Brain tumours

Question 1

How common are primary brain tumours?

Answer 1

Incidence 8 per 100,000
10% neoplasms
16th most common adult cancer - disproportionate killer in young adults
2nd most common paediatric cancer below leukaemia
Less than 2% of all malignant tumours but 20% of childhood
Majority supratentorial in adults
In children - majority posterior fossa
Most gliomas - astrocytoma (85-90%), oligodendroglioma (5%)

Question 2

How common are secondary brain tumours?

Answer 2

10x more common than primary brain tumours

Question 3

Which cancers are secondary brain tumours most likely to metastasise from?

Answer 3

Non-small cell (1)
Small cell (2)
Breast (3)
Melanoma (4)
Renal cell (5)
GI (6)

Question 4

What are gliomas?

Answer 4

Neuroepithelial origin seen within hemispheres mostly but also cerebellum, brainstem and cord
Unknown cause
Associated with neurofibromatosis
Spread by direct extension and rarely metastasise outside CNS

Question 5

What are the 2 types of gliomas?

Answer 5

Astrocytomas (85-90%)

Oligodendromas (5%)

Question 6

What are astrocytomas?

Answer 6

Gliomas arising from astrocytes
Grades I-IV
Grade I grows slowly over many years
Grade IV (glioblastoma multiforme) causes death within several months
Usually benign in children and cerebellar

Question 7

What are oligodenromas?

Answer 7

Most common in 40s-50s
Arise from oligodendrocytes
Grow slowly usually over several years
Calcification common
May have seizures
WHO grade II
All IDH-1 mutation positive

Question 8

What are meningiomas?

Answer 8

More common in elderly and women
Benign and arise from arachnoid mater and may grow to large size usually over years pushing into brain
Close to skull - erode bone or cause local hyperstosis
Often occur along intracranial venous sinuses which they may invade - usually below tentorium
Common sites - parasagittal region, sphenoidal ridge, subfrontal region, pituitary fossa, skull base

Question 9

What are neurofibromas?

Answer 9

Schwanomas
Solid benign tumours arising from schwann cells and occur principally in the cerebellopontine angle
May be bilateral in neurofibromatosis type 2

Question 10

What are ependymomas?

Answer 10

Arise from ependymal cells

Line ventricles and spinal cord

Question 11

What are craniophyaryngiomas?

Answer 11

Very often benign tumours

Often diagnosed in younger patients

Question 12

What can increase your risk of brain tumour?

Answer 12

More common in affluent groups
Ionising radiation
Vinyl chloride
Immunosuppression
FHx

Question 13

What is the WHO grading for primary brain tumours?

Answer 13

Grade I - good prognosis, often benign
Grade II - > 5 year prognosis, premalignant tumour
Grade III - prognosis of 2-5 year survival rate, cancer, malignant, active growth, and mitotic activity on microscope
Grade IV - < 1 year survival prognosis, most common phenotype, active growth, mitotic activity and necrosis, vascular proliferation, very malignant

Question 14

What are the 2 pathways to malignant glioma?

Answer 14

Common

Less common

Question 15

What is the common pathway to malignant glioma?

Answer 15

Especially in those under 50-60
Initial genetic error of glucose glycolysis
Mutation of isocitrate dehydrogenase I
Results in build-up of 2-hydroxyglutarate
Triggers genetic instability in glial cells and subsequent inappropriate mitosis - cancer

Question 16

What is the less common pathway to malignant glioma?

Answer 16

More common in those over 50-60
No IDH-1 mutation
Instead have catastrophic genetic mutation
Results in poor prognosis even for low grade tumours

Question 17

Why can tumours lead to a rise in ICP?

Answer 17

Intracranial compartment is a complaint system
Initially when tumour is small, there will be no symptoms despite the rising ICP – due to brain being compliant and able to remove CSF from ventricle to spinal cord in order to offset the increase in pressure
Comes a point where no more CSF can be relocated – very sharp and rapid rise in ICP resulting in symptoms and eventually death if nothing done
Rising pressure results in midline shift of brain and herniation through foramen magnum – results in brain damage resulting in local and systemic symptoms

Question 18

What are the 4 cardinal presenting symptoms of brain tumours?

Answer 18

Symptoms of raised ICP
Progressive neurological deficit
Seizures
Lethargy/tiredness caused by pressure on the brainstem

Question 19

What are the symptoms of raised ICP?

Answer 19

Progressive headache
- Worse on waking from sleep (don’t wee at night so accumulation of fluid)
- Pain so bad it can wake patient up
- Pain increased by coughing, straining and bending forwards (increased venous pressure in brain)
- Sometimes relieved by vomiting – reduces fluids and thus pressure
Drowsiness
+/- vomiting
Papilloedema
- Swelling of optic disc due to obstruction of venous return from retina due to raised ICP
- Loss of crisp optic nerve head margins
- Venous engorgement
- Retinal oedema
- Haemorrhages
Distortion of upper brainstem as midline structures displaced – impairment of consciousness, progressing to coning and death
False localising signs eg 6th nerve lesion, 3rd nerve lesion, hemiparesis

Question 20

What are the symptoms of progressive neurological deficit?

Answer 20

Depends on part of brain that is affected
Temporal lobe – dysphasia, amnesia
Frontal lobe – hemiparesis, personality change, Broca’s dysphasia, lack of initiative, unable to plan tasks
Parietal lobe – hemisensory loss, reduction in 2-point discrimination, dysphasia, astereognosis (unable to recognise object from touch alone)
Occipital lobe – contralateral visual defects
Cerebellum – DASHING – Dysdiadochokinesis, Ataxia, Slurred speech, Hypotonia, Intention tremor, Nystagmus, Gait abnormality

Question 21

What symptoms of seizures might indicate tumour?

Answer 21

Sinister when of recent onset
Partial/focal seizures more common with tumours
- Motor
- Sensory
- Temporal lobe pattern – olfactory aura or déjà vu or a funny feeling in the gut/stomach a few minutes before and/or during the seizure

Question 22

What are the differentials of brain tumours?

Answer 22

Other causes of space-occupying lesions

• Aneurysm
• Abscess
• Cyst
• Haemorrhage
• Idiopathic intracranial hypertension

Question 23

What investigations should you do for a brain tumour?

Answer 23

CT and MRI
- MRI superior for posterior fossa lesions
- Determine size and location of lesions
- High grade tumours have irregular edges and high growth rate
Blood tests – FBC, U&Es, LFTs, B12 ect
Biopsy via skull burr-hole to determine cancer grade and confirm
Lumbar puncture contraindicated when possibility of mass lesion since withdrawing CSF may provoke immediate coning – herniation of brain through foramen magnum resulting in brainstem compression as it passes through foramen magnum and potential death
PET
CXR – as mets more common than primary

Question 24

How do you treat brain tumours?

Answer 24

Surgery to remove mass – if possible or just debulk tumour
Chemotherapy for glioma
- Given at same time as surgery and then for 1st 6 weeks post-op
- Temozolomide
- Not all tumours are sensitive – some tumours have high methyl-guanine-methyl-transferase – an enzyme that reverses the therapeutic effect of temozolomide
- Best to determine if tumour is sensitive before administration – if it has methylated MGMT (enzyme silenced) then sensitive
- Little real value – vincristine, procarbazine and temozolomide
Oral dexamethasone for cerebral oedema
- Most powerful synthetic steroid
- Rapidly improves brain performance in all tumours
- Reduces tumour inflammation/oedema
- Must give no later then 14:00 since keeps patient awake
Can give anticonvulsants for epilepsy eg oral carbamazepine
Radiotherapy if mets