Meningitis & Encephalitis

Exam Cram

• Meningitis describes inflammation of the meninges (connective tissue around brain & spinal cord) and Encephalitis describes inflammation of the brain; both are commonly caused by infection

• Presentation: 

  • Meningism: headache, photophobia, neck stiffness & fever

  • Confusion/ delirium, seizures and fever

• Investigations: lumbar puncture +/- CT-H

• Management: ceftriaxone, dexamethasone, acyclovir (depending on organism)

Outline

Background

Core condition associated with significant morbidity and mortality.

• Encephalitis = infection of brain

• Meningitis = infection of meninges, connective tissue surrounding brain

Assessment

Presentation

• Meningitis : 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

Presentation

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

Management

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. 

The timeline below is controversial. I will start with the rational behind it, then discuss reasons against. 

1. CT-Head

2. Lumbar Puncture

3. IV Treatment

This is the traditional pathway. A CT-H is used to rule out raised ICP to ensure the patient doesn't cone during the lumbar puncture procedure. The Lumbar Puncture is the most useful investigation to guide the diagnosis and long term management. Taking this after antibiotics may ensure a negative result which is difficult to intepret. 

The argument against that pathway is time. The majority of ?meningitis patients will not have raised ICP and there is an argument a CT-H creates an unnecessary delay. If the patient is very unwell and the lumbar puncture is experiencing significant delays, it is reasonable to start treatment prior to getting the CSF sample. Ultimately patient safety trumps is paramount. 

Auto-immune Encephalitis

• Antibodies: anti-NMDA

• Associatd with ovary teratoma

• Presentation: cognition and memory defects, insidious; seizures & psychosis, abnormal movements

• Management: steroids

Resources and References

Page written in 2024.