Red flag to remember
Declining level of consciousness, unequal or sluggish pupils, widening pulse pressure, bradycardia, or irregular respirations (Cushing triad) indicating rising intracranial pressure — notify provider now.
What is encephalitis?
Unlike meningitis, which inflames the meninges, encephalitis affects the brain itself, so altered mental status and focal neurologic deficits are prominent. It presents with fever, headache, altered level of consciousness, seizures, and behavioral changes. It is a medical emergency because of the risk of increased intracranial pressure and lasting neurologic damage.
Key points to remember
- Caused mainly by viruses; herpes simplex virus is the most common sporadic cause and arboviruses (West Nile) spread through mosquito bites.
- Hallmark is altered mental status (confusion, behavioral changes, decreased level of consciousness) along with fever, headache, seizures, and focal deficits.
- Diagnosis relies on lumbar puncture (elevated lymphocytes, normal-to-elevated protein, normal glucose in viral cases), MRI, and PCR of cerebrospinal fluid.
- IV acyclovir is started immediately and empirically when herpes simplex encephalitis is suspected, before confirmation, because early treatment reduces mortality.
- Major complications include increased intracranial pressure, seizures, syndrome of inappropriate ADH, and permanent cognitive or motor deficits.
Common causes
- Viral (HSV), mosquito-borne
- Brain tissue inflammation
Signs & symptoms
- Fever, severe HA, ↓LOC
- Seizures, confusion
- Focal neuro deficits
Nursing priorities
- Perform frequent neurologic assessments and monitor for signs of increasing intracranial pressure.
- Administer IV acyclovir promptly as ordered and ensure adequate hydration to protect the kidneys.
- Institute seizure precautions and maintain a quiet, dimly lit environment to reduce stimulation.
- Maintain the head of bed at about 30 degrees with the head midline to promote venous drainage and control ICP.
- Monitor fluid balance, electrolytes, and intake/output for SIADH and dehydration.
Labs & values
CSF in viral encephalitis: elevated lymphocytes, protein normal to mildly elevated, glucose normal
Normal CSF opening pressure:5 to 15 mmHg (70 to 180 mm H2O)
Serum sodium135 to 145 mEq/L — monitor for hyponatremia from SIADH
Patient teaching
- Complete the full course of antiviral therapy as prescribed.
- Prevent mosquito-borne encephalitis by using insect repellent, wearing protective clothing, and avoiding standing water.
- Report recurrent headache, confusion, seizures, or behavioral changes during recovery.
- Understand that rehabilitation may be needed for residual cognitive or motor deficits.
- Maintain follow-up appointments to monitor recovery and neurologic status.
Red flags: report now
- Declining level of consciousness, unequal or sluggish pupils, widening pulse pressure, bradycardia, or irregular respirations (Cushing triad) indicating rising intracranial pressure — notify provider now.
- New or prolonged seizure activity (status epilepticus) requiring emergency intervention.
References
Clinical references for this topic
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