Neuroradiology #15 – Long case

42-year-old male:
* Presenting with dizziness, vertigo and loss of coordination

What is it?

A focal expansile single lesion.

How is it like?

* Nodular
* Solid
* Hyperdense
* With moderate perilesional edema and mass effect deforming the 4th ventricle without signs of active hydrocephalus (not shown)
* With avid enhancement

Where is it?

Left posterior fossa.

Is the lesion intraaxial (cerebral hemisphere) or extraaxial (cerebellopontine angle)?

TIPS

Suggestive of extraaxial location:
1) Peripheral location and wide dural contact
2) Changes in the adjacent skull vault bone
3) Dural Tail

Definitive for extraaxial location:
1) CSF cleft.
2) Interposed vessels, cortex or dura.

The lesion is intraaxial, located in the left cerebellar hemisphere.

Which are the differentials for intra- and extraaxial posterior fossa tumours?

DIFFERENTIAL DIAGNOSTIC FOR INTRAAXIAL POSTERIOR FOSSA TUMOUR

* HEMANGIOBLASTOMA: Most frequent posterior fossa primary tumour in adults. Strong association with von Hippel Lindau disease. Cystic tumour with mural peripheral solid avidly enhancing nodule. Perilesional pathologic vessels.

* METASTASES: Most frequent posterior fossa tumour in adults. Expanisve focal lesion, single or multiple, well defined, solid-necrotic, great edema, and mass effect.

* GLIOMA: Pilocytic astrocitomas (cystic tumour with solid mural nodule) and diffuse brainstem gliomas (often low-grade, infiltrative, ill-defined lesions without enhancement) much more common in peadiatric population. High-grade gliomas (infiltrative ill-defined lesions with heterogeneous enhancement and necrosis) are uncommon in the posterior fossa.

* MEDULLOBLASTOMA: Paediatric population (more common): Intraventricular, midline; young adults; parenchymal, paramedial, focal solid enhancing lesion. Different subtypes that share hypercellularity as main feature: CT hyperdense, T2 Hypointense and difussion restriction. High propensity for CSF dissemination.

* LYMPHOMA: Focal solid enhancing single lesion or multiple cloud-like enhancing lesions. Hypercellularity as main feature: CT hyperdense, T2 hypointense and diffusion restriction.

* SUBEPENDYMOMA: Adults, intraventricular 4th ventricle. Plastic. None or little enhancement.

* EPENDYMOMA:Paediatric population: intraventricular posterior fossa; young adults: supratentorial periventricular. Plastic, heterogeneous, solid-necrotic, enhancing tumour.

DIFFERENTIAL DIAGNOSTIC FOR EXTRAAXIAL POSTERIOR FOSSA TUMOUR

* MENINGIOMA: Calcifications and bone hyperostosis

* SCHWANNOMA: Intralesional cyst and bone remodelling

* EPIDERMOID: No enhancement, restricted diffusion

* ARACHNOID CYST: CSF behaviour

MAIN CAUSES OF CT HYPERDENSITY

* Mineralization
* Hemorrhage
* Hypercellularity
* Melanin

The images, now supported by diffusion and ADC map, highly suggest and hypercellular tumour

There are two most reasonable diagnostics.

Which are the two most reasonable diagnostics?

MEDULLOBLASTOMA AND LYMPHOMA : Could be appropiate diagnositc options for a lesion with this semiology.
The final histologic diagnosis was: Primary CNS lymphoma

MAIN BRAIN LESIONS WITH CHARACTERISTIC DIFFUSION RESTRICTION

* Abscess
* Lymphoma
* Acute infarct
* Epidermoid

Special tip


In the DSC Perfusion sequence:

* Low relative cerebral blood volume (rCBV) assessed in the colour maps
* T1 Leakage effect assessed in the curve could have helped in the preoperative diagnostic of lymphoma against medulloblastoma.

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