Brain MRI Scans Show Potential for an Early Diagnostic Marker for Dyslexia

Because developmental dyslexia responds to early intervention, diagnosing at risk children before or during kindergarten could decrease problems and frustration in school.

The study’s findings were published January 17, 2012, in the online early edition of the journal Proceedings of the [US] National Academy of Sciences. Developmental dyslexia affects 5%-17% of all children; up to one in two children with a family history of dyslexia will have problems with reading themselves, experiencing poor spelling, decoding abilities, and difficulties with fluent word recognition. Because of phonologic processing, children with dyslexia have problems mapping oral sounds to written language.

The Children’s Hospital Boston (MA, USA) researchers, led by Nora Raschle, PhD, of the laboratories of cognitive neuroscience, performed functional MRI imaging in 36 preschool-age children (average age, 5½) while they performed tasks requiring them to decide whether two words started with the same speech sound. They used an elaborate protocol to get these young children to hold still in the MRI scanner.

During the phonologic tasks, children with a family history of dyslexia had reduced metabolic activity in certain brain regions (the junctions between the occipital and temporal lobes and the temporal and parietal lobes in the back of the brain) when compared with controls matched for age, IQ, and socioeconomic status.

“We already know that older children and adults with dyslexia have dysfunction in the same brain regions,” stated senior investigator Nadine Gaab, PhD, also of the laboratories of cognitive neuroscience. “What this study tells us is that the brain’s ability to process language sounds is deficient even before children have reading instruction.”

In both the at-risk and control groups, children with high activation in these brain areas had better prereading skills, such as rhyming, knowing letters and letter sounds, knowing when two words start with the same sound, and being able to separate sounds within a word.

The children at risk for dyslexia demonstrated no increase in activation of frontal brain areas, as has been seen in older children and adults with dyslexia. This suggests that these regions become active only when children begin reading instruction, as the brain tries to compensate for other deficits.

Research has revealed that children with dyslexia frequently have negative experiences in school, being called lazy or unmotivated. Their frustration can lead to impulsive, aggressive, and antisocial behaviors and an increased probability of dropping out of high school and entering the juvenile justice system. “We hope that identifying children at risk for dyslexia around preschool or even earlier may help reduce the negative social and psychological consequences these kids often face,” noted Dr. Raschle.
Whereas various neuropsychologic interventions exist for dyslexia, the disorder typically is not diagnosed until the child has reached third grade, when they are less effective, Dr. Gaab added.

“Families often know that their child has dyslexia as early as kindergarten, but they can't get interventions at their schools,” she said. “If we can show that we can identify these kids early, schools may be encouraged to develop programs.”

Drs. Gaab and Raschle plan to monitor the children over time to see if the brain patterns they observed correlate with a later diagnosis of dyslexia.

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Children’s Hospital Boston