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Meningitis

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Overview

Meningitis is the inflammation of the meninges and bacterial meningitis is the inflammation of the meninges due to bacteria. 

Meningococcal meningitis is the inflammation of the meninges due to Neisseria meningitidis (the meningococcus) and meningococcal septicaemia refers to sepsis caused by Neisseria meningitidis.

Viral meningitis is more common and benign than bacterial meningitis, but all cases of suspected meningitis should be considered bacterial until proven otherwise.

Epidemiology

  • Viral meningitis is more common 
  • Bacterial meningitis peaks in prevalence in infants and teenagers/young adults
  • Bacterial meningitis is rare – most healthcare professionals only see 1 or 2 cases

Causes

Bacterial Causes

  • Neonates (<3 months):
  • Infants and young children (3 months – 6 years):
    • Neisseria meningitidis
    • Streptococcus pneumoniae
    • Haemophilus influenzae
  • Adults and older children (6-60 years):
    • Neisseria meningitidis
    • Streptococcus pneumoniae
  • Elderly (>60 years):
    • Streptococcus pneumoniae
    • Neisseria meningitidis
    • Listeria monocytogenes
    • Immunocompromised
    • Listeria monocytogenes
    • Tuberculosis

Viral Causes

  • Enteroviruses e.g. coxsackie virus, echovirus  – most common
  • Herpes viruses e.g. herpes simplex (HSV), herpes zoster virus, cytomegalovirus (CMV)
  • Mumps
  • Measles
  • HIV

Risk Factors

  • Young age
  • Older age (>65 years)
  • Immunodeficiency e.g. HIV/chemotherapy
  • Incomplete immunisation
  • Cancer
  • Liver or kidney disease
  • Smoking
  • Overcrowding
  • Cochlear implants
  • Exposure to infected people
  • Any cause of hyposplenism e.g. sickle cell disease

Presentation

Overview

There are no reliable ways of differentiating between viral and bacterial meningitis. Bacterial meningitis should be considered in any patient with the following features:

  • Headaches
  • Neck stiffness
  • Fever
  • Altered consciousness
  • Vomiting
  • Confusion
  • Photophobia
  • Seizures
  • Petechial or purpuric rashes – indicate meningococcal infection and sepsis
  • Kernig’s sign – seen in around 10% of patients with bacterial meningitis
    • Pain in the lower back or back of the thigh when extending the knee when the hip is flexed to 90°
  • Brudzinski’s sign – seen in around 9% of patients with bacterial meningitis
    • Forced flexion of the neck results in reflex hip flexion

Features similar to meningitis, particularly neck stiffness and nuchal rigidity, are collectively known as meningism.

Features suggesting raised intracranial pressure

Features suggesting raised intracranial pressure may be present. These are important to identify as they change management steps:

  • Focal neurological deficits:
  • Cranial nerve palsies:
    • CN III (oculomotor nerve) – ptosis, dilated and fixed pupil, the eye is ‘down and out’
    • CN IV (trochlear nerve) – defective downward gaze and vertical diplopia
    • CN VI (abducens nerve) – defective eye abduction and horizontal diplopia
    • CN VII (facial nerve) – facial drooping
    • CN VIII (vestibulocochlear nerve) – balance problems/hearing impairment
  • Papilloedema
  • Reduced or fluctuating level of consciousness:
  • Abnormal posture or posturing
  • Abnormal ‘doll’s eye’ movements

Differential Diagnoses

Bacterial meningitis

  • CSF findings:
    • Colour: cloudy/turbid
    • Protein: elevated, >1.5g/L
    • Glucose: <50% of plasma glucose
    • White cell count: raised, mostly neutrophils
    • Opening pressure, usually raised

Viral meningitis

  • Clinical features may be identical
  • CSF findings:
    • Colour: clear
    • Protein: raised/upper limit of normal
    • Glucose: normal
    • White cell count: raised, mostly lymphocytes
    • Opening pressure: may be normal/raised

Encephalitis

  • Fever and altered behaviour, speech, or motor function suggest encephalitis
  • CSF findings may be the same as viral meningitis

Tuberculous meningitis

  • Pulmonary features of tuberculosis may be present e.g. cough/haemoptysis/weight loss 
  • CSF findings:
    • Colour: slightly cloudy, may have a fibrin web
    • Protein: elevated, usually much more than bacterial meningitis
    • Glucose: <50% of plasma glucose
    • White cell count: raised, mostly lymphocytes

Fungal meningitis

  • Patients may have HIV/other causes of immunodeficiency
  • CSF findings:
    • Colour: cloudy
    • Protein: protein
    • Glucose: <50%
    • White cell count: raised, mainly lymphocytes
    • Opening pressure: elevated
    • Other: India ink staining may be positive

Subarachnoid haemorrhage

Both may have meningism

  • Patients usually have a sudden-onset “thunderclap” headache
  • CSF findings:
    • Colour: may be bloodstained or xanthochromia seen ≥12 hours after
    • Protein: elevated/upper limit of normal
    • Glucose: normal/low
    • White cell count: elevated
    • Red cell count: elevated, significantly higher than white cells
    • Opening pressure: elevated

Referral and Investigations

Referral in primary care

  • Immediate IM benzylpenicillin then emergency transfer to hospital via 999
    • Do not delay admission to hospital if antibiotics are not available immediately
    • Withhold IM benzylpenicillin if allergic

In secondary care

  • Blood cultures within 1 hour of arrival to hospital:
    • Ideally before giving antibiotics but do not delay treatment
  • Lumbar puncture (LP) within 1 hour of arrival to hospital and CSF analysis:
    • Ideally before giving antibiotics but do not delay treatment
    • Do not perform if contraindicated – see below
    • Details on interpreting lumbar puncture results can be found here
  • Blood glucose – for hypo-/hyperglycaemia
  • CT scans are not normally indicated:
    • Unless there are features of raised intracranial pressure
  • Full blood count (FBC):
    • May show leukocytosis or neutropenia/thrombocytopenia if severe
  • Liver function tests (LFTs):
    • May be raised
  • Urea and electrolytes (U&Es):
    • May show acidosis or electrolyte abnormalities
  • C-reactive protein (CRP):
    • Raised in infection
  • Coagulation screen:
  • Venous blood gas:
    • May show elevated lactate which can suggest shock
  • Serum pneumococcal/meningococcal PCR
  • Viral PCR
  • HIV testing – with consent in all patients

Lumbar puncture contraindications

Contraindications to a lumbar puncture include:

  • Signs of raised intracranial pressure (mentioned above in Presentation)
  • Shock
  • Extensive or spreading purpura
  • Infection at the lumbar puncture site
  • Coagulation abnormalities:
    • Derangement from the normal range
    • Platelets below 100×109/L
    • Patient on anticoagulation
  • Respiratory insufficiency

Management

In the community

  • 1st-line: IM benzylpenicillin + emergency admission to hospital via 999
  • Do not give benzylpenicillin if allergic

In hospital

  • 1st-line: initial empirical IV antibiotics (even if viral) while awaiting LP results:
    • If <3 months: IV cefotaxime + amoxicillin/ampicillin
    • If 3 months – 50 years: IV cefotaxime/ceftriaxone
    • If >50 years: IV cefotaxime/ceftriaxone + amoxicillin/ampicillin
    • If allergic to penicillin or cephalosporins, prescribe IV chloramphenicol
  • Targeted antibiotics once cultures and sensitivities identified
  • Consider giving IV dexamethasone to reduce the chance of neurological complications (e.g. sensorineural deafness) except in:
    • Septic shock
    • Meningococcal septicaemia
    • Immunodeficiency
    • Meningitis post-surgery

Confirmed viral meningitis

  • 1st-line: supportive care, some specialists may start aciclovir

Intensive care referral

Involve the intensive care team if patients have:

  • Signs of increased intracranial pressure
  • Frequent or uncontrollable seizures
  • Altered mental state (Glasgow Coma Scale score less than 9 or a drop of 3 or more)
  • Signs of sepsis
  • A rapidly evolving rash
  • Consider intubation if GCS <12.

All patients

  • Notify Public Health England – meningitis is a notifiable disease
  • Give prophylaxis to people who have had close contact within the last 7 days:
    • Options are oral ciprofloxacin or rifampicin

Monitoring

  • All children should be reviewed by a paediatrician 4-6 weeks after discharge
  • Give prophylaxis to people who have had close contact within the last 7 days:
    • Options are oral ciprofloxacin or rifampicin

Complications

  • Neurological complications:
    • Sensorineural hearing loss – most common
    • Seizures
    • Cognitive impairment
    • Motor deficits
    • Visual impairments
    • Focal neurological deficits
  • Septic shock
  • Intracerebral abscess
  • Increased intracranial pressure

Prognosis

  • The prognosis depends on the pathogen, the age of the patient, and the severity of the illness
  • Viral meningitis has a good prognosis and usually resolves within 10 days
  • Poor prognostic factors in adults are:
    • Low GCS on admission
    • Tachycardia
    • No rash
    • Thrombocytopenia
    • Elevated ESR
    • Positive blood culture

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