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September lectures yr 3 (2018) > Infections of the CNS > Flashcards

Infections of the CNS Flashcards

1
Q

Define: meningitis:

A

inflammation of the meninges - can have inflammation of all 3 layers
- normally just the subarachnoid and pia mater

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2
Q

Define: encephalitis:

A

inflammation of the brain parenchyma

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3
Q

Define: myelitis:

A

inflammation of the spinal cord

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4
Q

Define: radiculitis:

A

inflammation of the nerve roots

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5
Q

Define: abscess:

A

local suppuration leading on to collection or abscess

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6
Q

What are the characteristics of acute meningitis?

A

Inflammatory cells in the CSF
Pleocytosis (the presence of an abnormally large number of lymphocytes in the cerebrospinal fluid) is the hallmark of meningitis but some fungi and immunocompromised patient can have meningitis without having cells in CSF

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7
Q

What can cause meningitis?

A

viruses, bacteria (most common ones), fungi, parasites, drugs (aspirin, ibuprofen), autoimmune, malignancy and aseptic meningitis

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8
Q

What are the clinical presentations of meningitis?

A

fever
headache - cough and sneeze can cause it to worsen due to increased ICP
photophobia
neck stiffness
focal weakness
With or without altered consciousness
signs of meningeal irritation- Kernig’s sign and brudzinski’s sign

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9
Q

What is Kernig’s sign?

A

thigh is flexed at the hip and knee at 90 degree angles and subsequent extension in the knee is painful

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10
Q

What is Brudzinski’s sign?

A

forced flexion of the neck elicits a reflex flexion of the hips
- unable to press head to chest

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11
Q

What are some key questions to ask in a pt history if you are querying CNS infection?

A 
Travel 
RF for HIV 
Immuno-compromised
Exposure to insects - Lymes disease
Exposure to sick animals
Ingestion of contaminated food, water
Illness of community e.g. measles / mumps
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12
Q

What are some key examinations if you are querying CNS infection?

A 
Lymphadenopathy 
Rash 
Oral examination - candida/leukoplakia 
IV drug sites
Head injuries 
Other sites for infection
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13
Q

What is the incidence of bacterial meningitis and what are the most common causes in adults?

A

annual incidence in western countries = 06-4/100,000 - THIS can be up to 10x higher in less developed

Streptococcus pneumoniae 
Neisseria meningitides (both @80%)
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14
Q

What the most common causes of bacterial meningitis in children?

A

Haemophilus influenza type B
Meningococcus
Pneumococcus

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15
Q

What are common infections in vulnerable pt groups?

A

aerobic gram -ve = e.coli, klebsiella, pesudomonas, salmonella
Staphylococcus aureus - esp in immunocompromised/or pt has a central line

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16
Q

What are the initial investigations and management for meningitis?

A

Examine CSF - lumbar puncture
Raised ICP and cerebral herniation are well recognised complications of severe bacterial meningitis therefore a decision needs to be made as to wether or not to do a LP
- CSF sent for gram stain, C&S, sugar and protein measurement and PCR
initiate anti-bacterial and anti-viral therapies with steroids

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17
Q

What is the normal opening pressure of CSF and how does it vary in different types of meningitis??

A

12-20 cm CSF

  • bacterial = raised
  • viral = normal/mildly raised
  • TB = raised
  • Fungal = raised
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18
Q

How does the appearance of CSF change in different types of meningitis?

A 
Bacterial = turbid, cloudy, purulent 
Viral = clear - looks normal
TB = clear or cloudy 
Fungal = clear or cloudy
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19
Q

How does the CSF WCC change in different types of meningitis?

A 
normal = <5 
bacterial = raised  >100
viral = raised 5-1000
TB = raised 5-500
Fungal = 5-500
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20
Q

How does the CSF white cell type vary in different types of meningitis?

A 
bacterial = neutrophils 
viral = lymphocytes
TB = lymphocytes 
fungal = lymphocytes
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21
Q

How does the CSF protein level vary in different types of meningitis?

A 
Normal <0.4 g/L
bacterial = raised
viral = mildly raised
TB = markedly raised 
fungal = raised
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22
Q

How does the CSF glucose level vary in different types of meningitis?

A 
Normal 2.6-4.5 mmol
bacterial = very low
viral = normal/slightly low
TB = very low 
fungal = low
23
Q

What are the treatments for meningitis?

A

3rd gen cephalosporin (cefotaxime / ceftriaxone) = initial

If penicillin resistant strep suspected = use vancomycin with or without rifampicin is added

steroid given shortly before abx - improves the outcome of pneumococcal meningitis in adults and haemophilus in children

24
Q

What are the complications of meningitis?

A

reduced consciousness - due to raised ICP
cerebral oedema
raised ICP - can cause papilloedema - if this has occurred advised not to do lumbar puncture
seizures
infarctions
venous sinus thrombosis
subdural effusion/emphysema

25
Q

Is meningitis a notifiable disease?

A

yes - public health authorities should be contacted

26
Q

What does strep pneumoniae look like?

A

Small 0.8 micron, non-spore forming, non-motile gram +ve cocci
diplococci
coated in a capsule of complex polysaccharide
Meningitis often follow a recent nasopharnygeal colonization of virulent strain

27
Q

What are the risk factors for contracting pneumococcal meningitis?

A 
Co-existing pneumonia - 25% 
acute sinusitis 
acute otitis media - 30%
HIV 
Immuno-compromised state 
More severe than other forms - 11-19% comatose, 7-21% seizures, aphasia, cranial palsies, hemiparesis
28
Q

what is the prognosis for pneumococcal meningitis?

A

75% Intracerebral complications
40% systemic complications
sequela - hearing loss, other cranial palsies, hemiparesis Prescribe antibiotics/steroids

29
Q

What does neisseria meningitidis look like?

A

Non-spore forming, non-motile, gram -ve dilococcus
appears as kidney shaped
13 serogroups
B,C,Y europe and america

30
Q

What are key clinical presentations of meningococcal meningitis?

A

Rash (non-blanching petechial purpuric rash) - as soon as its noticed give abx to prevent sepsis occurring
Urticarial and maculopapular rash may also occur
Septicaemia and meningitis
Shock/DIC (disseminated intravascular coagulation) can lead to coma and death

31
Q

What is the treatment for meningococcal meningitis?

A

penicillin G and ampicillin are the drugs of choice

3rd gen cephalosporin

32
Q

What is the incidence of TB meningitis?

A

increasing even in developed countries due to increased travel, increased incidence of HIV and increasing multi drug resistance
UK 6000 cases of TB annually - 5-10% thought to have CNS TB
its only natural reservoir is humans - infect through inhalation - replicate in alveoli and then spread
In CNS foci they are subependymal

33
Q

What are the duration of symptoms like in TB meningitis?

A

vary from days to months

release of tubercle leads to vasculitis, adhesions and inflammation

34
Q

What are the diagnostic tests for TB meningitis?

A

direct microscopy for AFB - ZN stain
CSF cultures - more likely to be +ve but several weeks to become +ve
PCR- only sensitive in 50%
Immunological test of the ability of T lymphocytes to produce gamma interferon in response to TB antigen

35
Q

What is the treatment for TB meningitis?

A

4 drugs for 2 months
followed by 2 drugs for 9-12 months
Drugs: rifampicin, isoniazid, pyrazinamide, ethambutol

Adjunctive steroids reduce mortality, continue for 4-8 weeks and tapered gently

36
Q

what are some other examples of bacterial meningitis?

A 
syphilitic meningitis 
lyme neuroborreliosis 
nocardia
listeria
brucella
leptospirosis
37
Q

What are some examples of viral meningitis?

A 
enterovirus  - most common
coxssackie
HSV 1 / 2 
CMV/ EBV
HIV 
MMR
38
Q

What are some examples of fungal meningitis?

A 
rare but devastating 
incidence has increased due to immune suppression 
They can also space occupy
- cryptococcus neoforms - commonest form -more common in HIV 
- histoplasma capsulatum
- blastomyces dermatidis
- coccidioides 
- candida and aspergillus
39
Q

What are some of the key characteristics of cryptococcus neofromans?

A

dimorphic (yeast/filamentous phase)
Brain MRI shows cryptococcomas
low grade fever
Indian ink staining of CSF is positive in 80%
cryptococcal antigen can be tested - can have significantly raised ICP

40
Q

What is the treatment for cryptococcus neofromans?

A

amphotericin B
flucytosine
fluconazole

41
Q

What are the main facts about encephalitis?

A 
inflammation affecting brain parenchyma 
viruses are the most common causes
toxoplasma, amoebae and bacteria can cause it too 
paraneoplastic process 
autoimmune limbic encephalitis 
metabolic conditions
42
Q

What does encephalitis present as?

A 
severe headache
reduced consciousness
seizures
focal neurological signs
altered behaviour 
hallucinations 
fever
43
Q

What are the investigations for encephalitis?

A 
lumbar puncture
imaging if required
CSF for PCR 
antibody testing (IgM and IgG)
serum for atypical pathogens
44
Q

What is the acute management for encephalitis?

A 
antivirals 
control immediate complications 
prevent late complications 
intravenous acliclovir 
ampicillin and getamicin for listeria 
ganciclovir/foscarnet/cidofovir for CMV and HHV6
45
Q

What does HSV1 cause?

A

viral encephalitis
1 = 90% and 2=10% - access brain via nasal mucosa
primary infection occurs via oral mucosa and then spread along the trigeminal nerve to the trigeminal ganglion

46
Q

What are the key clinical presentations induced by HSV encephalitis?

A 
flu like prodrome 
93% were febrile in one study 
disorientation in 76%
speech disturbance in 59%
behavioural change in 41%
seizure in 33%
lethargy, drowsiness, confusion and coma
47
Q

What is the treatment for HSV induced encephalitis?

A

aciclovir reduces the risk of fatal outcome from 70% to less than 20%
given for 14-21 days
mortality is reduced the morbidity remains high
2/3s of survivors have significant neuropsychiatric sequela

48
Q

What are the complications of treatment for hsv encephalitis?

A

impaired memory
behavioural changes
dysphasia
epilepsy

49
Q

What are brain abscess?

A

space occupying lesions because of inflammation of the parenchyma leading to suppuration and surrounded by well vascularised capsule

  • incidence= 1/10000
    spread: blood, contiguous focus, direct inoculation
50
Q

What are the causes of brain abscesses?

A 
otogenic infection 
paranasal sinusitis
blood borne infection 
peridontal infection 
trauma or neurosurgery
bacterial meningitis

Present very similarly to encephalitis

51
Q

What is the clinical presentation of brain abscess?

A

fever, headache, focal neurological signs, reduced consicous levels, raised ICP and papilloedema

52
Q

What investigations are carried out for brain abscesses?

A

FBC/ inflammatory markers
blood cultures
CT/MRI

53
Q

What are the treatments for brain abscesses?

A

abx
seizure control
pressure monitoring for raised ICP
surgical aspiration

September lectures yr 3 (2018) (56 decks)

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