10.3 subarachnoid haemorrhage and meningitis Flashcards
(76 cards)
1
Q
What is the function of the dura mater?
A
Surrounds and supports the dural sinuses
2
Q
What are the 2 layers of the dura mater?
A
Endosteal layer
Meningeal layer
3
Q
What a layers form the leptomeninges?
A
Arachnoid mater
Pia mater
4
Q
Where is the pia mater?
A
Innermost meningeal layer, adheres closely to the brain and pierced by blood vessels.
5
Q
Where are the 2 layers of the dura mater not adherent to each other?
A
When enclose venous sinuses
When forming dural septa (4 important ones)
1. Falx cerebri (between cerebral hemispheres)
2. Falx cerebelli (between cerebellar hemispheres)
3. Tentorium cerebelli
4. Diaphragma sella
6
Q
Where is the diaphragma sella?
A
Covers the superior surface of the pituitary gland and contains a hole to allow the passage of the infundibulum
7
Q
Where does an extra dural bleed occur?
A
Between endosteal layer and skull
8
Q
Describe the pathological process of an extra dural bleed?
A
Typically due to trauma affecting the middle meningeal artery. Resulting in a lentiform bleed as shown on a CT scan.
9
Q
In which dural bleed do we get a lucid interval?
A
Extra dural bleed
10
Q
Where does a subdural bleed occur?
A
Between the meningeal layer and arachnoid
11
Q
Describe the pathological development of a subdural bleed
A
Trauma results in torn bridging veins. Appears on CT scan as crescent bleed
12
Q
Where is the subarachnoid space located?
A
Located between arachnoid and pia
13
Q
What are cisterns?
A
Larger areas of the subarachnoid space that occur where the brain moves away from the skull.
14
Q
What lies within the subarachnoid space?
A
CSF
15
Q
What is the function of CSF?
A
- Physical support of neural structures
- Excretion (of brain metabolites)
- Intracerebral transport (hormone releasing factors)
- Control of chemical environment
- Volume changes reciprocally with volume of intracranial contents (swelling/blood)
16
Q
How is CSF formed?
A
Formed by choroid plexuses (and extra-choroidal structures) that filter plasma from the blood to produce CSF
17
Q
What drives the flow of CSF through the ventricular system?
A
Propelled by newly formed fluid, ciliary action of ventricular ependyma, vascular pulsations
18
Q
Describe the flow of CSF
A
Lateral ventricles (interventricular foramen)
- > 3rd ventricle-(aqueduct of Sylvius)
- > 4th ventricle (median and lateral apertures)
- > subarachnoid space/cisterns (small amount into spinal cord)
19
Q
What is a subarachnoid haemorrhage?
A
Extravasation of blood into the subarachnoid space
20
Q
What are the causes of subarachnoid haemorrhage?
A
Trauma
Spontaneous
21
Q
What other key clinical manifestation can subarachnoid haemorrhages cause?
A
Stroke (6%)
22
Q
What patient groups are most likely to experience subarachnoid haemorrhage?
A
Females
Black/Finnish/Japanese
50-55yrs
23
Q
What is the prognosis of a subarachnoid haemorrhage?
A
Bad
50% mortality, 60% suffer some longer term morbidity following the event
24
Q
What are risk factors of a subarachnoid haemorrhage?
A
• Hypertension
• Smoking
• Excess alcohol consumption
• Predisposition to aneurysm formation
• Family history
• Associated conditions
- Chronic kidney disease (resultant effect on vessel wall)
- Marfan’s syndrome (effect on connective tissues of vessels)
- Neurofibromatosis (unclear mechanism, if any link)
• Trauma
• Cocaine use
25
How does a patient with a subarachnoid haemorrhage present?
```
Thunderclap Headache - very painful/dehabilitating
dizziness
Orbital pain
Diplopia
Visual loss
```
26
What is the causation of spontaneous subarachnoid haemorrhages?
Rupture of a saccular berry aneurysm (80%)
| Rupture of other arterial venous malformations. (10%)
27
What causes the development of berry aneurysms?
Pressures on the arterial wall, intracranial arteries lack an external elastic lamina and have a thin adventitia.
28
Where do berry aneurysms commonly occur?
Bifurcation points - caused by haemodynamic effects at branch points in the circle of Willis
Large cerebral arteries
Common sites, making up 75% of all aneursyms:
1. Anterior communicating artery / proximal anterior cerebral artery (30%)
2. Posterior communicating artery (25%)
3. Bifurcation of the middle cerebral artery as it splits into superior and inferior divisions (20%)
29
What are the clinical features of a subarachnoid haemorrhage?
Thunderclap headache
• Explosive in onset and severe, often reported as worst
headache ever or even ‘like being hit on the head with a
cricket bat’
• Diffuse pain
• Can last from an hour to a week
Frequently loss of consciousness and confusion
Meningism
• Neck stiffness
• Photophobia
• Headache
May be focal neurology
May be history of sentinel bleed (previous headache)
May present as cardiac arrest (if intracranial pressure rises
rapidly following bleed leading to profound Cushing response)
30
Berry aneurysms in the anterior communicating artery/ proximal anterior cerebral artery can cause what distinct sign?
Visual problems/tunnel vision/bilateral hemianopia due to compression of the optic chiasm
May affect frontal lobe or even pituitary
31
What specific symptoms can be caused due to a posterior communicating artery aneurysm?
Can compress the adjacent oculomotor nerve causing an ipsilateral third nerve palsy
32
What happens after a bleed into the subarachnoid space?
Microthrombi - can occlude smaller distal arteries leading to brain injury
Vasoconstriction from CSF irritant
Cerebral oedema - response to hypoxia and extravasated blood.
Sympathetic activation which can lead to myocardial damage /MI
Apoptosis of brain cells.
Early rebleeding
Acute hydrocephalus - may block normal drainage points of CSF
Global cerebral ischaemia
33
What imaging is done to investigate a subarachnoid haemorrhage?
Urgent non-contrast CT scan. Blood itself in the subarachnoid space is the contrast.
34
How will a CT scan of a subarachnoid haemorrhage appear?
• Prominent filling of the basal cisterns in a five pointed ‘star’ pattern
• Blood may be seen within the ventricles (maybe due to
reflux from subarachnoid space)
35
If a CT head confirms a subarachnoid haemorrhage, what should we do next?
CT angiogram as will allow direct visualisation of bleeding aneurysm of
aneurysm sac. Vital for planning surgery
36
If the history of the patient suggest subarachnoid haemorrhage but the CT is negative what do we do next?
Lumbar puncture to test for bilirubin in the CSF, which gives CSF a yellow tinge after centrifuging - xanthochromia. Should wait at least 6 hours (12 hours ideal) from onset of symptoms for RBC to undergo lysis.
37
What in Xanthochromia?
A yellow tinge to the CSF
38
What is a traumatic tap?
Blood vessel breaking on the way to the subarachnoid space, causing Blood within the CSF sample.
39
In a CSF sample from a lumbar puncture in a patient with a subarachnoid haemorrhage what is the usual results?
```
High protein
WCC not raised
Normal glucose
High red cell count
Increased opening pressure during the lumbar puncture.
Frank blood or xanthochromia
```
40
Describe the technique used to perform a lumbar puncture
Identify iliac crests (giving L4-L5 level)
Give local anaesthetic
Insert LP needle between spinous processes and through the supraspinous and interspinous
ligaments
Feel give as pass through ligamentum flavum and dura
Remove needle stylet and collect CSF in sterile containers (allow to drip, don’t aspirate!)
41
How do we stabilise a patient with a subarachnoid haemorrhage?
Support airway if consciousness level is diminished
Monitoring cardiovascular parameters - sympathetic stimulation
CCB (nimodipine) - prevent vasospasm and secondary ischaemia
Support circulation - fluids
Neurological observations
Neurosurgery within 48 hours if good neurological status to prevent rebleeding
42
What surgery is done to treat a subarachnoid haemorrhage due to a berry aneurysm?
• Decompressive surgery (craniectomy)
• Coiling - Insertion of (frequently) a platinum wire into the
aneurysm sac, which causes thrombosis of blood
within the aneurysm itself
• Clipping - Placement of a spring clip around the neck of the aneurysm, causing it to lose blood supply and
‘shrivel up’
43
Why is surgery vital on a patient that has had a subarachnoid haemorrhage?
Rebleeding occurs in up to 30% in first 2/52 within 2 weeks in unoperated patients
44
What is the commonest cause of death following aneurysmal SAH
Delayed ischaemia from cerebral vasospasm
45
What is encephalitis?
Infection of the CNS parenchyma
46
What is meningitis?
Infection of the meninges
| - commonly cause inflammation of the leptomeninges but can rarely affect the dura
47
What is the most common cause of meningitis?
Bacterial or viral infection
| Can occasionally be caused by fungal disease or non infectious modalities such as trauma or surgery
48
What are the typical causative organisms of meningitis in neonates?
E. coli
Group B streptococcus
Listeria monocytogenes
49
What are the typical causative organism of meningitis in children?
Haemophilus influenzae type B (HiB vaccine
| given, ‘meningococcus’) Neisseria meningitidis (vaccines given for some strains
50
What is the typical causative organisms of meningitis in the elderly?
```
Streptococcus pneumoniae (vaccines now given)
Listeria monocytogenes
```
51
What are risk factors of meningitis?
CSF defects (e.g. spina bifida)
Spinal procedures (e.g. surgery, lumbar puncture)
Endocarditis (as a focus of bacteraemia)
Diabetes (immunosuppression)
Alcoholism
Splenectomy (immunosuppression)
Crowded housing (students at risk)
52
What are the triad of meningism?
Headache
Neck stiffness (unchallenged rigidity)
Photophobia
53
What are the clinical features of meningitis?
```
The triad of ‘meningism’ with fever
Associated symptoms
• Flu-like symptoms
• Joint pains and stiffness
• Seizure
• Meningococcal rash (non blanching) • Drowsiness
• Patient may be in shock
Reduced GCS
```
54
What clinical features of meningitis can present specifically in babies?
Inconsolable crying / off feeds
Rigidity / floppiness
Bulging fontanelle (late sign)
55
How long do the signs and symptoms take to develop in meningitis?
Develops over hours with bacterial meningitis
| Develops over days with viral meningitis
56
When is meningitis rash commonly seen?
With meningococcal meningitis
57
Describe a meningitis rash
Red spots under the skin, non-blanching.
Larger lesions are termed purpuric
Smaller lesions are termed petechial
Usually found on the trunk, legs, mucous membranes and conjunctivae. Occasionally on the palms and soles
58
What are the main causative organisms of community acquired bacterial meningitis?
Streptococcus pneumonia - most common
Neisseria meningitides
Haemophilus influenzae
59
What is PCV13?
Pneumococcal conjugate vaccine. Reduced prevalence of pneumococcal meningitis
60
What are risk factors for community acquired bacterial meningitis?
* Young and old the most affected (<5 years, >65 years)
* Crowding
* Immune problems (non immunised infants, cancer, asplenia)
* Cochlear implants
61
How does pneumococcal meningitis infection occur?
Streptococcus pneumoniae normally colonise the nasopharynx but can be displaced causing infection
1. Ascent of bacteria through Eustachian tube to middle ear (otitis
media). Prolonged infection in this area can lead bacteria to spread
directly into CSF (through mastoid sinuses)
2. Seeding to lower respiratory tract (pneumonia). Lung inflammation allows bacteria to enter blood (bacteraemia). Invasion of CSF via capillaries that traverse choroid plexus or subarachnoid space
Neonates can get pathogens from maternal source (placenta/reproductive tract secretions)
62
What is the pathological process of bacterial meningitis?
Bacteria quickly multiply once in the subarachnoid space
Inflammatory mediators induced
Lots of leucocytes enter CSF
Inflammatory cascade results in cerebral oedema and raised intracranial pressure
63
What are the complications of bacterial meningitis?
* Septic shock (due to bacteraemia)
* Disseminated intravascular coagulation (due to bacteraemia)
* Coma (raised ICP)
* Seizures (irritation of brain parenchyma)
* Hearing loss (Vestibulocochlear nerve/cochlea swelling)
* Hydrocephalus (blockage of CSF drainage pathways)
* Focal paralysis (potentially due to cerebral abscess)
64
What 2 signs are looked for on examination of a patient with suspected meningitis?
Kernig sign
| Brudzinski sign
65
What is Kernig sign?
* Supine patient With thigh flexed to 90 degrees
* Extension of knee is met with resistance
* More common in children (up to 53%)
66
What is brudzinski sign?
• When neck is Flexed there is an involuntary flexion of knees and hips • More common in children (up to 66%)
67
What is the 1st line investigation in meningitis?
Lumbar puncture
CT head
PCR
68
In untreated bacterial meningitis, CSF is usually?
* Cloudy- high numbers of white cells (lymphocytes and neutrophils)
* Elevated protein (immune proteins)
* Low glucose (bacteria metabolise it)
* Positive gram stain
High white cells, primarily neutrophils (which phagocytose bacteria)
69
In viral meningitis, CSF is usually?
* Clear or cloudy (immune cells and protein)
* Normal or raised protein
* Normal glucose
High white cells, primarily lymphocytes to mount an adaptive response
70
Why might a lumbar puncture need to be delayed in investigating meningitis?
If there is raised ICP there is a possibility of brain herniation occurring.
• 5% of patients with acute bacterial meningitis
• Performing an LP increases chances of this occurring
• Sudden decrease in pressure (removal of CSF)
Delay if there are Clinical signs of:
• Decreasing consciousness
• Brainstem signs
• Recent seizure
71
Why might a CT head be done in meningitis?
Used to find contraindications of a lumbar puncture
72
Why is a PCR done in meningitis?
Done from blood and CSF to diagnose patients who received empirical antibiotic treatment. Distinguishing bacterial from viral causes
73
Ideally, when should a blood culture be done from a patient with suspected meningitis?
Within 1 hour of hospital arrival and before antibiotics
74
What is the treatment for meningitis?
Admit to hospital
Empirical antibiotics (broad spectrum) Eg Vancomycin + (Ceftriaxone or Cefotaxime)
Supportive therapy
• Intubation if altered consciousness
• Fluids if shocked (caution with raised ICP)
• Oxygen, analgesia, antipyretics
• Dexamethasone(to prevent hearing loss)
If viral
• Aciclovir for Herpes
75
What are potential complications of meningitis?
▪ Septic shock (due to bacteraemia)
▪ Disseminated intravascular coagulation (due to bacteraemia)
▪ Coma (due to raised ICP)
▪ Cerebral oedema (due to cerebral inflammation)
▪ Raised ICP
▪ Death (due to brain herniation, sepsis)
▪ SIADH (maybe direct effect on hypothalamus/pituitary?)
▪ Seizures (due to irritation of brain parenchyma)
▪ Hearing loss (due to swelling of vestibulocochlear nerve or
cochlea itself. Perilymph is continuous with subarachnoid
space)
▪ Intellectual deficits (due to direct brain damage)
▪ Hydrocephalus (due to interruption of CSF drainage pathways
and effect on arachnoid granulations)
▪ Focal paralysis (maybe due to cerebral abscess)
76
What causes the maculopapular rash seen in meningococcal septicaemia?
Caused by microvascular thrombosis due to many
factors, including
Sluggish circulation
Impaired fibrinolysis
Increased tissue factor expression in endothelial cells
