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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
What are the classical signs and symptoms you would see in meningitis?
Triad of meningism with fever (44%) * Heache * Neck stiffness * Photophobia
26
What associated symptoms do you see in meningitis?
* Flu like symptoms * Joint pain * Rash * Reduces GCS/ seizure
27
What features of menigitis would you specifically see in babies?
* Insolable crying/ high pitched * Reduced feeds * Floppy * Bulging fontanelle
28
In what type of meningitis would you see a rash?
Most commonly in meningococcal meningitis
29
Describe the rash seen in meningitis
* 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
Why is rash not definitively a disgnostic criteria for meningitis?
* can show up a lot later in the infection * petechiae can occur from screaming children without illness
31
What are the common bacterial causes of meningitis in adults and children?
**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
What vaccines are given to try to reduce rates meningitis in the UK?
**PCV13- pneumococcal conjugate vaccine** * 13 variants of pneumococcal strep vaccinated against **Hib vaccine against haemophilus influenza** * introduced in 1990s
33
What are some of the risk factors for developing community aquired menigitis?
* Young and old most affected (\<5 and \>65 years) * Crowding * Immune problems (non immunised, cancer, asplenia) * Cochlear implants (creates a pathway to meninges)
34
How can bacteria reach the CNS to cause meningitis?
* 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
How can neonates get pathogens from the mother?
* Placenta/ reprodctive tract secretions
36
What are the effects of having a bacterial infection in the subarachnoid space?
* Inflammation → lots of leucocytes enter CSF * Inflammatory cascade results in cerebral oedema and raised ICP
37
What are some of the complications of meningitis?
* 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
What is the Kernig sign for diagnosing meningitis?
* Patient **supine** with thigh flexed to 90 degrees * Extension of knee is met with **resistance** * Common in children
39
What is the Brudzinski sign?
When the neck is flexed there is **involuntary flexion** of knees and hips More common in children (66%)
40
What is the first line investigation for meningitis?
**Lumbar puncture**
41
What will you see in the CSF in untreated bacterial meningitis?
* Cloudy - high numbers of white cells * Elevated protein (immune proteins) * Low glucose (bacteria metabolise glucose) * Positive gram stain
42
What will you see in the CSF in untreated viral meningitis?
* Clear or cloudy (immune cells and protein) * Normal or raised protein * Normal glucose
43
What is the benefit of lumbar puncture if menigitis is suspected (apart from diagnosis)?
Lumbar puncture will **reduce ICP** if raised by removing CSF
44
What are clinical signs of rICP?
* Decreasing conciousness * Brainstem signs * Recent seizure
45
What other tests can be done to diagnosis meningitis?
**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
How do you treat meningitis?
**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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