SUMMARY AND RECOMMENDATIONS
The diagnosis of a patient with aseptic meningitis may be difficult because of the large variety of potential etiologic agents and the overlap between self-limited viral illnesses and potentially fatal bacterial infections.
Management — A careful history should include travel and exposure history, including exposure to rodents (LCMV), ticks (Lyme borrelia, RMSF, ehrlichia), mosquitoes (West Nile virus, St. Louis encephalitis virus) and patients with tuberculosis, sexual activity (HSV-2, HIV, syphilis), travel (C. immitis, A. cantonensis) and contact with other individuals with similar symptoms or viral exanthems (enteroviruses). The patient should also be questioned about medications and other comorbidities.
The opening CSF pressure should be noted and CSF should be sent for cell count, glucose, protein and culture or specific antigen or nucleic acid tests for viruses, as well as culture for bacteria. Whether additional studies (eg, culture for fungi and mycobacteria) should be performed will depend on the clinical presentation (see discussion above and individual topic cards).
Based upon the history, physical examination and CSF findings, patients can often be classified as having probable bacterial or viral meningitis, although overlap can be frequent, particularly if bacterial meningitis has been partially treated with previous antibiotics.
Suspected bacterial meningitis — For patients with suspected bacterial meningitis, antibiotics should be initiated promptly.
Suspected viral meningitis — The approach to empiric therapy in the patient with viral meningitis will depend upon the clinical appearance of the patient and underlying host factors. Patients who are elderly, immunocompromised, or have received antibiotics prior to presentation may be considered for empiric therapy for 48 hours, even if viral meningitis is the suspected diagnosis. Otherwise, the clinician can consider observing the patient without antibiotic therapy.
If HIV is a diagnostic consideration, then blood testing for HIV RNA and HIV antibody should be performed.
If aseptic meningitis due to HSV is suspected (eg, concomitant genital lesions), empiric therapy with acyclovir (10 mg/kg intravenously every eight hours) can be administered.
Unclear etiology — When it is not clear whether the patient has a viral or bacterial process, we recommend empiric antibiotics after obtaining blood and CSF cultures or observation with repeat lumbar puncture in 6 to 24 hours. If the patient is symptomatically improved and culture results are negative, then antibiotics can generally be stopped without a repeat LP. However, repeat LPs may be indicated in patients with persistent symptoms who do not have a clear diagnosis.
DRUG-INDUCED MENINGITIS — Drug-induced meningitis is an unusual adverse reaction that is usually a diagnosis of exclusion ． A number of drugs can induce symptoms and signs of aseptic meningitis including nonsteroidal antiinflammatory drugs (NSAIDs) ， certain antibiotics (eg, trimethoprim-sulfamethoxazole) , intravenous immune globulin， rofecoxib, cetuximab, antiepileptic drugs and OKT3 antibodies.
Two mechanisms have been proposed for drug-induced meningitis: a delayed hypersensitivity type reaction and direct meningeal irritation．
The CSF profile typically has a neutrophilic pleocytosis. Symptoms often resolve a few days after drug discontinuation.
There are also multiple reports of drug-induced meningitis in patients with autoimmune disease． Many of these reports implicate use of NSAIDs. It is unclear whether these patients are inherently at increased risk or whether the incidence is greater as a result of the prevalent usage of nonsteroidal antiinflammatory drugs．