Meningitis 061021

Question 1

What are the routes of pathogen entry into the CNS

Answer 1

 Haematogenous (e.g. pneumococcus, meningococcus)
 Direct implantation (e.g. trauma)
 Local extension (e.g. from the ear)
 PNS into CNS (e.g. rabies)

Question 2

Neurological damage is caused by

Answer 2

o Direct bacterial toxicity
o Indirect inflammatory process and cytokine release and oedema (n.b. tight space, oedema = bad)
o Shock, seizures and cerebral hypoperfusion

Question 3

4 sepsis processes

Answer 3

• Capillary Leak – albumin and other plasma proteins leads to hypovolaemia
• Coagulopathy – leads to bleeding and thrombosis (endothelial injury results in platelet release reactions, the protein C pathway and plasma anticoagulants are affected)
• Metabolic Derangement – particularly acidosis
• Myocardial failure – and multi-organ failure

Question 4

Chronic meningitis

Answer 4

o Similar presentation to acute meningitis (fever, headache, neck stiffness) but lower mortality (0.000055%)
o More common in immunosuppressed patients
o Involves the meninges and basal cisterns of the brain and spinal cord with dilatation of ventricles
o Complications:
 Tuberculous granulomas
 Tuberculous abscesses (i.e. enhancing thick-walled abscesses)
 Cerebritis

Question 5

Aseptic meningitis

Answer 5

o Presentation: headache, stiff neck, photophobia
o A non-specific rash may accompany these symptoms
o Organisms (80-90% of organisms) – VIRAL:
 Coxsackie group B
 Echoviruses
o Usually occurs in children <1 year
o Self-limiting disease that resolves in 1-2 weeks

Question 6

Whats the leading cause of encephalitis

Answer 6

o Mainly transferred by mosquitoes and birds (European birds spend the winter in Southern Europe and Africa)
o West Nile Virus has spread across the USA but hasn’t reached the UK yet

Question 7

Nonviral encephalitis examples

Answer 7

o Bacterial – Listeria monocytogenes
o Amoeba (spread by direct extension through cribriform plates):
 Naegleria fowleri Habitat – warm water
 Acanthamoeba spp. & Balamuthia mandrillaris Brain abscess, aseptic & chronic meningitis
o Toxoplasmosis (obligate intracellular protozoal parasite – Toxoplasma gondii):
 Spread via the faeco-oral, transplacental or organ transplant route
 Causes severe infection in immunocompromised patients
 Affected organs = grey & white matter of brain, retinas, alveolar lining of lungs, heart, skeletal muscle

Question 8

meningitis treatment

Answer 8

• Ceftriaxone is good at killing N. meningitidis, S. pneumoniae, HiB and E. coli
o However, Ceftriaxone does NOT cover Listeria monocytogenes  this requires amoxicillin
o Hence why, if >50yo, treat with amoxicillin