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Flashcards in Skull base Deck (17):
1

What is the differential diagnosis of a lesion at the CPA angle?

Acoustic neuroma
Meningioma
Epidermoid
Cholesterol granule

2

What are the lateral skull base approaches?

Retrosigmoid
Translabrynthine
Transcochlear
Total petrosectomy

3

What sutures join at the asterion?

Lamdoid, occipitomastoid and parietomastoid sutures

4

How do you work up a patient with Cushings syndrome?

24 h urinary free cortisol for total level of cortisol
Comparison of midnight and 8 am salivary cortisol for loss of diurnal variation
ACTH
Low dose dexamethasone test will suppress a normal pituitary not a pituitary adenoma (to distinguish pseudocushings)
High dose dexamethasone test to distinguish ectopic from pituitary cause
Petrosal sinus sampling

5

What stereotactic radiosurgery?

Focused high dose delivery of radiation in a single fraction

6

What is the difference between conformity and selectivity?

Conformity is how close the given dose is to the planned dose; Selectivity is the irradiation of the tumour and not normal brain.

7

What governs the biological response with SRS?

Radiation dose (most important), cell response, volume irradiated, observation time

8

What are the mechanisms of SRS?

Direct effect on DNA and indirect with free radicals etc

9

When use SRS vs External beam?

SRS needs a defined target with safety margin , can be used with radioresistant lesions and can be given as a boost for EBRT

10

What are the landmarks for percutaneus glycerol rhizotomy?

Hartel (1912) method: 3cm lateral to the angle of the mouth, mid-pupillary line and 1/3 from the tragus to the lateral canthus

11

Surgical management of a frontal mucocoele?

Look it up:
Think about decompression and reconstruction or de-functioning of the frontal sinus

12

How can you minimize brain retraction?

Brain anaesthesis (pCO2, hyperosmolar)
Bone removal
CSF drainage

13

What are the principles of operating on skull base lesions?

Adequate approach
Minimize brain restraction
Devascularize early
Internally debulk
Reconstruct

14

What tests are used to confirm Cushing's disease?

Urinary 24h cortisol
Salivary cortisol
Loss of cortisol diurnal rhythm
ACTH
Dexamethasone suppression test (central vs ectopic)
Inferior petrosal sinus sampling

15

Why measure colour vision?

Loss of colour vision suggests a compression neuropathy

16

Where is Trautmann's triangle?

The area anterior to the sigmoid sinus below the level where the superior petrosal sinus joins

17

What are the features of LiFraumeni syndrome?

p53 mutation resulting in breast, brain and soft tissue / bone sacrcomas at a young age