Pathology of Brain Tumours

Question 1

what is the equation that Reflects pressure gradient to get into the cranium?

Answer 1

CPP = MAP – ICP
CPP is cerebral perfusion pressure
MAP is mean arterial pressure
ICP is intracranial pressure

Question 2

what is the equation that reflects the amount of blood actually getting to the brain?

Answer 2

CBF = CPP/CVR
CBF is cerebral blood flow
CPP is cerebral perfusion pressure
CVR is cerebrovascular resistance

Question 3

what is the equation that reflects how ICP and vessel resistance impede inward flow?

Answer 3

CBF = (MAP – ICP)/CVR

Question 4

what is cushing reflex?

Answer 4

Late reflex to brainstem ischemia in raised ICP will result is increased MAP to ensure CPP is maintained
occurs just before death

Question 5

describe cerebral autoregulation

Answer 5

maintains CBF at an appropriate level during changes in CPP

radius of blood vessel can change to maintain CBF

Question 6

what is the normal CBF?

Answer 6

50ml/min/100g

Question 7

what changes in pressure can a normal CBF be maintained?

Answer 7

50-150mmHg

Question 8

what occurs when the CPP is less than 50mmHg?

Answer 8

blood vessel dilates
Cannot perfuse brain adequately with oxygen and nutrients
Loss of function

Question 9

what occurs when the CPP is more than 150mmHg?

Answer 9

blood vessel constricts
Loss of control of blood flow – ischaemic forced vasodilation
Brain swelling – brain oedema
ICP = MAP - thus no flow

Question 10

what are the effects of intracranial space occupying lesions?

Answer 10

Amount of tissue increases
Raises ICP – CBF is now at risk
CBF = (MAP – ICP)/CVR

Question 11

what are the effects if intracranial space occupying lesion is focal eg tumour?

Answer 11

can cause internal shift (herniation) between the intracranial spaces
Right-left, left-right
Cerebrum inferiorly via tentorium,
Cerebellum inferiorly via foramen magnum

Question 12

what are the 6 types of brain herniation?

Answer 12

cingulate
central
uncal
cerebellotonsillar
upward
transcalvarial

Question 13

how does the pathology explains the clinical signs?

Answer 13

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

Question 14

what is the difference in sites of brain tumours in adults and children?

Answer 14

Adults – 70% above tentorium

Children – 70% below tentorium

Question 15

what is the most common type of brain tumour?

Answer 15

65% in adults, nearly all in children
By resemblance of cell of origin
Glial cells – glioblastoma

Question 16

what is the less common type of brain tumour?

Answer 16

Secondary

Breast, lung, kidney, colon, melanoma

Question 17

give the name and cell of origin of primary brain tumours

Answer 17

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

Question 18

what is Ischaemic penumbra?

Answer 18

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

Question 19

what is Glioma (astrocytoma)?

Answer 19

Resemble cells of astrocyte differentiation
CNS supporting cells
Diffuse edges – not encapsulated
Do not metastasise outside the CNS

Question 20

what is the prognosis of Glioma (astrocytoma)?

Answer 20

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

Question 21

what is Medulloblastoma?

Answer 21

Primitive neuroectoderm
Small blue round cell tumour
Children especially but not exclusively
Posterior fossa especially brainstem

Question 22

what is the prognosis of Medulloblastoma?

Answer 22

Poor outcome because of central site and difficult access for surgery

Question 23

what is Meningioma?

Answer 23

From “arachnocytes” – cells that make up the coverings of the brain
Connective tissue tumours

Question 24

what is the prognosis of Meningioma?

Answer 24

“Benign” – not metastasise – but can be locally aggressive and can invade the skull

Question 25

what are nerve sheath tumours?

Answer 25

Around nerves - not restricted to CNS – can be in PNS 
Acoustic neuroma is most common
CNVII 
Posterior fossa
Unilateral deafness

Question 26

what is the prognosis of nerve sheath tumours?

Answer 26

Benign lesion but removal technically difficult and can cause collateral CN injury (CNVII very close)

Question 27

what is Pituitary adenoma?

Answer 27

Benign tumour of posterior pituitary in pituitary fossa
Often secrete a pituitary hormone (panhypopituitarism)
Hormone secreted reflected in clinical signs, eg growth hormone – acromegaly, giantism
Grow superiorly and impinge on optic chiasma – visual signs depending on exact site

Question 28

what is the prognosis of Pituitary adenoma?

Answer 28

Benign tumour

Often secrete a pituitary hormone and impinge on optic chiasma

Question 29

what is CNS lymphoma?

Answer 29

High grade neoplasm
Usually diffuse large B-cell lymphoma
Often deep and central site
Generally do not spread outside of CNS

Question 30

what is the prognosis of CNS lymphoma?

Answer 30

Difficult to biopsy

Difficult to treat as drug do not cross blood-brain barrier

Question 31

what is Capillary haemangioblastoma?

Answer 31

Space occupying
May bleed
Most often in cerebellar hemispheres

Question 32

describe secondary brain tumours

Answer 32

Mostly carcinomas
Common tumours
Present with focal signs usually
Some can be removed surgically – site matters
Tend to be encapsulated and surrounded by oedema
Histology that of the primary tumour