Viral meningitis
Definition: Viral meningitis is an acute inflammation of the meninges caused by viruses, typically resulting in a milder, self-limiting course compared to bacterial meningitis.
- Also called aseptic meningitis.
Etiology
Most common viruses: Enteroviruses (Coxsackie, Echovirus) – most common overall. Herpes simplex virus (HSV-2 > HSV-1). Varicella-zoster virus (VZV). Mumps virus. HIV (early infection)
Pathogenesis
- Viral entry via respiratory or gastrointestinal tract
- Hematogenous spread → CNS
- Infection of meninges → inflammatory response without bacterial pus formation
Clinical Features
- Onset: Acute or subacute. Usually less severe than bacterial meningitis
- Meningeal Syndrome: Headache. Low to moderate fever. Neck stiffness (milder than bacterial). Photophobia. Nausea/vomiting
- General Condition: Patient usually less toxic than in bacterial meningitis. Consciousness usually preserved. Neurological signs. Mild or no focal deficits. Rare seizures
CSF Findings
Typical viral CSF pattern: ↑ Opening pressure (mild/moderate). Clear CSF. ↑ Lymphocytes (lymphocytic pleocytosis). Mild ↑ protein. Normal glucose (key distinction)
Diagnosis
- Lumbar puncture (primary test)
- PCR for viral DNA/RNA (highly specific)
- Exclusion of bacterial meningitis is essential
Differential Diagnosis
1. Bacterial meningitis: Neutrophils in CSF. ↓ glucose. More severe, toxic patient
2. Tuberculous meningitis: Subacute/chronic. ↑ protein much higher. ↓ glucose
3. Encephalitis: Prominent altered consciousness. Focal neurological deficits. Seizures early
Treatment
- Mostly supportive therapy: Hydration. Analgesics. Antipyretics
- Specific therapy (if indicated): Acyclovir (HSV/VZV suspected)
Prognosis: Usually excellent. Self-limiting (days to weeks). Full recovery common
Complications: Rare. Persistent headache or fatigue. Post-viral asthenia