Flashcards in Skull base Deck (17):
What is the differential diagnosis of a lesion at the CPA angle?
What are the lateral skull base approaches?
What sutures join at the asterion?
Lamdoid, occipitomastoid and parietomastoid sutures
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
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
What stereotactic radiosurgery?
Focused high dose delivery of radiation in a single fraction
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.
What governs the biological response with SRS?
Radiation dose (most important), cell response, volume irradiated, observation time
What are the mechanisms of SRS?
Direct effect on DNA and indirect with free radicals etc
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
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
Surgical management of a frontal mucocoele?
Look it up:
Think about decompression and reconstruction or de-functioning of the frontal sinus
How can you minimize brain retraction?
Brain anaesthesis (pCO2, hyperosmolar)
What are the principles of operating on skull base lesions?
Minimize brain restraction
What tests are used to confirm Cushing's disease?
Urinary 24h cortisol
Loss of cortisol diurnal rhythm
Dexamethasone suppression test (central vs ectopic)
Inferior petrosal sinus sampling
Why measure colour vision?
Loss of colour vision suggests a compression neuropathy
Where is Trautmann's triangle?
The area anterior to the sigmoid sinus below the level where the superior petrosal sinus joins