Pathology of Brain Tumours Flashcards
(29 cards)
Explain the concept of flow
Flow always occurs down a pressure gradient
What is CPP and how is it calculated?
CPP = Cerebral perfusion pressure
-Reflects pressure gradiant to get into the cranium
CPP = MAP - ICP
What is CBF and how is it calculated?
CBF is cerebral blood flow
CBF = CPP/ CVR
-where CVR = cerebrovascular resistance
CBF = (MAP-ICP)/CVR
What does CBF = (MAP-ICP)/CVR show?
ICP and vessel resistence impede inward flow
What does a CPP
Cannot perfuse brain adequately with oxygen and nutrients
Loss of function
What does a CPP of >150mmHg mean?
Loss of control of blood flow (ischaemic forced vasodilation)
Brain swelling - brain oedema
ICP=MAP so no flow
What are the causes of raised ICP?
Inflammation (meningitis, encephalitis, abscess)
Vascular
-Incracranial haemorrhage: (natural disease or traumatic)
-Brain swelling:
(traumatic brain injury: physical (e.g. head knock) or physiological (e.g. cardiac arrest))
Tumours
Hydrocephalus
What is the Subfalcine space?
Opening in the falx cerebri
What is the tentorial hiatus?
Opening in the tentorium cerebelli
What effects do intracranial space occupying lesions cause?
- Amount of tissue increases
- Raised ICP
- CBF = (MAP-ICP)/CVR
- If ICP increases CBF is at risk
If focal (e.g. tumour, haematoma) this can cause herniation between the intracranial spaces
- Right -> left (vice versa)
- Cerebrum inferiorly via tentorium
- Cerebellum inferiorly via foramen magum
What is a cingulate herniation?
Cerebrum herniates under falx cerebri
What is central herniation?
Cerebrum through tentorial hiatus via central pressure
What is uncal herniation?
Hippocampus throiugh tentorial hiatus
What is cerebellotonsillar herniation?
Tonsils through foramen magnum
What is upward herniation?
Cerebellum through tentorial hiatus
What is transcalvarial herniation?
Brain tissue herniating through skull fracture
How can clinical signs show raised ICP?
GCS = Squeeze on cortex and brainstem
Pupillary dilation = stretch and squeeze on CN III
Localising signs = Squeeze on decussation of corticospinal tracts and posterior columns
What is the epidaemiology for Brain tumours?
2% deaths from malignant disease
6th most common group of adult malignancies
20% of paediatric tumours and second most common group of tumours in children
8-10/100k per year in general population
Adults = 70% above tenorium Children = 70% below tentorium
How do you classify brain tumours?
Primary = 65% in adults, nearly all in children
Secondary:
-Breast, lung, kidney, colon, melanoma
How do you classify primary brain tumours?
By resemblance of cell of origin:
-Glial cells = glioblastoma, astrocytoma (glioma), oligodendroglioma, ependymoma
- Primitive neuroectoderm = medulloblastoma
- Arachnoidal cell = meningioma
- Nerve sheath cell = Scwannoma, neurofibroma
- Pituitary gland = adenoma
- Lymphoid cell = lymphoma
What is ischaemic penumbra?
- Tumours are space occupying
- Squeeze nearby tissue and cause local ischaemia
- Local loss of function around
- If remove oedema around tumours, can improve function (recoverable function)
- Can salvage in tumours and head injury
Describe Glioma (astrocytoma)
Resemble cells of astrocyte differentiation
- CNS supporting cells
- Diffuse edges- not encapsulated
- Do not metastasise outside CNS
How is prognosis predicted in Glioma (astrocytoma)?
Grades of differentiation predict prognosis:
-High grade termed glioblastoma (glioblastoma multiforme) and 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
- Chuldren especially but not exclusively
- Posterior fossa especially brainstem
Poor coutcome because of central site and difficult access for surgery
