tutorial 3 - meningitis & septicaemia Flashcards
What organism most commonly causes chronic meningitis?
Mycobacterium tuberculosis
What are the gross findings of examination of the brain in acute bacterial meningiti
Congestion (redness), swelling/oedema (widened gyri, narrow sulci), pus accumulation, haemorrhage
What are the histological findings of the subarachnoid space in acute bacterial meningitis?
Congested blood vessels, infiltration of neutrophils, fibrin exudate
What type of chronic inflammation does TB cause?
Granulomatous inflammation
What are the components of a TB granuloma?
Inner caseous necrosis, collar of activated lymphocytes surrounded, activated macrophages (called epithelioid cells), Langhans giant cells
What are Langhans giant cells?
Giant cells in TB granulomas formed by fusion off multiple macrophages
What type of immune cells are present in TB granuolomas?
Lymphocytes
What are the histological findings in the subarachnoid space in TB meningitis?
multiple TB granulomas
What are the gross findings of examination of a brain with TB meningitis?
Nodules on meningeal surface (actually multiple adjacent granulomas)
What is the pathogenesis of septic shock caused by N. meningitidis?
Infection causes septicaemia, systemic inflammatory state triggered, complement activated, endothelial cell activation leads to:
1. increased vascular permeability
2. vasodilation -> shock
3. DIC -> microthrombi formation (skin, adrenals, kidneys)
Why is DIC also sometimes caused consumption coagulopathy?
Because platelets and clotting factors are widely consumed in the thrombotic process resulting in haemorrhage
What are the 3 key organs affected by microthrombi & haemorrhage in DIC?
- Skin - petechial/ecchymotic rash
- Adrenal glands - necrosis/haemorrhage (Waterhouse-Friderichson Syndrome)
- Kidneys - micro-thrombi in glomeruli leads to renal failure
What is the term for adrenal necrosis/haemorrhage due to DIC?
Waterhouse - Friderichsen Syndrome
