Dyslexia: Is it time to rethink or examine the diagnosis?

Some years ago, a student informed me that she was encountering a problem with my classes.

When asked to explain a little further, she told me that she had been diagnosed as dyslexic.

I asked if she could be a little more specific about the particular difficulties she was encountering.

Responding, “I can’t understand what you are talking about”, she explained that the ideas I was expressing were complex and she found them difficult to grasp.

I enquired how I might help her with this problem. She replied that she would welcome a single sheet of A4 for each lecture containing a set of bullet points that summarised the key points.

This anecdote exemplifies some of the confusion that surrounds “dyslexia”, a term used to describe a variety of problems. Researchers tend to describe as dyslexic all those who struggle to decode text.

Others, often clinicians, argue that only some poor decoders are dyslexic. Still others contend that decoding difficulty is but one part of a much broader dyslexic condition.

It is hardly surprising, therefore, that diagnosis is deemed to be highly subjective and lacking in scientific rigour. 

While special tests and symptom profiles are commonly used, there is no means of making a consistent and meaningful judgement.

As the list of so-called signs and symptoms is lengthy, most people reporting reading difficulties will demonstrate some of them.

Many such symptoms are found in good readers, and those diagnosed as dyslexic often differ substantially from one another.

Many clinicians still employ IQ tests as a basis for diagnosis, even though this practice has been discreditted and no longer has any scientific support.

Meanwhile, research studies in neuroscience and genetics, often used by proponents to justify the dyslexia construct, are typically conducted with poor decoders (not a so-called dyslexic subgroup), and currently offer no additional diagnostic information.

The key problem is that dyslexia diagnoses have moved far away from their original focus (severe reading difficulty) to incorporate an ever-increasing range of cognitive and self-regulatory deficits including poor working memory, processing speed limitations, attention/concentration problems, difficulties in analysing and synthesising complex information, and in organising and expressing ideas.

For any students who struggle to cope with academic demands for such reasons, there are obvious equity issues within our highly competitive higher education sector between those who are diagnosed dyslexic and those who are not and, instead, are considered to be academically weaker performers.

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Chindren with Autism: EphB Link through Family Genes

Harvard Medical School researchers at McLean Hospital have found that a gene family linked to autism, EphB, is essential for proper brain wiring during development.

The findings suggest that the abnormal brain wiring that results from mutations in this gene family could contribute to autism symptoms.

"Using animal models, we were able to see that EphB is required for normal brain development. Mutations in EphB that compromise its function led to abnormal connections between key brain regions involved in processing of sensory information," said Christopher Cowan, HMS associate professor of psychiatry at McLean Hospital.

The findings were reported by McLean Hospital researchers and collaborators in the Proceedings of the National Academy of Sciences on Jan. 22, 2014.

Christopher Cowan

Recent genetic analysis had revealed an EphB gene as a new candidate risk factor for human autism, so investigators targeted the gene in animals to assess its role in the proper development of communication networks between the thalamus and the cortex, the regions of the brain responsible for processing information from the senses, such as touch and hearing.

"Some individuals with autism show abnormalities in sensory perception and processing, including touch, sound and vision," Cowan explained.

Investigators, from left: Yuhong Guo, Jesse Kumar, Laura Smith, Chris Cowan, Adam Harrington, Maria Carreira, Makoto Taniguchi and Rachel Penrod-Martin. 

Not pictured: Carly Hale and Mike Robichaux. 

Image: Patrick O'Connor.

"We found that EphB genes are essential for normal wiring of at least two key parts of the brain that process sensory information, particularly regions involved in touch and sound," Cowan said.

"Our findings suggest that defects in early brain wiring might underlie at least some of the sensory-associated symptoms found in individuals with autism spectrum disorders."

Future work, supported in part by the Simons Foundation Autism Research Initiative, seeks to extend these findings to better understand the relationship between EphB genes and the risk for developing autism.

Understanding the underlying causes of autism may help in the development of effective treatments.

More information: "EphB receptor forward signaling regulates area-specific reciprocal thalamic and cortical axon pathfinding." Robichaux MA, Chenaux G, Ho HY, Soskis MJ, Dravis C, Kwan KY, Sestan N, Greenberg ME, Henkemeyer M, Cowan CW. Proc Natl Acad Sci U.S.A.. 2014 Jan 22. 

Air pollution and genetics combine to increase risk of autism

Exposure to air pollution appears to increase the risk for autism among people who carry a genetic disposition for the neurodevelopmental disorder, according to newly published research led by scientists at the Keck School of Medicine of the University of Southern California (USC).

"Our research shows that children with both the risk genotype and exposure to high air pollutant levels were at increased risk of autism spectrum disorder compared to those without the risk genotype and lower air pollution exposure," said the study's first author, Heather E. Volk, Ph.D., M.P.H.

Heather Volk is assistant professor of research in preventive medicine and pediatrics at the Keck School of Medicine of USC and principal investigator at The Saban Research Institute of Children's Hospital Los Angeles.

The study, "Autism spectrum disorder: Interaction of air pollution with the MET receptor tyrosine kinase gene," is scheduled to appear in the January 2014 edition of Epidemiology.

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental disability characterized by problems with social interaction, communication and repetitive behaviors.

The Centers for Disease Control and Prevention estimates that one in 88 children in the United States has an ASD.

ASD is highly heritable, suggesting that genetics are an important contributing factor, but many questions about its causes remain. There currently is no cure for the disorder.

"Although gene-environment interactions are widely believed to contribute to autism risk, this is the first demonstration of a specific interaction between a well-established genetic risk factor and an environmental factor that independently contribute to autism risk," said Daniel B. Campbell, Ph.D.

David Campbell is assistant professor of psychiatry and the behavioral sciences at the Keck School of Medicine of USC and the study's senior author.

"The MET gene variant has been associated with autism in multiple studies, controls expression of MET protein in both the brain and the immune system, and predicts altered brain structure and function."

"It will be important to replicate this finding and to determine the mechanisms by which these genetic and environmental factors interact to increase the risk for autism."

Independent studies by Volk and Campbell have previously reported associations between autism and air pollution exposure and between autism and a variant in the MET gene.

The current study suggests that air pollution exposure and the genetic variant interact to augment the risk of ASD.

Campbell and Volk's team studied 408 children between 2 and 5 years of age from the Childhood Autism Risks From Genetics and the Environment Study, a population-based, case-control study of preschool children from California.

Of those, 252 met the criteria for autism or autism spectrum disorder. Air pollution exposure was determined based on the past residences of the children and their mothers, local traffic-related sources, and regional air quality measures. MET genotype was determined through blood sampling.

Campbell and Volk continue to study the interaction of air pollution exposure and the MET genotype in mothers during pregnancy.

Researchers unravel genetics of dyslexia and language impairment

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 study is published online and in the July print issue of the American Journal of Human Genetics.

Jeffrey R. Gruen

Senior author Jeffrey R. Gruen, M.D., professor of pediatrics, genetics, and investigative medicine at Yale, and colleagues analyzed data from more than 10,000 children born in 1991-1992 who were part of the Avon Longitudinal Study of Parents and Children (ALSPAC) conducted by investigators at the University of Bristol (UK).

Gruen and his team used the ALSPAC data to unravel the genetic components of reading and verbal language.

In the process, they identified genetic variants that can predispose children to dyslexia and language impairment, increasing the likelihood of earlier diagnosis and more effective interventions.

Dyslexia and language impairment are common learning disabilities that make reading and verbal language skills difficult.

Both disorders have a substantial genetic component, but despite years of study, determining the root cause had been difficult.

In previous studies, Gruen and his team found that dopamine-related genes ANKK1 and DRD2 are involved in language processing.

In further non-genetic studies, they found that prenatal exposure to nicotine has a strong negative affect on both reading and language processing.

They had also previously found that a gene called DCDC2 was linked to dyslexia. In this new study, Gruen and colleagues looked deeper within the DCDC2 gene to pinpoint the specific parts of the gene that are responsible for dyslexia and language impairment.

They found that some variants of a gene regulator called READ1 (regulatory element associated with dyslexia1) within the DCDC2 gene are associated with problems in reading performance while other variants are strongly associated with problems in verbal language performance.

Gruen said these variants interact with a second dyslexia risk gene called KIAA0319. "When you have risk variants in both READ1 and KIAA0319, it can have a multiplier effect on measures of reading, language, and IQ," he said.

"People who have these variants have a substantially increased likelihood of developing dyslexia or language impairment."

"These findings are helping us to identify the pathways for fluent reading, the components of those pathways; and how they interact," said Gruen.

"We now hope to be able to offer a pre-symptomatic diagnostic panel, so we can identify children at risk before they get into trouble at school. Almost three-quarters of these children will be reading at grade level if they get early intervention, and we know that intervention can have a positive lasting effect."

More information: dx.doi.org/10.1016/j.ajhg.2013.05.008