Meningitis describes inflammation of the meninges of the brain and spinal cord, most commonly and most seriously due to bacterial infection.
Community-acquired bacterial meningitis typically presents
with fever, meningism (headache, neck stiffness and photophobia)
and deterioration in conscious level. The natural history involves a rapid progression to subpial encephalopathy, venous thrombosis, cerebral oedema and death. Therefore empirical
intravenous antibiotic therapy should be commenced as soon as the diagnosis is suspected. Urgent lumbar puncture is required to confirm the diagnosis and ultimately to guide treatment. Since the differential diagnosis of this presentation includes abscess, empyema and subarachnoid haemorrhage, initial CT imaging, where available immediately, is desirable to confirm that lumbar
puncture is necessary and safe. A 2007 Cochrane review demonstrated improved mortality and neurological outcome associated with administration of steroids (dexamethasone 0.15 mg/kg up
to 10 mg four times daily for 4 days).
The common organisms responsible for spontaneous bacterial meningitis are Streptococcus pneumonia, Haemophilus influenzae and Neisseria meningitides, the latter occurring in sporadic outbreaks. Neonates are susceptible to group B streptococcus, Escherichia coli and Listeria.
Meningitis in the context of surgery typically follows a more insidious course, but nonetheless remains a feared complication
requiring prompt intervention. Typical organisms are Staphylococcus aureus, Enterobacteriaceae, Pseudomonas and Pneumococci.
Meningitis after head injury is common, affecting 25 per cent of patients with base of skull fracture and CSF leak. Repair of the CSF leak may be required, and empirical antibiotics should have activity against commensal nasal organisms including Gram-positive cocci and Gram-negative bacilli in the presence of symptoms/signs of clinical meningitis.
Ventriculitis refers to infection in the ventricles, commonly as a complication of meningitis or due to contamination from a shunt or external drain. Where a drain is present, treatment may include administration of intrathecal antibiotics through it.