VHOSPITAL.CLINIC · Differential Diagnosis
Encephalitis vs Meningitis
Clinical comparison — shared symptoms, key differences, distinguishing diagnostic tests, treatment pathways, and when to seek urgent evaluation.
Condition Overview
Condition A
Encephalitis
Encephalitis is inflammation of the brain parenchyma, most commonly caused by viral infections (herpes simplex, enteroviruses). It presents with fever, altered consciousness, seizures, and focal neurological deficits; early antiviral treatment is crucial.
Condition B
Meningitis
Meningitis is inflammation of the meninges (membranes surrounding the brain and spinal cord), caused by bacteria, viruses, or fungi. Bacterial meningitis is a medical emergency causing severe headache, neck stiffness, fever, and potentially fatal if untreated.
Shared Symptoms — Why They're Confused
Both conditions present with 5 overlapping symptoms, making clinical differentiation essential.
Key Clinical Differences
Encephalitis
- Headache and fever
- Neck stiffness (bacterial meningitis > encephalitis)
- Altered consciousness (encephalitis > bacterial meningitis)
- CSF pleocytosis
Meningitis
- Infection of brain parenchyma causing altered consciousness and behaviour
- Seizures, focal neurological signs, psychiatric symptoms
- HSV is most common cause — requires emergency aciclovir
- MRI shows temporal lobe signal change in HSV encephalitis
Distinguishing Diagnostic Tests
| Test | Encephalitis | Meningitis |
|---|---|---|
| CSF analysis | Lymphocytic pleocytosis, elevated protein, HSV PCR positive (HSV encephalitis) | Bacterial: neutrophilic pleocytosis, very high protein, very low glucose; Viral: lymphocytes |
| MRI brain | T2/FLAIR signal in temporal lobes (HSV); diffuse oedema in encephalitis | Normal or meningeal enhancement; no parenchymal changes |
| EEG | Diffuse slowing or periodic lateralised discharges — brain parenchyma involved | Normal in viral meningitis; mildly abnormal in bacterial |
Treatment Approaches
Encephalitis
- •IV aciclovir (HSV encephalitis) immediately — do not wait for PCR
- •Treat other causes (autoimmune: immunoglobulins/steroids)
- •Anti-epileptic drugs for seizures
- •ICU for airway protection
Meningitis
- •Bacterial: IV ceftriaxone + dexamethasone immediately
- •Viral: supportive care
- •LP after CT head if no contraindications
- •Notify public health for bacterial meningococcal cases
When Doctors Consider Each Diagnosis
🔵 Consider Encephalitis when:
- →Altered consciousness, behaviour change, seizures, temporal lobe changes on MRI — start aciclovir immediately
🟢 Consider Meningitis when:
- →Predominantly headache + fever + neck stiffness + photophobia, normal consciousness — meningism triad
Explore Each Condition in Detail
Related Clinical Pages
Medical References
Content on this page is informed by evidence-based clinical sources including:
- World Health Organization (WHO)Global health guidance and disease classification
- National Health Service (NHS)UK clinical guidelines and patient information
- National Institute for Health and Care Excellence (NICE)Evidence-based clinical practice guidelines
- Centers for Disease Control and Prevention (CDC)US public health data and clinical recommendations
- PubMed – NCBIPeer-reviewed biomedical literature and clinical studies
- Cochrane LibrarySystematic reviews and meta-analyses in evidence-based medicine
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