Key Facts

Bacterial meningitis is a life-threatening emergency requiring immediate antibiotics. Lumbar puncture should not delay treatment. Dexamethasone reduces mortality in pneumococcal meningitis and should be given before or with the first dose of antibiotics.

Epidemiology

Bacterial meningitis: ~2-5 per 100,000/year in UK. Viral meningitis: more common (~5-10 per 100,000/year) but usually self-limiting. Peak incidence: neonates and young children, and adolescents/young adults (meningococcal). Vaccination has dramatically reduced incidence (MenB, MenACWY, PCV, Hib).

Aetiology

Bacterial (by age group):

• Neonates (<3 months): Group B Streptococcus, E. coli, Listeria monocytogenes
• Children (3 months-6 years): N. meningitidis, S. pneumoniae, H. influenzae (reduced by Hib vaccine)
• Adults: S. pneumoniae (commonest in >50 years), N. meningitidis (commonest in adolescents)
• Elderly/immunocompromised: S. pneumoniae, Listeria monocytogenes, Gram-negatives
• Post-neurosurgery/trauma: S. aureus, Gram-negatives, coagulase-negative staphylococci

Viral: enterovirus (commonest), HSV-2, mumps, VZV, HIV

Other: TB (subacute, basal meningitis), fungal (Cryptococcus — immunocompromised)

Pathophysiology

Bacteria reach the meninges via haematogenous spread (most common), direct extension (sinusitis, otitis media), or direct inoculation (trauma, surgery). Bacterial multiplication in CSF → inflammatory response (cytokines, neutrophil recruitment) → blood-brain barrier disruption → cerebral oedema, raised ICP → reduced cerebral perfusion → ischaemia/infarction. Meningeal irritation causes classic signs of meningism.

Classic Features

• Headache: severe, generalised
• Fever: often high
• Neck stiffness (meningism): resistance to passive neck flexion
• Photophobia: light sensitivity
• Nausea/vomiting
• Altered consciousness: confusion → drowsiness → coma

Signs of Meningism

• Kernig sign: pain/resistance on extending the knee with hip flexed to 90°
• Brudzinski sign: involuntary hip/knee flexion on passive neck flexion

Meningococcal-Specific

• Non-blanching petechial/purpuric rash: meningococcal septicaemia; may progress to DIC, shock (Waterhouse-Friderichsen syndrome — bilateral adrenal haemorrhage)

Neonatal/Infant

• Non-specific: irritability, poor feeding, bulging fontanelle, high-pitched cry, hypotonia
• Neck stiffness may be ABSENT in neonates

Red Flags

• Non-blanching rash + fever → meningococcal sepsis → give IM benzylpenicillin in community IMMEDIATELY
• GCS ≤12 or declining → ITU
• Seizures → complicated meningitis
• Focal neurological signs → consider abscess or empyema

Urgent Bloods

• Blood cultures: BEFORE antibiotics if possible (positive in ~50% of bacterial meningitis)
• FBC, CRP, procalcitonin: raised in bacterial infection; procalcitonin helps differentiate bacterial from viral
• U&Es, glucose: paired plasma glucose with CSF glucose
• Coagulation: DIC screen (meningococcal sepsis)
• Lactate: raised in sepsis
• Meningococcal/pneumococcal PCR: on blood (even after antibiotics)

Lumbar Puncture

• Perform unless contraindicated: signs of raised ICP (papilloedema, focal deficit, GCS <12, seizures) → CT head first → if mass lesion/midline shift → do NOT LP → treat empirically
• CSF analysis: opening pressure, appearance, WCC + differential, protein, glucose (with paired plasma), Gram stain, culture, PCR (meningococcal, pneumococcal, viral panel)

CSF Findings

Imaging

• CT head: before LP if contraindications to LP present; identifies complications (abscess, hydrocephalus, empyema)
• MRI brain: meningeal enhancement; complications

Empirical Antibiotics (NICE NG51 / BNF)

Adults:

• IV ceftriaxone 2g BD (or cefotaxime 2g QDS) — first-line
• Add IV amoxicillin 2g 4-hourly if age >60, immunocompromised, or Listeria risk (covers Listeria)
• IV dexamethasone 0.15mg/kg QDS × 4 days: give BEFORE or WITH first antibiotic dose; continue only if pneumococcal meningitis confirmed (discontinue if meningococcal); reduces mortality and neurological sequelae in pneumococcal meningitis (de Gans trial)

Neonates:

• IV cefotaxime + IV amoxicillin (covers GBS, E. coli, Listeria)

Post-neurosurgery/trauma:

• IV vancomycin + IV meropenem (covers S. aureus, Gram-negatives)

Duration

• Meningococcal: 7 days IV
• Pneumococcal: 14 days IV
• Listeria: 21 days IV (amoxicillin ± gentamicin)
• GBS (neonatal): 14-21 days IV

Supportive

• ITU if GCS <12, shock, respiratory failure
• Fluid resuscitation (avoid overhydration — risk of cerebral oedema)
• Seizure management: IV lorazepam, levetiracetam, or phenytoin
• ICP management if raised

Public Health (Meningococcal)

• Notify Public Health England (notifiable disease)
• Close contact prophylaxis: ciprofloxacin 500mg STAT PO (adults) or rifampicin 600mg BD × 2 days
• Close contacts: household members, kissing contacts, those who shared a bedroom in past 7 days

Referral Criteria

• All suspected bacterial meningitis: emergency hospital admission
• ITU: shock, GCS deterioration, respiratory failure
• Infectious diseases: complex/atypical organisms

Bacterial meningitis mortality: overall ~20%; pneumococcal ~30%, meningococcal ~5-10%, Listeria ~20-30%. Neurological sequelae in ~20-30% of survivors: hearing loss (most common — 10%), cognitive impairment, seizures, focal neurological deficits, hydrocephalus. Meningococcal septicaemia: mortality ~10-20%; survivors may require amputation (DIC/purpura fulminans). Viral meningitis: excellent prognosis; self-limiting over 7-10 days. TB meningitis: ~30% mortality; significant morbidity in survivors.

UK Meningitis Vaccination Schedule

When NOT to LP (CT First)