March 1, 2012

Brain MRI scans may provide an early diagnostic marker

Children at risk for dyslexia show differences in brain activity on MRI scans even before they begin learning to read, finds a study at Children’s Hospital Boston. Previously, it was unclear whether this activity difference resulted from the struggle to learn to
read or predated the difficulty. Since many children with developmental
dyslexia respond to early intervention, identifying children at risk before or
during kindergarten could head off difficulties and frustration in school, the
researchers say.

Developmental dyslexia affects 5 to 17 percent of all children; up to 1 in 2 children with a family history of dyslexia will struggle with reading themselves, experiencing poor spelling and decoding abilities and difficulties with fluent word recognition. Because they
have problems recognizing and manipulating the underlying sound structures of
words (known as phonological processing), children with dyslexia have
difficulty mapping oral sounds to written language.

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

During the phonological tasks, the imaging showed that 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 differences in brain function in the same brain regions,” says 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 shows these differences even before children have reading instruction.”

In both the at-risk and not-at-risk groups, children with high activation in these brain areas had better pre-reading 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 (like saying “cowboy” without the “cow”).

The children at risk for dyslexia showed no increase in activation of frontal brain regions, 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.

Studies have shown that children with dyslexia often have negative experiences in school, being labeled as lazy or unmotivated. Their frustration can lead to aggressive, impulsive and anti-social behaviors and an increased likelihood 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,” says Raschle.

While various reading interventions are available for dyslexia, the condition generally isn’t diagnosed until the child has reached second or third grade, when the available interventions are less effective, Gaab adds.

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

However, the researchers are not able to diagnose children with fMRI yet, Gaab states. “This is the beginning of a long line of research that will help us focus on early intervention and might lead to policy changes to implement and improve the identification of children at risk. It remains unclear whether brain imaging adds any predictive value beyond the ‘paper-pencil assessments’ we already use with our children.  Further studies are needed to determine whether imaging adds to what we
currently do to identify these children’s difficulties, especially because it
is more expensive than the current practice,” she said.

The lab of Dr. Gaab, one of the researchers on this team, plans to follow the children over time to see if the brain patterns they observed correlate with a later diagnosis of dyslexia. At the present time,  this lab is investigating how early these brain differences appear, how they develop and whether they can be used to identify children who are at risk for dyslexia in pre-school or even in infancy. Through funding provided by the National Institutes of Health (NIH) and private foundations, researchers in the Gaab lab
are able to extend their studies, and are currently actively enrolling preschool-aged children and infants.

For more information about the Gaab Laboratory and details on participating in studies investigating early signs of dyslexia in infancy or preschool, please see the Gaab
Lab website

The work reported in the original article described here was funded by the Charles H. Hood Foundation, a Children’s Hospital Boston pilot grant, the Swiss National Foundation, the National Institute of Child Health and Human Development and the Janggen-Pohn Stiftung.

Original Article