Nonintrusive Imaging Technique Useful For Identifying Language Regions In Kids' Brains

April 08, 1999

If you think it's tough to coax a child to stop fidgeting while getting a haircut, imagine asking a youngster to be immobile for repeated five-minute periods -- and to take language and number tests at the same time. That's what researchers at Washington University School of Medicine in St. Louis were up against when they wanted to obtain brain images from 17 children and teen-agers to learn about language development.

All but two kids passed the squirm test, suggesting that an advanced imaging technique called functional magnetic resonance imaging (fMRI) can be used to study the developing brain. The findings also bring hope that neurosurgeons can soon use fMRI as a nonintrusive way to identify language regions in youngsters' brains that need to be avoided during brain surgery. And the findings suggest that children already use the same side of the brain to handle language that most adults use.

Collections of neurons in certain areas of the brain allow us to speak and understand language. These areas occur in both sides, or hemispheres, of the brain. But most adults rely primarily on areas in the middle of the left hemisphere for language. The same appeared to be true in the subjects studied by neuroradiologist Benjamin C. P. Lee, M.D., and his colleagues at the medical school. "We found that language was lateralized to the left hemisphere even in children as young as 7 years old," said Lee, an associate professor of pediatrics and of radiology.

He is lead author of the study published in the February 1999 issue of the Journal of Child Neurology. E. Mark Haacke, Ph.D., professor of radiology, was principal investigator for the study.

Lee became determined to evaluate fMRI in children after observing how scared and confused many of his patients with epilepsy became during the traditional test to evaluate language function. These children have a form of epilepsy resulting from lesions that disrupt electrical pathways in the brain. Removing the lesions often reduces the severity of their seizures, but the Wada test, used for decades to identify language areas in the brain so they can be avoided during the surgery, can be traumatic. The test also is used prior to neurosurgery to remove brain tumors or to repair damaged blood vessels in the brain.

In the Wada test, doctors inject a drug called amobarbital (Amytal) into an artery in the patient's neck while they are awake, which temporarily numbs half their brain. If the person loses speech as a result, the neurosurgeon knows that the active language areas are located in the numbed hemisphere. Lee said even adults who understand what the hour-long test entails have trouble undergoing the procedure. Children and adults with epilepsy, who often have mental retardation, can become uncontrollable.

"Anything that can eventually replace that test should be done," Lee said.

Because fMRI requires no injections or loss of mental functions, researchers have been investigating it as a less intrusive way to evaluate brain function. The method detects rapid changes in active brain areas, unlike traditional magnetic resonance images that highlight anatomy. But fidgeting distorts fMRI images and makes them unusable for evaluating brain function, so few studies of children had been done. Lee and his colleagues used a variety of methods to convince healthy children ages 7 to 18 to lie still for fMRI imaging. Lee wanted to evaluate healthy children before trying the fMRI imaging on those with epilespy.

The researchers rewarded the healthy children for time spent in the fMRI scanning machine with pizza parties and money and also strove to make them feel comfortable with the study process. "We took a great deal of care talking to them before the study and explaining what would happen, sometimes even doing a trial run so they knew exactly what to expect," Lee said.

The investigators also made certain the children could spell and generate words in their heads without moving their mouths, which causes head movements that ruin images. The brain's language areas become activated during this thinking process as well as during speech.

For their efforts, the researchers were rewarded with useful fMRI images from 15 of the 17 youngsters. All the subjects were imaged as they spelled words such as "cat" and "dog." The words were picked to suit their language skills by Royal Grueneich, Ph.D., assistant clinical professor of neurology.

These trials involved a series of five words presented to the youngsters over headphones. The children were given five seconds to spell a word before the next one in the series was delivered. A 25-second break followed in which they were asked to count silently, with the whole process repeated five times for each trial.

In other trials, the six teens were tested using a similar procedure for their ability to generate words from a sequence of five beginning letters. Both the word spelling and the word generation trials were performed at least twice. The images from the trials revealed that the left hemisphere was the language center for 10 of the children who completed both trials successfully. Four children also favored the left side of the brain in one trial, and one child didn't show greater left hemisphere activity, or lateralization, in either trial. Lee said an inability of the latter children to focus appropriately or perform the language tasks well might have hampered the detection of lateralization.

Previous studies with the Wada test and other imaging methods had drawn similar conclusions about language activity in children's brains. But the images were created after data were pooled and averaged from images of many patients, which may mask differences between individuals. Even so, Lee was not completely surprised by the current study's findings. "In adults, most people handle language on one side of the brain, so why shouldn't young children, who speak using the same (mental) mechanism."

But he was excited about using fMRI for future evaluations of children. And he has already begun comparing fMRI's use with the Wada test for patients with epilepsy.
Note: For more information, refer to Lee, B. C. P., Kuppusamy, K., Grueneich, R., El-Ghazzawy, O., Gordon, R. E., Lin, W., Haacke, E.M. "Hemispheric Language Dominance in Children Demonstrated by Functional Magnetic Resonance Imaging," Journal of Child Neurology, vol. 14 (2): 78-82, February 1999.

Washington University in St. Louis

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