Changing terminology for children's language disorders: reflections on special issue of Perspectives of the ASHA Special Interest Groups

In 2016-7, I joined with expert colleagues to try to tackle the thorny issue of terminology for children who had difficulties speaking or understanding in their native language. This was incredibly challenging: we had a panel of 57 experts, moderated by Maggie Snowling and me, engage in a Delphi process, whereby we iteratively rated and commented on statements to do with identification and diagnosis to converge on a set of recommendations (Bishop et al., 2016; 2017). There was substantial disagreement between experts, who came from a range of disciplines and nationalities, but the one thing we agreed upon was that the current situation – of a plethora of different terms being used with various meanings – was doing a grave disservice to families and their children affected by language problems. There was a lack of recognition of language problems among professionals and the general public, as well as a paucity of research relative to other conditions of similar severity and prevalence. Eventually we converged on a recommendation that the term 'Developmental Language Disorder' (DLD) should be used to describe children with persistent problems with language expression or reception that had no obvious cause, and that impacted on everyday life.

Publication of the 2017 recommendations had considerably greater impact than I had anticipated, thanks to the generally enthusiastic take-up of the new terminology, which has been adopted by professional organisations in the UK, Ireland and Australia. A brief summary of the salient points was written by Susan Ebbels for the Royal College of Speech and Language Therapists.

Following the publication of the CATALISE papers, big changes have happened just in a couple of years:

• The terminology has stimulated development of grassroots advocacy, with campaigns to promote awareness of DLD adopting ingenious and innovative methods to publicise events. See e.g. here.
• The DLD label has raised awareness that this is a life-long condition*. Adults with DLD have started to talk about their experiences on social media (e.g. here). 
• Figures on terminology from Web of Science show that DLD is starting to overtake the term 'Specific Language Impairment' in published papers.
   



Figure 1: N publications with full term 'Specific Language Impairment' or 'Developmental Language Disorder' in the Topic field; data from Web of Science


Nevertheless, despite these positive developments, not everyone has been convinced that adoption of DLD is a good thing. This is not surprising: a couple of years ago, I reflected on some of the reasons why this particular topic is a terminological minefield (Bishop, 2017). It is difficult to balance the pros and cons of new terminology, especially when one is dealing with a condition that is heterogeneous, changes with age, can co-occur with many other problems, and is of relevance to several professions with very different perspectives, in particular speech-language therapists/pathologists, educators and medics.

Resistance to new terminology appears to be strongest in the USA, with the American Speech-Language-Hearing Association being particularly cautious about replacing the term Specific Language Impairment with DLD. This week they published a set of papers by individuals with different viewpoints on the topic, and reading through this I was reminded of many of the debates we had in the course of our Delphi exercises. The special issue includes a  tutorial overview by Karla McGregor and colleagues (McGregor et al., 2020), who summarise the background to the CATALISE project, and subsequent developments. They are supportive of DLD, not least because of the way the new terminology has boosted the profile of children's language problems and stimulated greater efforts towards advocacy. But we need to take seriously the concerns of those who have doubts.

Two authors in particular, Larry Leonard and Mabel Rice, were concerned that if we adopt DLD as the preferred term, decades of research on SLI would be ignored and ultimately forgotten. Both of them have made major lifetime contributions to the field, and so their concerns are understandable. It is vital that we heed Larry's advice (Leonard, 2020) to ensure that we include the search term SLI as well as DLD when drawing together relevant literature, to ensure valuable work from previous decades is not lost.

A related issue is that, although they overlap, SLI and DLD are not identical. In general, DLD is a more inclusive term, as it does not require that nonverbal IQ is 85 or over (although it does exclude cases of intellectual disability**), and it is compatible with the presence of other neurodevelopmental disorders, especially developmental co-ordination disorder and attention-deficit-hyperactivity disorder. Rice (2020) remains strongly opposed to the use of DLD, mainly because this would entail including children with nonverbal IQs below 85 (who were termed cases of nonspecific language impairment, or NLI, in a big epidemiological study, the Iowa study). Yet this stance is hard to reconcile with her view that nonverbal ability is independent of language. She spends several paragraphs presenting evidence that it is possible to have low nonverbal ability and good language, or high nonverbal ability and poor language, culminating in the statement: 'The common assumption that children with SLI are not very smart is unwarranted, as is the assumption that all children with strong language aptitude are smart.' It is unclear to whom she is referring as making this 'common assumption'. A major reason why the CATALISE group decided to drop 'cognitive referencing' in defining DLD was because the bivariate distribution of nonverbal IQ and language demonstrates rather a weak association – just as she claims - but this makes it clear that any division into those above and below an IQ threshold is arbitrary (see Figure 2). Just to be absolutely clear, in proposing we do away with nonverbal IQ criteria for DLD, the CATALISE consortium were not saying that children with SLI are 'not very smart'. We were saying that they key thing is what your language is like, and that nonverbal ability is largely irrelevant when making that judgement.

Figure 2: Language composite measure plotted against non‐verbal IQ for 603 eight‐year‐old children in the Iowa study. Figure from Reilly et al (2014). Blue points correspond to SLI, and green points to NLI. NB Axes resized to address criticism by Rice (2020), who found the scaling misleading.

Rice goes on to argue that we need to study children's mastery of specific grammatical markers over time to get a precise measure of children's language in SLI, yet she then goes on to present data showing that children with NLI are also identified by low scores on those markers. Although she claimed a difference in language profiles, this was not evident from the data she presented, and in general, most studies that have looked for qualitative differences between NLI and SLI have failed to find these (see also further evidence from McGregor et al, 2020). Rice maintains that only by sticking with SLI would we find sufficiently clear findings to advance our understanding, and that if we adopt less precise categories, this will lead to muddying of the waters and less replicable results. I regard this as a hypothesis that can be tested, but for which there is currently no good evidence. In fact, it was the failure to find such evidence in my own studies 25 years ago that led me to start to question the construct of SLI (Bishop, 1994).

Larry Leonard makes the sensible suggestion that if we study DLD we should also provide data on which children would meet the more restrictive definition of SLI:  this would, in fact, allow us to test Rice's hypothesis. The best way to do this, and to build on prior studies with SLI would be to make raw data open (see Meyer, 2018), so that results can be analysed to investigate the extent to which findings depend on levels of nonverbal ability, attention, motor skills and so on. There is already precedent for this with the EpiSLI database from the Iowa study (Tomblin, 2010) – this includes data on children who would meet broader DLD criteria as well as more selective SLI cases. This way we could investigate empirically the impact of the choice of criteria, rather than just asserting that one classification approach is better than the other.

I turn next to the other commentary that is predominantly negative about a change of criteria to DLD, that by Murza and Ehren (2020). Their perspective is diametrically opposed to that of Rice. They explain that for speech-language pathologists (SLPs) working in the school system, there is a mismatch between what is taught in their university courses (including diagnosis of SLI) and what they experience in the classroom. There were some parallels here with the views of education experts on the CATALISE panel, some of whom felt the whole debate about labels was irrelevant, and would empathise with the view that: 'No matter the label, students should receive the services they need, and no label should drive services'. But, as Murza and Ehren recognise, labels are needed to demonstrate eligibility for services, and in the USA, this is determined by the Individuals with Disabilities Education Act (IDEA), which has its own set of labels: these don't include either SLI or DLD. I felt a sense of despair coming through from this article, as the authors documented the confusing array of possible terms they could use, each of which had an operational definition, but with that definition varying from one state to another. The impression was that SLPs in US education are up against a massive, unbending bureaucracy that they had to negotiate in order to deliver services to a subset of the children that might benefit from them. In principle, yes, it would be nice to have some consistent terminology that mapped on to the population they were serving, but their conclusion was that they lacked the time, money, energy and focus to embark on a campaign to adopt new labels. This was a considerably more sober and downbeat chapter than that of Rhea Paul, who regarded DLD as potentially compatible with IDEA criteria, and a useful focus for advocacy efforts. 

When discussing relevance of labels for SLP practitioners, another issue concerned insurance eligibility. Karla McGregor reported that she had been told by an insurer: 'If a child just isn't talking or not talking clearly - it is not covered'. The authors also noted a common concern that the term Developmental would be interpreted by insurers, and perhaps others, as implying that the condition would improve of its own accord. But SLPs should not take these kinds of responses lying down: it is grossly inequitable if insurers are willing to pay for a condition such as ADHD or Developmental Co-ordination Disorder, but not for speech-language therapy for a child with DLD. The arguments can and should be made, and it is hoped that the growing awareness of, and advocacy for DLD will empower US SLPs to be more proactive in demanding that children with language disorders are taken seriously and given the support they need.

* Damian Quinn, a man with DLD, has written an autobiography. The timing in relation to CATALISE is probably co-incidental, but this will help with growing awareness that children with DLD do not disappear when they become adults!

** The introductory article for the special issue stated that DLD is used for children 'with or without intellectual disability'. This is wrong. Where the child meets criteria for intellectual disability, the diagnosis would be Language Disorder associated with Intellectual Disability.

P.S. (24 Feb 2020). All the materials from the CATALISE project, including anonymised ratings and comments from the 57 panel members, are available on Open Science Framework.

References

 Bishop, D. V. M. (1994). Is specific language impairment a valid diagnostic category? Genetic and psycholinguistic evidence. Philosophical Transactions of the Royal Society, series B, 346, 105-111. 

Bishop, D. V. M. (2017). Why is it so hard to reach agreement on terminology? The case of developmental language disorder (DLD). International Journal of Language & Communication Disorders, 52(6), 671-680. doi:10.1111/1460-6984.12335

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2016). CATALISE: a multinational and multidisciplinary Delphi consensus study. Identifying language impairments in children. . PLOS One, 11(7), e0158753. doi:doi:10.1371/journal.pone.0158753

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2017). Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. Journal of Child Psychology and Psychiatry, 58(10), 1068-1080. doi:10.1111/jcpp.12721

Leonard, L. B. (2020). A 200-year history of the study of childhood language disorders of unknown origin: changes in terminology. Perspectives of the ASHA Special Interest Groups, 5(1), 6-11. doi:https://doi.org/10.1044/2019_PERSP-SIG1-2019-0007

McGregor, K. K., Goffman, L., Owen Van Horne, A., Hogan, T. P., & Finestack, L. H. (2020). Developmental Language Disorder: Applications for advocacy, research, and clinical service. Perspectives of the ASHA Special Interest Groups, 5(1), 38-46. doi:https://doi.org/10.1044/2019_PERSP-19-00083

Meyer, M. N. (2018). Practical tips for ethical data sharing. Advances in Methods and Practices in Psychological Science. doi:https://doi.org/10.1177/2515245917747656

Murza, K. A., & Ehren, B. J. (2020). Considering the language disorder label debate from a school speech-language pathology lens. Perspectives of the ASHA Special Interest Groups, 5(1), 47-54. doi:https://doi.org/10.1044/2019_PERSP-19-00077

Paul, R. (2020). Children's language disorders: What's in a name. Perspectives of the ASHA Special Interest Groups, 5(1), 30-37. doi:https://doi.org/10.1044/2019_PERS-SIG1-2019-0012

Rice, M. (2020). Clinical lessons from studies of children with Specific Language Impairment. Perspectives of the ASHA Special Interest Groups, 5(1), 12-29. doi:https://doi.org/10.1044/2019_PERSP-19-00011

Reilly, S., Tomblin, B., Law, J., McKean, C., Mensah, F. K., Morgan, A., . . . Wake, M. (2014). Specific language impairment: a convenient label for whom? International Journal of Language & Communication Disorders, 49(4), 416-451. doi:10.1111/1460-6984.12102

Tomblin, J. B. (2010). The EpiSLI database: a publicly available database on speech and language. Lang Speech Hear Serv Sch, 41(1), 108-117.

Developmental language disorder: the need for a clinically relevant definition

There's been debate over the new terminology for Developmental Language Disorder (DLD) at a meeting (SRCLD) in the USA. I've not got any of the nuance here, but I feel I should make a quick comment on one issue I was specifically asked about, viz:

As background: the field of children's language disorders has been a terminological minefield. The term Specific Language Impairment (SLI) began to be used widely in the 1980s as a diagnosis for children who had problems acquiring language for no apparent reason. One criterion for the diagnosis was that the child's language problems should be out of line with other aspects of development, and hence 'specific', and this was interpreted as requiring normal range nonverbal IQ (nviq).

The term SLI was never adopted by the two main diagnostic systems -WHO's International Classification of Diseases (ICD) or the American Psychiatric Association's Diagnostic and Statistical Manual (DSM), but the notion that IQ should play a part in the diagnosis became prevalent.

In 2016-7 I headed up the CATALISE project with the specific goal of achieving some consensus about the diagnostic criteria and terminology for children's language disorders: the published papers about this are openly available for all to read (see below). The consensus of a group of experts from a range of professions and countries was to reject SLI in favour of the term DLD.

Any child who meets criteria for SLI will meet criteria for DLD: the main difference is that the use of an IQ cutoff is no longer part of the definition. This does not mean that all children with language difficulties are regarded as having DLD: those who meet criteria for intellectual disability, known syndromes or biomedical conditions are treated separately (see these slides for summary).

The tweet seems to suggest we should retain the term SLI, with its IQ cutoff, because it allows us to do neatly controlled research studies. I realise a brief, second-hand tweet about Rice's views may not be a fair portrayal of what she said, but it does emphasise a bone of contention that was thoroughly gnawed in the discussions of the CATALISE panel, namely, what is the purpose of diagnostic terminology? I would argue its primary purpose is clinical, and clinical considerations are not well-served by research criteria.

The traditional approach to selecting groups for research is to find 'pure' cases - quite simply, if you include children who have other problems beyond language (including other neurodevelopmental difficulties) then it is much harder to know how far you are assessing correlates or causes of language problems: things get messy and associations get hard to interpret. The importance of controlling for nonverbal IQ has been particularly emphasised over many years: quite simply, if you compare language-impaired vs comparison (typically-developing, or td) children on a language or cognitive measure, and the language-impaired group has lower nonverbal ability, then it may be that you are looking at a correlate of nonverbal ability rather than language. Restricting consideration to those who meet stringent IQ criteria to equalise the groups is one way of addressing the issue.

However, there are three big problems with this approach:

1. A child's nonverbal IQ can vary from time to time and it will depend on the test that is used. However, although this is problematic, it's not the main reason for dropping IQ cutoffs; the strongest arguments concern validity rather than reliability of an IQ-based approach.

2. The use of IQ-cutoffs ignores the fact that pure cases of language impairment are the exception rather than the rule. In CATALISE we looked at the evidence and concluded that if we were going to insist that you could only get a diagnosis of DLD if you had no developmental problems beyond language, then we'd exclude many children with language problems (see also this old blogpost). If our main purpose is to get a diagnostic system that is clinically workable, it should be applicable to the children who turn up in our clinics - not just a rarefied few who meet research criteria. An analogy can be drawn with medicine: imagine if your doctor identified you with high blood pressure but refused to treat you unless you were in every other regard fit and healthy. That would seem both unfair and ill-judged. Presence of co-occurring conditions might be important for tracking down underlying causes and determining a treatment path, but it's not a reason for excluding someone from receiving services.

3. Even for research purposes, it is not clear that a focus on highly specific disorders makes sense. An underlying assumption, which I remember starting out with, was the idea that the specific cases were in some important sense different from those who had additional problems. Yet, as noted in the CATALISE papers, the evidence for this assumption is missing: nonverbal IQ has very little bearing on a child's clinical profile, response to intervention, or aetiology. For me, what really knocked my belief in the reality of SLI as a category was doing twin studies: typically, I'd find that identical twins were very similar in their language abilities, but they sometimes differed in nonverbal ability, to the extent that one met criteria for SLI and the other did not. Researchers who treat SLI as a distinct category are at risk of doing research that has no application to the real world.

There is nothing to stop researchers focusing on 'pure' cases of language disorder to answer research questions of theoretical interest, such as questions about the modularity of language. This kind of research uses children with a language disorder as a kind of 'natural experiment' that may inform our understanding of broader issues. It is, however, important not to confuse such research with work whose goal is to discover clinically relevant information.

If practitioners let the theoretical interests of researchers dictate their diagnostic criteria, then they are doing a huge disservice to the many children who end up in a no-man's-land, without either diagnosis or access to intervention. 

References

Bishop, D. V. M. (2017). Why is it so hard to reach agreement on terminology? The case of developmental language disorder (DLD). International Journal of Language & Communication Disorders, 52(6), 671-680. doi:10.1111/1460-6984.12335

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2016). CATALISE: a multinational and multidisciplinary Delphi consensus study. Identifying language impairments in children. PLOS One, 11(7), e0158753. doi:10.1371/journal.pone.0158753

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2017). Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. Journal of Child Psychology and Psychiatry, 58(10), 1068-1080. doi:10.1111/jcpp.12721

Labels for unexplained language difficulties in children: We need to talk

The view from the Tower of Babel

This week saw the publication of a special issue of the International Journal of Language and Communication Disorders, focusing on labels for children with unexplained language difficulties. Two target articles, one by Sheena Reilly and colleagues, and one by me, are accompanied by an editorial by Susan Ebbels, twenty commentaries, and a final paper where Sheena and I join forces with Bruce Tomblin to try to synthesise the different viewpoints. These articles are free for anyone to access.

Terminological battles are often boring and seldom come to any consensus, so why are we putting time into this thorny issue? Quite simply, because it really matters. As we argue in the articles, having a label affects how a children are perceived, what help they are offered, and how seriously their problems are taken. 'Specific Language Impairment' has very poor name recognition compared to dyslexia and autism, despite being at least as common. Furthermore, unless we can agree on some common language, it's difficult to make progress in research, and to discover, for instance, the underlying causes of language difficulties, how common they are in different parts of the world, or what interventions work.

I was first confronted with the full extent of the problem when I tried to analyse the amount of research and research funding associated with different developmental disorders (Bishop, 2010). There are other conditions, notably autism and dyslexia, where there is plenty of debate about diagnostic criteria, or even about whether the condition exists. But even so, the terminology is reasonably consistent. For children's language difficulties, this is not the case - they can be described as cases of language difficulty, disorder, impairment, disability, needs or delay, with various prefixes such as 'developmental', 'specific' or 'primary'. Some researchers will use such labels with precise meanings, often excluding children who have co-existing conditions, whereas others use them more descriptively. This made it extremely difficult to do a sensible internet search to estimate the amount of research funding associated with children's language difficulties.  

The confusion over labels has, I think, also contributed to the lack of public recognition of language difficulties in children. A couple of years ago, I joined together with Courtenay Norbury, Maggie Snowling, Gina Conti-Ramsden and Becky Clark with the goal of remedying this situation. We started a campaign for Raising Awareness of Language Learning Impairments (RALLI) (Bishop et al., 2012), and set up a YouTube channel to provide basic information. We spent some time debating what terminology to use: "Language learning impairment" was our preferred choice, but many of our videos talk of Specific Language Impairment, simply because that is a more familiar label. The lack of an agreed label proved a real stumbling block for our attempts at public engagement, and we decided that, as well as producing videos, one of our goals would be to get the terminology issue discussed more widely, in the hope of achieving some consensus. It was a very happy coincidence that Sheena Reilly and colleagues were crystallizing their own position on this question in an article in IJLDC, and that they, and the Editors, were willing to include my article, and the commentaries of other RALLI founders, in the published debate.

One thing that came across when reading commentaries on our articles was the disconnect between research and practice. One point on which I agree with Sheena and colleagues is that there is no justification for drawing a distinction between children whose language problems are comparable with below average nonverbal ability, and those who have a mismatch between good nonverbal skills and low language. Research has failed to find any difference between children with uneven or even nonverbal-verbal profiles in terms of responsiveness to intervention or underlying causes. Such a distinction is, however, widely used in educational and clinical settings to decide which children gain access to extra support in school.  Another issue raised by the Reilly et al paper is whether it is logical to use other exclusionary criteria, and to distinguish, for instance, between children who do and don't have autistic features in association with a language problem.  

As Susan Ebbels noted in her editorial, in everyday settings "diagnostic labels and criteria were being used creatively in disputes over access to services both by those seeking to obtain services for children (often parents and their lawyers) who could be accused of ‘diagnostic shopping’ and also by those seeking to deny services (often due to financial constraints) who may use particularly restrictive criteria in order to reduce the number of children qualifying for services". 

We can't afford to ignore this confused situation any longer. The time has come to have a wider debate on these issues, with the aim of reaching a consensus about how terms are used. The Royal College of Speech and Language Therapists has set up a moderated discussion forum where people can give their views on the best way forward. Please do consider adding your voice: it is important that all those affected by this issue have a say, whether you are a speech-language therapist/pathologist, psychologist, teacher, health professional, legal expert, policymaker, a parent of a child with language difficulties, or someone who has experienced language difficulties. We'd also love to hear from those outside the UK - whether English-speaking or not. You can access the discussion forum here.

Finally, to raise awareness of this debate, during the week of 24th-31st August I will be taking over  the @WeSpeechies Twitter handle as guest curator. On Tuesday 26th at 8.a.m. BST there will be a live twitter debate on this topic. Feel free to join in, even if you aren't a regular tweeter.

References
Bishop, D. (2010). Which Neurodevelopmental Disorders Get Researched and Why? PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0015112  
Bishop, D., Clark, B., Conti-Ramsden, G., Norbury, C., & Snowling, M. (2012). RALLI: An internet campaign for raising awareness of language learning impairments Child Language Teaching and Therapy, 28 (3), 259-262 DOI: 10.1177/0265659012459467

Slides on this topic are available here.

Addendum Friday 29th August 2014

We've had a great week of interactions on Twitter. A transcript for the week is available here.

I'll look through this and aim to organise the material in due course, but meanwhile would encourage anyone who is interested to continue the discussion on Twitter. I'm appending below some tweets that I generated throughout the week to generate debate.

As noted above, the chat links in to a special issue of the Internat. J Lang. Comm Dis which is free to access here http://t.co/ncTUaYvyoI.  NB it is not all that obvious but there are 10 commentaries after each target article.

If you want to join the discussion on Twitter, feel free to comment at any time, but, please include the #WeSpeechies hashtag, so we can aggregate comments easily. Also if your comment relates to a numbered question, please add Q1, etc so we can relate them.

Monday started with my attempt to summarise each of the  twenty commentaries in a Tweet-length message.

Summaries from commentaries

Paediatricn Gillian Baird: ICD &DSM classifications talk of 'language disorder'; implies distinct from normal variation.  Disorder’ used for conditions without obvious aetiology; functional effect described separately in ICFDH.

Lauchlan/Boyle, ed psych view. Must ask: ‘Will label change the child's life for the better? Aetiology often irrelevant

Bellair et al: community SALTs. No one label works for both research & clinical. SLI has problems but we can manage them.

Mabel Rice: "SLI has yet to receive widespread adoption in clinical practice, in spite of the great need for it." critical of DSM5: excluded "well-researched category of SLI", included SCD, "with a minimal research base"

Kate Taylor SLP. SLI underidentified. Changing the term won't resolve the issue, which is one of measurement rather than label.

Conti-Ramsden: Any Consensus Panel on terminology must be international and include voices from different languages,

Hansson et al: ICD10 labels don't map on to use by researchers in Sweden . : Sweden: phonological & grammatical difficulties seen as part of language impairment. Soc comm probs separate

Clark & Carter: Survey:Scottish SALTs unclear re terms & diagnostic criteria. Move from exclusionary to inclusionary criteria.

Hüneke & Lascelles http://t.co/9rVKJzoBZV. Concern that watering down terminology will mean kids lose scarce resources. Prefer medical term 'developmental dysphasia' that gets problems taken seriously

Strudwick/Bauer http://t.co/GSY5Xwz283 Concern that labels don't capture comorbidities; most ch with 'SLI' have other problems

Michael Rutter, psychiatrist "both clinical & research classifications needed but they require a different approach"

Rutter: Specific’ implies ‘pure’ language impairment; "not supported by any of the available evidence"

Larry Leonard: Many researchers already use broader definition of SLI: do not use term to mean children have a pure profile. communicatn with the public/other disciplines will be even harder if we adopt generic label ‘language impairment.

Snowling: DSM5 treats Communication Disorders separately from Specific Learning Disorders, yet they often co-occur

Aoife Gallagher,SALT; ethical issue:"who owns diagnosis once it has been given.. who ultimately has the right to take it away"

Andrew Whitehouse: ‘SLI’ provides neat criteria for researchers but label hides behavioural & aetiological heterogeneity

Dockrell/Lindsay Educational perspective re SLI is missing yet day-to-day support of learning/development provided by teachers. in England ‘speech, language & communication needs’ (SLCN) indicates primary need is with language & communication

Grist & Hartshorne: http://t.co/QKeQbQFsdy Children & young people we work with rarely describe selves as having SLI or SLCN

Norbury @lilaccourt Relaxing diag criteria will increase demand for services.SALTs shld focus on severe & persistent impairmts

Parsons et al @wordaware Shockwaves through SALT profession if nonverbal IQ criteria and delay/disorder distinction removed .Use of marketing approaches to development of a new term, including consultation with parents & young people.

Wright: legal perspective Much time spent in tribunal appeals arguing re labels: eg is it delay or disorder, is it specific?

Questions for debate

On Tuesday we had a live twitter chat with four question topics, and later in the week, I added further numbered question. Here is the total list – we'd love to hear your thoughts on any or all of these:

Q1 What is your view on use of the diagnostic label SLI? Does it reflect a medical model and is this appropriate.

Q2 is What are appropriate criteria for identifying children's language problems

Q3; Should IQ, ASD features, hearing loss determine whether language-impaired children can access services?

Q4 What terminology is most appropriate for children who have unexplained language problems?

Q5 ICD11 will use'Developmental Language Disorder' and DSM5 uses 'Language Disorder'. What do people think of these terms?

Q6 In research SLI still widely used but without requiring IQ discrepancy. Should we retain SLI but with this broader meaning, or is it just confusing?

Q7 In UK education, Speech, Language and Communication Needs (SLCN) is popular term. Is it used outside UK? Is it useful?

Q8 In UK clinical practice, distinction between language 'delay' & 'disorder' is used, but it has no research support.  Where does delay/disorder distinction come from? How defined?

Q9 Is there any support for a return to the more medical term 'developmental dysphasia'?

Q10. Reilly et al and several commentators suggest we drop 'Specific' and use the term 'Language Impairment' instead .What wld be advantages (e.g. avoids unfair exclusion) and disadvantages (e.g. too broad)?

Q11 What do people think of terms 'Language Learning Impairment' or 'Primary language impairment'? '

Q12 Do diagnostic labels actually help children and families?

Q13 Shld terminology/diagnostic criteria be responsibility of speechies, or shld other professions & families have a say? Assumptions/practices seem v. different in education/medicine/psychology vs speech-language therapy/pathology

Q14 In yr area, who does intervention with kids whose language problems are associated with autism?

Q15 Some  people take pride in identifying themselves as dyslexic. Does this ever happen for kids with language problems? If not, why not?

Q16 Has anyone encountered situation where child not offered intervention bcs language problems attributed to social deprivation?

Q17 Insurance considerations seldom important in UK, but affect label use elsewhere. Do US insurers just require DSM?

Overhyped genetic findings: the case of dyslexia

A press release by Yale University Press Office was recently recycled on the Research Blogging website*, announcing that their researchers had made a major breakthrough. Specifically they said "A new study of the genetic origins of dyslexia and other learning disabilities could allow for earlier diagnoses and more successful interventions, according to researchers at Yale School of Medicine. Many students now are not diagnosed until high school, at which point treatments are less effective." The breathless account by the Press Office is hard to square with the abstract of the paper, which makes no mention of early diagnosis or intervention, but rather focuses on characterising a putative functional risk variant in the DCDC2 gene, named READ1, and establishing its association with reading and language skills.

I've discussed why this kind of thing is problematic in a previous blogpost, but perhaps a figure will help. The point is that in a large sample you can have a statistically strong association between a condition such as dyslexia and a genetic variant, but this does not mean that you can predict who will be dyslexic from their genes.

Proportions with risk variants estimated from Scerri et al (2011)

In this example, based on one of the best-replicated associations in the literature, you can see that most people with dyslexia don't have the risk version of the gene, and most people with the risk version of the gene don't have dyslexia. The effect sizes of individual genetic variants can be very small even when the strength of genetic association is large.

So what about the results from the latest Yale press release? Do they allow for more accurate identification of dyslexia on the basis of genes? In a word, no. I was pleased to see that the authors reported the effect sizes associated with the key genetic variants, which makes it relatively easy to estimate their usefulness in screening. In addition to identifying two sequences in DCDC2 associated with risk of language or reading problems, the authors noted an interaction with a risk version of another gene, KIAA0319, such that children with risk versions in both genes were particularly likely to have problems.  The relevant figure is shown here.

Update: 30th December 2014 - The authors have published an erratum indicating that Figure 3A was wrong. The corrected and original versions are shown below and I have amended conclusions in red.

Corrected Fig 3A from Powers et al (2013)

Original Fig 3A from Powers et al (2013)

There are several points to note from this plot, bearing in mind that dyslexia or SLI would normally only be diagnosed if a child's reading or language scores were at least 1.0 SD below average.

1. For children who have either KIAA0319 or DCDC2 risk variants, but not both, the average score on reading and language measures is at most no more than 0.1 SD below average at most.
2. For those who have both risk factors together, some tests give scores that are from 0.2 to 0.3 SD below average, but this is only a subset of the reading/language measures. On nonword reading, often used as a diagnostic test for dyslexia, there is no evidence of any deficit in those with both risk versions of the genes. On the two language measures, the deficit hovers around 0.15 SD below the mean.
3. The tests that show the largest deficits in those with two risk factors are measures of IQ rather than reading or language. Even here, the degree of impairment in those with two risk factors together indicates that the majority of children with this genotype would not fall in the impaired range.
4. The number of children with the two risk factors together is very small, around 2% of the population.

In sum, I think this is an interesting paper that might help us discover more about how genetic variation works to influence cognitive development by affecting brain function. The authors present the data in a way that allows us to appraise the clinical significance of the findings quite easily. However, the results indicate that, far from indicating translational potential for diagnosis and treatment, genetic effects are subtle and unlikely to be useful for this purpose.

*It is unclear to me whether the Yale University Press Office are actively involved in gatecrashing Research Blogging, or whether this is just an independent 'blogger' who is recycling press releases as if they are blogposts.

Reference
Powers, N., Eicher, J., Butter, F., Kong, Y., Miller, L., Ring, S., Mann, M., & Gruen, J. (2013). Alleles of a Polymorphic ETV6 Binding Site in DCDC2 Confer Risk of Reading and Language Impairment The American Journal of Human Genetics DOI: 10.1016/j.ajhg.2013.05.008
Scerri, T. S., Morris, A. P., Buckingham, L. L., Newbury, D. F., Miller, L. L., Monaco, A. P., . . . Paracchini, S. (2011). DCDC2, KIAA0319 and CMIP are associated with reading-related traits. Biological Psychiatry, 70, 237-245. doi: 10.1016/j.biopsych.2011.02.005
 

Neuronal migration in language learning impairments: a suggestion

Specific language impairment (SLI) and dyslexia are related developmental disorders in which a child has difficulty learning to talk (SLI) or to read (dyslexia). Many children have both problems, although they can occur separately (Bishop & Snowling, 2004), and they are sometimes grouped together as ‘language learning impairments’. There's good evidence that genes are implicated in causing these conditions (Bishop, 2009).

A popular account maintains that the genes implicated in language learning impairments affect a very early process in the developing brain known as neuronal migration (Galaburda et al., 2006). It’s an attractive theory that has the potential to provide a link from genes to behaviour. However, when I looked at the evidence, I found myself not entirely convinced. Here I’ll briefly review research on this topic, explain my reservations, and conclude by proposing a study that needs doing. I’m not an expert in neuroanatomy or neuroimaging, so I’ll be interested to see if others think this proposal is sensible.

Abnormalities found in 1979 case report. Solid circles show ectopias/dysplasias, and shaded area shows micropolygyria (based on Galaburda et al, 1985) .

Over thirty years ago, Galaburda and Kemper published a post mortem study of the brain of a man with developmental dyslexia who died from an accidental fall at the age of 20 years. He’d had delayed language development, and was diagnosed with dyslexia in the first grade. His Stanford-Binet IQ of 105 was well in advance of his reading attainments. He developed epilepsy at 16 years of age. His brain showed areas of displaced neurons (ectopias) in the left cerebral hemisphere, especially around the left planum temporale. There was also an area of polymicrogyria, i.e. excessive number of small convolutions, giving a lumpy appearance to the cortex. This raised the possibility that we might find the origins of dyslexia not in the gross features of brain structure, but at the microscopic level, in the organisation of neurons. However, as the authors noted: “It is not possible to tell from a single case whether or not the anatomical findings have any causative relationship to the clinical findings – much less whether the malformation is responsible for the seizure disorder, the learning disability, both, or neither” (p. 99). They also noted that the kinds of neuroanatomical abnormality that they found in their patient were probably too rare to explain dyslexia in general, which has a prevalence of around 5-10% in the population.

A subsequent report added further evidence for a link to dyslexia (Galaburda et al, 1985). Similar abnormalities were found in three further post-mortem cases, and in none of these was epilepsy described, though one had delayed speech and one had “notable language difficulties”. Three additional cases, this time of female dyslexics, were reported by Humphreys et al (1990), but these were less compelling: the evidence for migrational abnormalities was less strong, and other pathologies could have been implicated.

There’s a general problem with the methodology of these studies, which is that they were not conducted blind. The cellular abnormalities that were described require an expert eye and clinical judgement, and you wouldn’t necessarily see them unless you were looking for them. Could they just be spurious findings? Galaburda and colleagues noted that similar anomalies are sometimes reported as incidental findings in unselected autopsy brains, and so a key question was whether the findings in dyslexic brains were really unusual. Accordingly, Kaufman and Galaburda (1989) analysed ten control brains using identical procedures to those used for dyslexic brains. They found abnormal cells in three control brains, but the anomalies were far less numerous than those seen in the dyslexic brains. This provides useful context, but ideally, we need a study where the neuroanatomist is given both dyslexic and control brains and asked to analyse them without knowing which was which, to avoid the perceptual and cognitive biases that can affect even the most scrupulous of observers.

The anomalies described by Galaburda and colleagues reflect disruption at an early stage of brain development, when neurons are being formed and organised into coherent structures. This website from Pasco Rakic has some nice animations showing how a brain is formed when neurons are first generated in the foetus. Neurons formed in the ventricular zone travel out to the surface of the cortex along radial glial fibres, gradually building up six distinct layers of the cortex from the inside out. Studies with rodents, and evidence from humans with developmental disorders, indicate that this process can be disrupted in a range of ways. In some people, a proportion of cells fail to migrate at all, and can be seen as clusters of abnormal cells around the ventricles. This condition, known as periventricular heterotopia, does not normally impair cognitive function but does cause epilepsy. In other cases, there is partial migration followed by arrest, leading to lissencephaly, typically associated with epilepsy and severe intellectual impairment(Guerrini& Parrini, 2010). In mice, a naturally-occurring genetic mutation leads to the phenotype of the reeler mouse, which has severe motor co-ordination problems linked to disorganisation of the usual laminar structure of the cortex, because the migrating neurons fail to penetrate to the surface of the brain. The cases studied by Galaburda and colleagues had a range of anomalies, described as ectopias, dysplasias, heterotopias, ‘brain warts’ and polymicrogyria, associated with disruption affecting different stages of neuronal migration and postmigrational development (Barkovich et al, 2012).

What makes this work exciting is a potential link to genetic studies of dyslexia. There are replicated associations of dyslexia with several genes, including DYX1X1, KIAA0319, DCDC2 and ROBO1. As Galaburda et al (2006) noted in their review, mutations of these genes have been linked to migrational anomalies in rodents. It looks, therefore, as though the route from brain to behaviour could be neatly explained by postulating a genetic influence on neuronal migration that leads to a brain that is not optimally connected.

Some puzzles, however, remain. First, the genetic variants associated with dyslexia are not mutations. They are common in the general population. Associations with dyslexia are found in studies with very large samples, but they are not very strong. For instance, one can deduce from the published data on the KIAA0319 locus that there is a low-risk version of the gene that is found in 39% of normal readers and 25% dyslexics, and a high-risk version that is found in 30% of normal readers and 35% dyslexics. If the dyslexic risk variant causes anomalies of neuronal migration, then we should see lots of people with those anomalies, many (most) of whom will not be dyslexic. Of course, it is all a matter of degree; it is possible that each risk variant has only minor effects on neuronal migration, and causes problems only if it occurs in conjunction with other genetic or environmental risks. Neuronal migration can be affected by environmental factors, such as toxins, nutrition, and disease or trauma affecting the brain. So the ubiquity of these risk alleles does not rule out a causal route via neuronal migration mechanisms, but it does make the story more complicated.

What if we look at the association between neuronal migration disorders and dyslexia from the other direction, i.e. assessing reading ability in individuals with known migrational abnormalities? Chang et al (2005) did this in people with periventricular nodular heterotopia - a disorder in which a proportion of neurons fail to migrate from the ventricular zone. Most of their participants had normal range IQ. On the Wide Range Achievement tests of reading and spelling, their mean scores were average or above-average. Many of them did, however, do poorly on the Nelson-Denny reading test and on this basis, the authors concluded they were dyslexic. But this test, which stresses speed, was designed for college students, not for the general population. The fact that most participants were older than college students, and all were on anti-epileptic medication, makes the claim of dyslexia in these people far from convincing. Minimally, this study should have included a comparison group to control for age, background and medication status.

A final issue is why migrational abnormalities haven’t been noted in MRI studies of dyslexia. In studies of children with specific language impairments, a Brazilian group has reported remarkably high rates of polymicrogyria (De Vasconcelos Hage et al, 2006). However, this does not seem to be a general explanation for SLI. My colleagues tell me there were no cases of this in people with SLI who participated in a recent MRI study that we published, and none was mentioned in a series reported by Webster etal (2008). MRI studies of dyslexia have been considerably more numerous, yet, as far as I can establish, none has mentioned migrational anomalies. Of course, many MRI studies focus on averaged data, which would mask individual variations. So, a key question is whether the failure to report migrational abnormalities in MRI studies is because (a) no-one was looking for them, (b) they are too subtle to see on regular MRI scan, or (c) they aren’t involved in most cases of language learning impairments.

I was intrigued by this question, so I looked for literature on detectability of neuronal migration anomalies on MRI scan. My impression is that these wouldn’t necessarily be detected unless you were looking for them, and if you were, detectability depends on the type and location of anomalies. Wagner et al (2011) devised an automated method of MRI analysis that was successful in picking up 82% of Type IIA cortical dysplasias and 92% of Type IIB, compared to 65% and 91% detected by an expert neuroradiologist. Periventricular nodular heterotopia seems a more obvious pathology that is routinely detected on MRI scan.

On this basis, I’d say there’s a study out there crying out to be done. There are plenty of reports of MRI scans comparing dyslexic vs control brains. We could revisit those scans using the automated methods developed by Wagner et al to test the hypothesis that the rate of neuromigrational anomalies is higher in the dyslexic vs control samples. It’s clear that MRI scans won’t pick up everything, and subtle anomalies may be missed. However, if the neuronal migration account of language learning impairments is correct, we should nevertheless expect to see a measureable difference in the rates of anomalies between cases of dyslexia/SLI vs. controls. And if genetic information is available as well, then a comparison could be done between those with and without risk variants.

References

Barkovich, A. J., Guerrini, R., Kuzniecky, R. I., Jackson, G. D., & Dobyns, W. B. (2012). A developmental and genetic classification for malformations of cortical development: update 2012. Brain, 135(5), 1348-1369. doi: 10.1093/brain/aws019

Bishop, D. V. M. (2009). Genes, cognition and communication: insights from neurodevelopmental disorders. The Year in Cognitive Neuroscience: Annals of the New York Academy of Sciences, 1156, 1-18.

Bishop, D. V. M., & Snowling, M. J. (2004). Developmental dyslexia and Specific Language Impairment: Same or different? Psychological Bulletin, 130, 858-886.

Chang, B. S., Ly, J., Appignani, B., Bodell, A., Apse, K. A., Ravenscroft, R. S., . . . Walsh, C. A. (2005). Reading impairment in the neuronal migration disorder of periventricular nodular heterotopia. Neurology, 64(5), 799-803.

De Vasconcelos Hage, S. R., Cendes, F., Montenegro, M. A., Abramides, D. V., Guimarães, C. A., & Guerreiro, M. M. (2006). Specific language impairment: linguistic and neurobiological aspects. Arquivos de Neuro-Psiquiatria, 64, 173-180.

Galaburda, A. M., & Kemper, T. (1979). Cytoarchitectonic abnormalities in developmental dyslexia. Annals of Neurology, 6, 94-100.

Galaburda, A. M., Sherman, G. F., Rosen, G. D., Aboitiz, F., & Geschwind, N. (1985). Developmental dyslexia: four consecutive cases with cortical anomalies. Annals of Neurology, 18, 222-233.

Galaburda, A. M., LoTurco, J. J., Ramus, F., Fitch, R. H., & Rosen, G. D. (2006). From genes to behavior in developmental dyslexia. Nature Neuroscience, 9, 1213-1217.

Guerrini, R., & Parrini, E. (2010). Neuronal migration disorders. Neurobiology of Disease, 38, 154-166.

Wagner, J., Weber, B., Urbach, H., Elger, C., & Huppertz, H. (2011). Morphometric MRI analysis improves detection of focal cortical dysplasia type II Brain, 134 (10), 2844-2854 DOI: 10.1093/brain/awr204

Webster, R. I., Erdos, C., Evans, K., Majnemer, A., Saigal, G., Kehayia, E., . . . Shevell, M. I. (2008). Neurological and magnetic resonance Imaging findings in children with developmental language impairment. Journal of Child Neurology, 23(8), 870-877. doi: 10.1177/0883073808315620