Meningitis and Encephalitis

Abstract

Meningitis is characterized by severe generalized headache, fever, neck stiffness, and a change in mental status. There is often also nausea, vomiting, photophobia and skin rash. Elderly patients may have no fever; change in mental status may be the only symptom. Encephalitis is characterized by a change in the level of consciousness, seizures, flu-like illness, memory loss, and behavioral changes, with or without fever. Immunosuppressant medications make patients especially susceptible to central nervous system infections.

During the initial stabilization of the patient, intubation and ventilation are required if altered mental status corresponds to a Glasgow Coma Scale less than or equal to 8. Further examination should specifically evaluate for cutaneous manifestations of pertinent infections as well as meningeal signs. Together with routine lab work, blood for culture and sensitivity is required. Serum virology may also be sent. An emergent head CT scan should be done. A lumbar puncture should be urgently obtained; however, empiric broad-spectrum antibiotics should not be held pending this procedure. CSF analysis is usually helpful in identifying the type of infectious agent and may inform the empiric antimicrobial regimen before culture and/or PCR results are available. EEG may be helpful in cases of limbic encephalitis or when seizures are suspected. MRI plays a helpful role in better defining necrotizing lesions that may be seen in herpes encephalitis. To cover bacterial causes, empiric treatment usually entails high-dose I.V. ceftriaxone, vancomycin, and ampicillin (if at risk for Listeria). The concomitant use of dexamethasone may decrease morbidity and mortality. For viral/herpetic encephalitis, intravenous acyclovir is the mainstay agent, and steroids are usually avoided.