Guest post: Structural changes in the cerebellum may be a cause for autism in children

In November we joined up with The Medic Collective, a group of medical students at Cambridge inspiring school students to dive deeper into their passions for medicine alongside widening access, in their Article Of The Month competition. The theme was Paediatrics, and we are delighted to share this wonderful post by a year 12 school student Victoria about the link between the cerebellum and autism!

Autism spectrum disorders are a group of disorders that are characterised by communication and social skill deficits, behaviour that is stereotyped and repetitive, and deficits in cognitive function. Being a spectrum, the manifestation of this disorder can range from severe to milder forms such as Asperger syndrome. It often begins to present at around age three, coinciding with the rapidly expanding language and social skills seen in normal development (Rogers et al., 2013). The aetiology of autism is multifactorial. The Wakefield paper of 1998 suggesting that autism is linked to the MMR vaccine has since been disproven and retracted, and newer studies have further refuted the link between vaccines and autism (Taylor et al., 2014); (Uno et al., 2015)(Jain et al., 2015). Further research trying to unravel the causes and risk factors have hinted that it is a multifactorial disorder: A mix of genetic, prenatal, and/or perinatal environmental factors are implicated, however much is unknown. The following article discusses how the cerebellum, although classically associated with balance, may in fact be the key to understanding autism…

Background: By The Medic Collective

Introduction

The causes of autism have been a matter of interest to medical researchers and practitioners for many years.  Autism is a very complex developmental disorder, where children “seem to live in their own world” and “lack social awareness”, which can often hold back a child from developing their social skills (Rochester, 2020). For many years, autism has been researched thoroughly in order to find a cause, and even a cure, with various different outcomes. However, it is becoming clear that the cerebellum in the brain may be central to autism, being one of the “the most consistently documented location[s] of […] abnormality” in autistic individuals (Schreibman, 2005).

Cerebellar vermis

Autism has been attributed to a number of different causes, many of which relate to structural changes to the cerebellum. Scientific research shows that the cerebellar vermis is one of the main origins of autism. The cerebellar vermis is located between the two hemispheres of the cerebellum and it contributes to body posture and locomotion (Silvertant, 2019), meaning that it coordinates speech and body movement.

Changes in specific lobules have resulted in major changes to children’s behaviour, and therefore have become strongly associated with autism: Children with autism have been seen to have unsettled hand-eye coordination, which is noticeably related to the cerebellar vermis. Statistical exploration of the results of a study in 1994 on vermis lobules in autistic children showed two subgroups of people. It demonstrated that 86% possessed vermian hypoplasia, the underdevelopment of lobules VI-VII, while 12% showing signs of vermian hyperplasia, the enlargement of these vermis lobules (Courchesne, et al., 1994). This means that any significant change to the size of lobules VI-VII can lead to similar symptoms to autism.

Right Crus I

Researchers, having tested other areas of the cerebellum, have found that the Right Crus I (RCrusI) appears to be linked with autism (Deweerdt, 2020). The RCrusI is a region in the cerebellum and despite its specific function being unknown, previous work suggested that it is involved in social and cognitive processing. A study involving 81 typical children and 81 autistic children undergoing fMRI brain scans showed that there was more communication between the RCrusI and part of the frontoparietal network in the children with autism (Furfaro, 2017). As a result of the different amount of activity in the RCrusI, the frontoparietal network is also greatly affected, providing a basis for the inability of most autistic children to control their behaviour.

Purkinje cells

Another structural change in the cerebellum is associated with Purkinje cells (PCs). PCs are some of “the largest and most elaborate” forms of neurons, which can be found in the cerebellum (Hansen, 2016). Many sources indicate that there are fewer and smaller PCs in those with autism (Fernández, Sierra-Arregui, & Peñagarikano, 2019). This means that, due to PCs having important connections in the cerebellum, and that children with autism have fewer of these, they could be seen as a large contributing factor to the disorder. According to post-mortem studies by Hampson and Blatt, “75 percent of autism cases had fewer PCs than controls, and in one study, the remaining PCs were 24 percent smaller” (Hansen, 2016). This shows that a common factor of autism is the overall smaller dimensions or lack of Purkinje cells in autistic children.

Conclusion

Overall, structural changes in the cerebellum are likely to be associated with autism in children. Future research into autism in paediatrics will allow us to understand in greater detail the interaction of the various elements of the condition and identify the primary cause(s). This will hopefully lead towards more rapid progress towards a treatment or cure for autism.

Written by Victoria, year 12

Bibliography

Courchesne, E., Saitoh, O., Yeung-Courchesne, R., Press, G. A., Lincoln, A. J., Haas, R. H., & Schreibman, L. (1994, January). Abnormality of cerebellar vermian lobules VI and VII in patients with infantile autism: identification of hypoplastic and hyperplastic subgroups with MR imaging. Retrieved from National Library Of Medicine: https://pubmed.ncbi.nlm.nih.gov/8273650/

Deweerdt, S. (2020, March 9th). Brain’s motor hub plays unsung role in social skills, cognition. . Retrieved from Spectrum News: https://www.spectrumnews.org/news/brains-motor-hub-plays-unsung-role-in-social-skills-cognition/

Fernández, M., Sierra-Arregui, T., & Peñagarikano, O. (2019, May 7). The Cerebellum and Autism: More than Motor Control. Retrieved from Intech open: https://www.intechopen.com/books/behavioral-neuroscience/the-cerebellum-and-autism-more-than-motor-control

Furfaro, H. (2017, December 18). Study on cerebellum’s role in autism homes in on ‘social’ region. Retrieved from Spectrum News: https://www.spectrumnews.org/news/study-cerebellums-role-autism-homes-social-region/

Hansen, S. (2016, January 14). A role for the cerebellum in autism: New review synthesises the evidence. Retrieved from Hussman autism: https://www.hussmanautism.org/cerebellum-review/

Jain A, Marshall J, Buikema A, Bancroft T, Kelly JP, Newschaffer CJ. Autism occurrence by MMR vaccine status among US children with older siblings with and without autism. JAMA. 2015 Apr 21;313(15):1534-40. doi: 10.1001/jama.2015.3077. Erratum in: JAMA. 2016 Jan 12;315(2):204. PMID: 25898051.

Rochester, U. o. (2020). Autism Spectrum Disorder (ASD). Retrieved from University of Rochester Medical Center: https://www.urmc.rochester.edu/childrens-hospital/developmental-disabilities/conditions/asd.aspx

Rogers TD, McKimm E, Dickson PE, Goldowitz D, Blaha CD, Mittleman G. Is autism a disease of the cerebellum? An integration of clinical and pre-clinical research. Front Syst Neurosci. 2013 May 10;7:15. doi: 10.3389/fnsys.2013.00015. PMID: 23717269; PMCID: PMC3650713.

Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine. 2014 Jun 17;32(29):3623-9. doi: 10.1016/j.vaccine.2014.04.085. Epub 2014 May 9. PMID: 24814559.

Schreibman, L. (2005). What causes autism? The science and fiction of autism.

Silvertant, M. (2019, January 23). Autistic Brain Differences – the Cerebellum. Retrieved from Embrace ASD: http://www.embraceasd.com/autistic-brain-differences-the-cerebellum/

Uno Y, Uchiyama T, Kurosawa M, Aleksic B, Ozaki N. Early exposure to the combined measles-mumps-rubella vaccine and thimerosal-containing vaccines and risk of autism spectrum disorder. Vaccine. 2015 May 15;33(21):2511-6. doi: 10.1016/j.vaccine.2014.12.036. Epub 2015 Jan 3. PMID: 25562790.

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