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Clinical neuroscience > Subarachnoid haemorrhage and meningitis > Flashcards

Subarachnoid haemorrhage and meningitis Flashcards

1
Q

What is the epidemiology of subarachnoid haemorrhage?

A
  • Cause around 6% of all strokes
  • Slightly more females affected
  • Most are under 50
  • 50% mortality
  • 60% of patients suffer some longer term morbidity
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2
Q

What are the risk factors for subarachnoid haemorrhage?

A
  • Hypertension
  • Smoking
  • Excess alcohol consumption
  • Predisposition to aneurysm formation
  • Family history
  • Associated conditions
  • Trauma
  • Cocaine use
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3
Q

What are some conditions associated with subarachnoid haemorrhage?

A
  • Chronic kidney disease (resultant effect on vessel wall)
  • Marfan’s syndrome (effect on connective tissues of vessels)
  • Neurofibromatosis (unclear mechanism, if any link)
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4
Q

Why do subarachnoid haemorrhages usually occur?

A
  • Rupture of an aneurysm in the circle of Willis
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5
Q

What is an aneurysm?

A
  • Aneurysm is a weakness in a vessel (usually artery) wall which can cause an abnormal bulge
  • May be a genetic predisposition to aneurysm formation
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6
Q

What are the causes of aneurysms?

A
  • May be caused by haemodynamic effects at branch points in the circle of Willis
  • Higher resulting flow rate in progressively smaller branches, turbulence
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7
Q

What are the majority of aneurysms?

A
  • Berry aneurysms
  • Make up 75% of all aneurysms
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8
Q

What are the common sites of berry aneurysms?

A
  • Anterior communicating / proximal anterior cerebral artery (30%)
  • Posterior communicating artery (25%)
  • Bifurcation of the middle cerebral artery as it splits into superior and inferior divisions (20%)
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9
Q

What parts of the brain are affected by a berry aneurysm in the anterior communicating/proximal anterior cerebral artery?

A
  • Can compress the nearby optic chiasm
  • May affect frontal lobe or even pituitary
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10
Q

What parts of the brain are affected by a berry aneurysm in the posterior communicating artery?

A
  • Can compress the adjacent oculomotor nerve causing an ipsilateral third nerve palsy
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11
Q

What does bleeding into the subarachnoid space cause?

A
  • Early brain injury
  • Cellular changes
  • Systemic complications
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12
Q

What are the features of early brain injury caused by bleeding into the subarachnoid space?

A
  • Microthrombi (may occlude more distal branches)
  • Vasoconstriction as a result of blood in the CSF irritating the cerebral arteries
  • Cerebral oedema - general inflammatory response to tissue hypoxia and extravasated blood
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13
Q

What are the cellular changes caused by bleeding into the subarachnoid space?

A
  • Oxidative stress
  • Release of inflammatory mediators can activate many pathways as well as activation of microglia
  • Platelet activation (formation of thrombi)
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14
Q

What are the systemic complications caused by bleeding into the subarachnoid space?

A
  • Sympathetic activation - early Cushing response
  • Myocardial necrosis due to sympathetic activation
  • But subarachnoid haemorrhage has typical ECG features
  • Systemic inflammatory response can affects multiple systems
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15
Q

What are the clinical features of subarachnoid haemorrhage?

A
  • Thunderclap headache
  • Frequently loss of consciousness and confusion
  • Meningism
  • May be focal neurology
  • May be history of sentinel bleed
  • May present as cardiac arrest (due to profound Cushing response)
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16
Q

What are the features of thunderclap headache?

A
  • Explosive in onset and severe
  • Often reported as the worst headache ever or like being hit on the head with a cricket bat
  • Diffuse pain
  • Can last from an hour to a week
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17
Q

What are the features if meningism?

A
  • Neck stiffness
  • Photophobia
  • Headache
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18
Q

What are the investigations for subarachnoid haemorrhage?

A
  • CT head
  • CT angiogram
  • Lumbar puncture
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19
Q

What is a classical CT finding for subarachnoid haemorrhage?

A
  • Prominent filling of the basal cisterns in a five pointed star pattern
  • Blood may be seen within the ventricles (may be due to reflux from the subarachnoid space)
20
Q

What does CT angiogram show in the case of a subarachnoid haemorrhage?

A
  • Will allow direct visualisation of bleeding aneurysm of aneurysm sac
  • Vital planning surgery
21
Q

What is the technique for lumbar puncture?

A
  • Identify iliac crests at L4-L5 level
  • Give local anaesthetic
  • Insert LP needle between spinous processes
  • 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 it to drip, don’t aspirate)
22
Q

What are the lumbar puncture findings in subarachnoid haemorrhage?

A
  • Increased opening pressure (as there is now additional volume in the subarachnoid space)
  • Frank blood or xanthochromia may be seen
  • High protein
  • White cells often not raised
  • Glucose not affected
  • High red cell count
23
Q

What is xanthochromia?

A
  • Yellow colouring of the CSF due to metabolism of haemoglobin to bilirubin within the subarachnoid space
  • Seen at least 12 hours post bleed
  • More specific than frank blood for subarachnoid haemorrhage
24
Q

What is the treatment for subarachnoid haemorrhage?

A
  • ABC approach
  • Neurological observations - look for trends which may suggest increasing ICP
  • Neurosurgery
25
Q

Outline the ABC approach used to treat subarachnoid haemorrhage?

A
  • Support airway if diminished consciousness level
  • Give oxygen
  • Support circulation - fluids and maybe nimodipine to alleviate cerebral vasospasm
26
Q

What are the different types of neurosurgery used to treat subarachnoid haemorrhage?

A
  • Decompressive surgery (craniectomy)
  • Coiling
  • Clipping
  • All performed by neurosurgeons
27
Q

How does coiling happen?

A
  • Insertion of a platinum wire into the aneurysm sac, which causes thrombosis of blood within the aneurysm itself
28
Q

How does clipping happen?

A
  • Placement of a spring clip around the neck of the aneurysm, causing it to lose blood supply and shrivel up
29
Q

What are the typical organisms that cause meningitis in neonates?

A
  • E. coli
  • Group B streptococcus
  • Listeria monocytogenes
30
Q

What are the typical organisms that cause meningitis in children?

A
  • Haemophilus influenzae type B (HiB vaccine given, ‘meningococcus’)
  • Neisseria meningitidis (vaccines given for some strains)
31
Q

What are the typical organisms that cause meningitis in the elderly?

A
  • Streptococcus pneumoniae (vaccines now given)
  • Listeria monocytogenes
32
Q

What are the risk factors for meningitis?

A
  • 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)
33
Q

What are the clinical features of meningitis?

A
  • The triad of meningism with fever
  • Associated symptoms
34
Q

What are the features of the triad of meningism?

A
  • Headache
  • Neck stiffness (nuchal rigidity)
  • Photophobia
35
Q

What are the associated symptoms of meningitis?

A
  • Flu-like symptoms
  • Joint pains and stiffness
  • Seizure
  • Meningococcal rash (non blanching)
  • Drowsiness
  • Patient may be in shock
36
Q

What are the symptoms of meningitis in babies?

A
  • Inconsolable crying/off feeds
  • Rigidity/floppiness
  • Bulging fontanelle (late sign)
37
Q

How does infection enter the meninges?

A
  • Bugs which normally live in the nose gain entry to the circulation and cause a bacteraemia
  • This causes damage to vessel walls in the brain and meninges, allowing the pathogen to enter the subarachnoid space
38
Q

What happens once infection gets into the meninges?

A
  • Once in the subarachnoid space, pathogens multiply rapidly
  • This causes purulent CSF and severe meningeal inflammation
  • Vasospasm of cerebral vessels can cause cerebral infarction
39
Q

How does meningitis cause raised ICP?

A
  • Oedema of brain parenchyma
40
Q

Why does meningococcal septicaemia cause maculopapular rash?

A
  • Caused by microvascular thrombosis due to many factors including:
  • Sluggish circulation
  • Impaired fibrinolysis
  • Increased tissue factor expression in endothelial cells
41
Q

What investigations are done to diagnose meningitis?

A
  • Bloods including sepsis screen and PCR
  • Maybe chest X-ray or midstream urine if you suspect a particular septic focus
  • Lumbar puncture findings
42
Q

What are the lumbar puncture findings in bacterial meningitis?

A
  • Cloudy CSF
  • High protein
  • High white cells, primarily neutrophils
  • Low glucose (metabolised by bacteria and white cells)
43
Q

What are the lumbar puncture findings in viralnmeningitis?

A
  • May be clear but can be cloudy (due to immune cells and proteins)
  • Protein level may be normal or raised
  • High white cells, primarily lymphocytes to mount an adaptive response
  • Normal glucose
44
Q

What is the supportive treatment for meningitis?

A
  • Analgesia
  • Antipyretics
  • Fluids if shocked
45
Q

What is the medical treatment for meningitis?

A
  • IV ceftriaxone
  • Dexamethasone to prevent hearing loss
  • If viral, give acyclovir for herpes or ganciclovir for CMV
46
Q

Why can meningitis lead to hearing loss?

A
  • Due to swelling of vestibulocochlear nerve or effect on cochlea
47
Q

What are some of the complications of meningitis?

A
  • Septic shock and disseminated intravascular coagulation (due to bacteraemia)
  • Coma (due to raised ICP)
  • Cerebral oedema (due to cerebral inflammation)
  • Death
  • Seizures (due to irritation of brain parenchyma)

Clinical neuroscience (19 decks)

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