[Computed tomographic and magnetic resonance tomographic findings in pilocytic astrocytoma].

PURPOSE: In a retrospective study we examined the predilection sites, the CT and MR morphology and the contrast behaviour of intracranial pilocytic astrocytoma (PA) in a large number of patients.

MATERIAL AND METHODS: The study consists of 47 patients (18 male, 29 female, mean age 10.1 years) with histologically proven PA.

RESULTS: The chief predilection site turned out to be the hypothalamic region (15/47 = 32%). The other regions involved were (in descending order): brain hemispheres 8/47 = 17%; cerebellar vermis 7/47 = 15%, cerebellar hemispheres; thalamic nuclei and pontomedullar region 4/47 = 8.5% each; pineal gland 2/47 = 4%; pons, lamina tecti and optic fascicle 1/47 = 2% each. The PA presented 24/47 = 51% cysts; 7/47 = 15% calcifications; 2/47 = 4% necrosis and 1/47 = 2% perifocal oedema. In three cases (3/47 = 6%) CT and 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 surrounding structures, and to disseminate into the intracranial and spinal subarachnoid space.