Meningitis (Bacterial)

Question 1

Define Meningitis & State Bacterial causative agents

Answer 1

Life-threatening inflammation of the meninges caused by pathogens (in bacterial meningits, the meningeal covering looks white with exudative material)

Bacteria:

• Neisseria meningitidis (meningococcal) - gram -ve
• Streptococcus pneumoniae (pneumococcal)
• Haemophilus influenzae B - gram -ve
• Group B Streptococcus (S. agalactiae)
• Listeria monocytogenes
• E.Coli** (almost exclusively babies) - **gram -ve
• Tuberculosis (in reactivated)

Question 2

Explain the aetiology/risk factors for Meningitis

Answer 2

• Immunocompromising conditions (Listeria)
  
  • Leukaemia, Lymphoma
  • HIV
  • Old age
  • Asplenia/Hyposplenia leaves one susceptible to encapsulated bacteria (S. pneumoniae, H. influenzae b)
  • Sickle cell disease
• Crowding/close contact
  
  • N. meningitidis - uni students
  • Strep pneumoniae & HiB respiratory droplet
• Recent travel to endemic areas e.g. Sub-Saharan Africa (N. meningitidis)
• Unpasteurised cheese/milk (Listeria)
• Alcohol misuse (Listeria)

Question 3

Summarise the epidemiology of meningitis

Answer 3

• Strep pneumoniae can affect all age groups
• Babies/Infants:
  
  • Group B strep (Ass/w extended labour/delivery)
  • Listeria monocytogenes
  • E. coli
• Young teens/adults:
  
  • Neisseria mengitidis: sharing respiratory or throat secretions (saliva or spit). This typically occurs during close (coughing or kissing) or lengthy (living together) contact - common in university students
• Older people:
  
  • Listeria monocytogenes: This affect elderly people because they have a degree of immunocompromisation

Question 4

Recognise the presenting symptoms of meningitis

Answer 4

• (Acute) headache
• Neck Stiffness
• Fever
• Seizures
• Photophobia
• Vomiting
• Irritability, refusing feeds (in babies)
• Altered mental status (this could be the only presenting sign in elderly pts)
• If a patient has a non-blanching purpuric rash ± above symptoms suspect MENINGOCOCCAL SEPTICAEMIA

Cerebral function usually remains normal in a patient with meningitis while in encephalitis, abnormalities in brain function are a differentiating feature, including altered mental status.

NOTE: Do not exclude the diagnosis of meningitis just because ALL classic symptoms are absent.

Question 5

Recognise the signs of meningitis on physical examination

Answer 5

• Signs of raised ICP (focal neuro signs)
  
  • CN palsy (eye movements)hearing difficulty (CN8)
  • Bulging fontanelle
  • Papilloedema (enlarged blind spot is seen)
  • Cushing’s triad (HTN, bradycardia, dyspnoea)
• Confusion (low AMTS)
• Photophobia
• Fever
• non-blanching Purpuric rash
• Kernig’s sign (not sensitive - 9%)
  
  • Cannot/Too painful to straighten leg whilst hip is flexed
• Brudzinski’s sign (not sensitive -11%)

Forced flexion of the neck elicits a reflex flexion of the hips

Question 6

Identify appropriate investigations for meningitis and interpret the results

Answer 6

If meningiococcal septicaemia is suspected, give empirical IV Ceftriaxone/Cefotaxime IMMEDIATELY before any investigations

• 1st LINE: Lumbar Puncture within 1 HOUR OF ARRIVAL and ideally prior to giving antibiotics (but don’t let it delay).
• C/Is include (don’t use CT to determine raised ICP):
  
  • Signs of raised ICP (Cushing’s triad, papilloedema, low GCS)
  • Coagulopathy
  • Infection at site
• Assess the CSF for​
  
  • CSF/Plasma glucose ratio - low glucose CSF in bacterial meningitis
  • CSF cell count (high WCC, may be normal if immunocompromised)
  • CSF MCS & Gram stain

If there is C/I to LP, then delay it until C/I are resolved

Bloods (as part of ABCDE assessment)

• FBC:
  
  • Raised WCC & CRP
  • Coagulation screen to show signs of DIC (diminished platelets, prolonged PT, increased d-dimer, low fibrinogen)
• BLOOD CULTURE (x2 sets)
  
  • within 1 hour of arrival at the hospital and ideally prior to giving antibiotics to identify the causative organism and target treatment accordingly.
• VBG shows elevated lactate with sepsis (> 4 mM)
• Whole blood PCR to test for N. meningitidis

Question 7

Generate a management plan for meningitis

Answer 7

• In the community, give IM BENZYLPENICILLIN to suspected meningococcal meningitis (indicated by non-blanching rash) cases before URGENT REFERRAL to hospital - if non-meningiococcal only offer IM BENPEN if urgent transfer is not possible
• Treatment:
  
  • Give empirical antibiotics, IV Ceftriaxone (along with dexamethasone - not if septicaemia)
    
    • Do not let blood culture delay Abx
  • Once MC&S returns, give targeted antibiotics
  • If loss of consciousness, consider IV acyclovir to cover viral encaphalitis

Question 8

Identify the possible complications of meningitis and its management

Answer 8

• Septic shock
• Hearing loss
• Cognitive problems
• Seizures (benzodiazepines)
• Hydrocephalus (self-resloves)
• Waterhouse-Friedrichsen:
  
  • In meningiococcal sepsis, the inflamatory process causes tissue factor release which triggers DIC causing large ecchymoses and haemorrhage
  • Bilateral Haemorrhage into the adrenal glands lead to failure –> leading to shock

Question 9

Summarise the prognosis for patients with meningitis

Answer 9

• Generally, with prompt and adequate antimicrobial and supportive therapy, the outcome after acute bacterial meningitis is excellent.
• However, prognosis does depend on multiple factors such as age, presence of comorbidity, causative pathogen, and severity at presentation

Question 10

Viral, Parasitic and Fungal causative organisms:

Answer 10

VIRAL (aseptic meningitis)

• Enterovirus - MOST COMMON
  
  • coxsackieviruses
  • echoviruses
• HSV 2

FUNGAL

• Cryptococcus neoformans
• Candida albicans
• Coccidoides

Protozoan/Parasite:
* TOXOPLASMOSIS (intracellular obligate)