CNS cancer and raised intracranial pressure

Question 1

Name some CNS tumours

Answer 1

pilocytic astrocytoma 
diffuse astrocytoma 
oligodendrogliomas 
medulloblastoma 
meningioma
metasteses

Question 2

Which are specifically tumours of neuroepithelial origin?

Answer 2

astrocytoma
oligodendroglioma
Ependymoma
Lymphoma 
Medulloblastoma
pineal tumours 
tumours of the choroid plexus

Question 3

in adults where do brain tumours mainly occur?

Answer 3

supratentorial

Question 4

in children where do brain tumours mainly occur?

Answer 4

posterior fossa ie infratentorial compartment (think adults are above children in height)

Question 5

which histological type of CNS tumour is the most common?

Answer 5

neuroepithelial tumours, main one specifically being the astrocytomas

Question 6

What are the broad classifications of the effects of CNS tumours?

Answer 6

classification
raised intracranial pressure
seizures

Question 7

what is the most frequent primary brain tumour?

Answer 7

astrocytomas

Question 8

what are the two classifications of astrocytomas?

Answer 8

diffuse astrocytomas

pilocytic astrocytomas

Question 9

What are the different classifications of diffuse astrocytoma according to grade?

Answer 9

grade 2 - diffuse astrocytoma
grade 3- anaplastic astrocytoma
grade 4 - glioblastoma

Question 10

What are the 2 common characteristics to the group of diffuse astrocytomas?

Answer 10

they infiltrate the brain diffusely

they progress to higher grade tumours = undergo progressive anaplasia

Question 11

what is seen microscopically in a tumour that is grade 2 diffuse astrocyoma?

Answer 11

nuclear atypia

Question 12

What is seen microscopically in grade 3 anaplastic astrocytomas?

Answer 12

nuclear atypica and mitoses

Question 13

What is seen microscopically in grade 4 glioblastomas?

Answer 13

nuclear atypia, mitoses, necrosis and vascular proliferation

Question 14

How does contrast enhancement correlate with tumour grade?

Answer 14

the higher grade tumours have microvascular proliferation as the tumour has higher energy requirements (not present in low grade tumours) so the contrast agent leaks out of these blood vessels and is seen on scan = contrast enhancement

Question 15

what mutation do astrocytomas and oligodendrogliomas have in common?

Answer 15

IDH 1 mutation - isocitrate dehydrogenase

Question 16

What mutation do oligodendrogliomas have that astrocytomas (and hence glioblastomas) do NOT have by definition?

Answer 16

1p 19q deletion

this deletion is what distinguishes oligodendrogliomas from astrocytomas by definition

Question 17

doe glioblastomas de novo have IDH mutation?

Answer 17

No - this is what distinguishes them from oligodendrogliomas that have come from astrocytomas

Question 18

What techniques do we use to classify CNS tumours histopathologically?

Answer 18

H and E 
immunohistochemistry
molecular/cytogenetics
- 1p1 9q del.
- IDH1 mutation

Question 19

what are the aims of histopathological classification?

Answer 19

tumour type 
tumour grade (histology) 
prognostic and predictive markers (cytogenetics/mutations)

Question 20

what microscopic feature distinguishes pilocytic astrocytomas from diffuse astrocytomas?

Answer 20

Rosenthal fibres

Question 21

Where are the pilocytic astrocytomas found and who are they most commonly found in?

Answer 21

cerebellum

children

Question 22

what are the features of medulloblastomas?

Answer 22

type of embryonal tumour
very poorly differentiated
high mitotic rate
lots of apoptosis
highly malignant and fatal if not treated
can be risk stratified into low, standard and high to tailor therapy according to risk - done by morphology, immunohistochemistry and molecular medicine

Question 23

what grade are meningiomas mainly?

Answer 23

grade 1

Question 24

Which tumours commonly metastasise to the brain?

Answer 24

lung 
breast 
melanoma 
GIT
kidney

Question 25

is staging used in CNS tumours?

Answer 25

no

Question 26

what key differences are there in terms of CNS tumours compared to other tumours?

Answer 26

• no staging
• mass effect is important
• integrated histological, immunohistochemical and molecular diagnosis

Question 27

what are the causes of raised intracranial pressure

Answer 27

tumours 
head injury 
stroke 
cerebral haemorrhage 
infectious diseases

Question 28

What is the shape of the pressure-volume curve of expanding intracranial lesions?

Answer 28

exponential

Question 29

what structures can be compressed by a brain tumour?

Answer 29

ventricles
uncal herniation
tonsillar herniation = coning

Question 30

what are the effects of uncal herniation?

Answer 30

compression of the occulomotor nerve CN3
this nerve normally supplies all the muscles of the eye (including levator palpebrae superioris) except lateral rectus and superior oblique
this results in the eye looking DOWN AND OUT in response to the unopposed action of the superior oblique
also get ptosis AND importantly you get DILATATION of the pupil as the CN3 also supplies the Edinger-Westphal nucleus which is responsible for pupillary constriction
you can also get compression of the contralateral corticospinal tract in the cerebral peduncles and this leads to IPISIALTERAL HEMIPARESIS
also can get compresssion of the posterior cerebral artery leading to infarction of the OCCIPITAL LOBE
duret/herniation haemorrhage due to tearing of the penetrating vessels from the basilar artery in the brainstem - final common mechanism of death

Question 31

what are the consequences of tonsillar herniation?

Answer 31

haemorrhagic necrosis of the cerebellar tonsils

compressed the medulla which contains the cardiorespiratory centre = CARDIORESPIRATORY ARREST