Postoperative evaluation for intracranial recurrence of medulloblastoma: MR findings with gadopentetate dimeglumine.

PURPOSE To characterize the gadopentetate dimeglumine-enhanced MR features of recurrent medulloblastoma. METHODS The postsurgical gadopentetate dimeglumine-enhanced MR images of 48 patients (206 head examinations) with prior resection of medulloblastoma were retrospectively evaluated for enhancement in the brain parenchyma, meninges (dura, pia-arachnoid), and ventricles. RESULTS Nineteen patients had recurrent tumor as determined by clinical course and positive imaging studies. Seventeen patients with recurrent disease had intracranial enhancement predominating in the pia-arachnoid (63%) or as a focal nodular brain lesion (26%). Three of these patients also had intraventricular metastases. None of the clinically healthy patients had these findings. One patient had recurrent tumor presenting within the fourth ventricle. Only 3 of 8 intraventricular lesions observed in the 4 patients initially enhanced with gadopentetate dimeglumine. Another patient with recurrent disease had extensive skeletal metastases without involvement of the central nervous system. Dural enhancement was observed in patients both with (42%) and without (38%) recurrent tumor. CONCLUSION The MR findings of pia-arachnoidal or focal nodular brain enhancement are highly specific in the diagnosis of recurrent medulloblastoma. Pia-arachnoidal or focal brain enhancement were also the most frequent patterns associated with recurrent tumor. Dural enhancement alone is not a reliable indicator of recurrent medulloblastoma. Not all intraventricular metastases enhance with gadopentetate dimeglumine, and careful evaluation for nonenhancing lesions within the ventricles should be made on postoperative MR examinations.