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Clinical neuroscience > L16 - Meningitis and subarachnoid haemorrhage > Flashcards

L16 - Meningitis and subarachnoid haemorrhage Flashcards

1
Q

Dural septa

A

Falx cerebri
Falx cerebelli
Tentorium cerebelli
Diaphragma sella - layer of dura with a hole for the pituitary stalk

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2
Q

Cisterns

A

Enlarged spaces between the brain and the skull where CSF can collect

Functions:

  • Render brain weightless
  • Excretion of brain metabolites
  • intracerebral transport of hormone releasing factors
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3
Q

What percentage of strokes are subarachnoid

A

6%

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4
Q

Who is more likely to get a subarachnoid stroke?

A

Women 1.6:1
50- 55 yr olds
Black, Finnish and Japanese’s people

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5
Q

Prognosis of subarachnoid haemorrhage

A

50% mortality

60% longer term morbidity

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6
Q

Risk factors of subarachnoid haemorrhage

A 
Hypertension 
Smoking 
Trauma
Cocaine 
Family history 
Excess alcohol consumption 
Predisposition to aneurysm formation - Marfan’s
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7
Q

Presentation of subarachnoid haemorrhage

A 
Thunderclap headache 
Nausea and vomiting 
Dizziness
Orbital pain 
Diplopia 
Visual loss 
Meningism - bleeding into the subarachnoid space cause if inflammation
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8
Q

Pathophysiology of subarachnoid haemorrhage

A

Rupture of berry aneurysm in the circle of Willis usually at bifurcation points

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9
Q

Common sites of Berry aneurysms

A

Anterior communicating artery - 40%
- can compress the optic chiasm

Posterior communicating artery - 25%
- compress CN III

Middle cerebral artery as it bifurcates into superior and inferior - 20%

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10
Q

Why are intracerebral arteries prone to aneurysm

A

Lack external elastic lamina

Thin adventitia

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11
Q

Sentinel headaches

A

Headaches month prior to the subarachnoid haemorrhage due to small leaks from the aneurysm

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12
Q

What happens after a subarachnoid bleed?

A

Microthrombi can occlude distal arteries
Vasoconstriction of cerebral arteries as the CSF is irritated
Cerebral oedema
Myocardial damage due to sympathetic activation
Early rebleeding
Acute hydrocephalus - blood blocks CSF drainage
Global cerebral ischaemia

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13
Q

How does cerebral oedema occur?

A

Decreased oxygen delivery to an area of the cerebral cortex causes ischaemia
Less ATP produced therefore less Na+/K+ ATPase activity
Higher Na+ conc inside the cell causes depolarisation
Na+ influx
K+ efflux
Water follows sodium therefore influx of water causing oedema

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14
Q

Investigations of a subarachnoid haemorrhage

A

1st line - CT without contrast

If there is a convincing Hx but negative CT, do a lumbar puncture at L3/L4 or L4/L5

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15
Q

Lumbar puncture

A

Wait at least 6 hours
Preferably 12+ hours

For the blood in the CSF to lyase, therefore can detect the bilirubin
CSF has a yellow tinge after centrifugation - xanthochromia

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16
Q

Traumatic tap

A

Needle inadvertently enters an epidural vein

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17
Q

Xanthochromia

A

Yellow tinge of the CSF due the presence of bilirubin

18
Q

CSF contents of subarachnoid haemorrhage

A

High protein (plasma proteins from blood)
No WCC ( not infection)
Normal glucose
High RBC

19
Q

After diagnosis

A

Angiography is performed to confirm the location of the aneurysm

20
Q

Treatment of a subarachnoid haemorrhage

A

Stabilisation

Airways - Assess whether they need airway support
Breathing- Give oxygen
Circulation - fluids and nimodopine

Possibly operate

21
Q

When to operate

A

Within 72 hours of bleed
On patients with good neurological status
Prevents rebleeding

22
Q

Types of surgical procedures

A

Decompression - craniotomy

Clipping - surgeon clamps base of the aneurysm with spring clip (open craniotomy) cutting off the blood supply causing it to shrivel

Coiling - neuro radiologists insert a platinum wire into the aneurysm sac which causes thrombosis of blood within the aneurysm which doesn’t occlude the artery

23
Q

Subarachnoid CT

A

Prominent filling of the basal cisterns in a 5 point star pattern
Blood may be seen within the ventricles - reflux from subarachnoid space

24
Q

Nimodopine

A

Calcium channel blocker prevents secondary vasospasm and secondary ischaemia

25
Q

Meningitis

A

inflammation of the meninges commonly due to infection

Often the leptomeninges

26
Q

Encephalitis

A

Infection (often viral) of the brain parenchyma

Meningitis can lead to encephalitis

27
Q

Signs and symptoms of meningitis

A 
Signs:
Non blanching rash 
Fever 
Reduced GCS 
Kernig sign 
Brudzinski sign 
Symptoms:
Photophobia 
Neck stiffness 
Headache 
Joint pains
Seizures
28
Q

Meningitis in children

A

Insoluble crying
Reduced feeds
Floppy
Bulging fontanelle

29
Q

Non blanching rash

A

Due to bleeds into the skin or mucosa - microvascular thrombosis

  • slow circulation
  • impaired fibrinolysis
  • increased tissue factor expression in endothelial cells

1-3mm - petechia (pin prick like)
Larger than 3mm - purpura

Usually found on legs, trunk, mucosal membranes and conjunctivae
Occasionally palms and soles

More common in younger patients

30
Q

Conjugate vaccine for meningitis

A

PCV13 - pneumococcal conjugate vaccine for 13 worst variants
- given to under 60s

PCV20 - given to the elderly

31
Q

Risk factor for community acquired meningitis

A

Young and old - less that 5 yrs old and over 65 years old
Crowding
Immunocompromised- non vaccinated, asplenic, cancer, diabetes
Cochlear implants - physical conduit to meninges
CSF defects - spina bifida
Spinal procedures - lumbar puncture
Endocarditis - bacteraemia
Alcoholism

32
Q

How does pneumococcal bacteria reach the meninges

A
  • commensal of nasopharynx
  • ascends through the Eustachian tube to middle ear (otitis media)
  • prolonged otitis media can lead to bacteria spread directly to CSF through the mastoid sinus
  • seeds to the lower resp tract (pneumonia)
  • lung inflammation causes vessels to become more leaky therefore bacteria enters the blood stream causing bacteraemia
  • invasion of CSF via capillaries the traverse the choroid plexus or subarachnoid space
  • neonates can get pathogen from mother (Ecoli)
33
Q

Effects of meningitis

A

Once bacteria is in the subarachnoid space, it multiplies exponentially as no resistance

  • inflammatory mediators are induced
  • leukocytes enter the CSF
  • inflammatory cascade causes cerebral oedema and raised ICP
34
Q

Complications of meningitis

A

Septic shock - meningococcal sepsis due to bacteraemia
DIC - disseminated intravascular coagulation - bacteraemia
Coma - raised ICP
Seizures - irritation of brain parenchyma
Hearing loss - cochlea swelling or CN VIII lesion
Hydrocephalus
Focal paralysis - cerebral abscess

35
Q

Positive Kernig sign

A

Supine patient with thigh flexed to 90 degrees
Resistance to knee extension as stretches meninges
More common in children

36
Q

Positive brudzinski sign

A

When neck is flexed, involuntary flexion of the knees and hips
More common in children

37
Q

Investigations of meningitis

A

Lumbar puncture - compare with blood culture
PCR
- blood and CSF
- distinguishes between viral and bacterial

Blood culture - May be influenced by antibiotic treatment
Sepsis screen

If septic:

  • mid stream urine sample
  • CXR
38
Q

CSF in meningitis

A

Bacterial:

  • WCC present - lymphocytes and neutrophils
  • cloudy due to WCC
  • elevated protein - immune proteins
  • low glucose - bacteria metabolism it
  • positive gram stain

Viral meningitis:

  • clear of cloudy
  • WCC
  • normal or raised protein
  • normal glucose
39
Q

Risk of lumbar puncture

A

Raised ICP increases the likelihood of brain herniation

Performing the LP increases this chance due to a sudden decrease in pressure from removal of the CSF

40
Q

When should a lumbar puncture be delayed

A
  • decreased consciousness
  • brainstem signs
  • recent seizures

CT can identify contraindications but a normal CT may not mean LP is safe

41
Q

Meningitis treatment

A

Admit to hospital
- empirical antibiotics asap - vancomycin + IV ceftriaxone or cefotaxime (neonatal meningitis)

Supportive therapy:

  • airways - intubation - altered consciousness
  • breathing - oxygen
  • circulation - fluids if sepsis shock - caution with raised intracranial pressure

Dexamethosone (corticosteroid) - prevents hearing loss by reducing swelling

Viral

  • acyclovir for herpes
  • ganciclovir - CMV

Supportive:

  • fluids if sepsis shock
  • analgesia
  • antipyretic

Clinical neuroscience (20 decks)

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