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Assessment and investigation of children with developmental language disorder
Gillian Baird
Speech and language problems are some of the most common developmental concerns resulting in referral to child health services in the preschool years, often in the first instance to speech and language therapy services. A speech and language problem in a young child is a symptom that needs a differential diagnosis, an investigation of causation where appropriate, and a management and treatment plan. Many children will see only the speech and language therapist and never need the services of the multiprofessional team; others will. This chapter addresses the approach to investigative assessment that is reasonable for the clinician to consider in a child with a speech and language impairment.
SPEECH AND LANGUAGE DEVELOPMENT
The typically developing child shows remarkably rapid acquisition of the skill of extracting meaning from language and communicating using speech. The precise process whereby children learn to understand language and then speak is not known, but a range of language and cognitive processes needs to be smoothly integrated. Infants are both socially motivated to attend to and highly sensitive to the stress patterns, rhythms, and spaces of speech (Jusczyk, 1997). Fine-tuning of auditory perception with increasing familiarity of the childâs own language is evident between 6 and 9 months of age (Kuhl, 2004). The child brings both motivation and an ability to read other peopleâs mental states to infer a speakerâs intended referent and meaningâthat is, to know what is being talked about and thus to what the sequence of sounds refers. This is characterized by joint attention, in which the childâs gaze switches to an object or action the speaker is focusing on (Pruden, Hirsh-Pasek, & Golinkoff, 2006). Cues from speech sounds alert the child to changing word meaning and support the learning of grammar. By the age of 5 the typically developing child has not only mastered the fundamental structural aspects of language but has acquired a knowledge of pragmaticsâthe ability to determine how to use verbal and nonverbal communicative signals (i.e., gesture and facial expression) to understand and convey a wide variety of different messages according to context.
DECIDING WHO HAS A SIGNIFICANT SPEECH AND LANGUAGE PROBLEM
There is a wide normal variation in the acquisition of speech and language. Using the MacArthur Scale of Communicative Development Inventory, Fenson et al. (1994) reported that at 16 months of age, 80% of children understand between 78 and 303 words. Those in the top 10% produce 154 words, and those in the lowest 10% produce none.
In the preschool years, many children who are late to talk improve spontaneously (Paul, 1996); however, predicting which child is going to improve spontaneously is difficult. Any single measure, particularly in a very young child, may be a poor predictor of outcome. Silva, McGee, and Williams (1983) assessed the same children at 3, 5, and 7 years of age and reported that, while some children failed at each of three assessment points, others failed at only one or two.
A common way of measuring a childâs abilities is to express a score as a centile (also known as percentile)âthat is, in terms of the percentage of children of the same age who would obtain an equivalent or lower score. Thus the 50th centile is average, the 90th centile is well above average (only 10% do better than this), and the 10th centile is well below average (90% of children will score higher than this). Traditionally it is those children on the lowest centiles of speech and language acquisition who have been considered to have an impairment, although exactly which centile marks impairment (bottom 10th centile versus bottom 3rd centile) at any given age remains a matter of debate. An epidemiological study defined specific language impairment (SLI) as having two of five language composite scores below the 10th centile and estimated the preschool prevalence of language impairment (LI) as approximately 7% of children (Tomblin et al., 1997), although the authors noted that a more stringent criterion would yield a much lower rate. In the same sample, speech delay was found in 3.6%, with a comorbidity (i.e., co-occurrence of two disorders) between persisting speech and language impairment of nearly 2%. Of those children with persisting language impairment, 5â8% had speech delay, and 11â15% of those with a persisting speech delay had a language impairment (Shriberg, Tomblin, & McSweeny, 1999).
It should be noted that the specific test battery used will affect findings, and some difficulties may be more obvious than others. For instance, more recent studies have shown that serious language impairments are not always obvious in children who have good phonological ability (i.e., ability to analyze speech sounds) and appear, superficially, at least, to read well (Nation, Clarke, Marshall, & Durand, 2004; Spaulding, Plante, & Farinella, 2006). Persistent severe delay in receptive or expressive language skills is likely to have predictive significance; degree of parental concern may also be a very good guide to severity of problem.
CLASSIFYING SPEECH AND/OR LANGUAGE PROBLEMS
Speech and language problems may be classified in terms of the area of impairment:
- receptive language (understanding)
- expressive language
- speech (articulation)
- dysfluency
- other.
These are not mutually exclusiveâindeed, it is common to find more than one aspect of communicative functioning to be impaired.
Speech and language problems can also be classified in terms of underlying causesâthat is, etiology. Exhibit 1.1 lists factors that are associated with increased risk of speech or language impairment in children. Some problems are secondary to etiologies such as deafness, motor disorder, structural palatal problem, acquired brain disorder, and so forth. These causal factors are discussed in greater detail below. In other cases, the language disorder occurs in the context of a more complex syndrome, such as autistic dis order.
The disorder is regarded as primary where no obvious underlying etiology is detected and the language impairment is not part of another recognized syndrome. Primary problems are referred to as specific LI and are of two main types:
- Affecting structural aspects of language: lexical knowledge, syntax, and phonology. This may be manifested as an auditory processing deficit, difficulties with word retrieval and output, and dyspraxic speech impairments. Receptive and/or expressive components may be variably affected.
- Affecting mainly pragmatics and abstract understanding, also sometimes called âhigher order functions.â This may be manifested in social communication difficulties and problems comprehending and producing language beyond the here and now.
The term specific language impairment refers to the fact that the language impairment is disproportionate in relation to other aspects of development, especially nonverbal ability. However, it does not entail that the child is free from other problems. It is common to find associated impairments in motor skills, cognitive function, attention, and reading in children who meet criteria for specific language impairment (Hill, 2001).
EXHIBIT 1.1 : Factors associated with increased risk of speech or language impairment in children
Etiologies leading to secondary speech and language impairment
- hearing impairment
- genetic disorders (e.g., sex chromosome trisomies, 22q deletion)
- prenatal exposure to substances such as antiepileptic drugs, alcohol, narcotics
- acquired epileptic aphasia
- acquired disorders resulting from neurological damage (e.g., strokes)
- oromotor structural defects (e.g., cleft palate)
- motor dysfunction of central origin (e.g., cerebral palsy, cortical dysplasia, cerebellar hypoplasia) or of peripheral origin (neuromuscular disorders)
- impoverished environment socially and linguistically (has to be severely impoverished and/or in association with other factors)
Syndromes in which speech or language impairments are associated and often presenting symptoms
- autism spectrum disorder
- general learning difficulty (mental retardation)
- anxiety disorder associated with mutism
Factors associated with primary speech and language impairment
- male gender
- family history of speech and language problems
- specific learning disability affecting literacy acquisition
ROLE OF PRIMARY CARE PROFESSIONALS
Several professionals and disciplines need to be involved in the strategic planning of appropriate referral pathways for children with speech and language problems and in the clinical assessment.
Screening
Screening of speech and language problems as a population-based public health activity is not currently recommended in the United Kingdom or the United States. For screening to be feasible, it is necessary, first, to have screening tools that are sensitive and specific enough to detect children with problems and, second, to have an effective treatment in place for those who are identified. Neither requirement is currently met. Nelson, Nygren, Walker, and Panoscha (2006), in a review for the US taskforce, concluded that there was insufficient research to draw conclusions on whether to screen or enhance professional and parental surveillance, which tests to use, and which ages to test. Research on the effectiveness and outcome of early intervention is also limited.
The task of the primary care practitioner is to enable concern about a childâs speech and language development on the part of a parent or professional to be dealt with promptly and to be clear about local referral pathways. As a first step, any child with suspected speech and language delay should be referred for hearing testing.
If the problem is confined to speech and language, the child should usually be managed by the speech and language therapist. A general developmental screening questionnaireâfor example, the parent-completed Early Developmental Checklist (Glascoe & Robertshaw, 2006), which inquires about a range of development areasâmay be helpful in eliciting parental concerns systematically. If a more wide-ranging developmental delay is suspected, indicated by report of a problem in more than one area of development, or if there are concerns about social and communicative skills, the child should be referred to the Child Development Team (CDT) for a multiprofessional assessment.
Population screening for autism is not recommended in the United Kingdom (National Initiative for Autism Screening and Assessment, 2003), but awareness of the alerting signs of an autism spectrum disorder is recommended (see Exhibit 1.2) and should prompt referral to the CDT.
ROLE OF THE SPEECH AND LANGUAGE THERAPIST
Who is referred to speech-language therapists (SLTs) will be influenced by locality as well as other considerations. For instance, 8.4% of children had been referred to speech therapy by the age of 3 in the UK CHAT (Checklist for Autism) project (Baird et al., unpublished data from a general population cohort in South East England), yet Broomfield and Dodd (2004) estimated that in the United Kingdom, as many as 14.6% of children per birth year may be referred to speech and language therapy services in areas of social deprivation.
The first priorities of assessment are to:
- establish the nature of parental or other professional concerns;
- assess the type and impact of the speech/language problem;
- assess the severity of the problem;
- decide whether there are other developmental and/or emotional/behavioral problems;
- decide
- who needs âwatchful waiting and reviewâ
- who needs active treatment
- whether the problem is more complex because of other developmental/behavioral problems and needs further assessment, or
- whether there is no significant problem.
EXHIBIT 1.2 : Symptoms suggestive of autistic spectrum disorder
- Language delay: no babble or pointing or other gesture by 12 months, no single words by 16 months, no nonechoed 2-word phrases by 24 months
- Regression: loss of skills at any time
- Communication: delays in speech and l...
