Pathology of Brain Tumours Flashcards
How is CSF reabsorbed into the veins?
Via arachnoid granulations
What equation describes cerebral perfusion pressure? What does this reflect?
CPP = MAP - ICP
The pressure gradient to get into the cranium
What equation describes the cerebral blood flow?
CBF = CPP / CVR
CVR = cerebrovascular resistance
What term describes the fluid nature of the relationship between the CPP and CBF?
Autoregulation
What is the Cushing reflex?
A late reflex to brainstem ischaemia that results in increased MAP to ensure that the CPP is maintained
What is the result of a CPP less than 50mmHg
The brain cannot perfuse adequately with oxygen and nutrients
There is loss of function
What is the result of a CPP in excess of 150mmHg?
There is a loss of control of blood flow - ischaemic forced vasodilation
Brain swelling occurs - brain oedema
ICP = MAP - therefore no flow
Outline the main causes of raised ICP
Inflammation - meningitis, encephalitis, abscess
Vascular - intracranial haemorrhage, disease or traumatic
- Brain swelling/oedema, traumatic brain injury , physical or physiological e.g. MI
Tumours
Hydrocephalus
What is the falx cerebri?
A large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres. The falx cerebri attaches anteriorly at the crista galli in proximity to the cribriform plate and to the frontal and ethmoid sinuses. Posteriorly, it is connected with the upper surface of the tentorium cerebelli. Its superior margin is attached at midline to internal surface of skull, as far back as the internal occipital protuberance
What is the tentorium cerebelli?
An extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes
What are the effects of an intracranial space occupying lesion?
Amount of tissue within the cranium increases and therefore so dos the ICP - CBF is now at risk (CBF = (MAP-ICP)/CVR)
If focal, e.g. tumour or haematoma, can cause internal shift or herniation between the intracranial spaces
What are the six forms of brain herniation?
Cingulate Central Uncle Cerebellotonsillar Upward Transcalvarial
What pathology does the GCS relate to?
Squeeze onto cortex and brainstem
What pathology does pupillary dilation indicate?
Sneeze and stretch on CNIII
What pathology do localising signs relate to?
Squeeze on decussation of the corticospinal tracts and posterior columns
What is the most common site of brian tumours in adults? How does this differ in children?
Adults - 70% above the tentorium
Children - 70% below
What proportion of brain tumours in adults and in children are primary?
Adults - 65%
Children - almost all
What primary sites do secondary brain tumours most commonly spread to?
Breast, lung, kidney, colon, melanoma
What is a meningioma a cancer of?
Arachnoidal cell
What is a medulloblastoma a cancer of?
Primitive neurorectoderm
What are glioblastomas, astrocytomas (glioma), oligodendrogliomas and ependymomas cancers of?
Glial cells
What are ademona cancers of?
Pituitary gland
What are schwannoma and neurofibroma cancers of?
Nerve sheath cells
Describe the principal of the ischaemic penumbra
This refers to the space surrounding the core area of infraction, tumour or insult to the brain that is affected by local ischaemia but is distal enough to have some other arterial supply, and unlike the ischaemic core, may be salvageable if the ischaemia is resolved
Are gliomas able to metastasise outside or the CNS?
No
What is unique about medulloblastomas? What age group do they affect in particular?
They are blue. Children
Are meningiomas benign or malignant?
‘Benign’ but can display aggressive growth, causing surrounding tissue destruction
What is the most common form of nerve sheath tumour? Describe this form of tumour
Acoustic neuroma
Affects vestibulocochlear nerve CNVII
CNVII (facial) can be affected as also runs through IAM
Causes unilateral deafness
Removal technically difficult
What cells are most commonly affected by a CNS lymphoma?
B-cells
Tumours are usually large and diffuse
Often deep and central -difficult to resect
What makes brain tumours difficult to treat form a pharmacological perspective?
BBB
