- 50% meningitis - infectious cause of childhood death in all countries - pathogenic strains are found in 1% carriers, transmitted from person to person from asymptomatic carriers - septicaemia - non-blanching petechial rash (develops in 80% children) meningitis in 50% septicaemia in 7-10% septicaemia and meningitis 40%

CNS infection Flashcards by Justyna Gromala

Routes of entry for a CNS infection

haematogenous spread (commonest)
direct implantation
local extension
PNS into CNS

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Types of CNS infection

meningitis
encephalitis
myelitis (spinal cord)
Neurotoxin (CNS?PNSS)

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Commonest way to get CNS infection

haematogenous spread

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what causes neurological damage in meningitis?

direct bacterial toxicity
indirect inflammatory process and cytokine release and oedema
stick, seizures, and cerebral hypo perfusion

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mortality of meningitis

10%

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What % of poeple who have meningitis are left with neurological sequelae?

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Pathogens causing meningitis

Descending common:

neisseria meningitidis (meningococcus - gram negative diplococci)
streptococcus pneumonia (gram + diplococci)
haemophilus influenzae

listeria monocytogenes (gram-positive rods)
GBS
E coli

staphylococcus aureus
TB
treponema pallidum
cryptococcus neoformans
candida
coccidioidess immitis
histoplassma capsulatum
blastomycosis dermatiiidis

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three commonest causes of meningitis

neisseria meningitides (meningococcus)
streptococcus pneumonia
haemophilus influenzae

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N. meningitidis

50% meningitis
infectious cause of childhood death in all countries
pathogenic strains are found in 1% carriers, transmitted from person to person from asymptomatic carriers
septicaemia - non-blanching petechial rash (develops in 80% children)

meningitis in 50%
septicaemia in 7-10%
septicaemia and meningitis 40%

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Ix of choice for meningitis?

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What causes the clinical spectrum in septicaemia?

Capillary leak -> albumin and other plasma proteins leads to hypovolemia.

Coagulopathy -> leads to bleeding and thrombosis.
- Endothelial injury results in platelet-release reactions
- The protein C pathway.
- Plasma anticoagulants.

Metabolic derangement -> particularly acidosis

Myocardial failure….multi-organ failure.

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acute meningitis sx

fever
reduces GCS
neck stiffness
photophobia
N&V
lethargy
+ve Kernig +/- Brudzinski sign

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chronic meningitis - common pathogen and presentation

TB
gradual manifestation, intermittent fever
involves the meninges and basal cisterns of the brain and spinal cord.

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when is chronic meningitis more common?

in immunosuppressed

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aseptic meningitis - what is it?

meningitis in the absence of bacteria

-> most likely viral

causes headache, stiff neck and photophobia (and can have a nonspecific rash)

self limiting and resolves in 1-2 weeks

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Most common cause of viral meningitis?

enterovirus (coxsackievirus group B, echoviruses, polio) - 80-90%

HSV 1&2
mumps
measles
EBV/CMV
VZV

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What is encephalitis?

inflammation of the brain parenchyma

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Commonest cause of encephalitis

flaviridae e.g. western nile virus are becoming the leading cause of encephalitis internationally

togavirus family
flavivirus family
bunyavirus family

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Commonest causes of encephalitis

VIRAL (flaviviridae e.g. west nile virus, toga- and bunyaviriuses.)

bacterial: listeria monocytogenes

amoebic encephalitis: naegleria fowleri (warm water) Acanthamoeba species, and Balamuthia mandrillaris (brain abscess, aseptic or chronic meningitis)

Toxoplasmosis (kittens)

Viral: flaviridae

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Mx of brain abscess

drain it (neurosurgery)

antibiotics (xxx)

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what causes brain abscesses? (routes)

direct extension form otitis media/mastoiditis/paranasal sinuses

endocarditis/ haematogenously

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Pathogens causing abscesses

Streptococci (both aerobic and anaerobic)
Staphylococci,
Gram-negative organisms. (particularly in neonates)
Mycobacterium tuberculosis
fungi
parasites
Actinomyces and Nocardia species

different to meningitis and encephalitis because of different route of infection

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spinal infections - causes

Direct open spinal trauma, from infections in adjacent structures, from hematogenous spread of bacteria to a vertebra.

spinal infecitons - mangement

RFs for spinal infection

Advanced age Intravenous drug use Long-term systemic steroids Diabetes mellitus Organ transplantation Malnutrition Cancer

Ix for CNS infection

MRI > CT (better at detecting parenchymal abnormalities such as abscesses and infarctions) CSF samaple brain tissue

why is MRI superior to CT in

In CT scan you cannot comment on the meninges at all better at detecting parenchymal abnormalities such as abscesses and infarctions

Why would you do a CT in CNS infections?

to check for any raised ICP (GMC risk if someone has coning without CT scan) - pre LP

What % people carry strep pneumoniae in their nassopharynx?

1 in 5

What % people carry meningococcus in their nasopharynx?

1 in 10

Mx of meningitis

ceftriaxone 2g IV BD if older/immunocompromised: add amoxicillin 2g IV 4-hourly (to cover for listeria)

Mx of encephalitis

Meningoencephalitis

inflammation of meninges and brain parenchyma

What can chronic TB meningitis progress to

Can result in tuberculous granulomas, tuberculous abscesses, or cerebritis

Incidence of chronic Tb meningitis in Africa + mortality of chronic Tb meningitis

544 per 100,000 mortality: 5.5 deaths per 100,000 persons

Commonest infection of the CNS

aseptic meningitis

What age group does aseptic meningitis most commonly occur in?

children younger than 1 year

commonest causes of aseptic meningitis

Enteroviruses - coxsackievirus B - echoviruses

How is encephalitis transmitted?

Commonly person to person Via vectors: - mosquitoes - lice - ticks

Toxoplasmosis

Can cause infectious encephalitis An obligate intracellular protozoal parasite, Toxoplasma gondii. Via the oral, transplacental route or organ transplantation. Severe infection in immunocompromised patients. Affected organs include the gray and white matter of the brain, retinas, alveolar lining of the lungs, heart, and skeletal muscle.

Common form of vertebral infection

Pyogenic vertebral osteomyelitis common form of vertebral infection.

What can happen if spinal infections are left untreated?

- permanent neurologic deficits - significant spinal deformity - death.

CSF studies - what do you look at>

color/clarity cell counts chemistry (protein, glucose) stains (gram/auramine (ZN), india ink) culture (bacterial, fungal, TB) PCR

Normal CSF - CSF studies

Appearance: clear Cells x 10^6/L: 0-5 leukocytes Gram stain: -ve Protein g/L: 0.15 - 0.4 Glucose mmol/L: >60% blood glucose level

Purulent meningitis CSF studies + ddx

Appearance: turbid Cells x 10^6/L: 100-10,000 polymorphs (raised) Gram stain: +ve Protein g/L: 0.5-4.0 (high) Glucose mmol/L: <60% blood glucose (low) ddx bacterial meningitis (?meningococcus, ?pneumococcus, ?listeria)

Aseptic meningitis CSF studies

Appearance: clear or slightly turbid Cells x 10^6/L: 15-1000 lymphocytes Gram stain: -ve Protein g/L: 0.5-1.0 Glucose mmol/L: >60% blood glucose level ddx viral meningitis partially abx treated meningitis encephalitis brain abscess TB/fungal meningitis

TB meningitis CSF studies

Appearance: clear or slightly turbid Cels x 10^6/L: 30 - 1000 lymphocytes or some polymorphs Gram stain: -ve (scanty acid fast bacilli) Protein g/L: 1.0 - 6.0 Glucose mmol/L: <60% blood glucose ddx TB meningitis brain abscess cryptococcal meningitis

Limitations of CNS infection diagnostics

MRI oedema pattern and moderate mass effect cannot be differentiated from tumor or stroke or vasculitis in some patients. Infections in early stages and serological tests. Amount of CSF. PCR techniques. Methods to detect amoebic infections. Availability of good laboratory technique.

Mx of meningo-encephalitis (generic therapy)

Aciclovir 10 mg/kg IV TDS Ceftriaxone 2g IV BD If >50yo or immunocompromised add amoxicillin 2g IV 4 hourly

ABx for listeria meningitis?

amoxicillin 12 g (2g IV 4 hourly) plus aminoglycoside

ABx for H influenzae meningitis/CNS infection

cefotaxime 12g/d OR ceftriaxone 4g/d

abx for pseudomonas CNS infection

meropenem 6g/d OR ceftazidime 6g/d

gram -ve bacilli abx in CNS infection

Cefotaxime 12 g/d or Ceftriaxone 4g/d

ABx for GBS CNS infection

Pen G or Amoxicillin [plus aminoglycoside]

ABC for S.pneumoniae/N.meningitidis CNS infection

Pen G 18-24 mu/d or Amoxicillin 12 g/d or Ceftriaxone 4 g/d or Chloro 75-100 mg/kg/d