Brain tumours

Question 1

Give four ways of classifying brain tumours

Answer 1

Tissue of origin
Location
Primary or Secondary
Grading (WHO scale for CNS)

Question 2

Which types of cancer are most likely to metastasise to the brain?

Answer 2

Breast
Colon
Lung
Melanoma
Kidney

Question 3

What is the difference between “intra-axial” and “extra-axial” brain tumours? Which are more common?

Answer 3

Intra-axial tumours arise from the brain tissue itself whereas extra-axial tumours arise from other tissue
Extra-axial tend to be more common

Question 4

What are the three main types of intra-axial brain tumour and from which tissues do they arise?

Answer 4

Medulloblastoma - arises from primitive ectoderm
Gliomas - arise from glial cells
CNS lymphoma - arises from B-cells

Question 5

Describe the appearance and location of medulloblastoma. Why does this type of tumour have a poor prognosis?

Answer 5

Small, blue, round cell tumour
Most common in posterior fossa, especially around the brainstem
- poor prognosis due to this central location

Question 6

What are the four main types of Glioma?

Answer 6

Glioblastoma multiforme (grade 4 - worst outlook)
Astrocytoma (includes anaplastic astrocytoma)
Oligodendroglioma (subcortical white matter)
Ependymoma (ventricles/spinal canal)

Question 7

Which types of brain tumour are most likely to cause seizures?

Answer 7

Oligodendroglioma
- affects subcortical white matter
- often involves calcification of tissue
Astrocytomas

Question 8

Describe the features of astrocytomas

Answer 8

Do not metastasise (otherwise would be stage 4)
Most common in in frontal/temporal lobes and basal ganglia
May see a necrotic centre on imaging, although this is variable
Presents with seizures, headache and/or progressive neurological deficits

Question 9

Which drug can be used to treat glioblastoma? How effective is it?

Answer 9

Temozolamide (an oral alkylating agent)

Has no effect in 40% of cases

Question 10

Give the main types of extra-axial brain tumour

Answer 10

Meningioma - affects arachnoidal cells
 - with/without NF2 mutation
Nerve sheath cell tumours
 - Acoustic neuroma
 - Neurofibroma
Pituitary adenoma

Question 11

What clinical features make up the Cushings Triad?

Answer 11

Hypertension
Bradycardia
Irregular respirations (Cheyne-Stokes respiration)

Question 12

What is the Cushings reflex?

Answer 12

A hypothalamic response to brainstem ischaemia

- intracranial pressure increases in order to maintain cerebral perfusion pressure

Question 13

Describe how the Cushings reflex works

Answer 13

Caused by activation of the sympathetic nervous system
Sympathetic NS activation increases peripheral vascular resistance which increases blood pressure
This activated carotid artery baroreceptors which activate the parasympathetic NS which causes vagal-induced bradycardia

Question 14

What is the clinical significance of the Cushings triad?

Answer 14

Cushings triad signals risk of brain herniation

- need to release pressure in brain

Question 15

Describe the management of a patients exhibiting the Cushings triad

Answer 15

Temporary decompression: hyperventilate, elevate head of bed, administer mannitol
Surgery

Question 16

What type of brain stem ischaemia is most likely to trigger the Cushings reflex?

Answer 16

Ischaemia caused low cerebral blood flow due to raised ICP

Question 17

How is blood flow to the cranium maintained?

Answer 17

Pressure gradient to get into the cranium

CPP = MAP - ICP

Question 18

How does cerebrovascular resistance affect cerebral blood flow?

Answer 18

Increased cerebrovascular resistance decreases cerebral blood flow
CBF = CPP/CVR

Question 19

Give five causes of raised ICP

Answer 19

Inflammation
Intracranial haemorrhage
Brain swelling
Tumour
Hydrocephalus

Question 20

Describe and explain the various clinical signs of brain herniation

Answer 20

Reduced consciousness; GCS/AVPU
 - squeeze on cortex and brainstem
Pupillary dilation
 - squeeze/stretch on Cr N III (Oculomotor)
Squint
 - Squeeze/stretch on Cr N VI (Abducens)
Localising signs
 - Squeeze on decussation of corticospinal tracts and posterior columns

Question 21

What is meant by “ischaemic penumbra”?

Answer 21

Ischemic but still viable cerebral tissue

- penumbral area is supplied by collateral arteries anastomosing with branches of the occluded vascular tree

Question 22

How can tumours result in loss of brain function?

Answer 22

Tumours are space occupying so squeeze nearby tissue. This can cause local ischaemia.

Question 23

How can function of the area around a tumour be improved?

Answer 23

Removing oedema around tumour can improve function (this goes for head injury as well as tumours)

Question 24

How do secondary brain tumours most often present?

Answer 24

Usually present with focal signs
Tend to be encapsulated and surrounded by oedema
Histology is that of primary tumour
Signs/symptoms are generally associated with site rather than histology

Question 25

What is the main requirement for debulking surgery?

Answer 25

80% of tumour must be removed

Question 26

Give six surgical procedures to treat brain tumours

Answer 26

Resection
Biopsy
Craniotomy
Stereotaxis
Transsphenoidal
Endoscopic