Developmental language disorder
Developmental language disorder is identified when a child has problems with language development that continue into school age and beyond. The language problems have a significant impact on everyday social interactions or educational progress, and occur in the absence of autism spectrum disorder, intellectual disability, or a known biomedical condition. The most obvious problems are difficulties in using words and sentences to express meanings, but for many children, understanding of language is also a challenge. This may not be evident unless the child is given a formal assessment.
Recent work has moved toward standardising terms for children's language difficulties. In 2017, the CATALISE consortium recommended adopting "developmental language disorder" for a subset of language disorder within the broader category of speech, language, and communication needs, with the aim of clearer communication, greater public awareness, and improved access to services. Earlier labels such as "developmental dysphasia" and "developmental aphasia" were discouraged because they suggest parallels with adult, brain-injury related conditions. The North American term "specific language impairment" was also judged too narrow, as it focused on language in isolation and did not account for other difficulties that may co-occur.
Classification
Terminology
The term developmental language disorder was endorsed in a consensus study involving a panel of experts in 2017. The study was conducted in response to concerns that a wide range of terminology was used in this area, with the consequence that there was poor communication, lack of public recognition, and in some cases children were denied access to services. Developmental language disorder is a subset of language disorder, which is itself a subset of the broader category of speech, language and communication needs.The terminology for children's language disorders has been extremely wide-ranging and confusing, with many labels that have overlapping but not necessarily identical meanings. In part this confusion reflected uncertainty about the boundaries of DLD, and the existence of different subtypes. Historically, the terms "developmental dysphasia" or "developmental aphasia" were used to describe children with the clinical picture of DLD. These terms have, however, largely been abandoned, as they suggest parallels with adult-acquired aphasia. This is misleading, as DLD is not caused by brain damage.
Although the term DLD has been used for many years, it has been less common than the term specific language impairment, which has been widely adopted, especially in North America. The definition of SLI overlaps with DLD, but was rejected by the CATALISE panel because it was seen as overly restrictive in implying that the child had relatively pure problems with language in the absence of any other impairments. Children with such selective problems are relatively rare, and there is no evidence that they respond differently to intervention, or have different causal factors, from other children with language problems.
In the UK education system, the term "speech, language and communication needs" is widely used, but this is far broader than DLD, and includes children with speech, language and social communication difficulties arising from a wide range of causes.
The question of whether to refer to children's language problems as a 'disorder' was a topic of debate among the CATALISE consortium, but the conclusion was that 'disorder' conveyed the serious nature and potential consequences of persistent language deficits. It is also parallel with other neurodevelopmental conditions and consistent with diagnostic frameworks such as the DSM-5 and ICD-11. Where there are milder or more transient difficulties, 'language difficulties' may be a more appropriate term.
Areas of language difficulty
DLD can affect a range of areas of language and the degree of impairment in different areas of language can vary from child to child. However, although there have been attempts to define different subtypes, these have not generally resulted in robust categories. The recommendation of the CATALISE panel was that the specific areas of impairment should be assessed and documented for individual children, while recognizing that different children might have different combinations of problems. The areas which can be affected are:- Grammar – This involves the ability to combine words into grammatically correct sentences and to combine parts of words together such as adding grammatical endings to verbs like -ing or -ed or to add prefixes and suffixes like dis- or -ation. These different aspect of grammar are processed in the ventral stream in the same hemisphere, but in different parts of the brain: morphology is processed in the left anterior middle temporal gyrus and left anterior inferior temporal sulcus, and syntax is processed right below. This demonstrates the complexities of grammatical structure processing in the brain. A child with DLD might make certain grammar mistakes. For instance, a child may say 'me jump here', instead of 'I jumped here'. Comprehension of sentences can also be affected. For instance, there may be difficulty understanding meaning expressed by word order, and so confusion about what is blue in a sentence like 'the pencil on the shoe is blue', and a tendency to use general knowledge rather than linguistic cues to meaning, or problems in interpreting grammatical markers of number or tense.
- Semantics – This refers to children's ability to understand the meaning of words and how meanings are expressed by combining words together. Semantic processing mainly happens in the left inferior frontal gyrus. Children with DLD often have limited vocabulary and may make heavy use of a small set of words with rather general meanings. Children with developmental language disorder often struggle with lexical ambiguity—polysemous words such as "cold", which can denote low temperature, illness, or social distance. In autism spectrum disorder, research reports difficulties with possessive pronouns and with plural morphology. Some learners avoid plural inflection and instead use a singular noun with a numeral or plural quantifier.
- Word finding – Children with word finding difficulties may know a word, but have difficulty accessing it for production – similar to the tip of the tongue phenomenon. It reflects the inability to access specific lexical items for production, despite awareness of their existence within the mental lexicon. It is a common feature in developmental language disorders, in which children have trouble retrieving words during conversation and other expressive tasks. These problems can affect expressive vocabulary, disrupt narrative coherence, and impair social communication, and they vary across individuals—from occasional lapses to persistent retrieval deficits.
- Pragmatics – Pragmatics refers to the ability to select the appropriate message, or interpret what others say, in relation to context. It is affected by right hemisphere brain damage. Pragmatic difficulties can give an impression of oddity, with the content of language not fitting the environmental or social context; comprehension may be over-literal; the child may chatter incessantly, be poor at turn-taking in conversation and maintaining a topic.
- Discourse – Discourse refers to a level of organization of language beyond the sentence. A child with limitations in this domain may have limited ability to tell a story or describe a set of events in a logical sequence.
- Verbal memory and learning – Problems with remembering words or sentences can affect both the learning of new vocabulary, and the understanding of long or complex sentences. Young children with DLD may say their first words later than other children. It may also take children with DLD longer to learn and remember novel words. This is due to the effect of DLD on declarative memory.
- Phonology – Phonology is the branch of linguistics concerned with the way sounds are combined in words. Phonological information is stored in the superior temporal sulcus. Children with difficulties with phonology may fail to distinguish between certain speech sounds, such as 't' and 'k', so that 'cake' is produced as 'tate'. Such difficulties are not unusual as part of typical development in toddlers, but they would usually resolve by the time children are 4–5 years old. Difficulties with producing some speech sounds accurately may reduce intelligibility of speech. In addition, more subtle difficulties in recognizing specific sounds in words can lead to literacy difficulties.
Relationship with speech disorders
Although speech disorders can be distinguished from language disorders, they can also co-occur. When a child fails to produce distinctions between speech sounds for no obvious reason, this is typically regarded as a language problem affecting the learning of phonological contrasts. The classification of and terminology for disorders of speech sound production is a subject of considerable debate. In practice, even for those with specialist skills, it is not always easy to distinguish between phonological disorders and other types of speech production problem.
Speech sound disorder is any problem with speech production arising from any cause.
Speech sound disorders of unknown cause that are not accompanied by other language problems are a relatively common reason for young children to be referred to speech-language therapy. These often resolve by around 4–5 years of age with specialist intervention, and so would not meet criteria for DLD. Where such problems continue beyond five years of age, they are usually accompanied by problems in broader language domains and have a poorer prognosis, so a diagnosis of DLD with speech sound disorder is then appropriate.