Meningoencephalitis is inflammation of the meninges and brain. Patients present with encephalitis and associated meningitis, both of which are most commonly infectious in etiology. Clinically, patients present with symptoms of meningitis, including fever, headache, nausea, vomiting, and nuchal rigidity, as well as those of encephalitis, including abnormalities in brain function, altered mental status, personality changes, behavioral changes, sensory deficits, motor deficits, speech disorders, hemiparesis, flaccid paralysis, and paresthesias. Common causes include bacterial, viral, fungal, and protozoan pathogens, and further testing is guided by history, physical examination, and clinical presentation.

Immunocompromised patients, children, and elderly patients are at higher risk for infectious meningoencephalitis with specific pathogens. Meningoencephalitis also has noninfectious etiologies, including traumatic (irritation from blood), drug induced, sarcoidosis related, and carcinomatous.

There are reports of meningoencephalitis following exposure to Zika virus.