Pathology of Brain Tumours

Question 1

What are the two main tough fibrous sheets that keep the brain in place within the skull?

Answer 1

• Falx Cerebri

- Tentorium Cerebelli

Question 2

Main causes of raised intracranial pressure?

Answer 2

Localized lesions:

• Haemorrhage
• Tumours
• Abscesses

(Oedema post trauma - generalized)

Question 3

What effect can raised intracranial pressure have on the position of the brain in the skull?

Answer 3

Can cause herniation

Question 4

Common types of cerebral herniation?

Answer 4

• Left-right/right-left (across falx)
• Uncal herniation (cerebrum moves below tentorium)
• Coning/Cerebellotonsilar (cerebellum and tonsils inferiorly into foramen magnum)

Question 5

What is a subfalcine herniation?

Answer 5

Cause of raised ICP on one side of the falx cerebri, pushes the cingulate gyrus beneath the falx/falcine membrane to herniate the other side

• Falcine membrane also commonly laterally displaced
• Lateral ventricle on high ICP side crushed flat

Question 6

What is a tentorial/uncal herniation?

Answer 6

Brain herniates inferiorly at the edge of the tentorium

• Cerebral aqueduct is crushed and narrow

Question 7

What occurs during a cerebellar tonsillar herniation?

Answer 7

Cerebellar tonsils move inwards and inferiorly towards/through foramen magnum

• Crushes brainstem

Question 8

Why is there sometimes an ischaemic zone around tumours in the brain?

Answer 8

Tumours squeeze and exert pressure on the nearby tissue, causing local ischaemia

Question 9

Possible signs of raised intracranial pressure?

Answer 9

• Morning headaches and sickness

- Papilloedema (optic disc swelling, sometimes seen)

Question 10

Clinical signs that intracranial pressure is increasing?

Answer 10

• Pupillary dilation (squeeze/stretch on CN III)
• Falling GCS
• Brain stem death (when tonsils move into foramen magnum)

Question 11

Types of intracranial tumour?

Answer 11

• Primary
• Secondary (metastases)
• Other: from cells originating outside the brain and spinal cord (eg. meningioma)

Question 12

Types of primary intracranial tumours?

Answer 12

By resemblance of cell of origin:

• Glial cells: gliomas (glioblastoma/astrocytoma etc.)
• Embryonic neural cells: medulloblastoma
• Arachnoidal cell: meningioma
• Nerve sheath cell: schwannoma, neurofibroma
• Pituitary gland: adenoma
• Lymphoid: lymphoma
• Capillary vessels: haemangioblastoma

Question 13

Common origins of brain metastases?

Answer 13

• Breast
• Lung
• Kidney
• Colon
• Melanoma

Question 14

who tends to get malignancies of the embryonic neural cells?

Answer 14

Tends to be a childhood malignant tumour

Question 15

How do CNS tumours tend to differ between children and adults with regards to location?

Answer 15

• Adults: tumours tend to occur above the tentorium cerebelli
• Children: tumours usually below tentorium cerebelli

Question 16

What are some characteristics of gliomas?

Answer 16

• Resemble glial cells most
• Diffuse edges, not encapsulated
• Malignant, but don’t metastasize outside the CNS

Question 17

Examples of some types of gliomas?

Answer 17

Astrocytes - astrocytoma + glioblastoma

Oligodendrocytes - oligodendroglioma

Ependymal cells - ependymoma

Question 18

Differences between astrocytoma and glioblastoma?

Answer 18

• Astrocytoma: slow growing, similar to astrocyte cells on microscopy, small cells w single nucleus
• Glioblastoma: fast growing, large cells sometimes w multiple nucleii, atypical tumour with necrosis under microscope

Question 19

What does a medulloblastoma differentiate from? Characteristics?

Answer 19

• From primitive neuroectoderm
• Occurs in children especially
• Usually located in posterior fossa, often around brainstem

Question 20

What cells do meningioma’s differentiate from? Characteristics of meningioma?

Answer 20

• Differentiate from cells that make up the meninges (“arachnocytes” in lecture)
• Are benign, do not metastasize but can locally invade the skull
• Slow growing and resectable
• Can resemble an arachnoid granulation under microscope: small group of cells around eachother

Question 21

Where do nerve sheath tumours occur?

Answer 21

Around peripheral nerves

Originate from cells surrounding the nerves, eg. Schwannoma

Question 22

What is an acoustic neuroma? Some characteristics and signs?

Answer 22

• Schwannoma of CN VIII
• Occurs at angle between pons and cerebellum
• Results in unilateral deafness (presses on other cranial nerves as tumour expands)
• Removal technically difficult due to location

Question 23

Signs and characteristics of pituitary adenoma?

Answer 23

• Benign tumour, located in pituitary fossa
• May present with endocrine abnormalaties as tumour often secretes pituitary hormone
• May have visual impairment (bitemporal hemianopia) as tumour grows superiorly and impinges on optic chiasma

Question 24

Characteristics of a CNS lymphoma?

Answer 24

• Often deep and central within the brain
• Difficult to treat as drugs don’t cross BBB
• Generally non-metastatic

Question 25

What is a haemangioblastoma? Where do they most often occur?

Answer 25

• Tumour of intracranial blood vessels

- Most often in the cerebellum

Question 26

What type of cancer is most often seen in brain metastases?

Answer 26

• Carcinoma

Common, histology usually matches that of the primary tumour