What is the diagnostic approach for dengue encephalitis in a clinical setting?

Diagnostic Approach for Dengue Encephalitis in Clinical Setting

The diagnosis of dengue encephalitis requires a comprehensive diagnostic algorithm including clinical evaluation, cerebrospinal fluid (CSF) analysis, neuroimaging, and specific dengue testing. 1

Clinical Presentation and Epidemiology

• Patients with dengue encephalitis typically present with altered mental status (76.7%), seizures (63.3%), pyramidal tract signs (36.7%), meningeal signs (30%), and headache (26.7%) 2
• Fever is present in most cases (83%) and should prompt consideration of dengue in endemic regions or with relevant travel history 3
• Epidemiologic factors are crucial for suspicion, including:
  • Geographic location (endemic areas in Asia, Central/South America)
  • Season (typically summer/fall in endemic regions)
  • Recent travel history to endemic areas 1

Diagnostic Algorithm

Step 1: Initial Laboratory Evaluation

• Complete blood count (look for thrombocytopenia and leukopenia characteristic of dengue) 1
• Liver function tests (may show moderate to severe liver dysfunction) 4
• Renal function tests 1
• Coagulation studies (may reveal coagulopathy) 1

Step 2: Neuroimaging

• MRI is the preferred neuroimaging modality for all encephalitis cases (Grade A-I recommendation) 1
• CT scan should only be used if MRI is unavailable (Grade B-III) 1
• Neuroimaging findings in dengue encephalitis are diverse and may include:
  • Cerebral edema (most common finding)
  • Temporal and occipital lobe abnormalities
  • Meningeal enhancement
  • Frontal and subcortical hyperintense lesions 3
• Note that neuroimaging may be normal in 40-50% of dengue encephalitis cases 5

Step 3: CSF Analysis (Essential unless contraindicated)

• CSF examination is mandatory in all suspected encephalitis cases (Grade A-III) 1
• Typical findings include:
  • Lymphocytic pleocytosis (elevated cell count with predominant lymphocytes)
  • Elevated protein levels
  • Normal glucose levels 3, 2
• Important: CSF may be normal in up to one-third of dengue encephalitis cases 5

Step 4: Specific Dengue Testing

• Serum dengue-specific IgM antibodies (confirms recent infection) 3, 5
• CSF dengue-specific IgM antibodies (when available) 2
• Dengue PCR testing of CSF (highest diagnostic value for confirming neuroinvasion) 5
• Dengue NS1 antigen testing (useful in early infection) 1

Step 5: Electroencephalography (EEG)

• EEG should be performed in all encephalitis patients (Grade A-III) 1
• Typical findings include:
  • Generalized slowing (theta to delta range) in 55% of cases
  • Temporal spikes
  • Burst suppression pattern in severe cases 4
• EEG abnormalities correlate with altered sensorium and depth of coma 4

Step 6: Exclusion of Other Causes

• Rule out co-infections (especially other arboviruses like Japanese encephalitis) 4
• Consider autoimmune encephalitis in the differential diagnosis 1
• Evaluate for metabolic causes of encephalopathy 4

Common Pitfalls and Caveats

• Underdiagnosis is common due to varied clinical presentation and non-specific findings 5
• Neurological manifestations occur in up to 15% of dengue patients but are often missed 5
• Normal CSF or neuroimaging does not exclude dengue encephalitis 5
• Positive dengue serology without CSF confirmation may represent systemic dengue with encephalopathy rather than true encephalitis 3, 4
• Consider acute disseminated encephalomyelitis (ADEM) in patients with a recent history of dengue infection 1

Prognosis

• Mortality rates vary but can be significant (32% in some studies) 3
• Poor prognostic factors include:
  • Refractory seizures
  • Prolonged altered consciousness
  • Evidence of spinal cord involvement 3
• Early diagnosis and supportive care are essential for improving outcomes 3, 6