Specific language impairment

Specific language impairment (SLI) is diagnosed when a child's language does not develop normally and the difficulties cannot be accounted for by generally slow development, physical abnormality of the speech apparatus, autism spectrum disorder, acquired brain damage or hearing loss. Twin studies have shown that it is strongly genetic. Usually, language impairment is resulted from mutation in genes.

Specific language impairment (SLI) is diagnosed when a child has delayed or disordered language development for no apparent reason. Usually the first indication of SLI is that the child is later than usual in starting to speak and subsequently is delayed in putting words together to form sentences. Spoken language may be immature. In many children with SLI, understanding of language, or receptive language, is also impaired, though this may not be obvious unless the child is given a formal assessment.

Although difficulties with use and understanding of complex sentences are a common feature of SLI, the diagnostic criteria encompass a wide range of problems, and for some children other aspects of language are problematic (see below). In general, the term SLI is reserved for children whose language difficulties persist into school age, and so it would not be applied to toddlers who are late to start talking, most of whom catch up with their peer group after a late start.

The terminology for children’s language disorders is extremely wide-ranging and confusing, with many labels that have overlapping but not necessarily identical meanings. In part this confusion reflects uncertainty about the boundaries of SLI, and the existence of different subtypes. Historically, the terms ‘’developmental dysphasia’’ or ‘’developmental aphasia’’ were used to describe children with the clinical picture of SLI. These terms have, however, largely been abandoned, as they suggest parallels with adult acquired aphasia. This is misleading, as SLI is not caused by brain damage.

In medical circles, terms such as specific developmental language disorder are often used, but this has the disadvantage of being wordy, and is also rejected by some people who think SLI should not be seen as a ‘disorder’. In the UK educational system, speech, language and communication needs (SLCN) is currently the term of choice, but this is far broader than SLI, and includes children with speech and language difficulties arising from a wide range of causes.

Although most experts agree that children with SLI are quite variable, there is little agreement on how best to subtype them. There is no widely accepted classification system. In 1983 Rapin and Allen proposed a classification of developmental language disorders based on the linguistic features of language impairment, which was subsequently updated by Rapin. Note that Rapin is a child neurologist, and she refers to different subtypes as ‘syndromes’; many of those coming from the perspective of education or speech-language therapy reject this kind of medical label, and argue that there is not a clear dividing line between SLI and normal variation. Also, although most experts would agree that children with characteristics of the Rapin subtypes can be identified, there are many cases who are less easy to categorise, and there is also evidence that categorisation can change over time.

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