Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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April 22, 2021
Multinodular and Vacuolating Posterior Fossa Lesions of Unknown Significance (MV-PLUS)
- Background:
- Vacuolating neuronal tumor (MVNT) of the cerebrum is a relatively novel entity added to the revised 2016 World Health Organization classification, though first described in 2013.
- It is characterized by a cluster of intra-axial nodules with mixed neuro-glial cells demonstrating internal vacuolating architecture.
- The lesions are benign and nonprogressive, and given their benign biologic behavior, are considered a “do-not-touch” or “leave-me-alone” lesion.
- So far, there are a few published cases of MVNT of the cerebellum. However, their exact imaging similarities to supratentorial MVNT and stability across time suggesting a benign natural history support that these likely represent the same histopathologic entity involving the cerebellum.
- Clinical Presentation:
- Most of the patients undergo imaging for headaches, seizure, and, as with supratentorial lesions, in many cases it was thought to be an asymptomatic incidental.
- Key Diagnostic Features:
- Characteristic imaging features are variably sized (1–5 mm) nodular foci in the cortical ribbon and juxtacortical white matter, which may be discrete, clustered, and/or coalescent.
- The nodular foci are nonenhancing T2 hyperintense with no suppression on T2 FLAIR, no mass effect, and no diffusion restriction.
- Differential Diagnoses:
- Potential diagnoses: DNET, focal cortical dysplasia, hamartoma, and enlarged perivascular spaces
- DNET may appear similar and is exceedingly rare in the cerebellar cortex. Multicystic appearance usually involves more cortical thickness compared with MVNT, often with gyral expansion. There is usually some suppression of signal on T2 FLAIR. A rim of T2 FLAIR hyperintensity has been described in many cases.
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Ganglioglioma more commonly has an associated cyst. However, it can appear solid, typically with T2 prolongation involving the cortex diffusely with a lack of the distinct nodularity of MVNT.
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Cerebellar cortical dysplasia usually shows an alteration in the morphology and distribution of the folia with minimal thickening and no nodular lesion.
- Cerebellar dysplastic gangliocytoma (Lhermitte-Duclos lesion): Typical tigroid pattern with enlargement of the cerebellar hemisphere; may be associated with Cowden syndrome (hamartomatous colon polyps)
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Enlarged perivascular spaces: CSF-like signal on all sequences; spare cortical ribbon
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CLIPPERS: DDx for the first case shown; shows associated edema and perivascular enhancement; responds to steroid therapy
- Treatment:
- MVNT involving the posterior fossa (MV-PLUS) has been shown to be a benign, nonaggressive lesion that remains stable over time. Therefore, when incidentally discovered, surveillance imaging is adequate. When supratentorial and if proven to cause symptoms such as seizure, surgery may be considered.
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