MRI Brain (Volumetry, fMRI & MRS) in Autism

Autism Spectrum Disorder

MRI brain in ASD

To reach a feasible method for diagnosing Autism Spectrum Disorder (ASD) outcome measures: 1. Primary (main): Measurement of various brain structures, including the total brain volume, the volumes of specific brain regions (such as the amygdala, hippocampus, and cerebellum), and the thickness of the cortex. Detection of other concurrent lesions, e.g. tuberous sclerosis 2. Secondary (subsidiary): levels of various neurotransmitters, such as glutamate and GABA, and other metabolites, such as N-acetyl aspartate (NAA), in specific regions of the brain Assessing neural activity and connectivity in the brain in the resting state

Autism spectrum disorder (ASD) is a heterogeneous disorder (or collection of related disorders) of multifactorial etiology, and with a great range in severity of symptoms. ASD affects approximately 1 in 166 children and is four times more prevalent in boys than in girls. Core features of individuals with autism include 1) impairment in reciprocal social interactions; 2) verbal and nonverbal communication deficits; 3) repetitive and ritualized behaviors; and 4) a narrow range of interests. Approximately 30% of individuals with ASD manifest some degree of mental retardation. Magnetic-resonance (MR) examination allows researchers and clinicians to noninvasively examine brain anatomy in vivo. Structural MR examination is widely used to investigate brain morphology because of its high contrast sensitivity and spatial resolution, and because it entails no radiation exposure; the last feature is particularly important for children and adolescents. Functional magnetic resonance imaging (fMRI) has proven to be a useful tool to investigate aberrant neurobiological function in ASDs because of its excellent contrast properties, spatial resolution, and temporal resolution. fMRI uses specialized pulse sequences to localize metabolic correlates of neural activity linked to relevant neurocognitive processes Investigating brain network activity during the resting state has emerged as a new method that eliminates the caveats of task-based fMRI studies The fMRI signal is measured during the resting state and the data is analyzed based on a connectivity approach between subdivisions. To date, brain network activity during the resting state has been investigated in subjects with ASD and typical development in numerous studies. Overall, intrinsic connectivity between subdivisions of the brain is altered in patients with ASD compared to controls. MRS's finding is that gamma oscillations are reduced in ASD patients. Gamma oscillations are generated by GABAergic neurons and are involved in sensory binding and higher cognitive functions.

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