Autism, also known as autism spectrum disorder (ASD), is a general term for any number of complex brain development disorders. Behavioral characteristics of autism include varying degrees of difficulty in social interaction, problems with verbal and nonverbal communication, and repetitive behavior.
Though autism can be associated with intellectual disabilities, some people on the autism spectrum exhibit advanced abilities in areas like music, math, and art. Some people with autism have difficulties with attention span and motor coordination, and some experience health issues with sleep and the gastrointestinal tract.
Experts have long believed that autism traces its roots to early brain development, although obvious signs may not emerge until a child is two or three years old. Today, according to the DSM-5 diagnostic manual, autism disorders are collected under the umbrella diagnosis of autism spectrum disorder rather than being recognized as distinctive subtypes of autism.
Brain Connectivity and Autism
Because the brain controls behavior, and because changes in how specific parts of the brain function and communicate with each other can alter behavior, researchers have long speculated that impairments associated with autism may have associated changes in brain structure and function. The higher cognitive functions are controlled by areas of the brain that include complex interconnected networks. When these networks are altered or disrupted, changes in behavior can result.
With autism, the so-called “default mode network” which controls self-referential thought, reasoning, and understanding other people’s mental states may be disrupted or altered compared to people without autism. Functional magnetic resonance imaging (MRI) can help researchers understand brain networks and how they serve specific cognitive functions.
In autism, local networks may be hyper-connected, while long-range connections between major areas of the brain (like the default mode network) may be hypo-connected. These altered connections are believed to be due to imbalance between neuronal excitation and inhibition as well as developmental delay.
Premature Infants, Structural Brain Imaging, and Autism
Structural brain imaging of premature infants once they reach their term-equivalent age of 40 weeks’ gestation, has shown differences between children that develop autism and those that don’t. A study in Australia imaged the brains of 172 premature infants at term-equivalent age and conducted diagnostic interviews with parents to diagnose children with autism spectrum disorders at a follow-up visit when the children were age seven. Independent assessments of autism were also performed.
The study found subtle differences in the brain structure of premature babies who were later diagnosed with autism compared to premature babies who were not diagnosed with autism. In particular, newborns who were later diagnosed with autism had smaller cerebellums and more cystic lesions in cortical white matter than those who were not diagnosed with autism. The findings of reduced cerebellum size were consistent with previous research reporting reduced volume of the cerebellum in older children with autism.
Arterial Spin Labeling Perfusion MRI Studies
Functional brain imaging using arterial spin labeling (ASL) perfusion MRI has now been used in autism research. Arterial spin labeling perfusion MRI measures cerebral blood flow using a magnetically labeled blood tracer. The results of the studies combined data about how brain areas are functionally connected with information about metabolic energy consumption in the brains of patients with autism.
In children with normal development, there is a known relationship between how strongly areas of the brain are connected in a brain network and the amount of energy it requires. But in children with autism, the relation between strength of connection among brain areas and the amount of energy required was different in a part of the brain called the dorsal anterior cingulate cortex. This part of the brain is relevant in social interaction and understanding the feelings of others – cognitive processes that are often impaired in people with autism.
MRI Elucidates Connectivity, Energy Demand in the Brain
ASL perfusion MRI, combined with information on brain connectivity allowed researchers to show a relationship between brain connectivity and energy demand in the default mode network of children. But in children with autism, reduced perfusion (hypo-perfusion) of tracer-infused blood combined with increased local connectivity and decreased long-range connectivity with the dorsal anterior cingulate cortex.
This disrupted relationship between connectivity and perfusion in children with autism indicates differences in energy demand in critical parts of brain networks related to the symptoms of autism. The altered energy consumption in these parts of the brain could indicate a change in the balance between excitatory and inhibitory networks. The bottom line is that ASL perfusion MRI could represent a new way to identify imaging markers correlated with autism.
What ASL Studies Could Bring to Treatment of Autism Spectrum Disorder
What could this new research mean for treatment of those with autism spectrum disorder? Nobody is sure yet, but the ASL perfusion MRI studies, coupled with the Australian studies of premature infants who went on to develop autism suggest that both structural and functional brain imaging may become important in diagnosing autism. Educational specialists believe early intervention is one key to maximizing the abilities of those with autism in terms of academic and social development. If researchers are able to correlate patterns of energy use and connectivity in the brain with autism signs and symptoms, early detection could be made easier. This could potentially allow earlier educational intervention, which is associated with better outcomes in people with autism.
Neuroradiology and Advancing Understanding of Autism
Neuroradiology, like the work of SteleRAD radiologists Robert Baker, MD and Richard Spira, MD, is applicable in an enormous range of health and behavioral conditions, from stroke to brain cancer, and potentially to developmental disorders like autism. The owner-operator radiologists of SteleRAD cover all radiology subspecialties including neuroradiology and MRI, allowing SteleRAD to assist hospitals, physician practices, and imaging centers throughout South Florida. If you would like to know more about the services SteleRAD’s Board-certified radiologists provide, we invite you to call 954-358-5250 or contact us online at any time.