Viral Meningitis Diagnosis and Management

Clinical Presentation

Patients with viral meningitis typically present with meningism, characterized by neck stiffness, headache, and photophobia 1, 2
Fever may be present but is not universal in viral meningitis cases 1
Non-specific symptoms often accompany the presentation, including diarrhea, vomiting, muscle pain, and sore throat 1
Unlike bacterial meningitis, there is usually no reduced level of consciousness in adults with viral meningitis; altered mental status suggests an alternative diagnosis 1, 2
HSV-2 meningitis patients rarely have concurrent genital ulcers and often lack any history of genital disease 1
VZV meningitis can occur with or without the characteristic rash of chickenpox or shingles 1

Lumbar puncture (LP) is the cornerstone of diagnosis for suspected viral meningitis 1, 3
LP should be delayed if any of the following contraindications are present 3, 4:
CSF opening pressure should always be measured (unless LP is done in sitting position) 3, 4
CSF cell count typically shows pleocytosis, though patterns vary 3
CSF biochemistry findings suggestive of viral rather than bacterial etiology 3, 4
CSF PCR is the gold standard for confirmation of viral meningitis 1, 2
When viral meningitis is suspected, CSF should be tested for enteroviruses, herpes simplex viruses type 1 and 2 (HSV-1 and HSV-2), and varicella zoster virus (VZV) 1, 2

Bacterial meningitis - distinguished by more severe presentation, altered mental status, and different CSF profile 1, 6
Encephalitis - distinguished by altered consciousness and focal neurological signs 1, 2
Subarachnoid hemorrhage - can mimic meningitis symptoms 1
Space-occupying lesions - may present with headache and altered mental status 1
Encephalopathy due to infection outside the central nervous system 1

Enteroviruses are the most common cause (>90 serotypes exist) 1, 5
Herpes viruses, predominantly HSV-2 and VZV, are the second most common cause 1, 5
Less common viral causes include cytomegalovirus, Epstein-Barr virus, and mumps virus 1, 5
No specific pathogen is identified in 30-50% of presumed viral meningitis cases 1, 2

Viral meningitis should be assessed by an infection or neurological specialist 1
Identifying the viral pathogen allows for appropriate diagnosis, cessation of unnecessary antibiotics, reduction in investigations, and shorter hospital stays 1, 2
Currently, there are no treatments of proven benefit for most causes of viral meningitis 1, 2
Some clinicians treat herpes meningitis with aciclovir or valaciclovir, but evidence supporting this practice is lacking 1, 2

Do not rule out meningitis based solely on absence of classic symptoms, as these may not be present in all cases 6, 7
Do not rely on Kernig's sign or Brudzinski's sign alone, as they have low sensitivity (11% and 9% respectively) for diagnosing meningitis 6, 7
Do not delay antimicrobial therapy if bacterial meningitis is suspected while awaiting imaging or LP 8, 6
Do not assume normal CSF cell count excludes infection; early in the course of illness, CSF white cell count may be minimal or absent 3, 4
Do not routinely use aciclovir/valaciclovir as prophylaxis for recurrent herpes meningitis (HSV or VZV) 1, 2