Multiple brain masses

Question 1

Multiple masses DDx (3)

Answer 1

Multifocal primary from seeding.
Mets.
Syndromes (e.g. NF2)

Question 2

Tumour vs mimic (3)

Answer 2

Mimics include abscess, infarct, MS plaque.
Incomplete ring enhancement - think MS plaque.
Diffusion restricution is either lymphoma or stroke or abscess. Lymphoma will enhance homogenously

Question 3

Intra-axial vs extra-axial (6)

Answer 3

Signs of extra-axial location:
- CSF cleft
- Displaced subarachnoid vessels
- Cortical grey matter between mass and white matter
- Displaced and expanded subarachnoid spaces
- Broad dural base
- Bony reaction

Question 4

Why enhancement? (5)

Answer 4

Things don’t enhance because of the blood brain barrier.
When they do enhance, it’s because they are extra-axial OR because they have compromised the blood brain barrier.
Extra axial things, e.g. meningioma, will enhance. High grade tumours and infections enhance.
Low grade tumours aren’t bad enough to damage the blood brain barrier, so they don’t enhance.
Gangliomas and Pilocytic astrocytomas are the exceptions, low grade tumours that enhance

Question 5

Multiple masses (2)

Answer 5

In adults or kids, multiple masses means likely mets or infection.
Differentiating is done on diffusion (infection will restrict).

Question 6

Mets - trivia (8)

Answer 6

Commonest CNS met in kid is neuroblastoma (bones, dura, orbit - not brain).
Most common location for mets is supratentorial at the grey-white junction (much blood flow and abrupt vessel caliber change). Also see haematogenois spread of infection go there too
Most common morphology is round/spherical
Mets can be singular 50% of the time. Solitary mass in adult is more likely met than primary CNS neoplasm.
MRCT for bleeding mets (Melanoma, Renal, Carcinoid, Choriocarcinoma, Thyroid)
Mets usually have more surrounding oedema than similar sized CNS primary.
Next step in an adult is look for primary (lung, breast, colon)

Question 7

Multifocal brain tumours (3)

Answer 7

Lymphoma, multicentric GBM, Gliomatosis gerebri like to be multifocal.
Medulloblastoma, Ependymoma, GBM, oligodendrogliomas can be multifocal from seeding.
Syndromes: tumours with syndromes are more likely to be multifocal

Question 8

Tumour associated syndromes (4)

Answer 8

NF1 - Optic gliomas, Astrocytomas
NF2 - Multiple schwannomas, meningiomas, ependymomas
Tuberous sclerosis - Subependymal tubers, IV giant cell astrocytomas
VHL - haemangioblastomas