What is the best course of action for a 16-year-old male patient with a history of chronic generalized headaches, presenting with altered mental status, worsening headache, high-grade fever, episodes of vomiting, agitation, anorexia, and low sodium levels, with a Glasgow Coma Scale (GCS) score of 12/15 and normal Complete Blood Count (CBC) results?

Immediate Management: Suspected Viral Encephalitis with Empiric Acyclovir

This 16-year-old male requires immediate empiric intravenous acyclovir for presumed viral encephalitis, urgent lumbar puncture for CSF analysis, and emergent brain MRI—all while initiating treatment without delay. 1

Critical Clinical Recognition

This patient presents with the classic triad of viral encephalitis:

• Altered mental status (GCS 12/15 in ED, though documented inconsistently)
• High-grade fever for 4 days
• Severe headache with vomiting and agitation 1

The combination of fever (present in 91% of HSV encephalitis cases), altered behavior, agitation, and chronic headache history with acute worsening strongly suggests infectious encephalitis rather than metabolic encephalopathy. 1 The low sodium (134 mEq/L) and presence of intractable symptoms may further suggest antibody-mediated encephalitis, though hyponatremia can occur with various encephalitis etiologies. 1

Immediate Actions (Do Not Delay Treatment)

1. Start Empiric Acyclovir Immediately

• Begin IV acyclovir without waiting for diagnostic confirmation 1
• HSV encephalitis is the most common treatable cause of viral encephalitis, and delays in treatment are associated with poor outcomes and mortality 1
• The subtle presentations (behavioral changes, speech disturbances, low-grade fever) can be mistaken for psychiatric illness or substance abuse—with tragic consequences if treatment is delayed 1

2. Urgent Lumbar Puncture

• CSF analysis is critical for confirming diagnosis and must include: 2
  • Cell count and differential (looking for pleocytosis)
  • Protein and glucose
  • HSV PCR (most sensitive test for HSV encephalitis)
  • Bacterial culture and gram stain
  • Consider viral panel, autoimmune encephalitis antibodies 1
• Opening pressure should be measured (elevated pressure suggests increased intracranial pressure) 3

3. Emergent Brain MRI (Within 48 Hours)

• MRI is the imaging modality of choice, preferred over CT 2
• MRI with and without contrast should be obtained to evaluate for: 1
  • Temporal lobe involvement (classic for HSV encephalitis)
  • Diffusion restriction
  • FLAIR hyperintensity in mesial temporal structures 3
• CT head without contrast is appropriate initially if MRI is not immediately available, but should not delay treatment 1

Airway and Monitoring Considerations

ICU-Level Care Required

• GCS of 12/15 indicates severe brain injury requiring ICU admission 1
• Monitor for deterioration in mental status that may require intubation for airway protection 1
• Seizures occur in approximately one-third of encephalitis patients and can be the initial presenting feature 2, 4
• If intubation becomes necessary, use short-acting sedatives (propofol or dexmedetomidine) to allow frequent neurological assessments 1

Address the Hyponatremia

Sodium 134 mEq/L (Mild Hyponatremia)

• This is mild hyponatremia but clinically significant given the altered mental status 5
• The hyponatremia may be contributing to symptoms (headache, vomiting, altered mentation) or may suggest SIADH from encephalitis 1, 5
• Do NOT aggressively correct sodium in this setting—the primary issue is encephalitis, not hyponatremic encephalopathy 5, 6
• Monitor sodium closely; if it drops below 125 mEq/L with worsening symptoms, consider hypertonic saline 6
• Fluid restriction may be appropriate once infectious workup is complete and SIADH is confirmed 5

Investigation of Alternative Causes (Concurrent with Treatment)

While treating empirically for encephalitis, investigate other reversible causes: 1

• Metabolic disorders: Recheck electrolytes, glucose, liver function, ammonia (though low ammonia argues against hepatic encephalopathy) 1
• Toxicology screen: Rule out drug intoxication or withdrawal 1
• Autoimmune encephalitis: Send serum and CSF autoimmune panels (anti-NMDA receptor, anti-LGI1, others) 1, 2
• Bacterial meningitis: Blood cultures, procalcitonin if available 1

Critical Pitfalls to Avoid

• Never delay acyclovir while awaiting diagnostic confirmation—HSV encephalitis has high mortality if untreated, and early treatment dramatically improves outcomes 1
• Do not dismiss behavioral changes as psychiatric illness—this is a common and dangerous error that delays diagnosis of encephalitis 1, 2, 4
• Do not assume normal CBC rules out serious infection—this patient's WBC is normal despite likely encephalitis 1
• Do not perform lumbar puncture before neuroimaging if there are signs of increased intracranial pressure (papilledema, focal deficits, severely depressed consciousness)—but do not delay acyclovir 1
• Do not aggressively correct the mild hyponatremia—overly rapid correction risks osmotic demyelination syndrome, and the primary problem is encephalitis 6

Disposition and Follow-Up

• Admit to ICU or high-dependency unit for continuous neurological monitoring 2
• Continue acyclovir for minimum 14-21 days if HSV encephalitis is confirmed 1
• Arrange neurology consultation immediately 2
• Do not discharge without definitive or suspected diagnosis 2
• Plan for rehabilitation assessment, as sequelae may not be immediately apparent 2