Topic overview

Start with the big picture

Meningitis is inflammation of the leptomeninges and commonly presents with fever, headache, and neck stiffness; photophobia or altered mental status may also occur. Kernig and Brudzinski signs can increase suspicion, but their absence does not exclude the diagnosis. Causes and cerebrospinal fluid patterns vary: bacterial infection is associated with increased neutrophils, reduced glucose, and increased protein, while viral meningitis typically has increased lymphocytes and normal glucose. Tuberculous and fungal meningitis have their own characteristic CSF pattern. Encephalitis involves inflammation of brain parenchyma and may cause altered consciousness, focal neurologic deficits, or seizures. Viral causes predominate, with HSV-1 an important example. The deeper lesson develops these distinctions alongside diagnostic approaches, management, complications, prevention, and comparison tools.