Summary: Researchers uncovered a potential early marker for autism in infants: abnormally enlarged perivascular spaces (PVS) in the brain.
The study found that infants with enlarged PVS had a 2.2 times greater chance of developing autism compared to those with the same genetic risk. The researchers followed infants with a higher likelihood of autism due to having an older sibling with the condition.
Additionally, these infants showed an association between enlarged PVS and sleep problems later in life, suggesting a long-term impact of these early brain abnormalities.
Key Facts:
- Infants with enlarged perivascular spaces have over double the risk of developing autism.
- 30% of infants who later developed autism showed enlarged PVS by 12 months.
- The study links CSF abnormalities in infancy to later sleep disturbances and potentially other developmental disabilities.
Source: UNC
Throughout the day and night, cerebrospinal fluid (CSF) pulses through small fluid-filled channels surrounding blood vessels in the brain, called perivascular spaces, to flush out neuroinflammation and other neurological waste. A disruption to this vital process can lead to neurological dysfunction, cognitive decline, or developmental delays.
For the first time, researchers Dea Garic, Ph.D., and Mark Shen, Ph.D., both at the UNC School of Medicine’s Department of Psychiatry, discovered that infants with abnormally enlarged perivascular spaces have a 2.2 times greater chance of developing autism compared to infants with the same genetic risk. Their research also indicated that enlarged perivascular spaces in infancy are associated with sleep problems seven to 10 years after diagnosis.
“These results suggest that perivascular spaces could serve as an early marker for autism,” said Garic, assistant professor of psychiatry and a member of the Carolina Institute for Developmental Disabilities (CIDD).
The researchers studied infants at increased likelihood for developing autism, because they had an older sibling with autism. They followed these infants from 6-24 months of age, before the age of autism diagnosis.
Their study, published in JAMA Network Open, found that 30% of infants who later developed autism had enlarged perivascular spaces by 12 months. By 24 months of age, nearly half of the infants diagnosed with autism had enlarged perivascular spaces.
The importance of cerebrospinal fluid and sleep
Starting ten years ago, there has been a resurgence of research on the important functions of CSF in regulating brain health and development. Shen’s lab was the first to report that excessive volume of CSF was evident at 6 months of age in infants who would later develop autism. The current study showed that excessive CSF volume at 6 months was linked to enlarged perivascular spaces at 24 months.
Every six hours, the brain expels a wave of CSF that flows through perivascular spaces to remove potentially harmful neuroinflammatory proteins, such as amyloid beta, from building up in the brain. The CSF cleansing process is especially efficient when we are asleep, as the majority of CSF circulation and clearance occurs during sleep.
Disrupted sleep, however, can reduce CSF clearance from perivascular spaces, leading to dilation or enlargement, but this has previously only been studied in animal studies or in human studies of adults. This is the first study of its kind in children.
Shen, senior author of the JAMA Network Open paper, and Garic hypothesized that CSF abnormalities in infancy would be related to later sleep problems, based on Shen’s earlier research. The current sleep analysis revealed children who had enlarged perivascular spaces at two years of age had higher rates of sleep disturbances at school age.
“Since autism is so highly linked with sleep problems, we were in this unique position to examine CSF dynamics and sleep,” said Garic, who is the first author of the paper. “It was really striking to observe such a strong association separated by such a long period of time over childhood. But it really shows how perivascular spaces not only have an effect early in life, but they can have long-term effects, too.”
New clinical relevance in infancy
The research was done in conjunction with the Infant Brain Imaging Study (IBIS), a nationwide network of researchers investigating brain development, autism, and related developmental disabilities. The network consists of five universities, of which the University of North Carolina-Chapel Hill is the lead site.
For their study, Garic and Shen analyzed 870 MRIs from IBIS to measure excessive CSF volume and enlarged perivascular spaces. MRIs were obtained from babies during natural sleep at six, 12, and 24 months of age to observe changes over time.
The infant’s brain undergoes rapid development over this period. Previously, measurement of perivascular spaces was only thought to be clinically relevant for disorders of aging in older adults, such as in dementia. These findings suggest that younger populations may need to be considered and monitored for these types of brain abnormalities.
“Our findings were striking, given that neuroradiologists typically view enlarged perivascular spaces as a sign of neurodegeneration in adults, but this study reported it in toddlers,” said Garic. “This is an important aspect of brain development in the first years of life that should be monitored.”
Future studies and possibilities
Garlic and Shen hypothesize that excess CSF volume is stagnant or clogged and not circulating through the brain as efficiently as it should. For their next research endeavor, the researchers are planning to once again use MRIs to measure CSF in a sleeping infant’s brain, but this time focusing on the physiology and speed of CSF flow throughout the brain.
The research team is also working with other collaborators to quantify the size of perivascular spaces and the severity of behavioral outcomes. The team also plans to extend their research to neurogenetic syndromes associated with autism, such as Fragile X syndrome and Down syndrome.
“Collectively, our research has shown that CSF abnormalities in the first year of life could have downstream effects on a variety of outcomes, including later autism diagnosis, sleep problems, neuroinflammation, and possibly other developmental disabilities,” said Shen.
About this autism research news
Author: Kendall Daniels
Source: UNC
Contact: Kendall Daniels – UNC
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Enlarged Perivascular Spaces in Infancy and Autism Diagnosis, Cerebrospinal Fluid Volume, and Later Sleep Problems” by Dea Garic et al. JAMA Network Open
Abstract
Enlarged Perivascular Spaces in Infancy and Autism Diagnosis, Cerebrospinal Fluid Volume, and Later Sleep Problems
Importance
Perivascular spaces (PVS) and cerebrospinal fluid (CSF) are essential components of the glymphatic system, regulating brain homeostasis and clearing neural waste throughout the lifespan. Enlarged PVS have been implicated in neurological disorders and sleep problems in adults, and excessive CSF volume has been reported in infants who develop autism. Enlarged PVS have not been sufficiently studied longitudinally in infancy or in relation to autism outcomes or CSF volume.
Objective
To examine whether enlarged PVS are more prevalent in infants who develop autism compared with controls and whether they are associated with trajectories of extra-axial CSF volume (EA-CSF) and sleep problems in later childhood.
Design, Setting, and Participants
This prospective, longitudinal cohort study used data from the Infant Brain Imaging Study. Magnetic resonance images were acquired at ages 6, 12, and 24 months (2007-2017), with sleep questionnaires performed between ages 7 and 12 years (starting in 2018). Data were collected at 4 sites in North Carolina, Missouri, Pennsylvania, and Washington. Data were analyzed from March 2021 through August 2022.
Exposure
PVS (ie, fluid-filled channels that surround blood vessels in the brain) that are enlarged (ie, visible on magnetic resonance imaging).
Main Outcomes and Measures
Outcomes of interest were enlarged PVS and EA-CSF volume from 6 to 24 months, autism diagnosis at 24 months, sleep problems between ages 7 and 12 years.
Results
A total of 311 infants (197 [63.3%] male) were included: 47 infants at high familial likelihood for autism (ie, having an older sibling with autism) who were diagnosed with autism at age 24 months, 180 high likelihood infants not diagnosed with autism, and 84 low likelihood control infants not diagnosed with autism. Sleep measures at school-age were available for 109 participants. Of infants who developed autism, 21 (44.7%) had enlarged PVS at 24 months compared with 48 infants (26.7%) in the high likelihood but no autism diagnosis group (P = .02) and 22 infants in the control group (26.2%) (P = .03). Across all groups, enlarged PVS at 24 months was associated with greater EA-CSF volume from ages 6 to 24 months (β = 4.64; 95% CI, 0.58-8.72; P = .002) and more frequent night wakings at school-age (F = 7.76; η2 = 0.08; P = .006).
Conclusions and Relevance
These findings suggest that enlarged PVS emerged between ages 12 and 24 months in infants who developed autism. These results add to a growing body of evidence that, along with excessive CSF volume and sleep dysfunction, the glymphatic system could be dysregulated in infants who develop autism.
