CT AND MR FINDINGS IN PILOCYTIC ASTROCYTO MAS

Purpose: In a retrospective study we examined the predilection sites, the CT and MR morphology and the contrast behaviour of intracranial pi locytic astrocytoma (PA) in a large number of patients. Material and m ethods: The study consists of 47 patients (18 male, 29 female, mean ag e 10.1 years) with histologically proven PA. Results: The chief predil ection site turned out to be the hypothalamic region (15/47 = 32%). Th e other regions involved were (in descending order): brain hemispheres 8/47 = 17%; cerebellar vermis 7/47 = 15%, cerebellar hemispheres; tha lamic nuclei and pontomedullar region 4/47 = 8.5% each; pineal gland 2 /47 = 4%; pens, lamina tecti and optic fascicle 1/47 = 2% each. The PA presented 24/47 = 51% cysts; 7/47 = 15% calcifications; 2/47 = 4% nec rosis and 1/47 = 2% perifocal oedema. in three cases (3/47 = 6%) CT an d MRI showed no contrast enhancement. Conclusion: PA appear in almost all brain regions but there is a clear preference of the hypothalamic region. PA of the hypothalamic region are a special subgroup. They are often associated with neurofibromatosis 1, tend to infiltrate surroun ding structures, and to dissiminate into the intracranial and spinal s ubarachnoid space.