Module 2 - Head & Neck Flashcards
Classic MRI appearance of demyelination on CT and MRI
CT: homogenous low density lesion
MRI: partial ring enhancing lesion with mass effect on FLAIR
Classic appearance of abscess on CT and MRI
CT: low-density lesion with peripheral enhancement
surrounding low-density white-matter edema
MRI
- pus is bright on T2 weighted images
- the wall of the abscess typically lights up after contrast
- diffusion restriction within the abscess cavity
Classic appearance of tumour on T1 MRI with regards to contrast enhancement
- astrocytoma
- meningioma
- glioblastoma
- metastasis
- pleomorphic xanthoastrocytoma
- haemangioblastoma
- low grade astrocytoma: no enhancement
- meningioma: diffuse homogenous enhancement
- glioblastoma: irregular peripheral enhancement
- metastasis: ring enhancement
- pleomorphic xanthoastrocytoma: diffuse inhomogenous
- haemangioblastoma: mural nodular enhancement
Classic appearance of stroke on CT
hyperacute: 0 to 24 hours
acute: 24 hours to 1 week
subacute: 1 to 3 weeks
chronic: more than 3 weeks
early hyperacute
- hyperdense vessel
- loss of grey-white differentiation
- cortical hyperdensity, swelling
acute
- as above + mass effect
subacute
- fogging phenomenon
chronic
- a region of low density with a negative mass effect
What are the characteristic MR spectroscopy features of high grade glioma?
Markedly elevated choline and low NAA with inverted lactate peak
What are the indications for clot retrieval?
large vessel occlusion
○ Internal carotid: I/:/T lesions determine shape of clot as it reaches the bifurcation into MCA/ACA
○ M1: horizontal part of MCA
○ Proximal M2: to hairpin turn into sylvian fissure
○ Basilar
premorbid rankin <3
NIHSS >5
infarct <1/3 MCA terrtory
within 6 hours of onset
core <70 ml, ischaemia/penumbra mismatch
Define the ischaemic penumbra in terms of CBF and MTT
mean transit time increased, decreased blood flow but maintained CBV
potentially salvageable tissue
tissue at risk (Tmax >6) minus core (CBV and CBF low)
Define tissue at risk in brain perfusion
Tissue at risk = area where Tmax>6 seconds eg. Time it takes contrast to peak)
Define the core in terms of CBV, CBF and MTT
irreversibly infarcted tissue
matched areas of decreased CBF and CBV with increased MTT
CBF and CBV <30% of opposite side
What is the fogging phenomenon in stroke?
2 to 3 weeks following an infarct, the cortex regains near-normal density and imaging at this time can lead to confusion or missed diagnosis]
What are some features of benign (3) vs malignant (5)nodes in the head and neck?
benign
- fatty hilum
- wide
- homogenous, even shaped
malignant
- loss of hilum
- calcification
- >1cm
- round
- cystic
Radiological features of thyroid cancers (5)
- calcifications
- irregular
- taller > wide
- internal vascularity
- hypoechoic
+ nodal mets
( note that comet tails = benign)
Typical appearance of cavernous haemangioma
parenchymal “popcorn lesion” surrounded by T2 hypointensity (haemosiderin)
Typical appearance of pial AVM vs dural AVM
pial: nidus
dural: venous dilation, usually superficial cerebral vessels, no nidus
What is the “danger space” in head and neck anatomy?
Behind oesophagus, posterior to retropharyngeal space, medial to carotids from skull base to mediastinum
No normal contents
