Morphometric analysis of Corpus Callosum in autistic and typically developing Indian children

Autism spectrum disorder (ASD), a multifaceted neurodevelopmental disorder, is thought to reflect subtle abnormalities in the interhemispheric connections such as agenesis of corpus callosum (CC) (Lau et al., 2013; Lee et al., 2016; Paul et al., 2007; Valenti et al., 2020). Patients with agenesis of CC exhibit similar behavioural traits such as impaired social communication and interaction, which are the core diagnostic criteria of ASD (Paul et al., 2007). For this reason, morphometric alterations of CC have been the most examined white matter structure in ASD.

The CC is a thick bundle of nerve fibres that acts as a neural bridge integrating sensory, motor, and cognitive information and transfer between the contralateral hemispheres. Multiple neuroimaging studies have reported smaller size of CC in children with ASD compared to typically developing children (TD) (Allouh et al., 2020; Dimond et al., 2019; Hanaie et al., 2014; Prigge et al., 2013; Valenti et al., 2020; Yao et al., 2021), especially in the anterior CC (Schaer et al., 2013). While, other studies report increased CC tract in children with ASD compared to TD (Fingher et al., 2017; Loomba et al., 2021; Wolff et al., 2012; Zhang et al., 2020). The variation in findings could likely be due to the inclusion of different age groups, differing diagnostic criteria and heterogeneity within the disorder. Though the preponderance of existing literature suggests altered CC morphometry in ASD, it is still not clear whether this altered CC morphometry is the primary resultant or the repercussion of the disorder. Moreover, due to logistical difficulties in scanning low-functioning ASD children, only a countable number of studies have been carried out in this sample (Manes et al., 1999; Vitiello et al., 2019). Approximately 35.2% of children with ASD are low functioning (IQ ≤ 70), and 23.1% are categorised as a borderline range (IQ between 71 and 85) (Maenner et al., 2021), and it cannot be assumed that the findings reported in children with high functioning ASD can be generalised to children with low functioning ASD.

Numerous neuroimaging studies have previously reported that the morphometry of CC may vary across different ethnic and racial populations. For example, variations in the morphometry of CC have been observed among the Japanese (Hanaie et al., 2014), Iranian (Allouh et al., 2020), and Indian populations (Gupta et al., 2008). It has been noted that these population-related variations could be due to environmental and genetic factors (Suganthy et al., 2003; Woldehawariat et al., 2014). Moreover, it has been reported that Indians exhibit smaller brain sizes compared to the Caucasian, Chinese and Korean populations (Sivaswamy et al., 2019). Hence, establishing explicit baselines and examining the population-specific anomalies of brain abnormalities in neurodevelopmental disorders plays a vital role in understanding the neural basis of the disorder.

In this study, we aimed to examine the morphometric variations of CC using midsagittal magnetic resonance imaging (MRI) slice between children with ASD and typically developing children (TD) in the Indian population. We also evaluated CC morphometric differences based on autism severity, verbal IQ (VIQ) and full-scale IQ (FSIQ) in autistic children.

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