GERMINOMAS OF THE BASAL GANGLIA AND THALAMUS - MR FINDINGS AND A COMPARISON BETWEEN MR AND CT

OBJECTIVE. The purpose of this study was to describe the MR imaging appearance of germinomas in the basal ganglia and thalamus and to compare the MR findings with CT findings. MATERIALS AND METHODS. Eleven MR studies of 10 patients with pathologically proved germinomas in the basal ganglia or thalamus were retrospectively reviewed. In nine of the 10, the MR findings were compared with CT findings. All patients were male, and all except one were in their second decade of life. All the tumors were located in paraventricular areas. RESULTS. Most of the tumors were 4-7 cm in diameter. MR images showed that the tumors were mostly cystic in five patients, mostly solid with cystic components in four, and solid without cystic components in one. The solid portion mostly was isointense relative to the cerebral cortex for all MR pulse sequences. The cystic portion was hyperintense relative to CSF on T1- and T2-weighted images. MR images showed intratumoral hemorrhage in seven patients. It appeared as an area of hyperintensity on T1- and T2-weighted images in five patients and as a fluid-fluid level with marked hypointensity on T2-weighted images in two. Hemorrhage was not visualized on CT scans in any patient. Flecked or amorphous calcifications visualized on CT scans in two patients were hardly detectable on MR images. Peritumoral edema was usually minimal. CT scans and MR images obtained after injection of contrast material both showed heterogeneous and dense enhancement in the solid portions of the tumors. CONCLUSION. MR images of germinoma in the basal ganglia and thalamus show a large paraventricular mass. Cystic areas, focal hemorrhages, and minimal surrounding edema are common. Unlike CT, MR imaging allows characterization of intratumoral hemorrhage.