Viral Meningitis

The most common cause of meningitis overall, typically enteroviruses (coxsackievirus, echovirus), also HSV-2 (particularly with recurrent, "Mollaret's" meningitis), VZV, mumps (in unvaccinated populations), and HIV seroconversion.

Generally self-limiting with a benign course, in sharp contrast to bacterial meningitis, making the distinction between the two the central diagnostic task.

Fever, headache, photophobia, and neck stiffness, generally with a less toxic overall appearance than bacterial meningitis, and without the significant reduction in consciousness, focal deficit, or non-blanching rash that would point toward a bacterial or meningococcal cause.

CSF shows a lymphocytic pleocytosis (though a neutrophilic predominance can occur very early in enteroviral meningitis, potentially confounding initial interpretation), normal glucose, and normal or mildly elevated protein, a pattern clearly distinct from the bacterial pattern described in the Meningitis entry.

Enterovirus PCR of CSF is the primary confirmatory test where available; HSV/VZV PCR where clinically relevant.

• Supportive care: analgesia, antiemetics, hydration; most cases resolve within 7 to 10 days
• Empirical bacterial meningitis treatment should be started and only stopped once bacterial meningitis is confidently excluded (reassuring CSF pattern, negative Gram stain, clinical improvement, and, where used, a negative bacterial PCR panel), given the overlap in early presentation and the catastrophic consequence of missing bacterial disease
• HSV meningitis (as opposed to encephalitis) is generally self-limiting and antiviral treatment is not routinely required unless the presentation suggests concurrent encephalitis or the patient is immunocompromised
• Admission for observation is reasonable pending exclusion of bacterial disease, particularly where the clinical picture is not yet clearly reassuring

Referral: infectious disease for atypical or recurrent presentations, or diagnostic uncertainty.