How Brain Scans in Infants May Predict Autism

infant girl wearing winter hat.
(Image credit: Willrow Hood/Shutterstock)

Brain scans of infants as young as 6 months old may be able to predict whether a child will develop autism, a new study suggests.

In the study, researchers found that infants who later developed autism had higher amounts of cerebrospinal fluid — the clear liquid that cushions the brain within the skull — that could be seen on an MRI, compared with those who did not develop autism.

What's more, the researchers also found that the levels of CSF lined up so closely with the risk of autism that they could use measurements of CSF volume to predict the development of autism among "high-risk" infants, or those who had an older sibling with the condition. Measurements of CSF volume at 6 months predicted which high-risk infants were diagnosed with autism at age 2 with a 70 percent accuracy, the researchers said. [11 Facts Every Parent Should Know About Their Baby's Brain]

Although more studies are needed, the researchers say that one day, doctors might be able to monitor CSF to help gauge a child's risk of autism.

"Neuroimaging CSF could be another tool to help pediatricians diagnose autism as early as possible," study author Mark Shen, a postdoctoral fellow in psychiatry at the University of North Carolina at Chapel Hill School of Medicine, said in a statement. "It could help signal risk using regular MRIs that you find in any hospital."

Still, the researchers said there are a number of questions that need to be answered before doctors could use MRIs for this purpose. For instance, the researchers don't know whether this CSF anomaly is found  only among children at high risk for autism, or if it would be found more generally in all children who develop autism. The researchers also don't know if this anomaly contributes to the development of autism, or if it's simply a marker of another factor related to autism.

The results confirm those of an earlier study by the same group of researchers, which also found a link between CSF volume and the risk of autism. However, the earlier study was relatively small, involving 55 infants.

In the new study, the researchers examined MRIs from 343 infants at ages 6, 12 and 24 months. Of these, 221 infants were at a high risk of developing autism based on their family history, whereas 122 had no family history of autism.

At the end of the study, 47 infants in the high-risk group were diagnosed with autism by the time they were 2 years old. None of the infants in the comparison group developed autism.

Among infants who were at a high risk for autism, those who were ultimately diagnosed with the condition had, on average, 18 percent more CSF in an area known as the subarachnoid space, which surrounds the brain, at 6 months of age, compared with those who did not develop autism.

In addition, infants who developed more severe symptoms of autism had 24 percent greater CSF volume in the subarachnoid space, compared with those who did not develop autism.

The researchers hypothesize that this CSF anomaly could be a sign that the CSF is not properly circulating as it should. Normally, the CSF circulation helps to filter out potentially dangerous molecules.

"CSF is like the filtration system in the brain," said Shen, who began this work as a graduate student at the MIND Institute at the University of California, Davis. "As CSF circulates through the brain, it washes away waste particles that would otherwise build up." The researchers believe that an increase in CSF in the subarachnoid space "is an early sign that CSF is not filtering and draining when it should."

The result is that there could be a buildup of neuroinflammation that isn't being washed way," Shen said.

Future studies are needed to evaluate both the underlying causes of increased CSF volume, and the potentially harmful effects on brain development, the researchers said.

The study is published today (March 6) in the journal Biological Psychiatry.

Original article on Live Science.

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.