Recently a psychiatrist diagnosed my child with CdLS with Pervasive Development Disorder (PDD). We have seen a neurologist and after his tests he just said that he could have a form of Attention Deficit Hyperactivity Disorder ADHD. I've heard that fMRI's can diagnose ADHD. I would like to get an fMRI scan for my child so he could be better diagnosed instead of guessing and putting a child on medication.

SAC approved answer

fMRI stands for functional MRI. It basically measures changes in blood flow superimposed on anatomical information, so that you can see to which brain region there is increased blood supply when a certain mental or other task is performed. It can also measure alterations in steady state blood flow for instance when a test medication is given.

There is one such study for ADHD in which changes in steady state blood flow in the cerebellum were seen under Ritalin in a subset of ADHD boys. This was very preliminary and also not terribly striking - so at this point in time there is no routine use for fMRI in the diagnostic evaluation of ADHD children and their optimal medication need. And if your son has a really mild form of CdLS he would certainly not have "classic" ADHD anyways, since he would have an underlying disorder of which hyperactivity is a very common part - so the fMRI study results would not be easily understandable.

CB/TK 7-13-10

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