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
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.
