Pathology of Brain Tumours Flashcards
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
What is a meningioma?
From “arachnocytes” - cells that make up the coverings of the brain
Connective tissue tumours
“Benign” - not metastasise - but can be locally aggressive and invade the skull
Explain nerve sheath tumours
Around nerves - not restricted to CNS - can see in PNS
Acoustic neuroma is most common
- CNVII
- Posterior fossa
- Unilateral deafness
- Benign lesion byt removal technically difficult and can cause collateral CN injury (CNVII very close)
Explain pituitary adenoma
Benign tumour of posterior pituitary in pituitary fossa
Often secrete a pituitary hormone
- Many are non-functional but squeeze normal gland which stops working (panhypopituitarism)
- Hormone secreted reflected in clinical signs (e.g. growth hormone) acromegaly, giantism
Grow superiorly and impinge on optic chiasma - visual signs depending on exact site
Explain a CNS lymphoma
High grade neoplasm
Usually diffuse large B-cell lymphoma
Often deep and central site = difficult to biopsy
Difficult to treat as drug do not cross blood-brain barrier
Generally do not spread outside of CNS
Explain secondary tumours
- 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
