Pathology of Brain Tumours Flashcards
Flow always occurs down
a pressure gradient
Equation for cerebral perfusion pressure
CPP = MAP - ICP
Equation for cerebral blood flow
CBF = CPP/CVR
or
CBF = (MAP - ICP) / CVR
(CVR = cerebrovascular resistance)
Ischaemia causing raised ICP will result in
increased MAP, to ensure CPP is maintained
What happens at a CPP < 50 mmHg?
Brain cannot be perfused adequately with oxygen and nutrients which results in loss of function
What happens at a CPP > 150 mmHg?
Loss of control of blood flow causing ischaemic forced vasodilation and brain oedema, which results in ICP and MAP becoming equal - no blood flow
Examples of causes of raised ICP
Inflammation e.g. menignitis, encephalitis, abscess
Vascular e.g. intracranial haemorrhage, brain swelling
Tumours
Hydrocephalus
Effects of intracranial space occupying lesions
Amount of tissue increases
Raised ICP puts CBF at risk
Can cause herniation between the intracranial spaces if focal
What are the thick, fibrous sheets inside the cranium that keep the brain in place?
Falx cerebri
Tentorium cerebelli
Dura mater
What are the openings around the fibrous sheets inside the cranium?
Subfalcine space
Tentorial hiatus
Foramen magnum
A focal lesion/mass can cause
internal shift between the intracranial spaces
In what direction might the cerebrum herniate?
Inferiorly via the tentorium
In what direction might the cerebellum herniate?
Inferiorly via foramen magnum
What percentage of brain tumours are primary tumours in adults?
65%
How are brain tumours classified?
By their resemblance to their cell of origin
Examples of glial cell tumours
Glioblastoma
Astrocytoma
Oligodendroglioma
Ependymoma
Examples of primitive neuroectoderm tumours
Medullablastoma
Examples of arachnoidal cell tumours
Meningioma
Examples of nerve sheath cell tumours
Schwannoma
Neurofibroma
Examples of pituitary gland tumours
Adenoma
Examples of lymphoid cell tumours
Lymphoma
Examples of capillary tumours
Haemangioblastoma
Where are secondary tumours in the brain commonly metastasised from?
Breast Lung Kidney Colon Melanoma
Features of ischaemic penumbra
Local ischaemia of brain tissue surrounding a tumour
Local loss of function
Features of glioma
CNS supporting cells
Diffuse edges
Don’t metastasise outside of the CNS
What is the highest grade of astrocytoma termed?
Glioblastoma, worst prognosis
Why is the prognosis of glioblastoma poor?
Grows rapidly and responds poorly to surgery
Features of medulloblastoma
Small, blue, round-cell tumour
Found mainly in children
Occur in posterior fossa, especially in brainstem
Poor prognosis
Features of meningioma
From arachnocytes
Connective tissue tumours
Benign
Won’t metastasise but can be locally aggressive and invade the skull
Features of nerve sheath tumours
Occur around the nerves
May be seen in CNS and PNS
Acoustic neuroma most common - causes unilateral deafness
Benign lesion but difficult to remove surgically
Can cause contralateral cranial nerve damage
Features of pituitary adenoma
Benign tumour of posterior pituitary in pituitary fossa
Often secrete pituitary hormone
Many are non-functional
Cause panhypopituitarism
May result in acromegaly/gigantism due to growth hormone secretion
Grow superiorly and impinge on optic chiasma
Features of CNS lymphoma
High grade neoplasm Usually diffuse large B-cell lymphoma Often occur at deep and central sites Difficult to treat - drugs don't cross blood-brain barrier Generally don't spread outside CNS
Features of capillary haemangioma
Space occupying
May bleed
Most common in cerebellar hemispheres
Features of secondary brain tumours
Mostly carcinomas
Common metastases
Usually present with focal signs
Some can be removed surgically but dependent on site
Tend to be encapsulated and surrounded by oedema
