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Flashcards in Space Occupying Lesions Deck (67)
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1

what happens when the brain enlarges

some blood +/‐
CSF must escape from cranial vault
to avoid rise in pressure.
• Once this process is exhausted,
venous sinuses are flattened and
there is little or no CSF.
• Any further increase in brain volume
results in rapid increase in ICP

2

what can cause raised ICP

increased CSF (hydrocephalus)
focal lesion in brain (SOL)
diffuse lesion in brain (oedema)
increased venous volume
physiological (hypoxia, hypercapnia, pain)

3

what is hydrocephalus

accumulation of excessive CSF within the ventricular system of the brain

4

what is the normal volume of CSF

120-150 mls

5

how much CSF is made per day

500ml

6

where is CSF produced

by the choroid plexus in the lateral and fourth ventricles of the brain

7

what absorbs CSF

arachnoid granulations

8

what does the CSF usually contain

lymphocytes <4 cells
neutrophils 0
protein < 0.4 g/l
glucose >2.2 mmol/l
no RBCs

9

what does increased lymphocytes in CSF mean

inflammation/ infection

10

what does increased polymorphs in CSF mean

bacterial meningitis

11

what can cause hydrocephalus

obstruction to CSF flow (inflammation, pus and tumours)
decreased resorption of CSF (post SAH, meningitis)
overproduction of CSF (v. rare: tumours of choroid plexus)

12

what is non communicating hydrocephalus

obstruction of flow of CSF occurs within ventricular system

13

what is communicating hydrocephalus

obstruction to flow of CSF outside of the ventricular system (e.g. in subarachnoid space or at the arachnoid granulations)

14

what happens if hydrocephalus occurs before/ after the closure of cranial sutures

before- cranial enlargement

after- expansion of ventricles and increased in ICP

15

what is hydrocephalus ex vacuo

dilatation of the ventricular system and a compensatory increase in CSF volume secondaryto loss of brain parenchyma (e.g. in alzheimers)

16

what are the physical effects of raised ICP

• Intracranial shifts and
herniations – “Coning”
•Midline shift
•Distortion and pressure on cranial nerves and vital
neurological centres
• Impaired blood flow
• Cerebral Perfusion Pressure =
MAP – ICP
•Reduced level of consciousness

17

what are the causes of raised ICP

infections
tumours
stroke
aneurysm
epilepsy
seizures
hydrocephalus
hypoxemia
meningitis
haemorrhage

18

describe a tentorial herniation

when medial aspect of temporal lobe herniates over the tentorial cerebellum

=compression of CN 3 (pupillary dilatation and impaired eye movements on side of lesion)

19

describe a subfalcine herniation

unilateral expansion of cerebral hemisphere which displaces the singular gyrus underneath the falx cerebri= weakness and sensory loss on opposite side

20

describe a cerebellar herniation (uncal)

inferior descent of cerebellar tonsils below the foramen magnum (aka coning)
=puts pressure on brain stem

21

describe a central herniation

the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli

22

describe a transcalvarial herniations

herniation through any defect in the skull (e.g. following fracture)

23

what are the clinical signs of raised ICP

papilloedema
headache
neck stiffness
N&V

24

what are the most common space occupying lesions

tumours
abscess
haematomas
localised swelling (swelling and oedema around cerebral infarct)

25

what are the most common clinical presentations of tumours

focal symptoms
headache (worse in morning)
vomiting
seizures
visual disturbances
papilloedema

26

where do most brain tumours in children occur

below the tentorium cerebelli

27

where do most brain tumours in adults occur

above the tentorium cerebelli

28

what are the commonest cancers to mets to brain

breast, bronchus, kidney, thyroid, colon, malignant

29

how are brain tumours graded

mitosis
neovascularisation
necrosis
atypia
cellularity

30

what are the most common types of malignant primary brain tumour

astrocytomas

oligodendrogliomas
medulloblastoma (most common in children)