Saturday, 9 May 2015

Magnetic Resonance Imaging (MRI) findings in severe autism

"The aim of this study was to evaluate the frequency of neuroradiologic abnormalities in low-functioning autistic children compared to Intellectual Quotient and age-matched nonsyndromic children, using the same set of magnetic resonance imaging (MRI) sequences."

Accepting that the term 'low-functioning autism' is not one that I would personally use (indeed I'm not exactly enamoured by the term 'high-functioning' either), the results of the study by Alessandra Erbetta and colleagues [1] are briefly served up for your reading delight today. Mirroring other findings from this group [2], authors reported that: "MRI was rated as abnormal in 44% of autistic and 54% of children with intellectual disability" surveyed. Further: "The main results were mega cisterna magna in autism and hypoplastic corpus callosum in intellectual disability."

I'm not a 'brain man' insofar as having any experience of MRI or the 'neuroradiologic' findings reported by Erbetta on either publication occasion. I do however find the idea that MRI or similar imaging methods might be indicated when someone presents with 'severe' autism (severe as in severely impacting on both clinical presentation and interfering with the acquisition of adaptive skills) as being quite a sensible approach. Mega cisterna magna - significantly enlarged CSF retrocerebellar cisterns in the posterior fossa with normal cerebellar morphology (apparently) - is still the source of some debate as to exactly what such a finding means. Zimmer and colleagues [3], looking through almost 20,000 "consecutive CT/MRI of the brain" found 49 cases of "isolated mega cisterna magna" in their cohort. Despite presenting with "overall normal cognitive functioning" they suggested that such a finding might have some influence on aspects of memory and verbal fluency. I say all this acknowledging that the brain is a mighty complex organ that is also surprisingly flexible in terms of the various duties it performs. A possible link between mega cisterna magna and congential cytomegalovirus (CMV) infection [4] is also intriguing from an autism perspective (see here) as per the recent paper from Engman and colleagues [5].

The MRI results of those with severe autism also need to be compared against the data amassed from those perhaps not falling into that 'severe autism' categorisation. I've previously covered the paper by Roma Vasa and colleagues [6] (open-access) (see this post) who concluded that in 90% of cases of 'high-functioning' autism, there was very little too see from a brain imaging perspective. The more recent paper from Koolschijn et al [7] questioning the idea that autistic traits are specifically linked to brain morphometry adds to the idea that looking for a 'brain signature' for 'all autism' is probably not going to yield too many generalisable results, but rather the focus needs to be on endophenotypes.

Music: Daft Punk - Da Funk.

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[1] Erbetta A. et al. Low-Functioning Autism and Nonsyndromic Intellectual Disability: Magnetic Resonance Imaging (MRI) Findings. J Child Neurol. 2015 Apr 20. pii: 0883073815578523.

[2] Erbetta A. et al. Neuroimaging findings in 41 low-functioning children with autism spectrum disorder: a single-center experience. J Child Neurol. 2014 Dec;29(12):1626-31.

[3] Zimmer EZ. et al. Clinical significance of isolated mega cisterna magna. Arch Gynecol Obstet. 2007 Nov;276(5):487-90.

[4] Dogan Y. et al. Intracranial ultrasound abnormalities and fetal cytomegalovirus infection: report of 8 cases and review of the literature. Fetal Diagn Ther. 2011;30(2):141-9.

[5] Engman ML. et al. Prenatal acquired cytomegalovirus infection should be considered in children with autism. Acta Paediatr. 2015 Apr 21.

[6] Vasa RA. et al. Normal rates of neuroradiological findings in children with high functioning autism. J Autism Dev Disord. 2012 Aug;42(8):1662-70.

[7] Koolschijn PC. et al. Are Autistic Traits in the General Population Related to Global and Regional Brain Differences? J Autism Dev Disord. 2015 Apr 7.

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ResearchBlogging.org Erbetta A, Bulgheroni S, Contarino VE, Chiapparini L, Esposito S, Annunziata S, & Riva D (2015). Low-Functioning Autism and Nonsyndromic Intellectual Disability: Magnetic Resonance Imaging (MRI) Findings. Journal of child neurology PMID: 25895913