6th August 2024

Encephalitis and meningitis

Encephalitis occurs when there is inflammation of the brain parenchyma, whereas meningitis refers specifically to inflammation of the meninges. There may be overlap in the clinical syndrome, and they may indeed coexist (meningoencephalitis). A brief comparison is shown below.

	Encephalitis	Meningitis
Common causes	Primarily viral (e.g. HSV type 1, VZV (Varicella zoster virus), West Nile, rabies) Bacterial, fungal, parasitic, and autoimmune aetiologies much rarer	Bacterial: L. monocytogenes (<1 and >60 years), N. meningitidis, S. pneumoniae (most common) Viral: enteroviruses (most common), HSV type 1, HIV (rare)
Classical presenting features	Fever Headache Seizures Altered conscious level or mental state	Fever Headache Nausea Neck stiffness Photophobia Seizures (rarer) Altered conscious level or mental state
Examination findings	Focal neurological deficits Flaccid paralysis (West Nile virus) Rash or eruption	Meningism Purpura or petechiae (N. meningitidis) Focal neurological deficits (rarer)
Investigation findings	Radiology CT frequently normal MRI may show focal involvement (e.g. temporal lobes in HSV) Classical LP findings WCC ↑ (usually lymphocytes) Protein ↑ Glucose ↔ (↓ if mumps) EEG (electroencephalogram) Can show focal abnormality (e.g. temporal discharges) but findings are frequently non-specific	Radiology Not typically indicated unless signs of ↑ICP (intracranial pressure) MRI may show meningeal enhancement Classical LP findings WCC ↑↑ if bacterial, ↑ if viral or TB (all can be lymphocytic in early infection) Protein ↑↑ if bacterial, ↑ if viral, TB, syphilis or Lyme disease Glucose generally ↓ but can be ↓↓ especially if TB/fungal Values may not be as raised in early bacterial meningitis
Management strategies	If acute viral encephalitis suspected, aciclovir 10 mg/kg IV TDS (may require renal adjustment) until causative organism confirmed, which may require adjustment of therapy If meningeal irritation, also cover with ceftriaxone 2 g IV BD	If bacterial meningitis suspected, ceftriaxone 2 g IV BD and dexamethasone 10 mg IV QDS until causative organism identified, which may require adjustment of therapy or a switch to e.g. anti-TB or antifungal agents Viral meningitis must be confirmed prior to switching to supportive management – analgesia, fluids, antipyretics

Encephalitis

Meningitis

Common causes

Primarily viral (e.g. HSV type 1, VZV (Varicella zoster virus), West Nile, rabies)

Bacterial, fungal, parasitic, and autoimmune aetiologies much rarer

Bacterial: L. monocytogenes (<1 and >60 years), N. meningitidis, S. pneumoniae (most common)

Viral: enteroviruses (most common), HSV type 1, HIV (rare)

Classical presenting features

Fever

Headache

Seizures

Altered conscious level or mental state

Fever

Headache

Nausea

Neck stiffness

Photophobia

Seizures (rarer)

Altered conscious level or mental state

Examination findings

Focal neurological deficits

Flaccid paralysis (West Nile virus)

Rash or eruption

Meningism

Purpura or petechiae (N. meningitidis)

Focal neurological deficits (rarer)

Investigation findings

Radiology

CT frequently normal

MRI may show focal involvement (e.g. temporal lobes in HSV)

Classical LP findings

WCC ↑ (usually lymphocytes)

Protein ↑

Glucose ↔ (↓ if mumps)

EEG (electroencephalogram)

Can show focal abnormality (e.g. temporal discharges) but findings are frequently non-specific

Radiology

Not typically indicated unless signs of ↑ICP (intracranial pressure)

MRI may show meningeal enhancement

Classical LP findings

WCC ↑↑ if bacterial, ↑ if viral or TB (all can be lymphocytic in early infection)

Protein ↑↑ if bacterial, ↑ if viral, TB, syphilis or Lyme disease

Glucose generally ↓ but can be ↓↓ especially if TB/fungal

Values may not be as raised in early bacterial meningitis

Management strategies

If acute viral encephalitis suspected, aciclovir 10 mg/kg IV TDS (may require renal adjustment) until causative organism confirmed, which may require adjustment of therapy

If meningeal irritation, also cover with ceftriaxone 2 g IV BD

If bacterial meningitis suspected, ceftriaxone 2 g IV BD and dexamethasone 10 mg IV QDS until causative organism identified, which may require adjustment of therapy or a switch to e.g. anti-TB or antifungal agents

Viral meningitis must be confirmed prior to switching to supportive management – analgesia, fluids, antipyretics

Complete Guide to Clinical Genetics ST3 Application and Recruitment (2027)

Written by Medibuddy. Last updated: October 2026. Clinical Genetics is

Clinical Genetics ST3

Complete Guide to Clinical Radiology ST3 Application and Recruitment (2027)

Recruitment paused: NHS England is not running Clinical Radiology ST3+ recru

Clinical Radiology ST3

Complete Guide to Paediatric Surgery ST3 Application and Recruitment in United Kingdom (2026)

Written by Medibuddy. Last updated: October 2026. If you’re planning

Paediatric Surgery ST3

Take your subscriptions with you

Our mobile app allows you to access your interview and exam question banks wherever you are.