Lecture 34: Fever and Headache Flashcards
In meningitis explain where the infection is taking place using anatomical terms:
Inflammation occurs in the sub-arachnoid space and in later stages can extend to the surface of the brain.
(CSF - contains pathogen, WBC, inflammatory proteins, cell debris)
What are the most common causes of fever and a headache?
Viruses i.e Enterovirus, influenza - Spontaneously improve, often mild
Bacteria i.e N. mengitidis, strep. pneumoniae (serious, medical emergency)
Fungi (rare) i.e crytpococcus neoformans
What are the symptoms of inflammation in the meninges?
- Headache
- Photophobia
- Neck stiffness
- Drowsiness
Systemic responses may include:
- Fever
- Drowsiness
- Septic shock
- Rash (N. meningitidis)
What precedes bacterial meningitis?
Illness is preceded by nasopharyngeal colonisation
- 10-20% adults have N. meningitidis colonisation
If you suspect bacterial meningitis what tests should you order?
1st) Blood culture
- CSF
- Throat swab
- Bloods to detect bacterial DNA by PCR
CSF later b/c takes time and want to act very quickly
Whats kerings sign when it comes to meningitis?
Fever + Headache = Consider meningitis, probs wont be.
- Lift the legs slowly whilst patient supine, if meningitis will hurt occipital lobe + spine b/c caudea equina being stretched. If not meningitis then hamstrings will hurt.
This is not always accurate though
What level is CSF collected from and why:?
L4/5 because youd otherwise hit the spinal cord and this would be bad. At L4/5 you can brush past the caude equina
Compare and contrast CSF in bacterial vs viral meningitis:
Bacterial:
- Decreased glucose
- Increased protein, WBC (pred. neutrophils), maybe gram positive culture but usually not enough time
Viral:
- Normal glucose
- Protein (inc or norm), WBC increased (pred. lymphocytes)
- Culture and gram staining wouldnt happen.
Gram staining lacks sensitivity in determination because it depends on bacteria being sufficient conc.
Explain the steps of PCR:
1) Heat sample to displace DNA strands
2) Reduce heat and allow primers to anneal (Primers, short compl. stands DNA)
3) Increase temp to allow DNA polymerase to elongate complimentary strands
4) Heat to displace strands and repeat this step 20-40 times.
5. Visualise (Fluorescent tag might be used) on gel.
Whats the difference between petechiae and purpura?
Petechiae: Small bruises when cap. burst. dont blanch under pressure
Purpura: Large bruises
Meningitis characteristic rash abscence/presence is not a deal breaker
When and who does Meningitis occur in?
Winter more common
Mostly in very young children. Associated with socioeconomic status.
What can trigger the compliment cascade?
Compliment cascade:
3 triggers:
- Mannose binding lectin (binds bacterial sugar)
- Fc recognition
- Compliment can bind spontaneously
= can form MAC, can opsonise, chemotaxis.
What are the virulence factors of N. meningitidis?
- Express lipolpolysaccharide similar to human blood antigen (cross reactivity?)
- Express 19 different polysac capusules, preventing MAC formation and opsonisation
- Release molecules that bind factor H and downregulate compliment
- Type N pilli deactivate compliment and lectin pathways
- Release blobs of lipopolysaccharide in blood that might act as decoy for compliment
How does meningitis and the immune system cause such profound sickness?
- As infection progresses vasodilation is enhanced
- When high bacteria is present, neutrophils release DNA into small blood vessels clogging them (reduced blood flow and O2)
- DNA is sticky and traps bacteria, RBC and platelets
- This leads to shock, - reduced BP, tachycardia, reduced perfusion of organs
i.e high bacterial loads cause that release of neutrophil DNA and a disaster happens
Whats the treatment of bacterial meningitis?
- IV penicillin (citriaxone used in other hospitals)
- Resus
- Blood culture
- Pain relief, fluids, IV antibiotics
