General Flashcards
In what ways can an infection travel to the meninges?
Ears
Nasopharynx
Cranial trauma
Congenital meningeal defect
Blood
Why is bacterial meningitis so much worse than viral?
Bacteria produce exudate which forms a layer of pus throughout the meninges. The pus can also form into adhesions and cause lesions on cranial nerves.
How can joint stiffness and neck stiffness be tested?
What is the 1st line treatment for ?Bacterial Meningitis
If showing signs/symptoms:
IV Ceftriaxone
Before investigations
What initial investigations should be done for ?meningitis?
CC GG FP
CRP
Coag
Gas ABG (VBG will do if in child)
Glucose
FBC
PCR for N meningitidis
What are the contraindications to an LP?
Skin infection at site of LP
Raised ICP (specifically raised wrt distal CSF ie if there is a global rise in ICF, LP is not contraindicated)
Uncorrected coagulopathy
What are the clinical signs of raised ICP and if you are unable to clinically determine if there is raised ICP, what should you do before an LP?
CT head. Not 100% sensitive, but better than nothing!
Rely on clinical diagnosis first.
eg papilloedema
headache
Nausea
vomiting
confused in space and time
double vision
CSF analysis:
Mononuclear cells 10-100 (<5)
Polymorph cells Nil (Nil)
Protein 0.4-0.8 (0.2-0.4)
Cause?
Viral meningitis
The fluid will be clear, or possibly turbid. ie it will not have exudate in it.
CSF analysis:
Mononuclear cells <50 (<5)
Polymorph cells 200-300 (Nil)
Protein 0.5-2 (0.2-0.4)
Cause?
Bacterial meningitis
note the high protein from exudate, and the v high polymorph (granulocyte) count.
fluid will appear turbid/purulent from exudate
CSF analysis:
Mononulcear cells 100-300 (<5)
Polymorph cells 0-200 (Nil)
Protein 0.5-3 (0.2-0.4)
Cause?
TB meningitis
note v high mononuclear cells (peripheral blood cell with round nucleus (not a granulocyte))
After the administration of ceftriaxone, and investigations have been carried out. What is the next most approprite drug to give for bacterial meningitis?
Dexamethasone
Proven to reduce risk of neurological complications eg hearing loss.
Not in children under 3yo though.
Also give 15l oxygen.
What are the common additions with which encephalitis, rather than meningitis will present?
- Personality and behaviour change
- reduced GCS
- seizure
- focal neurological defects
(all possible in meningitis, but less common)
What are the most common causes of viral encephalitis?
What will exclude bacterial meningitis and point towards viral encephalitis in the hx?
HSV (commonest)
VZV
Often asymptomatic/symptoms are not as severe.
Lead in of more than a few days cannot be bacterial (if bacterial was left untreated for a few days, it would be very severe)
What investigations can help distinguish between bacterial meningitis and viral encephalitis?
CT
May show raised ICP with bacterial meningitis
MRI
commonly shows inflammation and swelling in temporal lobes with HSV encephalitis
CSF analysis
bacteria will use glucose, secrete protein, and there will be laods of granulocytes.
CSF PCR
highly sensitive for viral and bacterial organisms. Used to tailor abx for bacterial meningitis.
What is CSF gluscose levels measured against?
What how are the results interpreted - what do they suggest?
Blood glucose
sample must be taken at same time as LP
ratio is determined
CSF:blood
0.5-0.66:1 Normal
>0.5:1 Viral
<0.5:1 Bacterial
Bacteria use glucose!
