Ch89 Radiological differential diagnoses Flashcards
(34 cards)
What are the main causes of a mass in the posterior fossa of an adult?
Met Met Met
What is the differential diagnosis of a posterior fossa mass in an adult?
A - Tumour 1) Metastasis 2) Haemangioblastoma (10%) - mural nodule with cyst. Look for flow voids 3) Pilocytic astrocytoma - young adults 4) Brainstem glioma 5) Choroid plexus tumour 6) Cerebellar liponeurocytoma B - Infection (Abscess) C - Vascular (cavernoma / haemorrhage / infarct)
What are the radiological features of Lhermitte-Duclos?
Tiger stripes with widening of the folia. Non-enhancing. Can be focal or diffuse.
What is the DD of multiple posterior fossa lesions?
1) Metastases 2) Abscess 3) Haemangioblastoma (think VHL!) 4) Cavernomas
What proportion of paediatric tumours are in the posterior fossa?
2/3
What is the differential diagnosis of a posterior fossa tumour in a child?
1) PNET incl Medulloblastoma 2) Pilocytic astrocytoma 3) Brainstem glioma 4) Ependymoms 5) Choroid plexus papilloma 6) ATRT 7) Mets (neuroblastoma / rhabdomyosarcoma / Wilms)
What is the most common location for a medulloblastoma?
Roof of the 4th ventricle (fastigium)
How can medulloblastomas be differentiated from ependymomas?
1) Medulloblastomas may show the ‘banana sign’ where there is a cleft of csf between the lesion and the floor of the 4th V. 2) Medulloblastomas are haemogenous 3) Calcification more common with ependymomas 4) Ependymomas grow out of the foramen of lushka
What are the molecular subtypes of medulloblastoma?
1) Wnt (10%) - usually in the cerebellar peduncle. Associated with a mutation in the b-catenin gene. Best prognosis. 2) SHH (20%) - usually in the cerebellar hemisphere. Intermediate prognosis. Associated with mutations in PTCH, SUFU, GLI1 and GLI2. 3) Group 3 (30%) - Midline with prominant enhancement. MYC amplification; GABAergic expression. 4) Group 4 (40%) - Midline with little enhancement. CDK6 and MYCN mutations. Glutamatergic expression.
What is the most common location for a pilocytic astrocytoma in a child?
Cerebellar hemisphere
Where do ependymomas arise from?
Floor of the 4th ventricle
What is the DD of a CP angle lesion?
Vestibular schwannoma Meningioma Epidermoid Metastasis Trigeminal / facial schwannoma Arachnoid cyst Neurenteric cyst Aneurysm Extension of glioma Cholesterol granuloma
What are the causes of a cystic lesion in the CP angle?
Arachnoid cyst Epidermoid cyst (restricted DWI) Dermoid cyst (high T1 and midline) Cystic schwannoma Neurenteric cyst
What is the classical presentation of a vestibular schwannoma?
Progressive unilateral hearing loss with tinnitus Vertigo is rare CN5 involvement does not occur unless >3cm - check the corneal reflex! Facial nerve involvement suggests a meningioma
Where do CP angle meningiomas arise from?
The superior anterior edge of the IAC Facial nerve palsy before hearing loss and more commonly have trigeminal neuralgia
What lesions affect the petrous apex?
Gragenigo’s syndrome Cholesterol granuloma Aneurysm SCC Glomus tumour Chondrosarcoma
What is the differential diagnosis of a foramen magnum lesion?
Meningioma Chordoma Epidermoid Chondrosarcoma Metastasis Exophytic lesion arising from the brainstem
What is the DD of white matter lesions?
1) Ischaemia (small vessel) 2) Demyelination 3) Vitamin def 4) Viral (PML/ HSV. HIV/CMV) 5) Metabolic derangements (CPM) 6) Low grade glioma
What is the DD of a lesion in the corpus callosum?
Lymphoma MS Tumefactive demyelination Lipoma DAI
What is the DD of a pituitary tumour?
Adenoma / Carcinoma Craniopharyngioma Rathke cleft cyst Germ Cell Tumour Metastasis Aneurysm Astrocytoma Hypothalamic glioma Optic nerve sheath tumour Epidermoid cyst Chordoma Arachnoid cyst Pseudotumour i.e. physiological enlargement in puberty / pregnancy
What are the classical MR spectroscopy features of a low grade tumour?
Choline - Cr - NAA peaks form a 45 degree angle (Hunter’s angle)
What is the triad of clinical features associated with a pineal region GCT?
DI, Panhypopituitarism and visual deficit
Lesion in the pineal and pituitary region. What is the diagnosis?
Synchronous GCT
What are the two types of hypophysitis?
Lymphocytic (late pregnancy / post partum) and granulomatous
