What are the symptoms of viral encephalitis?

Symptoms of Viral Encephalitis

The classic symptoms of viral encephalitis include fever and abnormal mental status, often accompanied by headache, nausea, vomiting, disorientation, speech disturbances, behavioral changes, and seizures. 1

Core Clinical Presentation

Cardinal Symptoms

• Altered mental status (76-91% of cases)

  • Confusion, disorientation
  • Personality changes
  • Behavioral abnormalities
  • Lethargy, drowsiness
  • Progressive decline in consciousness, potentially leading to coma 1

• Fever (80-91% of cases)

  • May present as high fever or sometimes only low-grade pyrexia 1
  • Some patients may not be febrile on admission but typically have a history of febrile illness 1

Common Associated Symptoms

• Headache (often severe)

• Nausea and vomiting

• Seizures (33-41% of cases)

  • May sometimes be the initial presenting feature
  • More common in cortical involvement 1
  • Can be intractable in antibody-associated encephalitis

• Speech disturbances (59% of cases)

  • Dysphasia
  • Aphasia 1

• Focal neurological signs (37-78% of cases)

  • Visual field defects
  • Motor weakness
  • Sensory abnormalities 1

• Meningism (neck stiffness) (22% of cases) 1

Specific Clinical Patterns

HSV Encephalitis Presentation

• Disorientation (76%)
• Speech disturbances (59%)
• Behavioral changes (41%)
• Seizures (one-third of cases) 1
• May present with subtle symptoms that can be mistaken for psychiatric illness or substance abuse 1

Antibody-Mediated Encephalitis Presentation

• VGKC-complex antibody encephalitis:

  • Profound disorientation and confusion
  • Seizures
  • Anterograde and retrograde amnesia
  • Hyponatremia (60% of cases)
  • Faciobrachial dystonic seizures (pathognomonic) 1

• NMDA receptor antibody encephalitis:

  • Two-phase illness:
    1. First phase: seizures, confusion, amnesia, psychosis
    2. Second phase: involuntary movements (choreoathetosis, orofacial dyskinesia), fluctuating consciousness, dysautonomia, central hypoventilation 1

Age-Specific Considerations

Children

• Fever (67-80%)
• Seizures (61-78%)
• Behavioral changes/confusion/irritability (76%)
• Vomiting (57%)
• Focal neurological signs (37-78%) 1

Elderly

• May present atypically
• Increased risk for HSV encephalitis and its complications 2

Warning Signs of Severe Disease

• Rapid deterioration in consciousness level

• Status epilepticus

• Signs of increased intracranial pressure:

  • Papilledema
  • Hypertension with bradycardia
  • Irregular respirations
  • Posturing 1, 2

• Cerebral edema development following inflammatory response 2

• Stroke-like episodes (particularly with varicella-zoster virus vasculopathy) 2

Diagnostic Pitfalls

• Normal Glasgow Coma Score doesn't exclude encephalitis, as it may not detect subtle behavioral changes 1
• Symptoms can be mistaken for psychiatric illness, substance abuse, or alcohol intoxication 1
• Immunocompromised patients may present with atypical features and are more likely to have acellular CSF despite CNS infection 1
• Sub-acute presentation (weeks-months) should prompt consideration of autoimmune, paraneoplastic, or metabolic etiologies 1

Early recognition of these symptoms is crucial, as prompt diagnosis and treatment significantly impact survival and reduce permanent brain injury in survivors. Any patient presenting with altered consciousness, new seizures, or new focal neurological signs should be evaluated for possible encephalitis 1.