Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Encephalitis

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In one line

·A virus sneaks into brain tissue—or the body's defense system mistakenly attacks the brain—and both cause the brain to swell inside the hard skull.

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Normal physiology

·The brain is a soft, delicate organ that controls everything you think, feel, and do. It sits inside a hard skull and floats in a clear fluid called cerebrospinal fluid (CSF) that cushions it like bubble wrap. A special barrier—the blood-brain barrier—lines the tiny blood vessels inside the brain and acts like a strict security gate: it lets oxygen and sugar through to feed brain cells but blocks most germs, toxins, and even many medicines.

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What goes wrong

·A virus breaks through the blood-brain barrier and starts copying itself inside brain cells, killing them. Or the immune system gets confused and makes antibodies that attack the brain's own neurons by mistake. Either way, brain tissue swells, electrical signals misfire, and normal thinking, memory, and movement fall apart.

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Hallmark signs

·Fever
·Headache
·Confusion or change in behavior
·Seizures
·Weakness or trouble moving one side of the body
·Trouble speaking or understanding words
·Stiff neck
·Sensitivity to light (photophobia)

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Red flags · escalate now

·Seizures or repeated jerking movements
·Cannot stay awake or is very hard to wake up
·Sudden weakness or numbness on one side of the body
·Severe confusion or aggressive, strange behavior that is brand new
·Trouble breathing or very slow, irregular breathing

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Workup

·Lumbar puncture (spinal tap) with cerebrospinal fluid (CSF) analysis—cell count, protein, glucose, Gram stain, and culture
·CSF PCR (polymerase chain reaction) for herpes simplex virus (HSV-1 and HSV-2)
·Brain MRI with and without contrast (or head CT if MRI is not available quickly)
·Electroencephalogram (EEG)—recording of brain electrical activity
·Blood tests: complete blood count (CBC), comprehensive metabolic panel (CMP), and blood cultures
·CSF testing for autoimmune antibodies (anti-NMDA receptor, anti-LGI1, anti-CASPR2, anti-GAD65, others) if viral tests are negative or clinical picture suggests autoimmune encephalitis
·CSF opening pressure measured during lumbar puncture

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Treatment

·IV acyclovir 10 mg/kg every 8 hours (or 30 mg/kg/day divided into three doses), started immediately even before test results return
·Anti-seizure medication—lorazepam 0.1 mg/kg IV (up to 4 mg per dose) for active seizures; levetiracetam 1000–1500 mg IV load (then 500–1000 mg every 12 hours) or fosphenytoin 15–20 mg phenytoin equivalents (PE) per kg IV load for seizure prevention
·IV methylprednisolone 1 gram daily for 3–5 days or IV immunoglobulin (IVIG) 2 g/kg total dose divided over 2–5 days, if autoimmune encephalitis is suspected or confirmed
·Mannitol 0.25–1 g/kg IV bolus over 15–30 minutes or hypertonic saline (3% NaCl) 250 mL IV bolus to reduce intracranial pressure if signs of brain herniation appear (blown pupil, posturing, sudden decreased consciousness)
·Supportive care in the ICU—mechanical ventilation if needed to protect the airway, fever control with acetaminophen 15 mg/kg every 4–6 hours (max 4 grams per day in adults) or cooling blanket, head of bed elevated 30 degrees, and hourly neurologic checks

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NCLEX trap

·Encephalitis needs acyclovir started right away for HSV (herpes simplex virus, the most common treatable cause). The virus destroys brain cells in hours. Antibiotics kill bacteria, not viruses. Start acyclovir immediately — even before test results come back — to save brain tissue.
·Encephalitis swells the brain and can raise pressure inside the skull dangerously high. Always get a CT or MRI first to check for swelling before doing a lumbar puncture. If pressure is too high, the needle can make the brain shift and herniate (squeeze down through the opening at the skull base), which crushes the brainstem and kills the patient.
·In encephalitis, you must give acyclovir for 14 to 21 days, even if the patient looks better early. The virus hides deep in brain cells and is stubborn. Stopping too soon lets it come roaring back and destroy more brain tissue. Treat the full course.
·In encephalitis, fever is just one clue. The real danger is brain swelling that crushes the brainstem (the bottom part of the brain that controls breathing and heartbeat) or causes seizures that will not stop (status epilepticus). Treat swelling with careful fluid management and head-of-bed elevation, stop seizures with anti-seizure meds, and watch breathing closely. Fever control is secondary.
·Encephalitis — especially HSV encephalitis — often scars the temporal lobes (the brain's memory and emotion centers) permanently. Even with perfect treatment started early, some patients end up with lasting memory problems, behavior changes, or trouble learning. Warn the family early so they can plan for rehab and long-term support.
·Some encephalitis is caused by the immune system mistakenly attacking brain cells, not by a virus. Clues include unusual psychiatric symptoms (hallucinations, bizarre behavior), abnormal movements (jerking, stiffness), or certain antibodies in the CSF (like anti-NMDA receptor antibodies). These patients need immunotherapy — steroids, IVIG (intravenous immunoglobulin, donated antibodies that calm the immune system), or plasmapheresis (filtering the blood to remove attacking antibodies) — not just antivirals. Know the difference from CSF findings, imaging, and the clinical picture.

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