Brain Tumours

Question 1

what are the tour classifications

Answer 1

PRIMARY - malignant, benign

SECONDARY - metastases

Question 2

both types of primary tumour are generally classified by

Answer 2

CELL TYPE - those that arise from glial cells = gliomas, all others = non-glial tumours
LOCATION - glial = relationship to the tentorium, non-glial tumours = from the tissue it arises

Question 3

Describe Gliomas

Answer 3

one of the most common types of primary brain tumour
often named after the cells they rise from (astrocytomas = astrocytes)
classified by relationship to the tentorium (above/below)
SUPRATENTORIAL - in the cerebrum = mostly adults
INFRATENTORIAL - in the cerebellum = mostly children

Question 4

which gliomas have the worst prognosis of all CNS malignancies

Answer 4

brainstem gliomas

Question 5

tumours are grouped into grades depending on how quickly they grow - list them and expand

Answer 5

grade I - slow growing, often removable and curable
grade II - tend to spread recur more after treatment than grade I, most = eventually high grade tumours with poor prognosis
grade III - aggressive, tend to spread into surrounding brain tissue
grade IV - most aggressive malignant tumours, progress rapidly, poor prognosis

Question 6

the more normal the tumour cells look ……

Answer 6

the more slowly it is likely to develop, and the lower the grade

Question 7

the more abnormal the tumour cells look ….

Answer 7

the more quickly the tumour is likely to grow, and the higher the grade

Question 8

describe low grade tumours

Answer 8

generally extra-axial
classed as benign
may be life-threatening due to space-occupying nature

Question 9

describe high grade tumours

Answer 9

classed as malignant

usually intra-axial

Question 10

what is extra-axial

Answer 10

outside of the axis of the brain
does not arise from the brain itself
external to the pia mater
‘dural tail’

Question 11

what is intra-axial

Answer 11

arises from within the brain parenchyma

within the pia mater

Question 12

describe secondary tumour - brain mets

Answer 12

one of the most common complications of cancer
most common intracranial mass in adults (50%)
can be single but most often multiple tumours
intra-axial, extra-axial, intraventricular, grey/white matter junction, often associated with oedema

Question 13

cancers which commonly metastasise

Answer 13

breast, lung, renal, colon, melanoma

Question 14

Describe neurofibromatosis type 1

Answer 14

most common of the 2
tumours of the peripheral nerves causing lumps under the skin,
skeletal abnormalities - bowed legs, scoliosis, large head circumference
TREATMENT = controlling symptoms, surgery
malignant in about 3-5% of cases

Question 15

Describe neurofibromatosis type 2

Answer 15

very rare
hallmark finding = vestibular schwannomas - slow growing tumours of the schwann cells that form the myelin sheath on the vestibular branch of cranial nerve VIII
can compress or damage nearby structures - cranial nerves/brainstem
surgery amy risk hearing loss/paralysis
cochlear implants may be an option in this case

Question 16

how does tumour cause ICP and what can this result in

Answer 16

space occupying nature of the tumour

results in headaches, vomiting, papillaodema
subacute progressive deficit
new onset of fits
cranial nerve palsy - lack of function of a nerve (complete/partial weakness or paralysis of areas served by nerve)
drowsiness

Question 17

how is ICP caused

Answer 17

by mass effect as skull vault is fixed = no room for expansion, expanding haemorrhage/tumour/oedema increasing in volume, causing compression of the brain tissue, ventricles and extra-axial CSF become effaced, possible midline shift, blocking flow of CSF, possible hydrocephalus

Question 18

what occurs with ICP

Answer 18

brain tissue starts to herniate down through the foramen magnum (coning) where the brainstem becomes compressed - controls the essential functions for life

downward migration tears/compresses the critical blood vessels that supply the brainstem and the rest of the brain = ‘duret’ haemorrhage, ischaemia and cell death

also associated pressure on 3rd cranial nerve (oculomotor) causing decreased reactivity and dilation of the pupil (COMMON CLINICAL SIGN)

Question 19

what can be done for ICP

Answer 19

emergency craniotomy to relieve pressure

Question 20

describe papilloedema

Answer 20

optic nerve sheath is continuous with the subarachnoid space of the brain - short span between brain and eye and optic nerve is bathed in CSF, slight increases in CSF pressure = due to raised ICP = causes compression of the nerve, causing it to bulge into optic disc

Question 21

with tumours, imaging is essential for …

Answer 21

tumour detection - location, extent, relationship to surrounding structures
diagnosis
detection of tumour-related complications
treatment planning - surgery/radiotherapy/chemotherapy
monitoring and assessing treatment response
indicating patient prognosis

Question 22

role of CT in imaging tumours

Answer 22

quick
accesible
often first scan used especially in emergency situations
helpful in diagnosing particular tumours (near or involving bone) as its superior to MR at demonstrating bone and detecting calcification
also demonstrate mass effect/raised ICP and haemorrhage
used when MR contraindicated

Question 23

what are the risks of iv contrast

why preliminary done without

when is it given

Answer 23

nephrotoxic and potential risk of anaphylactic reaction

done w/o so as not to hide/mimic haemorrhage/calcifications

given once pathology suspected - increases efficiency of CT

Question 24

what is contrast-enhanced lesions due to

Answer 24

disruption of the blood-brain barrier (BBB) - tight endothelial layer on vessels that act as a filter for substances that reach the brain through the blood stream

permits the passage of the contrast material into the extracellular spaces of the tumour
majority of brain tumours enhance - enhancement characteristics allow diagnosis of tumour type
most accurate way of diagnosing tumour type is histological assessment of a biopsy of the tissue

Question 25

role of MRI in tumour imaging

Answer 25

modality of choice
more sensitive and specific due to superior contrast resolution
more sensitive for detection of early tumours
superior in imaging posterior fossa lesions due to CT beam hardening artefact
multiplanar capabilities, flexible protocols/sequences allow accurate assessment of

tumour diagnosis, location, extent (useful for surgery)
direct biopsies
plan the proper therapy
evaluate the therapeutic result

no ionising radiation
able to prove physiological (functional) information

Question 26

what is used in MR central nervous imaging for contrast

why

Answer 26

Gadolinium

in normal brain tissue it can’t pass through the vasculature into the interstitial space - in brain tumour BBB disrupted so it accumulates in the extracellular space of the tumour