Neuroimaging of juvenile pilocytic astrocytomas: an enigma.
OBJECTIVE
To present the imaging, metabolic, and clinical data obtained in five patients with juvenile pilocytic astrocytomas (JPAs) and discuss the paradoxical neuroimaging findings.


METHODS
Five patients with JPAs who had undergone structural imaging and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were studied. Normalized glucose utilization rates (GURs) in the tumor were compared with GURs in histopathologically verified low-grade astrocytomas and high-grade tumors.


RESULTS
All JPAs enhanced markedly after administration of contrast medium. Their glucose metabolism was significantly (P < .001) higher than that of low-grade astrocytomas and was similar to that of anaplastic astrocytomas. All patients with JPAs were in stable condition and showed no evidence of disease progression despite contrast enhancement and high tumoral glucose metabolism.


CONCLUSIONS
The paradoxical FDG PET findings and enhancement at structural imaging might reflect the unusual vascularity of pilocytic tumors, and the increased GUR might be related to expression of the glucose transporter.
Neuroimaging Branch, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892.
M J
MJ
Fulham
J W
JW
Melisi
J
J
Nishimiya
A J
AJ
Dwyer
G
G
Di Chiro
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001254:Astrocytoma / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D003287:Contrast Media; D003847:Deoxyglucose / Q000031:analogs & derivatives; D004338:Drug Combinations; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D005682:Gadolinium; D019786:Gadolinium DTPA; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008536:Meglumine; D009942:Organometallic Compounds; D004369:Pentetic Acid; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
D003287:Contrast Media; D004338:Drug Combinations; D005462:Fluorine Radioisotopes; D009942:Organometallic Compounds; D019788:Fluorodeoxyglucose F18; D008536:Meglumine; D004369:Pentetic Acid; D003847:Deoxyglucose; D005682:Gadolinium; D005947:Glucose; D019786:Gadolinium DTPA