Brain Tumours Flashcards
what are the tour classifications
PRIMARY - malignant, benign
SECONDARY - metastases
both types of primary tumour are generally classified by
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
Describe Gliomas
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
which gliomas have the worst prognosis of all CNS malignancies
brainstem gliomas
tumours are grouped into grades depending on how quickly they grow - list them and expand
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
the more normal the tumour cells look ……
the more slowly it is likely to develop, and the lower the grade
the more abnormal the tumour cells look ….
the more quickly the tumour is likely to grow, and the higher the grade
describe low grade tumours
generally extra-axial
classed as benign
may be life-threatening due to space-occupying nature
describe high grade tumours
classed as malignant
usually intra-axial
what is extra-axial
outside of the axis of the brain
does not arise from the brain itself
external to the pia mater
‘dural tail’
what is intra-axial
arises from within the brain parenchyma
within the pia mater
describe secondary tumour - brain mets
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
cancers which commonly metastasise
breast, lung, renal, colon, melanoma
Describe neurofibromatosis type 1
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
Describe neurofibromatosis type 2
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
how does tumour cause ICP and what can this result in
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
how is ICP caused
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
what occurs with ICP
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)
what can be done for ICP
emergency craniotomy to relieve pressure
describe papilloedema
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
with tumours, imaging is essential for …
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
role of CT in imaging tumours
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
what are the risks of iv contrast
why preliminary done without
when is it given
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
what is contrast-enhanced lesions due to
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
role of MRI in tumour imaging
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
what is used in MR central nervous imaging for contrast
why
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
