Listed are the pathologies that closely resemble each other, and these pathologies are the favourite questions in final FRCR part A exam.
DERMOID/EPIDERMOID/ARACHNOID CYSTS
Dermoid cyst
|
Epidermoid cyst
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Arachnoid cyst
| |
1
|
Contain Ecto- & Meso-dermal elements
(Hair follicles, Sweat/Sebaceous glands)
|
Contain only Ecto-dermal elements
|
-
|
2
|
Usually located midline
Ie. Sellar/para-sellar, also in scalp, spine, orbit
|
Usually located off midline
Ie. Cerebellopontine angle (CPA), 4th ventricle
|
-
|
3
|
Signal follow fat
|
Signal follow CSF (except in DWI & FLAIR)
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Signal follow CSF in ALL SEQUENCES
|
4
|
Heterogeneous (calcification, soft tissue)
|
Usually has no Calcification
|
No calcification / soft tissue
|
5
|
Well circumscribed uniloculat cyst (vs teratoma which is multilocular
|
Irregular, lobulated mass and insinuates
|
Well circumscribed
|
6
|
Obstruct CSF pathway
Rupture => fat droplets in cisterns => Chemical meningitis
|
Encase & compress adjacent structures eg Nerves
|
May have mass effect if large
|
7
|
No enhancement
|
Usually no enhancement
+/- border rim enhancement
|
No enhancement
|
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