Unleashing the Mystery of a Treated Case of Medulloblastoma

Abstract

Medulloblastoma (MB) is the most common malignant brain tumor in children. Despite advancement in treatment modalities, recurrence remains common, even among those treated with a combination of neurosurgery, craniospinal irradiation, and chemotherapy. The diagnosis of recurrence is usually not difficult in these cases. However, it may pose a challenge in cases with unusual clinical presentation and imaging. Imaging findings on magnetic resonance imaging, with application of perfusion, in conjunction with positron emission tomography-computed tomography can help in clinching the diagnosis in such cases. MB subgroups show consistent patterns even in cases of recurrence, and sonic hedgehog group MB may present as local recurrence showing enhancement with no diffusion restriction, as demonstrated in this case.

Keywords: MR perfusion; radiation-induced demyelination; radiation-induced glioma; recurrent medulloblastoma.

Fig. 1

Craniospinal irradiation therapy planning image demonstrating color map showing dose distribution of 95% of 11.6 Gy.

Fig. 2

Axial T2-weighted ( A ) and postcontrast images ( B ) demonstrating no evidence of residual disease postadjuvant craniospinal radiation therapy and chemotherapy.

Fig. 3

Axial T2-weighted ( A ), T2/FLAIR (fluid-attenuated inversion recovery) ( B ), and postcontrast images ( C ) reveal T2/FLAIR hyperintensities with corresponding postcontrast enhancement in pons, medulla, and left cerebellar peduncle ( arrowheads ).

Fig. 4

Axial T2-weighted ( A ), T2-fluid-attenuated inversion recovery ( B ), and postcontrast images ( C ) showing altered signal intensity ( arrowheads ) involving inferior colliculus, pons, and left cerebellar peduncle with mild decrease in edema but persistent postcontrast enhancement.

Fig. 5

Perfusion images reveal that the lesions show hypoperfusion.

Fig. 6

Fluorodeoxyglucose-positron emission tomography images reveal avidly enhancing soft tissue lesion noted in medulla extending into left cerebellum and superiorly involving pons (standardized uptake value-max 14.6).

Fig. 7

Axial noncontrast computed tomography image showing a hyperattenuating mass in the pons and left cerebellar peduncle ( arrowhead ).

Fig. 8

Axial diffusion-weighted images showing no diffusion restriction within the areas of altered signal intensity seen in Fig. 2 .

Fig. 9

Photomicrographs showing a cellular tumor of primitive embryonal cell morphology ( A ) with marked anaplasia seen in the form of cellular wrapping ( B ).