Brain tumours Flashcards
Give four ways of classifying brain tumours
Tissue of origin
Location
Primary or Secondary
Grading (WHO scale for CNS)
Which types of cancer are most likely to metastasise to the brain?
Breast Colon Lung Melanoma Kidney
What is the difference between “intra-axial” and “extra-axial” brain tumours? Which are more common?
Intra-axial tumours arise from the brain tissue itself whereas extra-axial tumours arise from other tissue
Extra-axial tend to be more common
What are the three main types of intra-axial brain tumour and from which tissues do they arise?
Medulloblastoma - arises from primitive ectoderm
Gliomas - arise from glial cells
CNS lymphoma - arises from B-cells
Describe the appearance and location of medulloblastoma. Why does this type of tumour have a poor prognosis?
Small, blue, round cell tumour
Most common in posterior fossa, especially around the brainstem
- poor prognosis due to this central location
What are the four main types of Glioma?
Glioblastoma multiforme (grade 4 - worst outlook)
Astrocytoma (includes anaplastic astrocytoma)
Oligodendroglioma (subcortical white matter)
Ependymoma (ventricles/spinal canal)
Which types of brain tumour are most likely to cause seizures?
Oligodendroglioma
- affects subcortical white matter
- often involves calcification of tissue
Astrocytomas
Describe the features of astrocytomas
Do not metastasise (otherwise would be stage 4)
Most common in in frontal/temporal lobes and basal ganglia
May see a necrotic centre on imaging, although this is variable
Presents with seizures, headache and/or progressive neurological deficits
Which drug can be used to treat glioblastoma? How effective is it?
Temozolamide (an oral alkylating agent)
Has no effect in 40% of cases
Give the main types of extra-axial brain tumour
Meningioma - affects arachnoidal cells - with/without NF2 mutation Nerve sheath cell tumours - Acoustic neuroma - Neurofibroma Pituitary adenoma
What clinical features make up the Cushings Triad?
Hypertension
Bradycardia
Irregular respirations (Cheyne-Stokes respiration)
What is the Cushings reflex?
A hypothalamic response to brainstem ischaemia
- intracranial pressure increases in order to maintain cerebral perfusion pressure
Describe how the Cushings reflex works
Caused by activation of the sympathetic nervous system
Sympathetic NS activation increases peripheral vascular resistance which increases blood pressure
This activated carotid artery baroreceptors which activate the parasympathetic NS which causes vagal-induced bradycardia
What is the clinical significance of the Cushings triad?
Cushings triad signals risk of brain herniation
- need to release pressure in brain
Describe the management of a patients exhibiting the Cushings triad
Temporary decompression: hyperventilate, elevate head of bed, administer mannitol
Surgery
What type of brain stem ischaemia is most likely to trigger the Cushings reflex?
Ischaemia caused low cerebral blood flow due to raised ICP
How is blood flow to the cranium maintained?
Pressure gradient to get into the cranium
CPP = MAP - ICP
How does cerebrovascular resistance affect cerebral blood flow?
Increased cerebrovascular resistance decreases cerebral blood flow
CBF = CPP/CVR
Give five causes of raised ICP
Inflammation Intracranial haemorrhage Brain swelling Tumour Hydrocephalus
Describe and explain the various clinical signs of brain herniation
Reduced consciousness; GCS/AVPU - squeeze on cortex and brainstem Pupillary dilation - squeeze/stretch on Cr N III (Oculomotor) Squint - Squeeze/stretch on Cr N VI (Abducens) Localising signs - Squeeze on decussation of corticospinal tracts and posterior columns
What is meant by “ischaemic penumbra”?
Ischemic but still viable cerebral tissue
- penumbral area is supplied by collateral arteries anastomosing with branches of the occluded vascular tree
How can tumours result in loss of brain function?
Tumours are space occupying so squeeze nearby tissue. This can cause local ischaemia.
How can function of the area around a tumour be improved?
Removing oedema around tumour can improve function (this goes for head injury as well as tumours)
How do secondary brain tumours most often present?
Usually present with focal signs
Tend to be encapsulated and surrounded by oedema
Histology is that of primary tumour
Signs/symptoms are generally associated with site rather than histology
What is the main requirement for debulking surgery?
80% of tumour must be removed
Give six surgical procedures to treat brain tumours
Resection Biopsy Craniotomy Stereotaxis Transsphenoidal Endoscopic
