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List the main differential diagnoses

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intracranial aneurysm imaging differential

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intracranial giant aneurysm imaging differential diagnosis CTA suprasellar mass

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https://radiopaedia.org/articles/basilar-artery-aneurysm

The lesion is most suggestive of a giant basilar-tip (or basilar apex) aneurysm, given the lobulated, intensely contrast-opacified mass in the interpeduncular/prepontine cistern. Basilar aneurysms can appear as a hyperattenuating lobulated structure anterior to the midbrain on CT, and CTA defines the parent artery and branches more clearly. Radiology reference
Main differentials:
  1. Giant or partially thrombosed basilar-tip aneurysm
    Most likely. A non-opacifying peripheral component may represent mural thrombus.
  2. Other posterior-circulation aneurysm
    For example, aneurysm of the superior cerebellar artery, posterior cerebral artery, vertebral artery, or PICA, depending on the precise vascular connection.
  3. Arteriovenous malformation or dural arteriovenous fistula with a venous varix
    Usually accompanied by serpiginous feeding/draining vessels and early venous filling on angiographic imaging.
  4. Highly vascular extra-axial tumor
    Such as meningioma, less likely if the lesion fills exactly like an artery and lacks dural attachment/hyperostosis.
  5. Hemangioblastoma or hypervascular metastasis
    Considered if MRI shows a true solid/cystic parenchymal mass rather than a vascular lumen.
  6. Thrombosed aneurysm mimicking a tumor
    The important tumor mimics include glioma, craniopharyngioma, pituitary macroadenoma, and suprasellar meningioma, depending on whether the lesion is actually centered higher in the suprasellar region. The textbook differential for chiasmal/suprasellar mass lesions includes pituitary tumors, suprasellar meningioma, supraclinoid aneurysm, craniopharyngioma, and glioma. Localization in Clinical Neurology, 8e, p. 359.
Best test to resolve the diagnosis: thin-section CT angiography, followed by catheter digital-subtraction angiography if intervention is being considered. Giant intracranial aneurysms, generally at least 2.5 cm, can behave as mass lesions. Localization in Clinical Neurology, 8e, p. 1396.
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