Adult medulloblastoma mimicking Lhermitte-Duclos disease: can diffusion weighted imaging help?

Lhermitte-Duclos disease, also known as dysplastic cerebellar gangliocytoma, is a rare cerebellar benign tumor with characteristic appearance of thickened cerebellar folia giving a laminated or striated appearance, quite diagnostic of the condition. We had seen a patient with medulloblastoma with imaging findings suspicious for thickened cerebellar folia reminiscent of Lhermitte-Duclos disease. However, it showed patchy contrast enhancement and restricted diffusion on diffusion-weighted imaging, which are not typically associated with Lhermitte-Duclos disease. Presence of restricted diffusion proved to be a useful diagnostic feature for differentiation between the two lesions. This patient highlights the importance of obtaining all the MR imaging sequences in suspected Lhermitte-Duclos disease and histological diagnosis if there is doubt.