Meningitis is inflammation of…
Leptomeninges (inner two layers - arachnoid and pia mater). May be direct or haematogenous.
Broad causes of meningitis
- Infection (most common)
- Autoimmune disease e.g. SLE
- Adverse reaction to medication
Most common bacteria pathogens causing meningitis per age group
- Newborns: strep agalacticae (GBS), e coli, listeria
- Adolescents: n meningitides, s. pneumoniae, h influenzae (unvaccinated)
- Adults & elderly: strep pneumoniae, n meningitides, listeria monocytogenes
Viral causes of meningitis
Common:
- Enteroviruses (coxsackie)
- HSV
- HIV
Uncommon:
- Mumps
- VZV
- Lymphocytic choriomeningitis
Other infections causes of meningitis (fungal, parasitic, other bacterial)
- Fungal: cryptococcal, coccidiodes
- Tubercular meningitis
- Parasitic: P falciparum
Ix and Rx algorithm for presentation of suspected bacterial meningitis
Blood cultures
Urgent LP
Commence dexamethasone and empiric antibiotics
CTB prior to LP if concern for raised ICP: focal neurology, papilloedema, new onset seizures, deteriorating conscious state
DDx meningitis
Focal CNS disease
SAH
Immunocompromised - risk of mass lesions
Initial rx regimen for suspected bacterial meningitis
- Gold standard
- If concern re listeria
- If concern for MRSA/reduced sens strep
- If severe hypersensitivity to pencillins
Dexamethasone 10mg IV with or prior to antis, then QID for 4/7
Cetriaxone 3g BD
ADD
Benpen 2.4g IV 4 hourly if concern for listeria (intrinsically resistant to cephalosporins) i.e. in >50y/o, immunocompromised.
Alternative if allergic: bactrim
ADD vancomycin
If gram stain - gram pos diplococci resembling staph OR strep (to cover MRSA, low sens strep), recent beta lactam use
IF severe hypersensitivity to penicillins - use moxifloxacin instead of cephalosporins
Which bacteria has dex shown efficacy against?
Reduces inflammation/damage from: strep pneumoniae, h influenzae, strep suis
No evidence for n meningitides - can consider stopping if it’s not the causative organism
Meningoencephalitis pathogens that may be associated with:
- Cerebellar ataxia
- Parotitis
- Gastrointestinal prodrome
- Flaccid paralysis
- EBV or VZV
- Mumps virus
- Shigellosis
- West Nile virus
HSV encephalitis:
- Classic imaging findings
- Complications
- Mortality rate
- Diagnosis
- treatment
- Imaging: frontoTEMPORAL lobe involvement on MRI
- Complications; seizures, ICH, cerebral oedema, brainstem herniation, long-term neurocog impairment
- Diagnosis: CSF HSV PCR positive. MRI brain is gold standard imaging for encephalitis.
- Morality: 30% with treatment, >80% without treatment
- Rx: IV acyclovir 10mg/kg TDS for 14-21 days
Encephalitis:
a. Most common infectious causes
b. Consider this organism in meningoencephalitis in elderly/immunocompromised
c. Consider this organism in HIV/immunocompromised
d. Non infectious causes
a. HSV is the most common cause of sporadic encephalitis
Consider: Murray Valley encephalitis virus, Hendra virus, enterovirus, JEV. Consider VZV, EBV, CMV, herpes B virus
b. Listeria
c. Toxoplasma gondii
d. Autoimmune e.g. anti-NMDAR encephalitis
VZV encephalitis:
- Imaging findings
- Clinical associations
- Treatment
Vasculitis, strokes, demyelination, cerebral oedema
Usually associated with vesicular rash. May also have meningitis
Rx: Iv acyclovir
EBV encephalitis
- Clinical features
- Prognosis
- Rx
- Usually no EBV symptoms. Odd visual disturbances
- Good prognosis
- Supportive care
Herpes B virus
- Cause
- Clinical features
- Mortality
Macaque monkey bites
Features: fevers, lymphadenitis, peripheral neuropathy followed by hemorrhagic meningoencephalitis
High morality
Rx: acyclovir
Lab investigations for encephalitis
- CSF PCRs
- Serum IgM and IgG
- CSF IgM
- Other?
CSF biochem:
Usually: elevated WCC with lymphocyte predominance, elevated protein, normal glucose, red cells usually absent
CSF PCRs:
- HSV-2, HSV-2, VZV, EBV, CMV, HHV6, enterovirus, measles, HIV, mumps, arboviruses, rabies
Serum IgG/IgM (most important if PCRs negative and not improving)
- VZV, EBV, CMV, measles, mumps, HIV borrelia
Consider the above depending on epidemiology Consider CSF IgM Consider resp PCR (rare) Consider fungal Ix Consider QFN gold
West Nile V. encephalitis clinical features
Flaccid paralysis
Maculopapular rash also seen in half of cases - not expected with other viral encephalitides
Encephalitis: involvement of thalamus or basal ganglia on imaging may indicate which viral aetiologies?
Respiratory viral infection
Creutzfeldt-Jakob disease
Arbovirus
TB
Aside from HSV, which other causes of viral encephalitis may have temporal involvement on imaging?
VZV, EPV, HHV6
Encephalitis: presence of hydrocephalus on imaging may suggest?
Non-viral aetiology, bacteria, fungal
What is the most common viral cause of meningitis
Enteroviruses (coxsackie or echovirus)
