US 6-year-oldsof 3.8%, withalso seen,when the child has somedifficulty in producing clear comorbid languageimpairment in around 12% of thesecases.speechbut the underlying languageskills are intact, e.g. in cases Little is known about risk factors and aetiology of phonologicalof dysarthria (seebelow). The child who persistsin using imma- disorders, although, as with other communication disorders,ture or deviant sound patterns but who has no physical b~sis boys are at greater risk than girls (Shriberg et at. 1999). Inter-for this disorder does not fit so neatly into this dichotomous vention is carried out by speech-languagetherapists, andview. Speechis undoubtedly the prese~ting problem, but the typically involves games and exercisesto develop the childsunderlying impairment appearsto be linguistic rather than one awareness phonemic contrasts (Deanet at. 1995). ofof motor control: a failure to learn which speech soundsare dis-tinctiv.ein the am.bientlanguage.Often th~ speech errors involve Developmental verbal dyspraxiaa persistenceof Immature patterns. For Instance, sounds pro-ducedin the back of the mouth, suchas k and g are not distin- Developmental verbal dyspraxia is a controversial diagnosticguishedin the childs output from those produced in the front of category that is defined differently by different experts,and notthe mouth, suchast and d, so that cat may be pronounced as usedat all by someauthorities (fora review seeCrary 1993). Thetat and dog asdod. The terms phonological disorder (DSM- central characteristicin most definitions is that there aredifficul-IV) and phonological impairment have superseded such labels ties in speechproduction that suggestan impairment of motoras functional articulation disorder to refer to such problems. programming, because is the length and complexity of what is itThe term phonological implies that the childs difficulties are uttered, rather than the specific speechsounds used,that is thelinguistic rather than motoric, perhapsakin to thoseof an adult main factor determining accuracy.In children with this diagno-mastering a foreign language. Most of us have difficulty in sis, one is likely to seespeecherrors that are inconsistent fromlearning to use a new set of speechsounds, not becauseour one occasion to the next, that are particularly evident in poly-articulators are in any way defective, but because have not we syllabic words, and that involve transpositions of speechinternalized the sound distinctions that are critical in the soundsrather than simple substitution of one soundfor another.language. For instance, Bradford & Dodd (1996) reported a dyspraxic Evidencethat a phonological disorder is not just a problem in child whoserenderingsof elephant on three separateoccasionsarticulating soundsaccuratelycan be obtained using specialized were ewint, wuwit and uwit.672
  10. 10. r" SPEECHAND lANGUAGE DIFFICULTIES Debate continues over the question of whether problems in Drought syndrome.However, Clark et at. (2000.),in a recentre- sequencingnon-verbal movementsshould be part of the diag- view of 47 cases,noted that most children with this condition nostic criteria: someauthorities maintain that to be regardedas have additional complex impairments, including mild pyrami- dyspraxic, the child should be impaired in imitating sequences dal tetraplegia, learning difficulties, behaviour problems and of non-speech movementsof the tongue and mouth. Not all chil- epilepsy.Crary (1993) noted that remarkably little clinical or re- dren who make inconsistentphonological errors haveextensive searchattention has beenpaid to developmental dysarthria, al- difficulties producing non-speech movements,raising the ques- though it was well describedby Morley et at. (1954) more than tion of where they should beclassified(Bradford & Dodd 1996). 40 yearsago. It appearsto be a strongly familial condition. In addition, there is the question of whether dyspraxia should be Dysarthria and anarthria involve difficulties affecting speech diagnosedin a child who hasbroader difficulties with expressive rather than language,and so one would expect to find normal language, or only in those with a relatively pure problem in language comprehension and normal literacy skills in pure speech output. In practice, many children who receivethis diag- cases.However, quite often the aetiological factors that cause nosis do have associatedproblems affecting language, literacy articulation difficulties also lead to problems in other areas,in- and phonological awareness (Stackhouse1992). cluding hearing and language. The lack of agreeddiagnostic criteria make it impossible to ma~e generalizations about risk factors, prevale?ce or .prog- Selective mutism nosls.The causeof developmentalverbal dyspraxia remains an enigma, but it appearsto be strongly familial (Morley 1972). It Selectivemutism is diagnosedwhen a child is able to speakbut is also worth noting that although their grammatical difficulties fails to do so except in very restricted situations, such as with have beenemphasizedin published accounts, the phenotype in close family. This disorder was previously known as elective the three-generationalfamily mentioned in the section on DLD mutism, but the terminology was modified in DSM-IV to avoid also involved severely dyspraxic speech (Hurst et at. 1990). the connotation of volitional behaviour.The diagnosisis strong- Crary (1993) providesan overview of approachesto interven- . lysuggestedwhen one finds mutism in a child whohasnoneuro- tion for developmentalverbal dyspraxia. logical or structural abnormalities of the articulators, and who has normal languagecomprehension,as well as a normal early A th . dd th . historyof usinglanguage. However, crucialpoint that needs the nar ria an ysar ria b bl h d . h h hold d o k. .. to eesta IS e 1St att ec I oesspea In somesituations. Anarthria or dysarthria is diagnosed when speech problems As Dummit et at. (1997) noted, this condition is more pro- arise becauseof structural or neurological abnormalities of perly regardedasa form of anxiety disorder rather than a speech articulatory control. Anarthria is the term used when there is and languagedisorder. Rates of comorbid anxiety and phobic no ability to produce speech,whereas dysarthria refers to dis- disorders are high, both in affected children and in their first- ordered articulation caused by weakness, incoordination or degreerelatives. However, differential diagnosiscan be compli- structural abnormalities of the articulators. It is important to cated by the fact that some children with selectivemutism do distinguish these articulation problems, where speech is im- have developmentallanguagedisorders (Kristensen2000), sug- paired because problems producing articulatory movements, of gesting that self-consciousness about inadequate communica- from developmentalphonological disorders, where the child is tion skills may play a.part in maintaining mutism. neurologically normal and capable of producing articulatory Persistent selectivemutism affects less than 1 in 1000 chil- movements(seeabove). Neurological conditions that can cause dren, although the frequency of transient mutism in children anarthria or dysarthria include cerebral palsy and Mobius starting school is much higher.Girls are two to three times more syndrome,in which there is agenesis cranial nerve nuclei and of likely to be affectedthan boys.The causes selectivemutism re- of associated facial immobility. Structural abnormalities of articu- main unknown. Although conventional wisdom maintains that lators that can lead to dysarthric speech include cleft palate and physical or sexual abuseor other kinds of trauma may precipic TreacherCollins syndrome.There are a number of other genetic tate selectivemutism, there is little evidenceof this (Black & syndromesthat are associatedwith unusual proportions of the Uhde 1995), and the strong familial component to the disorder articulators and/or hypotonicity which affects tongue control, suggests that Dummit et at. (1997) may be correct in regarding e.g.Down syndrome. this disorder as the extreme end of a biologically basedcon- Where no specificsyndromeis detected,one should bealert to tinuum of temperamentand social behaviour. the possibility of dysarthria when there is poor co-ordination or Behaviour modification methods have been shown to be ef- weaknessof facial muscles,as evidencedby drooling, feeding fective in re-establishing speech(Sluckin et at. 1991), but the problems, or difficulties imitating simple oral movementssuch long-term prognosis of selectivemutism is neverthelesspoor. as moving the tongue from side to side or pursing the lips. There is a high rate of personality disorder and psychiatric prob- Worster-Drought (1974) stressedthat anarthria can occur in lems associatedwith a history of selectivemutism (Kolvin & children in the absenceof any other neurological impairment, Fundudis 1981). Dummit et at. (1997) argued that therapeutic and he gave detailed descriptions of this condition, which is interventions should focus on alleviating anxiety, but there has known as both congenital suprabulbar paresis and Worster- beenno systematicresearchon the efficacyof this approach. 673