Flashcards in Space Occupying Lesions Deck (67)
Loading flashcards...
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
