Speech and language disorders

A common question asked of clinicians in general practice, child health, and child psychiatry concerns the long-term consequences of delayed speech and language development in the early years of life.(1) A previously held view was that most young children with speech and language problems would eventually develop normally. But this is an optimistic view—it is more likely to be true of children without major mental and physical handicaps. Allied questions which have to be addressed are whether the speech and language is abnormal? If so, which children will eventually develop normally? What is the long-term outcome? How do we understand and explain the causes? Therefore it is essential to have some skills in the diagnosis and management of these disorders.

In a brief chapter there is no space to discuss theoretical aspects of the development of speech and language, particularly the newer neurolinguistic concepts which are competently reviewed elsewhere.(2) The focus will be on those types of disorders that present in clinical settings, such as specific developmental speech and language disorders, deafness, and selective mutism. Classification and prevalence will only be addressed briefly for those disorders associated with mental handicap, brain damage, or autism.

Classification and concepts

To produce normal speech there must be a functional neurological system capable of learning the 'underlying structure of language', (3) including a sensory component which can perceive and decode the incoming signals, an intact apparatus subserving, directing, and programming speech sound production, and available stimulation by exposure to language in its various forms. However, in most speech and language disorders there is no evident physical aetiology—these are the developmental disorders.

Functional clinical classification

One of the older, but more useful, functional clinical classifications is that of Ingram (4) who described three main categories of speech and language disorders: primary, secondary, and developmental. Modifications of this classification were developed by other workers. (1„)

1. Primary disorders are disorders of word sound production, which occur in dysarthria or with cleft palate, with either demonstrable dysfunction or structural abnormality of tongue, lips, teeth, or palate.

2. Secondary disorders are disorders of speech sound production secondary to other diseases or environmental factors. These include marked intellectual impairment, demonstrable neurological disorders and cerebral palsy, deafness and specific psychiatric syndromes such as infantile autism, acquired dysphasia, and the effects of an adverse psychosocial environment.

3. Developmental speech and language disorder is a descriptive label for retardation of speech and language development in children who are otherwise apparently normal.

Ingram(4) views the last condition as a heterogeneous group of articulatory and language disorders in which speech and language development may not only be delayed but also be deviant. Nevertheless, he finds it useful to regard it as a spectrum of clinical disorders that range from mild to very severe.

Further, a distinction needs to be made between speech and language. Speech can be defined briefly as the articulatory skill associated with the production of word sound and spoken language. Language is a cognitive skill that utilizes a system of symbols(5) and whose main purpose is communication. It has various forms such as spoken, written, gesture, and sign.(6)

Stammer is a disturbance in fluency and patterning in time of speech which is disrupted by sound and syllable repetitions or sound prolongations (DSM-IV). Neither physical nor environmental factors have been shown to be consistent major determinants. However, it occurs in families and is more common in boys than girls—which suggests a genetic predisposition. Some young children have a transient trivial dysfluency, and parental anxieties and concerns may hinder the spontaneous improvement. In these circumstances, parental counselling by a speech therapist is usually helpful. Psychiatrists are seldom involved in the treatment of stammer, and the condition is not considered further in this chapter.

The ICD-10 classification

Specific developmental speech and language disorders are subdivided into those with a specific speech articulation disorder, an expressive language disorder, and a receptive language disorder. Following ICD-10 criteria,(7) specific developmental disorders of speech and language are those in which language delays are evident from the early stages of development, and are not a direct consequence of 'neurological or speech mechanism abnormalities, hearing impairment, mental retardation or environmental factors'. In addition, the impairments or delays are related to biological maturation of the central nervous system which become evident as the child grows older. There are wide variations in the age at which spoken language is acquired in normal children, and any delays or impairments are usually 'of little or no clinical significance as the great majority of "slow speakers" go on to develop entirely normally'. (7) This is the basis of the specific speech and language disorder syndrome. In this sense the syndrome may be considered to represent an extreme variation in normal development. As a general rule, any language delay must be sufficiently severe to fall outside the limit of two standard deviations on relevant measures to be regarded as abnormal. These conditions are much more common in boys than girls. The subclassification is as follows.

• Specific speech articulation disorder: the child's use of speech sounds is developmentally below that expected or appropriate for his or her mental age, although there is a normal level of language skills and non-verbal intelligence. The child's acquisition of speech sounds is delayed or deviant, and there are associated misarticulations with consequent problems for others in understanding the speech. The identified abnormalities do not have a clear basis in secondary pathology consisting of structural or neurological abnormalities.

• Specific developmental expressive language disorder: the child's ability to use expressive language is substantially poorer than the appropriate level for his or her mental age, but 'language comprehension is within normal limits'. There may or may not be associated articulation abnormalities. (7) The diagnosis should only be made when the severity of the delay in development of expressive language is beyond the limits of normal variation. A range of associated abnormalities and language difficulties have been described:(7) after the age of 3 years there may be a 'restricted vocabulary ..., overuse of small number of general words, ... short utterance length and word substitution ..., errors of syntax, especially omissions of word endings or prefixes, grammatical abnormalities' with prepositions, pronouns, verbs, etc., problems with fluency and sequencing, and possibly associated problems in word sound production. (7) Helpful non-verbal diagnostic features are that the child may employ appropriate non-verbal cues, such as gesture, facial expression, and mime, to communicate.

• Specific developmental receptive language disorder: 'the child's understanding of language is below that appropriate for his or her mental age'. (7) Commonly, expressive language is also affected and there are associated abnormalities in word sound production with the picture being one of a mixed receptive and expressive language disorder. Again, the diagnosis should only be made when the severity of delay in receptive language is beyond the normal limits of variation. In the early years, the child has difficulty in responding appropriately to verbal stimuli or in identifying familiar objects by name, or has difficulties in following simple instructions. Later, additional features include difficulties with grammar.

• Acquired aphasia consists of a loss of acquired language functions.(4) A birth-injured child cannot be described as having lost language functions, but more accurately as showing retardation of development of speech and language. In a 2- or 3-year-old child, acquired aphasia will initially be reflected in a language impediment and thereafter slowing of speech. When associated with epilepsy it is called the Landau-Kleffner syndrome, (8) in which there will be paroxysmal electroencephalographic abnormalities usually from the temporal lobes; the onset is between 3 and 7 years of age. Skills may be rapidly lost and impairment of receptive language becomes severe. It is thought to have a basis in an encephalitic process. Only one-third of children eventually make a complete recovery.

The categories of speech and language disorders are broadly similar in the ICD-10 and DSM-IV classificatory systems. Both give clear descriptions of diagnostic categories. However, ICD-10 provides a helpful definition of the concept of a developmental disorder which will be appreciated by both clinicians and researchers.

Neurolinguistic profiling

A classification has been developed based on neurolinguistic criteria. (2) This is commonly used by speech experts, and in their hands is a useful complementary assessment system. Research examining the profile of language impairment suggests that some of the subgroups correspond to different points in development rather than distinct disorders.

Prevalence

Specific retardation of speech and language

The rates reported in population studies are a function of the definition employed. Fundudis et a/.(1) reported that 4 per cent of 3300 3-year-old children failed to use three or more words strung together to make some sort of sense. However, the rate reduced to 2.3 per cent when allowance was made for those children who have wide milestone delays.(3) Stevenson and Richman(9) reported expressive language delays of 3.1 per cent in 705 3-year-olds.

Other conditions

It is impossible to provide accurate estimates of the prevalence of rarer conditions when studying a relatively small population of children. (1 The following is a rough guide to the rates of the different types of conditions associated with speech and language disorders.

The single most common cause of slow speech development in paediatric clinics is mental retardation (learning disorder).(4) If this is defined as an IQ of less than 70, then over 2.5 per cent of the child population are likely to be affected, with over half of these children showing articulation defects or severe language disorders, or both.(19 Deafness is one of the major causes of delay in speech and language development—about 2 in 1000 children have deafness severe enough to merit the use of hearing aids. When autism is narrowly defined, a rate of 4 in 10 000 children has been reported. (11) Serious and persisting language disorders (severe dysphasia) have been estimated at 0.4 in 1000 children^—the condition seems to be as rare as infantile autism. The rate of dysarthria is approximately 1 in 1000 births.(1)

Prognosis

Epidemiological research reveals that the rate of problem behaviour in 3-year-old children with language delay is four times that seen in a random sample of children.(!2) However, the predictive power of such early assessments is not great and the crucial question that remains is: How many children with language delay at 3 years of age will catch up in their cognitive and language ability and lose their behavioural disturbance?

Of the cohort of 3300 investigated by Fundudis et a/.}1) 4 per cent were previously speech retarded at the age of 3 years; one in five of these were found at school age to have serious language, intellectual, or physical handicaps and were labelled a 'pathological deviant' group. If this extreme group is then set aside and the residual group of 'specific speech-retarded children' with no other major impairments is compared with controls, the cohort is found to contain a subgroup with wider delays of milestones (28 per cent) and a subgroup with a circumscribed specific developmental delay of speech and language (72 per cent). There are firm grounds for believing that this latter group of children is very similar in speech and language development to those children with language delay described by Richman et a/h2) (and both consist mainly of children with moderate to severe developmental speech and language disorders.

The research carried out by Fundudis et a/.().) can be used to answer some questions about outcome at school age. A high percentage of the residual specific speech-retarded group still had significant cognitive and educational impairment, poor language development (including poor expressive language skills), and a more restricted type of language expression. In addition, the prognosis for behaviour was likewise poor. Speech delay was found to be a better predictor of impaired verbal intelligence than of performance intelligence. There was a better outcome for specific developmental expressive language delays, with most children showing substantial improvement by the age of five. In contrast, children with a receptive language disorder followed into adulthood show a relatively poorer outcome for conversational skills and fluency. (13>

Social influences on speech and language development

While some workers emphasize the biological determinants of speech and language, others stress the importance of psychosocial influences. Chomsky ^J postulates the presence of an innate language acquisition device which determines the deep-seated properties of organization and structure of all human languages. The emergence of speech is most easily accounted for by maturational changes, so that children of deaf parents are found to babble appropriately and to develop speech adequately, despite being brought up in a grossly abnormal linguistic environment. (15>

Environmental stimulation and social interchange, particularly with adults, facilitates progress in vocalization and language development in the early years. In contrast, even serious impoverishment of the social environment, for instance where children are institutionalized, usually may only give rise to moderate degrees of impaired vocalization, speech delay, and language retardation—with the retardation being confined mainly to language expression rather than to comprehension. (16>

Language and psychiatric disorder

Population studies with children with specific language delays show that about 50 per cent have significant behaviour problems, four times more common than the rate in the control group.(1,1Z> Baker and Cantwell(!8,» found that 300 children attending community speech and hearing clinics showed a stepwise increase in the rate of psychiatric disorder—with rates of 29 per cent for those with speech disorders and 45 per cent for those with speech and language disorders. Thus they concluded that children with communication disorders are at risk for an increased rate of psychiatric disorder. There are no identifiable behaviour patterns—except that those children with widespread language disorders are more likely to have a psychiatric disorder—and those with severe language disorders are more likely to have an associated autistic-like impairment of social relationships. (1§>

Speech and language disorders and behavioural abnormality: directionality of associations

Rutter and Lord(29 analysed the hypothesized direction of the association between speech and language impairment and psychiatric disorders in childhood. They addressed the previous common assumption that the usual relationship is that psychological disorder gives rise to language problems and offered five main patterns of probable directionality.

1. A psychiatric disorder gives rise to secondary speech and language problems, as exemplified in selective mutism and traumatic mutism.

2. There is a reverse causal process whereby a primary specific developmental language disorder gives rise to a psychiatric disorder. The mechanisms probably include a sense of frustration with poor communication and socioemotional problems, which in turn give rise to the psychiatric disorder. A similar explanatory mechanism has been suggested by Bishop/3,)

3. In autism there is a probable common underlying problem, which 'forms part of a broader cognitive impairment and results in the psychiatric disorder and the language problem including autism'.

4. Severe environmental privation may give rise to both psychiatric disorder and language problems, with the mechanisms for each disorder being rather different. Rutter and Lord(29 suggest that while language delay is a consequence of inadequate stimulation and learning experiences from adults including communication and interaction, socio-emotional difficulties are probably a consequence of impaired attachment experiences.

5. In mental retardation the children often present with delays in language development and a psychiatric disorder. Here, the directionality and relationships are complex and may have a basis in the different forms of organic brain damage that have given rise to the mental retardation. Additionally, there may be an interaction between the language problem and psychiatric disorder in both directions.

Hearing impairment

Both because of the rarity of moderate to severe hearing impairment and because the hearing-impaired infant sporadically babbles, deafness may remain unsuspected in early infancy. Often a mother will suspect that there is something unusual about her child's hearing, but she may not be taken seriously until there is concern about a poor expressional response to sudden meaningful noises. Such suspicions should be checked using reliable screening tests, which are available for use from about 6 months of age/21 Other accurate non-invasive assessment techniques are now available, such as evoked-response audiometry. The possibility of progressive hearing loss may need to be excluded by repeat audiometric examination. Probable causes of profound hearing impairment can be identified by taking a careful history, enquiring about conditions such as serious postnatal middle-ear infections, neonatal hyperbilirubinaemia, congenital rubella syndromes, etc.

Severe organic brain damage may cause deafness and also contribute to the poorer intellectual and educational performance of such children. About 16 per cent of deaf children have central nervous system dysfunction(22) and 30 per cent have one or more additional disabilities. (23)

Usually, epidemiological studies do not reveal an excess of social and family pathology in families of deaf children. (1) Surprisingly, deaf children of deaf parents often show better linguistic development than deaf children of hearing parent, which seems to favour early complementation of verbal and non-verbal methods of communication.

Speech and language disorder in hearing-impaired children

In a short review it is possible only to touch on some of the complex theoretical issues concerning speech, language, and the intellectual development of hearing-impaired children.(24) There is some evidence that the rules of language learned by most deaf children in their early years are similar to those learned by hearing children.^ In profoundly deaf children the development and acquisition of speech and language is different from that of children with normal hearing. This is reflected in their relatively superficial language skills, such as spoken language, but it also includes poorer inner-language abilities. (24>

Childhood deafness hampers the development of language and verbal abilities, but not necessarily that of non-verbal abilities. (1) However, this comparatively poorer performance on cognitive tasks appears to reduce with age and appropriate stimulation. In addition, there is evidence that the academic achievements of deaf children, particularly progress in reading, are poorer than those of hearing children. (25) Some consider that these cognitive and educational impairments are more an indictment of the educational system than an inevitable consequence of deafness.

Psychiatric problems in hearing-impaired children

Usually hearing children are better adjusted socially and behaviourally than hearing-impaired children. (22) Further, hearing-impaired children raised in families where other members are deaf often prove better adjusted than those raised in families where other members are not deaf. (29 However, 50 per cent of profoundly deaf children present with psychiatric disturbance in school; this is mostly antisocial behaviour, (1) but anxiety disorders are also reported. (27>

Assessment

In the assessment of children with speech and language problems a preliminary formulation and differential diagnosis can usually be made on the basis of biographical enquiry and careful clinical assessment. This should include observation of the child during interview, informal free-field assessment of hearing, speech, and language and capacity for imitation during play, cognitive ability, social and behavioural functioning, and neurological assessment.

Biographical enquiry is intended to provide information about psychosocial influences and relevant physical factors, such as cerebral insults, history of clumsiness, etc.

Observation constitutes an integral part of all forms of assessment. While gathering biographical information, clinicians should note whether the child uses non-verbal clues from its parents to understand comments or questions; or whether there is evidence of clumsiness of gait typical of the child with cerebral palsy. Expert assessment is indicated where there are doubts, which may include audiometry, evoked-response audiometry, and other specialized techniques.

Speech and language in its various forms

Speech may be delayed or articulation skills deviant. For instance, articulation may be defective in deafness, immature in mental retardation and developmental speech and language disorders, deviant and immature in autism, and variably disordered in selective mutism. The articulation defect in dysarthria is characteristic.

Language can be assessed on a number of modalities; for example, spoken, sign (manual), or written. Comprehension can be tested by assessing the child's ability to understand simple commands both with and without the provision of visual and gestural clues. Evidence of language may be obtained from the way the child communicates through gesture, mime, and conversation/2 29> 'Inner language', which reflects an understanding of a symbolic code, can be assessed indirectly by observing whether there is a meaningful use of objects and by constructiveness and creativity in play. More formal tests of comprehension, which do not include speech, are available for a child who presents with speech difficulty; standardized tests are available which allow a quantification of the extent of the language impairment.

In profound deafness the child does not attend to, or respond to, auditory stimuli, but will extensively use gestures, attempt conversation when older, and may be constructive in play. The assessment of deaf children with psychiatric disorder is intimately related to the individual child's communication, which in turn is influenced by medical, social, and cultural factors. (39 The use of an interpreter can clarify communication.

The younger autistic child may not respond meaningfully to auditory stimuli, and, indeed, may tend not to respond to any form of verbal or non-verbal communication. There is little indirect evidence of language either in terms of gesture, mime, imitation, or play. In mental retardation there is usually no evidence of deafness, but rather of limited language abilities and usually a delay in the development of articulation, together with other evidence of slowness of other developmental milestones. Evidence of constructive play reflects the presence of inner language and augurs well for the growth of language in general. Gestural imitation and play constitute a form of communication, which is impaired in infantile autism and in severe language retardation.

Cognitive ability

Clinical impressions can be deceptive and need to be validated by careful psychometric assessment of both non-verbal intellectual skills and language performance. A wide range of tests are now available, which measure performance rather than verbal abilities and also language skills.

Intervention in speech and language disorders

The severity spectrum(4) outlined above provides a rough guide as to when to intervene. Mild disorders are likely to improve spontaneously provided that there are no associated psychological and relationship problems. The course suggests spontaneous improvement by the ability to use meaningful three-word phrases by 36 months, a pattern of normal development in all other aspects of language, communication, and general milestones, and no evidence of medical conditions such as hearing impairment, learning disorder, etc.(29) In these circumstances, treatment may be deferred to school age. However, irrespective of the mildness of the disorder, parents will wish to have specific information about prognosis and may prefer an earlier intervention. There is no evidence that such action in itself has negative effects, provided that pressure and coercion are avoided.

If the disorder is less mild, joint home and school intervention programmes are indicated, including counselling the parents about structuring the child's communication environment, combined with classroom teaching which focuses on the linguistic, social, and educational needs of the child. (3)

Severe disorders merit early attention by speech therapists and teachers. Routine and didactic teaching of language skills in a structured manner is now less fashionable.(3) It is considered preferable to complement structured teaching with a range of methods to stimulate language, including focusing on teaching the child communication skills within a naturalistic setting.(3) At the severe end of the spectrum, in children with significant auditory comprehension difficulties, there is a debate as to whether the child should be given preferential oral language training alone. This is because of concerns that supplementary signed language may become the preferred and only communication modality.(3) However, the evidence for this is scant and the current wisdom is that there should be a preparedness to employ multimodal approaches in intervention with such children, i.e. using oral and sign-language methods and, where necessary, appropriate behavioural techniques.

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