Pathology of Brain Tumours Flashcards
what is the equation that Reflects pressure gradient to get into the cranium?
CPP = MAP – ICP
CPP is cerebral perfusion pressure
MAP is mean arterial pressure
ICP is intracranial pressure
what is the equation that reflects the amount of blood actually getting to the brain?
CBF = CPP/CVR
CBF is cerebral blood flow
CPP is cerebral perfusion pressure
CVR is cerebrovascular resistance
what is the equation that reflects how ICP and vessel resistance impede inward flow?
CBF = (MAP – ICP)/CVR
what is cushing reflex?
Late reflex to brainstem ischemia in raised ICP will result is increased MAP to ensure CPP is maintained
occurs just before death
describe cerebral autoregulation
maintains CBF at an appropriate level during changes in CPP
radius of blood vessel can change to maintain CBF
what is the normal CBF?
50ml/min/100g
what changes in pressure can a normal CBF be maintained?
50-150mmHg
what occurs when the CPP is less than 50mmHg?
blood vessel dilates
Cannot perfuse brain adequately with oxygen and nutrients
Loss of function
what occurs when the CPP is more than 150mmHg?
blood vessel constricts
Loss of control of blood flow – ischaemic forced vasodilation
Brain swelling – brain oedema
ICP = MAP - thus no flow
what are the effects of intracranial space occupying lesions?
Amount of tissue increases
Raises ICP – CBF is now at risk
CBF = (MAP – ICP)/CVR
what are the effects if intracranial space occupying lesion is focal eg tumour?
can cause internal shift (herniation) between the intracranial spaces
Right-left, left-right
Cerebrum inferiorly via tentorium,
Cerebellum inferiorly via foramen magnum
what are the 6 types of brain herniation?
cingulate central uncal cerebellotonsillar upward transcalvarial
how does the pathology explains the clinical signs?
Glasgow Coma Scale Squeeze on cortex and brainstem Pupillary dilation Squeeze and stretch on CNIII Localising signs Squeeze on decussation of corticospinal tracts and posterior columns
what is the difference in sites of brain tumours in adults and children?
Adults – 70% above tentorium
Children – 70% below tentorium
what is the most common type of brain tumour?
65% in adults, nearly all in children
By resemblance of cell of origin
Glial cells – glioblastoma
what is the less common type of brain tumour?
Secondary
Breast, lung, kidney, colon, melanoma
give the name and cell of origin of primary brain tumours
Glial cells – glioblastoma, astrocytoma (glioma), oligodendroglioma, ependymoma
Primitive neuorectoderm – medulloblastoma
Arachnoidal cell – meningioma
Nerve sheath cell – Schwannoma, neurofibroma
Pituiary gland - adenona
Lymphoid cell – lymphoma
Capillary vessels - haemangioblastoma
what is Ischaemic penumbra?
Tumours are space occupying
Squeeze nearby tissue and cause local ischaemia
If remove oedema around tumours, can improve function
Can salvage in tumours and head injury
what is Glioma (astrocytoma)?
Resemble cells of astrocyte differentiation
CNS supporting cells
Diffuse edges – not encapsulated
Do not metastasise outside the CNS
what is the prognosis of Glioma (astrocytoma)?
Grades of differentiation predict prognosis
High grade termed glioblastoma (glioblastoma multiforme) has worst outlook
Glioblastoma grows rapidly and responds poorly to surgery – median survival 36 weeks
Site is important in outcome regardless of grade
Low grade (cystic) grows very slowly
what is Medulloblastoma?
Primitive neuroectoderm
Small blue round cell tumour
Children especially but not exclusively
Posterior fossa especially brainstem
what is the prognosis of Medulloblastoma?
Poor outcome because of central site and difficult access for surgery
what is Meningioma?
From “arachnocytes” – cells that make up the coverings of the brain
Connective tissue tumours
what is the prognosis of Meningioma?
“Benign” – not metastasise – but can be locally aggressive and can invade the skull
