What is the management of suspected influenza encephalopathy?

Management of Suspected Influenza Encephalopathy

Patients with suspected influenza encephalopathy require urgent assessment by Intensive Care Unit staff for airway protection, ventilatory support, management of raised intracranial pressure, optimization of cerebral perfusion pressure, and correction of electrolyte imbalances. 1

Clinical Presentation and Recognition

Influenza encephalopathy presents with:

• Fever (present in 93% of cases) 2
• Altered mental status/encephalopathy
• Seizures (present in 68% of cases) 2
• Rapid progression (median 2 days from onset to hospitalization) 1
• May present with focal neurological signs, aphasia, and abnormal EEG 1
• Often preceded by respiratory symptoms, though these may be absent

Special Considerations

• Influenza A is particularly associated with acute necrotizing encephalopathy (ANE), a severe form with typical MRI abnormalities in the thalami, brainstem, and cerebral white matter 1
• H1N1 strain may cause more neurological manifestations than seasonal flu 1
• Patients rarely have viral antigens or nucleic acid in CSF 1

Immediate Management Algorithm

1. Airway and Breathing

   • Assess need for intubation and ventilatory support
   • Patients with falling level of consciousness require urgent ICU assessment 1

2. Circulation

   • Optimize cerebral perfusion pressure
   • Monitor for shock, which may accompany severe cases 3

3. Neurological Assessment

   • Immediate neurological specialist opinion (within 24 hours) 1
   • Assess for signs of raised intracranial pressure

4. Diagnostic Workup

   • Neuroimaging (CT or MRI) as soon as possible 1
   • Lumbar puncture unless contraindicated 1
   • Influenza testing by molecular assay from respiratory specimens 4
   • CSF analysis (protein, glucose, cell count, viral PCR)
   • Complete blood count (thrombocytopenia may be present) 2
   • Liver function tests (elevated enzymes common) 2

5. Treatment

   • Antiviral therapy (oseltamivir) should be started immediately upon suspicion 5
   • High-dose corticosteroids (methylprednisolone) 4, 2
   • Consider intravenous immunoglobulin (used in 66% of cases) 2
   • Anticonvulsants for seizure control 4
   • Mannitol for cerebral edema 4
   • In severe cases, consider additional immunomodulatory treatments such as tocilizumab (used in 51% of cases), plasmapheresis (32%), or anakinra (5%) 2

Monitoring and Follow-up

• Close monitoring in neurological ward, high dependency unit, or intensive care unit 1
• Monitor for complications:
  • Cerebral herniation (primary cause of death in 91% of fatal cases) 2
  • Seizures
  • Shock
  • Liver and renal dysfunction 3

Prognosis and Outcomes

• Mortality rate can be high (27% in recent pediatric cases) 2
• Among survivors, 63% had at least moderate disability at 90-day follow-up 2
• Some patients may recover fully within 2 weeks 4
• Outcomes range from complete recovery to severe neurological sequelae or death

Special Considerations

• Genetic testing for RANBP2 mutations should be considered, as these are associated with recurrent episodes of necrotizing encephalitis with respiratory viral infections 4, 2
• Annual influenza vaccination is especially important for ANE survivors and their household contacts 4
• Patients should not be discharged without either a definite or suspected diagnosis and arrangements for follow-up 1

Pitfalls to Avoid

1. Delaying antiviral treatment while awaiting confirmatory testing
2. Failing to recognize the rapid progression of influenza encephalopathy
3. Overlooking the need for multidisciplinary care involving neurologists, infectious disease specialists, and intensive care
4. Underestimating the severity - even previously healthy individuals can develop life-threatening complications
5. Missing the diagnosis in patients without respiratory symptoms

The management of influenza encephalopathy requires prompt recognition, aggressive treatment, and close monitoring to improve outcomes in this potentially devastating condition.