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Updates in the Diagnosis of Meningitis and Encephalitis


2022-04-04

Meningitis presents with some combination of neck stiffness, fever, headache, nausea, vomiting and photophobia. Encephalitis is distinguished from meningitis by the presence of abnormal brain function as evidenced by altered mental status, motor or sensory deficits, altered behaviour or personality changes, and speech or movement disorders. When meningeal and parenchymal involvement both occur, there can be a mixed presentation of meningoencephalitis as is often seen with viral infections. Meningitis may be due to bacterial, mycobacterial, fungal (mainly Cryptococcus neoformans) or viral causes. Encephalitis is most frequently associated with a viral infection.

Acute Bacterial Meningitis

The incidence of acute bacterial meningitis (ABM) has decreased in the last decade due to:

  • The introduction of Haemophilus influenzae type B and conjugated Streptococcus pneumoniae vaccines into childhood vaccination programmes. Recently, a conjugated vaccine against Neisseria meningitidis strains A, C, Y, W135 has also become commercially available.
  • Screening of pregnant women for Streptococcus agalactiae (Group B Strep) as advocated by numerous clinical guidelines, with antibiotic prophylaxis being given to women during delivery to decrease the burden of Group B strep neonatal sepsis.

Despite these interventions, it is estimated that 1.2 million cases of bacterial meningitis occur annually worldwide. Bacterial meningitis has a high morbidity (hearing loss, visual impairment, limb loss and cognitive impairment) and mortality if left untreated. Therefore, appropriate antibiotic treatment for the causative pathogen should be started as quickly as possible.

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