Friday, December 3, 2010

It's All In Your Head

I saw on my local news last night a brief story about a new study using magnetic resonance imaging (MRI) to look at the brains of individuals with autism. The idea was to identify regions of the brain that may behave differently in those with autism as compared to those without autism, with the ultimate aim being to provide an objective means of diagnosing the disorder.

Currently, autism is diagnosed using questionnaires and subjective measures, like the Autism Diagnostic Observation Schedule (ADOS) or the Autism Diagnostic Interview (ADI). These tools rely on questions asked of the parents, as well as a clinician's observations of the child's behavior. The subjective nature of the ADOS and ADI open the diagnosis up to some variability, depending on the biases of the clinician and others involved. The result is that there can be slight differences in the diagnostic scores between observers.

This new study may change that.

Published online ahead of print yesterday in the journal Autism Research and titled Atypical diffusion tensor hemispheric asymmetry in autism, Dr. Nicholas Lange, of Harvard Medical School and McLean Hospital, and his colleagues studied 30 males aged 7-28 years and 30 matched controls. They also performed a replication sample with 12 autistic males and 7 matched controls. Individuals with autism were high-functioning and satisfied the full criteria for idiopathic autism (i.e., autism with no clear cause).

The researchers used MRI to look at the white matter microstructure (WMM) of two regions of the temporal lobe: the superior temporal gyrus (STG) and the temporal stem. According to the authors, these regions contain "circuitry central to language, emotion, and social cognition" and would thus be promising candidates for understanding the neurobiology of autism. There seems to be some precedence for this, as the STG has been associated with early onset schizophrenia.

What Lange, et al., found was that these regions exhibited reversed asymmetry of activity compared to controls. In other words, from what I understand, they found that autistic individuals showed greater activity in the right hemisphere and decreased activity in the left hemisphere, while controls had the opposite. Someone a bit more versed in the jargon, please correct me on this if I am wrong (not being a neurologist or radiologist).

The promise this study's findings hold is an objective method of diagnosing autism. With an objective measure such as this, it may be possible to provide a definitive diagnosis earlier than the ADOS or ADI allow, thus providing parents the opportunity to start intervention (e.g., ABA) much sooner. The common idea is that the sooner one can start treatment, the better the outcome will be for the child.

In statements to the press, the researchers stress that their results are not ready for clinical application, and I agree. Although I do not have access to the full text of the study and some of the jargon is a bit above my head, I do realize that this is a small study and its results need to be independently replicated. A couple things come to mind that need to happen. First, they need a larger trial. There are just too few subjects in this one to obtain adequate power to ensure the results are real. Second, they need to use younger subjects. Because children are rapidly changing as they grow, the findings from this study may not hold up in a younger population, rendering the technique useless as a means of early diagnosis. Third, the subjects in this trial were described as high-functioning. Because of the subject selection, the results may not apply for individuals with more severe autism.

There is still a great deal that we do not know about autism, but studies such as this aim to shine a light on that vast unknown. Gradually, we uncover more and more about the physiology and etiology of autism. As the discoveries mount, we come that much closer to finding the cause(s) and, from there, treatments for autism spectrum disorders. Lange, et al., present an interesting study, but it is not a silver bullet. Much, much more work needs to be done before their findings can be applied in the field.

9 comments:

  1. Fascinating to think that even though autism probably "is" several disorders, they could have a common sign such as this. As a diagnostic tool alone, it would be very helpful, and if it can eventually point toward a therapy, so much the better.

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  2. Interesting development. Coming from a medical lab background, I really wish there was a readily-available, objective diagnostic tool to diagnose autism spectrum disorders. Perhaps this is a step in that direction? Perhaps.

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  3. If the findings hold up, consistently showing the same or similar differences between those with autism and those without, I think it would be really helpful in narrowing the focus of research into the cause(s). Even if the findings only apply to older individuals and not infants or toddlers, that kind of information would still be really useful.

    One other limitation that I thought of with this study is that all of the subjects had idiopathic autism. Would their findings apply equally to those with secondary autism (e.g., autism as a result of congenital rubella syndrome or Fragile X). And if the results comparing idiopathic vs. secondary are different, that, too, could aid the investigation into cause(s) (though it would also raise a number of questions).

    I hope that they expand their study and that it is replicated by others. It would be such a boon to autism research and bring us one step closer to helping the families coping with an ASD.

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  4. While there have been folks on my side of the debate who've scoffed at this new study, I welcome it. No matter what the cause or extent to which other parts of the body may be involved in the development of ASD, the fact is there must be certain conditions in the brain behind the symptoms ascribed to these disorders. This study sheds some light on what those conditions may be.

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  5. @Jake Crosby

    Thank you for stopping by. I'm glad that you can see the value of this sort of research, and I wish that some of your compatriots would focus a bit more on this sort of thing, too.

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  6. Todd congenital rubella syndrome or Fragile X are neither autism or secondary autism.

    Or are you suggesting that environmental factors such as rubella lead directly to autism ?

    Even DSM V does not share your opinion and it takes Autism to its broadest continuum.

    http://www.dsm5.org/ProposedRevisions/Pages/proposedrevision.aspx?rid=94

    Cheers

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  7. @John

    I did not say that CRS or Fragile X are autism. I gave them as examples of illnesses or disorders that can lead to autism. CRS and Fragile X are known risk factors for developing an autistic spectrum disorder. For CRS, see, for example, this case report: http://www.ncbi.nlm.nih.gov/pubmed/20171592.

    It states, as part of the background for the report, that "[p]sychiatric disorders are often seen among CRS patients, with an incidence of 4.12-7.3% for autism."

    It is not certain that someone with one of these disorders will have autism, but they do increase the risk.

    As for DSM V, keep in mind that it is primarily concerned with psychiatric symptoms, not with the actual causes of the disorders. Although, I do note that it says this (emphasis added):

    "Because autism is defined by a common set of behaviors, it is best represented as a single diagnostic category that is adapted to the individual’s clinical presentation by inclusion of clinical specifiers (e.g., severity, verbal abilities and others) and associated features (e.g., known genetic disorders, epilepsy, intellectual disability and others.)"

    Known genetic disorders, like Fragile X. And one can assume that the list of examples is not exclusive.

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  8. "Regarding how to incorporate subgroups of ASDs with an identifiable etiology (e.g., Fragile X, tuberous sclerosis) into the diagnostic framework, options include listing the medical condition on Axis III, including a subtyping scheme on Axis I (e.g., autism, Fragile X type), or excluding it from the diagnosis altogether, as is now done with Rett’s syndrome."

    http://www.dsm5.org/research/pages/autismandotherpervasivedevelopmentaldisordersconference%28february3-5,2008%29.aspx

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  9. @John

    From perusing your link, it appears that they may be considering moving Fragile X into a separate diagnosis, because, unlike some other genetic/physiological research coming out, it is "sufficiently specific or cohesive enough to allow for the identification of clinically meaningful subgroups or to be used as risk markers".

    So, with the revisions that will ultimately be DSM-V, we may see Fragile X as its own diagnosis, and not part of the ASD definition. Currently, however, it is a recognized risk factor for autism.

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