Pathology of Brain Tumours

Question 1

Explain the concept of flow

Answer 1

Flow always occurs down a pressure gradient

Question 2

What is CPP and how is it calculated?

Answer 2

CPP = Cerebral perfusion pressure
-Reflects pressure gradiant to get into the cranium

CPP = MAP - ICP

Question 3

What is CBF and how is it calculated?

Answer 3

CBF is cerebral blood flow

CBF = CPP/ CVR
-where CVR = cerebrovascular resistance

CBF = (MAP-ICP)/CVR

Question 4

What does CBF = (MAP-ICP)/CVR show?

Answer 4

ICP and vessel resistence impede inward flow

Question 5

What does a CPP

Answer 5

Cannot perfuse brain adequately with oxygen and nutrients

Loss of function

Question 6

What does a CPP of >150mmHg mean?

Answer 6

Loss of control of blood flow (ischaemic forced vasodilation)

Brain swelling - brain oedema

ICP=MAP so no flow

Question 7

What are the causes of raised ICP?

Answer 7

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

Question 8

What is the Subfalcine space?

Answer 8

Opening in the falx cerebri

Question 9

What is the tentorial hiatus?

Answer 9

Opening in the tentorium cerebelli

Question 10

What effects do intracranial space occupying lesions cause?

Answer 10

• 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

Question 11

What is a cingulate herniation?

Answer 11

Cerebrum herniates under falx cerebri

Question 12

What is central herniation?

Answer 12

Cerebrum through tentorial hiatus via central pressure

Question 13

What is uncal herniation?

Answer 13

Hippocampus throiugh tentorial hiatus

Question 14

What is cerebellotonsillar herniation?

Answer 14

Tonsils through foramen magnum

Question 15

What is upward herniation?

Answer 15

Cerebellum through tentorial hiatus

Question 16

What is transcalvarial herniation?

Answer 16

Brain tissue herniating through skull fracture

Question 17

How can clinical signs show raised ICP?

Answer 17

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

Question 18

What is the epidaemiology for Brain tumours?

Answer 18

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

Question 19

How do you classify brain tumours?

Answer 19

Primary = 65% in adults, nearly all in children

Secondary:
-Breast, lung, kidney, colon, melanoma

Question 20

How do you classify primary brain tumours?

Answer 20

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

Question 21

What is ischaemic penumbra?

Answer 21

• 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

Question 22

Describe Glioma (astrocytoma)

Answer 22

Resemble cells of astrocyte differentiation

• CNS supporting cells
• Diffuse edges- not encapsulated
• Do not metastasise outside CNS

Question 23

How is prognosis predicted in Glioma (astrocytoma)?

Answer 23

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

Question 24

What is Medulloblastoma?

Answer 24

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

Question 25

What is a meningioma?

Answer 25

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

Question 26

Explain nerve sheath tumours

Answer 26

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)

Question 27

Explain pituitary adenoma

Answer 27

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

Question 28

Explain a CNS lymphoma

Answer 28

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

Question 29

Explain secondary tumours

Answer 29

• 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