Flashcards in Space Occupying Lesions Deck (67):
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)
31
what is the most common type of benign primary brain tumour
meningioma
schwannoma
craniopharyngioma
pituitary adenoma
32
why are astrocytomas hard to resect
insidious brain infiltration
33
what is a glioblastoma
grade 4 astrocytoma
34
do grade 1 astrocytomas become malignant
no
35
what are the features of a astrocytoma (grades 2+)
nuclear atypia
mitosis
necrosis (4)
neovascularisation (4)
proliferation
anaplasia
palisading
36
what is the most common tumour in children
medulloblastoma
37
what are the features of a medulloblastoma
poorly differentiated
embryonal
occurs in midline of cerebellum
very radiosensitive- good prognosis
38
what are the causes of single brain abscesses
local extension (e.g. mastoditis)
direct implantation (e.g. skull fracture)
(tend to occur adjacent to the source)
39
what are the causes of multiple abscesses
haemotogenous spread (bronchopneumonia, bacterial endocarditis, congenital heart disease, IV drug use)
(tend to occur at grey and white matter boundary)
40
what are the symptoms of an abscess
fever
raised ICP
+ symptoms of underlying cause
41
what investigations and Tx for brain abscess
CT/ MRI to diagnose
apsirate for culture and Tx
weeks of antibiotics (hard to get into CNS)
42
what is bacterial meningitis
inflammation of the leptomeninges
and CSF within the subarachnoid space
43
how does bacterial meningitis cause raised ICP
severe oedema
44
what is seen in CSF in bacterial meningitis
polymorphs
low glucose
45
what can arachnoiditis cause
lack of CSF absorption = hydrocephalus = raised ICP
46
e coli:
what type of bacterial is it and who does it cause bacterial meningitis
gram -ve rod
neonates
47
H influenza:
what type of bacterial is it and who does it cause bacterial meningitis
gram -ve cocco-bacilli
infants and children
48
n meningitidis:
what type of bacterial is it and who does it cause bacterial meningitis
gram -ve diplococci
adolescents and young adults
49
s pneumoniae:
what type of bacterial is it and who does it cause bacterial meningitis
gram +ve cocci in chains
older adults or children
50
L monocytogenes:
what type of bacterial is it and who does it cause bacterial meningitis
gram +ve rods
older adults
51
what are missile and non missile injuries
missile= penetrating
non missile- blunt
52
what can penetrating brain injuries cause
focal damage
lacerations in region of brain damage
haemorrhage
53
does a high or low velocity penetrating brain injury cause more damage
high
54
what is a non missile injury and what determines the extend of its damage
sudden acceleration/ deceleration of head
smaller the contact time the larger the force
55
what is a primary brain injury
• Injury to neurones
• Irreversible
• Preventative measures
(hallmark is change in consciousness immediately)
56
what is a secondary brain injury
• Haemorrhage
• Oedema etc
• Potentially treatable
57
what are the types of scalp lesions
bruising (contusions)
lacerations
bleeding
(route for infection)
58
what are the types of skull fracture
• Linear ‐ straight sharp fracture line, that may cross
sutures (diastatic fracture)
•Compound ‐ associated with full thickness scalp lacerations
•Depressed
if base of skull fracture then compound or open as damage to paranasal sinus
59
what is coup and contra coup
in the context of brain surface contusions and lacerations:
-Coup- brain hits side of injury
-Contra coup- hits opposite side, tend to be worse than coup
60
what is a diffuse axonal injury
Occurs at moment of injury
a blunt trauma puts a shearing strain on axons which tear
affects central areas
causes reduced consciousness and coma
can lead to vegetative state
61
what can cause secondary injury to the brain
-Intracranial haematoma
• Reduced cerebral blood flow
• Hypoxic brain damage
• Excitotoxicity
• Oedema
• Raised ICP
• Infection
62
what does Ca2+ influc do to protease and phospholipase
activates them- causing lipid membrane disruption
63
where are most traumatic intracranial haematomas
intradural (sub dural, intracerebral, subarachnoid)
64
what are traumatic extradural haematomas like
•Usually a complication of
fracture in tempero‐parietal
region that involves middle
meningeal artery
• Immediate brain damage
often minimal
•But untreated, midline shift –
compression and herniation
65
what is a subdural haemorrhage and what causes it
• Collections of blood between the internal surface of dura mater
and arachnoid mater
• Caused by disruption of bridging veins that extend from the
surface of the brain into subdural space
66
what is the pressure put on the brain by a subdural haemorrhage like
Gyral contours preserved –
pressure evenly distributed
67