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Yr3 Medicine: Infectious Diseases > Infections of CNS > Flashcards

Infections of CNS Flashcards

1
Q

What is meningitis?

A

Inflammation of the meninges (most commonly due to infection)

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2
Q

Discuss the pathophysiology of meningitis

A

Bacteria reach the central nervous system either by haematogenous spread (the most common route) or by direct extension from a contiguous site. The bacteria multiply quickly once they have entered the subarachnoid space. Bacterial components in the cerebrospinal fluid induce the production of various inflammatory mediators, which in turn enhance the influx of leukocytes into the cerebrospinal fluid. The inflammatory cascade leads to cerebral oedema and increased intracranial pressure, which contribute to neurological damage and even death.

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3
Q

State the common causative bacteria of meningitis in:

  • Neonates & infants
  • Children
  • Adults
  • Elderly
  • Immunocompromised
  • HIV/AIDs
A
  • Neonates & infants: group B streptococci (most common), E-coli, Listeria monocytogenes
  • Children (3months to 6yrs): Neisseria meningitidis, Strep. pneumoniae, H.influenza
  • Adults: Neisseria meningitidis, Strep.pneumoniae
  • Elderly: Strep.pneumoniae, Listeria monocytogenes, N.meningitidis
  • Immunocompromised: Listeria monocytogenes, mycobacteria, CMV
  • HIV/AIDs: cryptococcal meningitis should be considered alongside the organisms in immunocompromised
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4
Q

State some viruses which cause viral meningitis

A
  • HSV
  • Enteroviruses (e.g. coxsackie virus)
  • Mumps
  • Measles
  • Varicella zoster virus
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5
Q

State some risk factors for meningitis

A
  • Immunocompromised
  • History of spinal procedures
  • Proximity to other people e.g. university halls, military
  • Neonates at most risk include those with low birth weight, transplacental infection or premature birth
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6
Q

What is the most common cause of meningitis: viral or bacterial?

Why is this?

A

Viral aetiology is most common (Coxsackie, echoviruses) due to introduction of vaccines against bacteria that would cause meningitis e.g. meningococcal vaccines, pneumoccocal vaccines and H.influenza viruses

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7
Q

You can distinguish between viral and bacterial meningitis clinically; true or false?

A

False- both present the same

(may be visible difference in lumbar puncture however in terms of clinical presentation they are indistinguishable)

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8
Q

You should wait to determine if meningitis is viral or bacterial before starting treatment; true or false?

A

FALSE- all cases of suspected meningitis should be treated as bacterial meningitis until proven otherwise

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9
Q

State the symptoms of meningitis

A
  • Fever
  • Headache
  • Neck stiffness
  • Photophobia
  • Non-blanching petechial rash (in meningococcal meningitis)
  • Altered mental status
  • Seizures
  • Shock
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10
Q

Describe the two signs you may see in meningitis

A
  • Kernig sign: pain when hip is fully flexed and knee is extended (pain due to stretching of meninges during movement)
  • Brudzinski sign: flexion of neck produces reflex flexion of the hip and/or knee (reflex flexion occurs primarily to reduce meningeal irritation)
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11
Q

Discuss how meningitis may present in neonates & infants

A

Non specific symptoms such as irritability, pyrexia, difficulty feeding, respiratory difficulty

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12
Q

What investigations would you do if you suspect meningitis, include:

  • Bedside
  • Bloods
  • Imaging

… consider whether you would do all investigations before starting treatment

A

If you suspect meningitis you should start empirical treatment immediately- this should not be delayed while you carry out investigations. However, investigations you would consider:

Bedside

  • Lumbar puncture: identify causative organism IF NO SIGNS RAISED ICP
  • ABG: check oxygenation andn other levels- particularly lactate to see if pt has sepsis
  • BMs: metabolic abnormalities in severe infection

Bloods​

  • FBCs: may find leucocytosis, anaemia, thrombocytopenia
  • U&Es: pts with meningitis often have metabolic abnormalities
  • LFTs: pts with meningitis often have metabolic abnormalities
  • CRP: inflammation
  • ESR: inflammation
  • Coagulation screen: coagulopathy common in severe infections
  • Blood cultures: identify causative organism
  • Viral/bacterial PCR: identify causative organism

Imaging

  • None specifically indicated for meningitis but may do to rule out other causes
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13
Q

Which pts is lumbar puncture contraindicated in?

A
  • Any signs of raised ICP
    • Focal neurological signs
    • Papilloedema
    • Bulging fontanelle
    • DIC
    • Signs cerebral herniation
  • Meningococcal septicaemia (blood cultures and PCR for meningococcus should be obtained)
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14
Q

Following collecting CSF sample via lumbar puncture, what analysis do we do? (HINT: look at/analyse 7 things)

A
  • Colour
  • White cells
  • Glucose
  • Protein
  • CSF opening pressure
  • Bacterial culture
  • Viral PCR
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15
Q

Using the 5 out of the 7 parameters previously mentioned (colour, white cells, glucose, protein, CSF opening pressure) compare the CSF in:

  • Bacterial meningitis
  • Viral meningitis
  • Tuberculous meningitis
  • Fungal meningitis
A

*NOTE: passmed says fungal is cloudy and has predominantly lymphocytes

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16
Q

Discuss the management of meningitis

A
  1. Start empirical antibiotics:
  • Abx choice:
    • <3 months: ​IV cefotaxime
    • >3 months: IV cefotaxime or ceftriaxone
  • If <3months or >50yrs:
    • ​Add IV amoxicillin
    • Treat for at least 14 days
    • If allergic to penicillin offer chloramphenicol
  • If pt is in primary care/community, IM benzylpenicillin should be given in suspected meningococcal disease

2. Provide additional therapy:

  • Add IV acyclovir if HSV encephalitis or viral meningitis suspected
  • If >3 months, give dexamethasone 0.15mg/kg QDS (max dose 10mg) in suspected or confirmed bacterial meningitis for at least 4 days
  • Fluids if necessary
  1. Offer prophylaxis
    * Household members and close contacts (within 7 days) should be offered either oral ciprofloxacin (agent of choice) or rifampicin- single dose ideally within 24hrs of initial diagnosis
17
Q

Why do we give dexamethasone in suspected or confirmed bacterial meningitis?

A

Reduces inflammation and hence reduces rate of hearing loss and other neurological complications associated with bacterial meningitis

18
Q

What empirical antibiotic would you give to neonates & infants; IV ceftriazone or cefotaxime?

A

IV cefotaxime as ceftriazone can worsen jaundice or cause acidosis particularly in newborns or premature babies

19
Q

Summarise how to treat viral meningitis

A
  1. Empirical antibiotics: viral and bacterial meningitis indistinguishable so if pt unwell start on antibiotics
  2. IV acyclovir if viral meningitis caused by HSV, CMV or varicella zoster is confirmed. NOTE: you may start acyclovir at same time as antibiotics if you suspect viral meningitis might be cause. Always give antibiotics till confirmed not bacterial then can stop them

*NOTE: most cases of viral meningitis are self limiting and symptoms improve over a couple of weeks however until you know if bacterial must treat as bacterial

20
Q

What is mollaret meningitis?

A

Form of aseptic meningiti characterised by recurrent episodes of meningism interspersed with weeks of being symptom free. Exact cause has yet to be confirmed but HSV-2 is thought to have a role in pathogenesis

21
Q

What is meant by meningococcal meningitis?

A

Meningitis caused by Neiserria meningitidis

22
Q

If a non-blanching rash (tested by Tumbler test) is detected in suspected meningitis, what does it suggest causative organism is?

A

Non-blanching rash= meningococcal meningitis therefore causative organism is Neisseria meningitidis

23
Q

State some complications of meningitis

A
  • Sensorineural hearing loss (most common)
  • Seizures & epilepsy
  • Focal neurological deficit
  • Sepsis
  • Intracerebral abscess
  • Hydrocephalus
  • Cognitive impairment & learning disability
  • Memory loss
  • Cerebral palsy
  • Waterhouse-Friderichsen syndrome (adrenal insufficiency secondary to adrenal haemorrhage)
24
Q

What is encephalitis?

A
  • Inflammation of the brain parenchyma associated with neurological dysfunction
  • Most often caused by viruses
  • Can occur together with meningeal inflammation producing meningoencephalitis
25
Q

Who is encephalitis more common in (which pt groups)?

A
  • Neonates
  • Elderly
  • Immunocompromised
26
Q

What is the most common causative organism of encephalitis?

What lobes does it most commonly affect?

A
  • HSV-1 causing herpes simplex encephalitis is most common (95% cases in adults).
  • It typically affects temporal & inferior frontal lobes lobes causing focal symptoms such as aphasia
  • Bacteria, fungi and parasites may also cause encephalitis.
  • Encephalitis may also be caused by autoimmune disorder
27
Q

State some risk factors for encephalitis

A
  • Immunocompromised
  • Age <1yr or >65yrs
  • Post infection e.g. varicella, EBV, mumps, enterovirus
  • Animal/insect bites e.g. ticks, mosquitos
28
Q

State the symptoms of encephalitis

A

Classically associated with triad of symptoms:

  • Fever
  • Headache
  • Altered mental status

May also have:

  • Nausea & vomiting
  • Seizures
  • Psychiatric symptoms
  • Focal neurological signs e.g. aphasia
  • Signs of meningism if have meningoencephalitis
29
Q

What investigations would you do for someone with suspected encephalitis, include:

  • Bedside
  • Bloods
  • Imaging
A

Bedside

  • Lumbar puncture: lymphocytosis, raised protein, send for PCR for HSV

Bloods (same as for meningitis)

  • FBC
  • U&Es
  • LFTs
  • CRP
  • ESR
  • Coagulation screen
  • Blood cultures
  • Viral/bacterial PCR

Imaging

  • CT or MRI head/brain
  • MRI brain (better than CT for brain, but may be harder to get)
30
Q

Discuss the management of encephalitis

A
  • IV aciclovir should be started in all cases of suspected encephalitis
  • Empirical treatment for meningitis (if present)
  • Careful fluid therapy (if required) so as not to worsen cerebral oedema
  • Monitoring and treatment of any accompanying seizures
  • Supportive care e.g. intubation
31
Q

Are corticosteroids reccommended in encephalitis?

A

NOT encouraged

32
Q

State some potential complications of encephalitis

A
  • Seizures
  • Ischaemic stroke
  • Cerebral haemorrhage
  • Neurological complications e.g. aphasia, amnesia, motor problems

Yr3 Medicine: Infectious Diseases (9 decks)

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