Infectious Disease

Meningitis

Bacteria reaching the subarachnoid space provoke an inflammatory response that raises intracranial pressure and injures cranial nerves, while meningococcal bloodstream invasion adds purpura, coagulopathy and shock.

Definition

Bacterial meningitis is inflammation of the meninges from bacterial infection of the subarachnoid space, confirmed on clinical features plus blood and cerebrospinal fluid results. Meningococcal disease is invasive Neisseria meningitidis infection, with or without meningitis.

First principles

The red flag combination is a prompt to act, not a diagnostic requirement

NICE names fever, headache, neck stiffness and altered consciousness or cognition as the red flag combination. Each element fails somewhere. Fever is less common in older adults. Neck stiffness is harder to detect in dementia, arthritis and cognitive impairment. Altered consciousness in young adults gets blamed on alcohol. Early symptoms can also resemble flu, a stomach bug or a hangover. Treat any convincing part of the combination as the trigger for emergency assessment.

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