Meningitis & Encephalitis

Outline

Background

Core condition associated with significant morbidity and mortality.

• Encephalitis = infection of brain

• Meningitis = infection of meninges, connective tissue surrounding brain

Assessment

Presentation

• Meningism: headache, neck stiffness, photophobia, phonophobia, fevers

• Encephalitis: drowsiness, seizures, fevers; pre viral symptoms

Examination

• Unwell 

• Reduced GCS, photophobia

• Purpuric rash

• Fever, tachycardia +/- tachypnoea, hypotension, hypoxic

• Kernig's sign: Knee extension causes neck flexion

• Brudinski's sign: neck flexion is painful

Investigations

• CT-H

• Lumbar Puncture

• Blood cultures

• Meningococcal PCR

• FBC, electrolytes and urea, CRP, LFTs,

Diagnosis 

Diagnostic criteria: clinical, largely based of CSF results

Differentials

• Post viral meningism

• Alcohol related hangover

• Sepsis

• Primary neurological disorder- stroke, epilepsy, subarachnoid haemorrhage

Classification: aetiology- as per organism

Management

Due to high morbidity and mortality, diagnosis can be made clinically to facilitate early treatment

• Ceftriaxone - bacterial meningitis

• Dexamethasone - for streph pneumonia meningitis

• Aciclovir- for viral meningitis

• IVF

• Consider Neurology for seizures  prophylaxis (usually Levetiracetam)

• Investigations: septic screen + meningococcal PCR, lumbar puncture and often CT-Head

CSF 

See specific page: for full break down of CSF results

See Lumbar Puncture page for details

By Organism

Categorized

• Bacteria

• Viral

• Fungi

• Everything else: parasites, protoza and prions!

Bacterial

Meningococcal Meningitis

• Severe mortality- common for the infection to cause death too rapidly for antibiotics to have an effect

• Non blanching purpura late sign

• Post exposure prophylaxis: ciprofloxacin

• Management:

  • Ceftriaxone, 

  • Pen allergy- chloramphenicol

Streph pneumonia meningitis

• High protein, low glucose (< 50%) and very high neutrophils

• Management: ceftriaxone + dexamethasone

Neisseria meningitidis

• High protein, low glucose (< 50%) and very high neutrophils

Listeria

• Raised lymphocytes, high protein, low glucose

• Gram +ve bacilli on CSF

• Risk factors

  • Foreign travel to France, 

  • Eaten cheese (unpasteurised)

  • Pregnant

• Management: amoxicillin + gentamicin

  • If pregnant, just amoxicillin

Lyme Disease: see page

• History: tick bite, fatigue, 

• Examination: mononeuropathy

Tuberculosis

CSF 

• Very high protein, low glucose and lymphocytosis

• Mildly high presssure, often 20-30

Viral

Enterovirus

• Mildly raised protein, lower limit glucose & normal opening pressure

• Raised Leukocytes > 50%

Herpes Encephalitis

• HSV: bitemporal lobe oedema

• Management: aciclovir ?always indicated

Fungus

Cryptococcus

• Raised pressure > 25-30mmhg

• Concomitant HIV

• Raised protein, low glucose

• Management: amphotericin B

Deeper Dive

Timing

If bacterial meningitis is suspected, antibiotics must be given within the first hour. Sometimes the GP or ambulance will give IM Ceftriaxone or benzylpenicillin. 

Indications for CT-H prior to LP

• Symptoms or signs of raised intracranial pressure

  • New focal neurology including seizures or posturing

  • Abnormal pupillay reactions

  • GCS < 10

  • Progressive and sustained fall in consciousness

Auto-immune Encephalitis (AE)

Exam Cram

• Autoimmune Encephalitis is a reversible cause of Dementia, associated with ovarian teratomas

• Presentation: acute cognition and memory deficits in young individual

• Diagnosis: presence of anti-NMDA on lumbar puncture, signs on MRI-H, acute unexplained confusion

• Management: steroids

Resources and References

Page written in 2024.