Quantitative rCBF measurements with Xenon 133 were found to be significantly higher than normal in autistic children, with maximal values in the frontal lobes and visual cortex. Minimal perfusion was observed in the temporal lobes. Decreased flow was also noted in the cerebellum and occipital lobes.
The areas of increased perfusion, most frequently located in lateral frontal lobes, are similar to our observations in obsessive compulsive disorder (OCD children). Tc 99m HMPAO images (Prado et al.) demonstrate increased frontal perfusion, and demonstrating also temporal, occipital and cerebellar hypoperfusion. (Figure 1)
In children with OCD there is a significant increase in frontal perfusion observed bilaterally in a large number (~ 81%) of the children and unilaterally in a limited number (6%) of the children, with a total of 87% of children demonstrating increased frontal perfusion. Among 50% of these children there is also increased perfusion in the posterior cingulate gyrus. Of note, there is furthermore hypoperfusion of temporal lobes mostly in the mesial aspects in 93% of OCD children examined to date.( Mena et al)
Increased frontal perfusion was also reported (Rubin et al.) in adults. Most probably this phenomenon denotes a co-morbidity phenomenon also that is clinically observed between autism and obsessive compulsive disorder.