Metabolic findings using [18F]fluorodeoxyglucose (FDG) with positron emission tomography (PET) and correlative anatomic findings with computed tomography (CT) or magnetic resonance imaging (MRI) were characterized in 13 children with infantile autism. Four of 13 patients had both an abnormal FDG-PET and an abnormal MRI, whereas seven of 13 patients had both a normal FDG-PET and a normal CT or MRI. Sixteen of a total of 195 brain areas qualitatively examined with FDG-PET had a hypometabolic abnormality on PET. Three of the five abnormal structural imaging studies revealed neuronal migrational anomalies (focal pachygyria). In two of the five patients with anatomic abnormalities, these were noted only after knowledge of the FDG-PET findings. Our experience reveals that anatomic and metabolic abnormalities can be found in children who exhibit autistic behavior. An FDG-PET study may provide evidence of metabolic dysfunction after an initially unremarkable MRI scan because subtle anatomic abnormalities (as those seen with neuronal migrational anomalies) may be found only after knowledge of a regional metabolic abnormality.

The treatment and subsequent developmental progress of six children with dorsal third ventricular cysts are described. This cystic malformation has a radiological appearance which is superficially similar to that of the dorsal cyst of alobar holoprosencephaly, especially when the third ventricular cyst is large. Indeed, previous reports have identified this abnormality as a form of holoprosencephaly. However, careful study reveals that the dorsal third ventricular cyst is a distinct entity both developmentally and clinically. The six patients in this series were effectively treated with shunts, and their subsequent developmental progress was assessed by means of the Prescreening Developmental Questionnaire-Revised as well as the Bayley Scales of Infant Development. The nomenclature and differences between this entity and the holoprosencephalies are reviewed. The authors conclude that dorsal third ventricular cysts have a developmental and clinical course more similar to that of arachnoid cysts than to that of the holoprosencephalies.

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