Central nervous system - Infection Flashcards
What are the typical presentations of meningitis?
i) Fever (85%), objective neck stiffness or meningismus (70%),
ii) Signs of cerebral dysfunction such as confusion (67%), delirium or declining consciousness
iii) Headache (50%), Vomiting (35%),
iv) seizures (30%), cranial nerve palsies or focal neurological signs (23%), Kernig’s (9%) or Brudzinski’s signs of meningismus, papilloedema (1%).
vi) Jolt accentuation of headache (100%)
What are the infectious causes of meningitis?
a) Bacteria
- < 1 month – E .coli, group B strep, Listeria Monocytogenes
- Rest – Strep pneumonia, N. Meningitides, Listeria Monocytogenes (elderly), H. Flu, M. TB
b) Viral – HSV, Enterovirus, others
c) Fungal - Cryptococcus
d) Parasitic - Toxoplasmosis
What are the causes of NON infectious Meningitis?
- SLE
- Vasculitis
- Drug induced
- Carcinomatosis
- Sarcoidosis
- Behcet’s disease
Atypical presentation of meningitis
i) Elderly: Lethargy, obtundation, absence of fever and minimal signs meningismus.
ii) Neutropenics: subtle signs due to impaired ability to mount inflammatory response.
iii) Neonates and infants: “a sick looking child with fever has bacterial meningitis until proven otherwise
How do you diagnose meningitis from LP?
i) 10% lymphocyte predominance in CSF / usually infants with gram negative infection, or in Listeria meningitis.
ii) 60-90% positive CSF on gram stain / Drops to 40-60% if prior antibiotics, with blood cultures rarely positive after treatment
iii) Posterior pharyngeal wall isolate (50% patients with systemic disease) or skin film / aspirate from purpuric lesion are useful even after antibiotics.
iv) Polymerase chain reaction (PCR) amplification of DNA in blood or CSF ie. N.meningitidis and for viruses. CSF antigen tests no longer offered routinely (QLD Health)
What are the management of Bacterial meningitis?
i) CT is performed before LP, in order to exclude alternate mass lesion diagnoses such as a cerebral abscess, subdural empyema or toxoplasma encephalitis.
- a normal scan does not exclude raised ICP (see below).
ii) Lumbar puncture is contraindicated irrespective of CT findings in shock, widespread rash or evidence of coagulopathy, drowsiness or impaired consciousness, signs of raised ICP (bradycardia, hypertension, papilloedema, periodic breathing) and with focal neurology.
iii) Immediate antibiotic therapy is paramount. Ceftriaxone 2g IV 12-hrly plus benzyl penicillin 1.8g -2.4g IV 4-hrly. Omit the penicillin (given for Listeria monocytogenes) if patient aged 3 months - 15 years, unless they are immunosuppressed.
Add vancomycin 500 mg IV 6-hrly if S.pneumoniae is suspected, or neutrophils are in CSF but no organisms seen, if viral meningitis or meningococcal disease are unlikely.
iv) Steroids. Dexamethasone 10 mg IV 6-hrly (0.15rnglkg) before or with first dose of antibiotic in adults for 4 days.
What are the epidemiologies for Meningococcal disease?
i) Potentially pathogenic meningococci present in 2-10% asymptomatic carriers. Droplet / oropharyngeal secretion spread (viability in air only a few seconds).
ii) Developed-world disease predominantly serogroups B, C, Y, W135 (in Australia 62% is B, 32% C but over 60% deaths are group C).
iii) Developing-world predominantly serogroup A.
What are the clinical syndromes for Meningococcal disease?
i) May be fulminant with rapidly spreading purpura, vascular collapse and coagulopathy with DIC (15-20%) ‘Meningococcaemia’. Note rash may be blanching macular or maculopapular in first 24 hours.
ii) Invasion of meninges (80-85%), purulent leptomeninges, encephalitis, or other organs affected such as heart, joints, eyes (uncommon).
iii) Transient bacteraemia with no sequelae.
iv) Chronic meningococcaemia (rare).
NOTE: Meningitis is not a prerequisite to diagnose meningococcaemia.
How do you manage Meningococcal disease? In more than 3 months old
) Immediate benzyl penicillin 1.2g IV or IM prehospital for suspected meningococcaemia (rigors, fever plus rash)/ meningococcal meningitis.
ii) - Cefotaxime 50mg /kg IV q 6 hrs max 2gram q 6hrs
- or Ceftriaxone 50mg /kg iv q12 hrs or 100mg /kg IV q24 hrs - max 2g IV plus benzyl penicillin 1.8-2.4 g until sensitivities known, immediately on suspicion meningococcaemia / bacterial meningitis in hospital, after blood cultures (do not await LP if sick).
- If Listeria suspected or immunocompromised – added Amoxicillin 50mg/kg up to 2gm IV 4 hrly
- add Vancomycin if Gram positive diplococci seen or Pneumococcal antigen positive – 12.5mg/kg up to 500mg IV 6 hrly
iii) Steroids. Dexamethasone 10 mg IV 6-hrly (0.15rnglkg) before or with first dose of antibiotic in adults for 4 days
iv) Correction hypovolaemia - may require large volumes of fluids and catecholamines to optimise cardiac function.
iv) IPPV for altered mental state, raising ICP, hypoventilation, hypoxia and pulmonary oedema.
v) Treatment of DIC, immunomodulation (experimental), surgery including fasciotomy, debridement, amputation, grafting
Management < 3 months of meningitis
- Amoxil 50mg /kg iv q 6hrs plus
- Cefotaxime 50mg /kg IV q 6hrs plus
- Add Vancomycin if pneumococcus likely – 15mg/kg iv q 6hrly
What are the complications of Meningitis?
- Sepsis
- DIC
- Seizures
- Focal neuro deficit
- Hearing loss
- Cognitive deficit
- SIADH – salt wasting
- Waterhouse – fredderichen syndrome
Chemoprophylaxis for Meningitis/ Meningococcaemia
- i) Close household contacts or kissing contacts, give rifampicin 600 mg orally bd for 2 days, or ceftriaxone 250 g IM (if pregnant / liver disease), or ciprofloxacin 500 mg orally (women on OCP).
ii) Vaccine - polysaccharide against groups A, C, W135, Y or conjugate against group C only (much longer term protection) for non-immunised contacts, except if outbreak serogroup B.
How do you define encephalitis?
• Inflammation of the brain
- clinical features - Fever, fits, change in GCS, neck stiffness
- CSF- elevated protein, normal glucose, WBC>20, lymphocytosis
• Exclusion other causes
- bacterial, fungal, TB meningitis, cerebral abscess/haemorrhage/infarction, Reye’s syndrome, metabolic/toxic encephalopathy
What is the aetiology of encephalitis?
n Proven or suggested in 40-63% cases
– VZV, respiratory & enteroviruses most commonly identified
– HSV represents 2-13% cases, but highest mortality rates 60-80%
– others include
n Influenza A/B, coxsackie, adenovirus, MMR, EBV, CMV, mycoplasma, chlamydia, HHV6, bartonella
n Most common cause refractory status
How do these patients with encephalitis present?
n Prodromal symptoms (<1/52 pre-onset)
– fever (70-80%), vomiting (37%), flu-like (30%), cough (28%), headache (25%), rash, sore throat, diarrhoea, malaise, anorexia, myalgia, lethargy, photophobia, eye discharge
n Presenting features
– coma (9-47%), fits (30-78%), focal neuro signs (33%), neck stiffness (10%), personality/behavioural changes, visual hallucinations
