For the first time, scientists have discovered a link between a child's brain size and composition and a future diagnosis of autism.
Researchers from the University of North Carolina School of Medicine found that babies with a family history of autism and an abnormally large part of their brain were 2.2 times more likely to develop autism compared to babies with the same genetic predisposition, but those brains were of normal size.
Cerebrospinal fluid (CSF) flows through the brain through small fluid-filled channels called perivascular spaces (PVS).
Perivascular spaces regulate fluid movement in the central nervous system and its drainage.
CSF is a body fluid in the tissue surrounding the brain and spinal cord. The colorless fluid helps the brain by providing protection, nourishment and waste removal, flushing out neuroinflammation and other neurological waste.
Disruption of this key process can lead to neurological dysfunction, cognitive decline, or developmental delays.
The studypublished in JAMA Network Open, found that children with enlarged perivascular spaces had a higher risk of being diagnosed with autism at age two.
Dr. Dea Garic, co-author of the study and professor of psychiatry, said: 'These results suggest that perivascular spaces could serve as an early marker for autism.'
The graph above shows the association between enlarged perivascular spaces and a future diagnosis of autism. A high probability of autism is defined as having a family history of the disorder and a low probability is defined as having no predisposition to autism
Above is a scan of the brain of a 24-month-old subject showing cerebrospinal fluid (blue) and perivascular space (green) labeled
The study also found that enlarged spaces in childhood were associated with sleep problems seven to 10 years after diagnosis.
For the study, researchers analyzed and scanned the brains of 311 babies, including children who were at increased risk for autism because of an older sibling with the disorder and children who had no familial risk.
They followed participants from six to 24 months old, before anyone had been diagnosed with autism. Brain images were taken at six months, 12 months and 24 months of age to observe changes over time.
Over the course of the study, 30 percent of children who later developed autism had an enlarged perivascular space at 12 months of age.
At 24 months, almost half of children diagnosed with the condition had enlarged spaces.
It was also found that excessive CSF volume in six-month-old children was associated with an enlarged PVS at two years of age.
The scientists also examined whether PVS and CSF volume had an effect on sleep problems later in childhood.
Every six hours, the brain sends CSF to the PVS to remove harmful proteins, which may include the amyloid proteins associated with Alzheimer's disease.
The CSF clearance process is extra efficient during sleep, with most of the circulation and clearance occurring during eye closure. However, disturbed sleep reduces the clearance of CSF from PVS, causing the spaces to become larger or distorted.
The sleep analysis showed that children who had an enlarged PVS at the age of two were more likely to have sleep disorders between the ages of seven and twelve.
Although this has been studied previously in animals, this study is the first to examine the relationship in children.
Dr. Garic added: 'Because autism is so strongly linked to sleep problems, we were in this unique position to investigate cerebrospinal fluid dynamics and sleep.
'It was really striking to see such a strong association, separated by such a long period in childhood. But it really shows how perivascular spaces have an effect not only at a young age, but also in the long term.'
Autism is notoriously difficult to recognize, with the average age of diagnosis in the US being around five years old. The process usually involves dozens of visits to multiple doctors and a battery of tests, which can be stressful for children and families.
The condition affects one in 36 children, meaning that more than 90,000 children are born with the developmental disorder in the US every year.
Autism is characterized by problems with social communication and interaction, difficulty expressing oneself, and repetitive behaviors and interests.
Senior author of the study Dr. Mark Shen said: 'Collectively, our research has shown that cerebrospinal fluid abnormalities in the first year of life can have downstream effects on a variety of outcomes, including later diagnosis of autism, sleep problems, neuroinflammation and possibly other developmental disorders. physical disability.'
And dr. Garic added: 'Our findings were striking given that neuroradiologists typically view enlarged perivascular spaces as a sign of neurodegeneration in adults, but this study reported this in toddlers.
'This is an important aspect of brain development in the first years of life that needs to be monitored.'