Viral meningitis
Viral meningitis is an acute lymphocytic-predominant meningeal infection, most often caused by enteroviruses, that presents with fever, headache, and neck stiffness milder than bacterial meningitis; diagnosis rests on CSF analysis and PCR, and management is supportive care after empiric antibacterial and, when HSV cannot be excluded, IV acyclovir coverage is stopped.
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What this article covers
- Overview
Definition: viral meningitis is an acute infection of the meninges caused by a virus, producing the clinical meningeal syndrome of fever, headache, and neck stiffness together with a cerebrospinal…
- Epidemiology
Enteroviruses are the leading cause, a member of the picornavirus family alongside echovirus and coxsackievirus, and they infect patients of all ages.
- Risk factors
Young age, particularly infants and children, given the predominance of enteroviral transmission in this group.
- Pathophysiology
Hematogenous or neural spread to the meninges: most viruses reach the meninges via viremia following mucosal or gastrointestinal entry (enteroviruses), while HSV and varicella zoster virus may spread…
- Clinical features
Core meningeal triad, typically milder than bacterial disease: fever, headache, and neck stiffness, often with a preceding upper respiratory or gastrointestinal prodromal illness.
- Differential diagnosis
Bacterial meningitis: CSF shows a markedly higher white cell count (1,000-5,000/mcL) with neutrophilic predominance and a low glucose (less than 40 mg/dL or CSF-to-serum glucose ratio under 0.4)…
- Diagnosis
Aseptic meningitis syndrome is defined by acute meningeal symptoms, fever, CSF pleocytosis (usually lymphocytic), and negative CSF bacterial cultures; viral meningitis is the diagnosis once other…
- Management
First, stabilize and initiate empiric therapy for the more dangerous mimics before the viral diagnosis is confirmed, starting within 30-60 minutes of presentation and without waiting for CT or lumbar puncture.
- Complications
Seizures, typically in the setting of higher fever or, more commonly, when parenchymal (encephalitic) involvement coexists.
- Prognosis
Excellent in the great majority of cases: most viral meningitis, especially enteroviral disease, resolves completely within 1 to 2 weeks without specific antiviral therapy or lasting neurologic deficit.
- Prevention
Meningococcal vaccination is recommended per standard immunization schedules and reduces the burden of meningococcal disease in the differential of acute meningitis presentations.
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Related articles
- Meningococcal meningitis
Meningococcal meningitis is an acute bacterial infection of the meninges caused by Neisseria meningitidis, an encapsulated gram-negative diplococcus that spreads by respiratory droplets and classically causes a petechial rash. It is an infectious disease emergency treated with empiric ceftriaxone and vancomycin plus dexamethasone, followed by penicillin or ceftriaxone once confirmed, with chemoprophylaxis for close contacts.
- Encephalitis
Encephalitis is inflammation of the brain parenchyma, most often viral (herpes simplex virus 1 being the classic treatable cause), presenting with fever, headache, altered mental status, and seizures; empiric IV acyclovir is started immediately whenever it is in the differential, pending confirmatory CSF PCR.
- Seizure (first, single, or provoked)
A first or provoked seizure requires a focused history to distinguish it from syncope or a nonepileptic event, urgent glucose and electrolyte testing, brain MRI, and outpatient EEG; an unprovoked seizure with normal imaging and EEG usually does not require antiepileptic drug therapy, since epilepsy is defined only after a second unprovoked seizure or a high-risk first one.
- Increased intracranial pressure
Sustained intracranial pressure above 20-22 mmHg from mass effect, edema, hydrocephalus, or venous outflow obstruction, diagnosed by clinical signs plus invasive monitoring and treated stepwise with head elevation, hyperosmolar therapy (mannitol or hypertonic saline), CSF diversion, and decompressive surgery when refractory.
- Status epilepticus
Status epilepticus is a generalized tonic-clonic seizure lasting more than 5 minutes, or repeated seizures without return to baseline, and is a neurologic emergency. Treatment is a timed escalation: IV benzodiazepine first, then an IV antiepileptic drug, then anesthetic coma with continuous EEG if convulsions persist.