Brain scans may diagnose dyslexia before kids can even read

Dyslexia, a learning disability, can severely impact a person's ability to read. A new study shows MRI brain scans might be able to diagnose the disorder earlier than conventional methods.

Dyslexia affects about 10 percent of Americans. The learning disability is most commonly diagnosed in second graders, according to the MIT researchers behind the new study. But, now they think they've found a link between poor pre-reading skills in children as young as kindergarten and the size of a certain brain structure associated with language and learning.

The arcuate fasciculus part of the brain has previously been found to be smaller and more disorganized in the brains of adults with poor reading skills, but the researchers hadn't been sure which came first: the brain structure differences or the poor reading skills.

"We were very interested in looking at children prior to reading instruction and whether you would see these kinds of differences," John Gabrieli, professor of brain and cognitive sciences and a member of MIT's McGovern Institute for Brain Research, said in a press release.

Researchers looked at about 1,000 kids at schools located throughout New England. They were tested at the beginning of kindergarten for their pre-reading skills, such as their abilities to put words together from sounds.

"The first step in reading is to match the printed letters with the sounds of letters that you know exist in the world," said study lead author Elizabeth Norton, a postdoctoral researcher at MIT.

They took a subset of 40 children and gave them a certain technique of MRI bran scans called "diffusion-weighted imaging," which shows the size and organization of nerves that carry information between different brain areas, known as white matter. The researchers focused on the white matter of the arcuate fasciculus structure and two others: the inferior longitudinal fasciculus (ILF) and the superior longitudinal fasciculus (SLF).

By comparing the scans along with the results from the pre-reading tests, the researchers found a correlation between the size and organization of the arcuate fasciculus and a child's ability to identify and manipulate language sounds.

They did not find a correlation, however, between other reading skills tested, including the ability to name familiar objects as quickly as you can (rapid naming) or the ability to name letters.

According to the researchers, the left arcuate fasciculus connects to the Broca's area -- which is a brain region involved in speech production -- along with the Wernicke's area, which is involved in understanding language. People with larger, more organized structures appear to have better communications between these two regions, they added.

"At the moment when the children arrive at kindergarten, which is approximately when we scan them, we don't know what factors lead to these brain differences," said Gabrieli. "We don't know yet how it plays out over time, and that's the big question: Can we, through a combination of behavioral and brain measures, get a lot more accurate at seeing who will become a dyslexic child, with the hope that that would motivate aggressive interventions that would help these children right from the start, instead of waiting for them to fail?" he asked.

The findings were published Aug. 14 in the Journal of Neuroscience.

"It is particularly exciting to envisage a future where this technology could be part of a cluster of indicators that would identify a risk of dyslexic difficulties," the British Dyslexia Association told the BBC. But, more research is needed before this test is used for diagnosis, the association added.

The Mayo Clinic has more information on dyslexia.