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Clinical Neuroscience > Meningitis and Sub-arachnoid haemorrhage > Flashcards

Meningitis and Sub-arachnoid haemorrhage Flashcards

1
Q

What are the 3 layers od the meninges?

A

Dura Mater

  • Endosteal layer
  • Meningeal layer

Arachnoid Mater

Pia Mater

  • thin layer closesly adhered to brain
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2
Q

What makes up the leptomeninges?

A

The arachnoid + pia mater

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3
Q

What are the 4 important dural septa?

A
  1. Falx cerebri (between cerebral hemispheres)
  2. Falx cerebelli (between cerebellar hemispheres)
  3. Tentorium cerebelli
  4. Diaphragma sella
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4
Q

Between what layers do epidural bleeds (extradural) occur?

A

Between the endosteal layer of the dura and the skull

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5
Q

Between what layers do subdural bleeds occur?

A

Between the meningeal and arachnoid layer

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6
Q

Where is the subarachnoid space?

A

Between the arachnoid and pia

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7
Q

What are cisterns?

A
  • Enlarged areas that occur in the subarachnoid space when the brain moves away from the skull
  • Filled with CSF
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8
Q

What are the functions of CSF?

A
  • Physical support of neural structures
  • Excretion of brain metabolites
  • Intracerebral transport (hormone releasing factors)
  • Control of chemical environment
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9
Q

Describe the flow of CSF through the ventricles of the brain

A
  • Formed in the choroid plexus
  • Into lateral ventricles
  • Through interventricular foramina to third ventricle
  • Through cerebral aqueduct to 4th ventricle
  • Through lateral and median aperture (Lushka and Megande) to subarachnoid space and small amount into spinal cord
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10
Q

How is CSF reabsorbed?

A

By arachnoid granulations that project into dural sinuses

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11
Q

How do spontaneous subarachnoid haemorrhages usually occur?

A

Rupture of saccular aneurysm (berry aneurysm) (80% of non traumatic)

Usully occur at bifurcation points of cerebral vasculature

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12
Q

In which demographics are subarachnoid haemorrhages more common?

A
  • More likely in females (1.6: 1)
  • More likely in black, Finnihs and Japanese populations
  • Average age onset 50-55yrs
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13
Q

How will a subarachnoid haemorrhage present?

A
  • Headache (48%) thunderclap- from nowhere
  • Dizziness
  • Orbital plan
  • Diplopia
  • Visual loss as aneurysms compress visual pathways
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14
Q

What is one of the most common sites for a berry aneurysm to occur?

A

The anterior communicating artery

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15
Q

Give some risk factors for develping saccular aneurysms?

A
  • Same as cardiovascular- hypertension, smoking etc
  • Alcohol +++
  • Connective tissue disorders (dilate aneurysm)
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16
Q

What do you do with small aneurysms (<5mm)?

A

Unlikely to rupture

Manage with surveillance

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17
Q

What might you find on examination of someone with a subarachnoid haemorrhage?

A

History: sudden onset thundercalp heache, nausea and vomiting, may have LOC on onset

On examination:

  • Normal mental state
  • Signs of meningism (due to bleeding irritating meninges) → neck stiffness, photophobia
  • Right third nerve palsy if posterior communicating artery aneurysm (compresses 3rd nerve)
  • No motor or sensory deficits
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18
Q

What can happen after a subarachnoid haemorrhage?

A
  • Microtrhombi can occlude smaller distal arteries
  • Vasoconstriction from CSF irritant
  • Cerebral oedema in response to hypoxia
  • Sympathetic activation → myocardial damage
  • Early rebleeding is quite common
  • Acute hydrocephalus
  • Global cerebral ischaemia
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19
Q

What is the first line investigation for subarachnoid haemorrhage?

A

CT Scan

Detects 93% of bleeds if done within 24 hours of bleed

20
Q

What should you do if you have a convincing history of subarachnoid haemorrhage, but the CT scan is negative?

A

Lumbar puncture

  • wait 6 hrs (12+ preferable)
  • Need time for lysis of red blood cells to take place and release bilirubin
  • Gives CSF yellow tinge - xanthochromia
21
Q

What will you see in the CSF results if there is a subarachnoid haemorrhage?

A
  • High protein
  • WCC not raised
  • Glucose normal
22
Q

What do you do once a diagnosis of subarachnoid haemorrhage is confirmed?

A

Angiography

Performed to confirm and locates the site of the aneurysm

23
Q

How do you treat subarachnoid haemorrhage?

A
  • Asses for airway support
  • Monitor cardiovascular parameters
  • Calcium channel blockers (Nimodipine → selective for cerebral vasculature) prevents vasopasm and secondary iscehmia
  • Operate on patients with good neurological stats within 72 hours to prevent re-bleeds
    • clamping neck of aneurysm
    • coiling (neuro-radiologists) inserting wire into aneurysm which causes thrombosis of blood
24
Q

What is the prognosis for subarachnoid haemorrhage?

A

Poor prognosis - 40% mortality within the first month if you reach hospital

33% survivors hae major neurological haemorrhage

25
Q

What are the classical signs and symptoms you would see in meningitis?

A

Triad of meningism with fever (44%)

  • Heache
  • Neck stiffness
  • Photophobia
26
Q

What associated symptoms do you see in meningitis?

A
  • Flu like symptoms
  • Joint pain
  • Rash
  • Reduces GCS/ seizure
27
Q

What features of menigitis would you specifically see in babies?

A
  • Insolable crying/ high pitched
  • Reduced feeds
  • Floppy
  • Bulging fontanelle
28
Q

In what type of meningitis would you see a rash?

A

Most commonly in meningococcal meningitis

29
Q

Describe the rash seen in meningitis

A
  • Bleeding into the skin/ mucosa causes non blanching rash
  • Larger lesions are pupuric, smaller lesions petechial
  • Usually found on trunk, legs, mucous membranes and conjunctivae
  • Occasionally on tehe palms and soles
  • Older patients can have rash less commonly than younger patients
30
Q

Why is rash not definitively a disgnostic criteria for meningitis?

A
  • can show up a lot later in the infection
  • petechiae can occur from screaming children without illness
31
Q

What are the common bacterial causes of meningitis in adults and children?

A

Streptococcus pneumonia (pneumococcal meningitis)

  • most common in UK and US

Neisseria meningitides (meningococcal meningitis)

  • meningococcal sepsis can occur without meningitis

Haemophilis influenza (Hib meningitis)

32
Q

What vaccines are given to try to reduce rates meningitis in the UK?

A

PCV13- pneumococcal conjugate vaccine

  • 13 variants of pneumococcal strep vaccinated against

Hib vaccine against haemophilus influenza

  • introduced in 1990s
33
Q

What are some of the risk factors for developing community aquired menigitis?

A
  • Young and old most affected (<5 and >65 years)
  • Crowding
  • Immune problems (non immunised, cancer, asplenia)
  • Cochlear implants (creates a pathway to meninges)
34
Q

How can bacteria reach the CNS to cause meningitis?

A
  • Colonisation of nasopharynx is normal
    • can ascend through eustacian tube to middle ear (otitis media)
    • prolonged infection can lead to bacteria spreading to CSF through mastoid sinuses
  • Pnemococcus can also spread to the lower respiratory tract causing pneumonia
    • Lung inflammation allows bacteria to enter blood (bacteraemia)
    • invades CSF via capillaries that transverse choroid plexus
35
Q

How can neonates get pathogens from the mother?

A
  • Placenta/ reprodctive tract secretions
36
Q

What are the effects of having a bacterial infection in the subarachnoid space?

A
  • Inflammation → lots of leucocytes enter CSF
  • Inflammatory cascade results in cerebral oedema and raised ICP
37
Q

What are some of the complications of meningitis?

A
  • Septic shock due to bacteraemia (multi organ failure
  • Disseminated intravascular coagulation
  • Coma (rICP)
  • Seizures (irritation of brain parenchyma)
  • Hearing loss (CN VIII nerve involved/ cochlea swelling)
  • Hydrocephalus (blockage of CSF drainage)
  • Focal paralysis (due to potential cerebral abscess)
38
Q

What is the Kernig sign for diagnosing meningitis?

A
  • Patient supine with thigh flexed to 90 degrees
  • Extension of knee is met with resistance
  • Common in children
39
Q

What is the Brudzinski sign?

A

When the neck is flexed there is involuntary flexion of knees and hips

More common in children (66%)

40
Q

What is the first line investigation for meningitis?

A

Lumbar puncture

41
Q

What will you see in the CSF in untreated bacterial meningitis?

A
  • Cloudy - high numbers of white cells
  • Elevated protein (immune proteins)
  • Low glucose (bacteria metabolise glucose)
  • Positive gram stain
42
Q

What will you see in the CSF in untreated viral meningitis?

A
  • Clear or cloudy (immune cells and protein)
  • Normal or raised protein
  • Normal glucose
43
Q

What is the benefit of lumbar puncture if menigitis is suspected (apart from diagnosis)?

A

Lumbar puncture will reduce ICP if raised by removing CSF

44
Q

What are clinical signs of rICP?

A
  • Decreasing conciousness
  • Brainstem signs
  • Recent seizure
45
Q

What other tests can be done to diagnosis meningitis?

A

PCR blood + CSF

  • helpful to diagnosie patients who recieved empirical antibiotic treatment
  • distinguishes bacterial from viral causes

Blood culture

  • but results can be influenced by previous antibiotic treatment
46
Q

How do you treat meningitis?

A

Admit to hopsital

  • Empirical antbiotics e.g vancomycin + (Ceftriaxone or Cefotaxime)
  • Supportive therapy
    • intubate if altered conciousness
    • fluids if shocked
    • oxygen
  • Dexamethasone to prevent hearing loss

If viral

  • Aciclovir for herpes

Clinical Neuroscience (18 decks)

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