LP results consistent with viral meningitis and low bacterial concern
Lymphocytic pleocytosis pattern
Normal CSF glucose
Microbiology reassurance
Negative Gram stain
Low clinical concern for bacterial meningitis
Symptom control
Oral hydration tolerated
Pain controlled with oral regimen
Safety net
Reliable follow-up within 24 to 72 hours
Clear return precautions
Transfer considerations
Higher capability needs
Need for MRI not available locally
Suspected encephalitis
Suspected abscess
ICU capacity needs
Vasopressor requirement
Airway support
Treatment
Empiric therapy until bacterial meningitis excluded
Initial antimicrobials
Empiric antibiotics when bacterial meningitis cannot be excluded
Ceftriaxone IV 2 g every 12 hours
Indication
Community-acquired meningitis coverage
Allergy alternative logic
If immediate beta-lactam allergy, consult for alternative regimen
Vancomycin IV weight-based dosing with trough targeting per local protocol
Indication
Pneumococcal resistance coverage
Renal monitoring
Creatinine daily while on therapy
Ampicillin IV 2 g every 4 hours
If age 50 years or older
Listeria coverage
If immunocompromised
Listeria coverage
Dexamethasone for suspected bacterial meningitis
Dexamethasone IV 10 mg every 6 hours for 4 days
If started before or with first antibiotic dose
Benefit greatest for pneumococcal meningitis
Stop if bacterial meningitis not supported
Viral meningitis confirmed
Antiviral therapy triggers
Acyclovir decision pathway
If encephalitis features
Altered mental status
Acyclovir IV 10 mg/kg every 8 hours using ideal body weight
Renal dosing adjustment
If eGFR reduced, extend interval per protocol
Hydration strategy
IV fluids to reduce crystal nephropathy risk
If suspected HSV meningitis with severe symptoms or immunocompromised
Acyclovir IV dosing as above
Transition consideration
Switch to oral valacyclovir when improving and able to take PO
Supportive care for viral meningitis
Analgesia and antipyresis
Acetaminophen PO 1000 mg every 6 hours as needed
Maximum daily dose per age and liver risk
Lower maximum with liver disease or heavy alcohol use
Ibuprofen PO 400 mg every 6 hours as needed
Renal and GI cautions
Avoid in significant renal impairment
Avoid in active GI bleeding
Antiemetics and hydration
Ondansetron ODT or PO 4 mg every 8 hours as needed
QT risk context
Avoid combining with other strong QT-prolonging agents when possible
IV crystalloid for dehydration
Bolus strategy
10 to 20 mL/kg if significant volume depletion
Headache refractory options
Metoclopramide IV 10 mg once
Dystonia prevention
Diphenhydramine IV 25 mg if prior dystonia or high risk
Magnesium sulfate IV 1 to 2 g once
If migraine-like phenotype prominent
Infection control and public health
Precaution adjustments
Stop droplet precautions when bacterial meningitis excluded and no meningococcal concern
Negative Gram stain and low clinical concern
Alternative diagnosis established
Notify public health when indicated
Suspected meningococcal disease
Reportable viral etiologies per local rules
De-escalation and stopping therapy
Narrowing decisions
If CSF profile and PCR consistent with viral meningitis and cultures negative
Stop empiric antibiotics when bacterial meningitis reasonably excluded
Shared decision documentation
Follow-up plan confirmed
If HSV and VZV PCR negative and no encephalitis features
Stop acyclovir
Clinical reassessment supporting non-HSV course
Special Populations
Pregnancy
Pregnancy considerations
Diagnostic priorities
Lower threshold for admission
Fetal monitoring needs if severe maternal illness
Medication safety
Acyclovir use in pregnancy accepted when HSV CNS infection suspected
Avoid NSAIDs in later pregnancy per obstetric guidance
Obstetric infections
Varicella exposure history
HSV genital lesions and timing
Geriatric
Older adult considerations
Atypical presentation
Minimal fever despite infection
Delirium predominant
Higher bacterial risk baseline
Lower threshold for empiric antibiotics
Lower threshold for admission
Medication cautions
NSAID renal risk
Acyclovir renal dosing strictness
Pediatrics
Pediatric considerations
Common etiologies by age
Enterovirus common in older infants and children
Neonatal HSV risk
Weight-based dosing
Ceftriaxone dosing per kg per local protocol
Acyclovir dosing per kg per pediatric guidelines
Disposition threshold
Infants under 3 months usually admitted
Social reliability requirements for discharge
Background
Epidemiology
Frequency and causes
Common etiologies
Enteroviruses as leading cause in many settings
HSV-2 as common cause of recurrent aseptic meningitis
VZV as cause with or without rash
Seasonality
Enterovirus peak in summer and early fall
Arbovirus peak with mosquito season
Outcomes
Viral meningitis usually self-limited in immunocompetent hosts
Morbidity increases in immunocompromised and extremes of age
Pathophysiology
Disease mechanism
Meningeal inflammation
Cytokine-mediated pain and photophobia
CSF pleocytosis reflecting immune response
CSF patterns
Viral typically lymphocyte predominant
Early neutrophil predominance possible in first 24 hours
Raised ICP mechanisms
Impaired CSF resorption
Cerebral edema in encephalitis spectrum
Therapeutic Considerations
Treatment rationale
Supportive care as mainstay
Analgesia
Hydration
Empiric antibiotics rationale
Early clinical overlap with bacterial meningitis
Mortality risk if bacterial treatment delayed
Acyclovir rationale
Prevent neurologic injury in HSV encephalitis
Benefit outweighs risk when suspicion moderate to high
Evidence framing
Empiric antibiotics in suspected meningitis supported by guideline consensus Class I recommendation
CT before LP criteria supported by guideline consensus Class I recommendation
Patient Discharge Instructions
copy discharge instructions
Discharge instructions
Diagnosis and expectations
Viral meningitis suspected or confirmed
Symptoms often improve over several days
Home care
Rest and fluids
Acetaminophen as directed on label
Ibuprofen only if safe for kidneys and stomach
Return to emergency department immediately
Worsening confusion
New seizure
New weakness or numbness
Severe worsening headache
Persistent vomiting or inability to keep fluids down
Fainting or signs of dehydration
New rash with purple spots
Trouble breathing
Follow-up
Primary care or clinic visit within 24 to 72 hours
Review pending CSF culture or PCR results if not finalized
References
Guidelines and key sources
Key references
Infectious Diseases Society of America guidelines for bacterial meningitis management for empiric therapy principles
Antibiotics not delayed for imaging when bacterial concern high
Dexamethasone timing tied to first antibiotic dose
Infectious Diseases Society of America guidelines for encephalitis for HSV evaluation and acyclovir use
Acyclovir recommended when encephalitis features present
MRI and EEG considered when encephalitis suspected
CDC clinical resources for meningitis and enterovirus guidance
Enterovirus epidemiology and seasonality
Public health reporting considerations
Pediatric bacterial meningitis score derivation and validation literature for children with CSF pleocytosis
Risk stratification for bacterial versus viral etiologies
Not validated for adults
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.