Perfusion impairments in infantile autism on technetium-99m ethyl cysteinate dimer brain single-photon emission tomography: comparison with findings on magnetic resonance imaging

The neuro-anatomical substrate of autism has been the subject of detailed investigation. Because previous studies have not demonstrated consistent and specific neuro-imaging findings in autism and most such studies have been performed in adults and school-aged children, we performed a retrospective review in young children in search of common functional and anatomical abnormalities with brain single-photon emission tomography (SPET) using technetium-99m ethyl cysteinate dimer (ECD) and correlative magnetic resonance imaging (MRI). The patient population was composed of 23 children aged 28-92 months (mean: 54 months) who met the diagnostic criteria of autism as defined in the DSM-IV and CARS. Brain SPET was performed after intravenous injection of 185-370 MBq of Tc-99m-ECD using a brain-dedicated annular crystal gamma camera. MRI was performed in all patients, including T1, T2 axial and T1 sagittal sequences. SPET data were assessed visually. Twenty patients had abnormal SPET scans revealing focal areas of decreased perfusion. Decreased perfusion of the cerebellar hemisphere (20/23), thalami (19/23), basal ganglia (5/23) and posterior parietal (10/23) and temporal (7/23) areas were noted on brain SPET, By contrast all patients had normal MRI findings without evidence of abnormalities of the cerebellar vermis, cerebellar hemisphere, thalami, basal ganglia or parietotemporal cortex, In conclusion, extensive perfusion impairments involving the cerebellum, thalami and parietal cortex were found in this study. SPET may be more sensitive in reflecting the pathophysiology of autism than MRI. However, further studies are necessary to determine the significance of thalamic and parietal perfusion impairment in autism.