Autism Spectrum Disorder (ASD) is a neurological disorder that is notorious for its heterogeneity, making early diagnosis imperative for the success of ASD patients. The earlier age of diagnosis, the earlier treatment plans can be set in place for critical times of development. Possible symptoms include, but are not limited to, lack of eye contact, delayed milestones, gaze fixation, repetitive behaviors, and social learning difficulties. Autism is a chronic condition that develops during prenatal life, and it is important for patients to be diagnosed between 2-4 years, even if the symptoms are not visible since most development for children occurs within these vulnerable years
Delaying the treatments and interventions for patients with ASD causes numerous difficulties in cognition, language, and adaptive behavior; thus, the identification of a reliable biomarker for ASD can supplement and validate existing clinical methods and can construct a more efficient diagnostic tool altogether that overcomes the limitations of clinical behavioral methods. As ASD is often considered a social learning disability, assessing the social cognition of babies can be difficult. Thus, biomarkers serve as a more objective benchmark for diagnosis.
A biomarker is a biological characteristic that can be objectively measured and evaluated as an indicator of biological or pathogenic processes. Possible biomarkers can be brain structures, levels of specific neurotransmitters, and hormonal imbalances. Using biomarkers to detect ASD would likely improve the prognosis of affected patients and encourage early screening for autism.
This article discloses a study that demonstrated the temporally divergent changes in overall brain volume in children diagnosed with ASD. Doctors and clinicians performing this study often noticed in their workplace that children with ASD had an arrest of growth in their brain size. This means that the child’s brain was significantly smaller in size around the first few months of their life, when compared with normal children. The brain size of the children with ASD plummeted when they turned one year old, which suggests brain overgrowth. This study was conducted to determine whether their observations were correct, and to further explore brain size as a possible biomarker in ASD diagnosis.
Using the pediatric records of head circumference, it was discovered that early brain overgrowth is, indeed, a common feature of ASD. The results of this study revealed that over 90% of the children with autism had head circumference values above the 85th percentile, and many showed evidence of abnormal brain growth as early as 6 to 8 months of age (Figure 1). Figure 1 indicates that around 1 to 2 months of age, the head circumference of children with ASD was statistically significantly below the CDC mean for healthy infants; however, by 6 to 14 months, the head circumference of the children was more than 1 standard deviation above the mean for healthy infants (Figure 1).
Figure 1. Early Brain Overgrowth
ASD: autism spectrum disorder; CDC: Centers for Disease Control; HC: head circumference. At birth and at 1 to 2 months of age, HC in the longitudinal ASD group was statistically significantly below the CDC mean for healthy infants, but by 6 to 14 months it was more than 1 SD (85th percentile) above the mean for healthy infants. The CDC mean of healthy infants at each age is 0. Error bars are SEM.
Source: Reprinted with permission from Courchesne E, Carper R, Akshoomoff N. Evidence of brain overgrowth in the first year of life in autism. JAMA. 2003;290:337-344. Copyright 2003, American Medical Association.
The rate of change regarding brain size is crucial in ASD detection. Infants who eventually got diagnosed with autism had normal or slightly below normal head circumference values at birth, but for many of these infants, these values heightened above the 85th percentile before their first birthday. Thus, a key factor may be the relative change from an average brain size to one that far exceeds normal size in a short span of time. The general finding of early brain overgrowth in autism as indexed by head circumference has been replicated by several independent research groups and confirmed with slightly older children using magnetic resonance imaging (MRI).
It is important for doctors and clinicians to diagnose ASD at an early age and introduce interventions in conjunction with family support. Although this article had significantly positive results that correlated brain structure with ASD, further research needs to be conducted in order to solidify these findings since the sample size was only 255. Future research should implement a multiplex immunoassay method, by analyzing brain structures and creating a diagnostic profile, in order to encompass the heterogeneity of ASD. The usage of machine learning may also be beneficial; this could possibly aid with identifying large patterns presented in the brain structure biomarker data and creating profile predictions subjective to each patient. Although the results of this study seem quite promising, multiple studies and trials still need to be conducted in order to confirm brain structure as a biomarker for the early detection of Autism Spectrum Disorder.
Pierce, Karen et al. “The power and promise of identifying autism early: insights from the search for clinical and biological markers.” Annals of clinical psychiatry : official journal of the American Academy of Clinical Psychiatrists vol. 21,3 (2009): 132-47. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872627/