NEURO 221 Meningitis Flashcards
What 4 routes can microbes enter the CNS via?
1) blood stream
2) direct implantation - trauma
3) local extension - from teeth, sinuses and ears
4) via the PNS e.g. rabie
What cells make up the BBB?
brain microvascular endothelial cells surrounded by astrocyte projections
What ways can a microbe enter the CNS if going via the blood stream?
Either at the BBB in the brain parenchyma
Or via the choroid plexus
What is the choroid plexus in the brain?
plexus lining the ventricles containing ependymal cells that produce CSF
Why is it easier to cross the BBB at the choroid plexus?
There are weaker tight junctions here (increased paracellular flux) and a fast rate of uptake/endocytosis (transcellular flux)
What is a brain abscess?
A focal infection of the brain parenchyma usually due to bacteria
What are the common microbes causing a brain abscess and what are the associations?
Associated with immunosuppresion
Acute abscess: mixed bacterial picture from oropharynx (streptococcus anginosus and bacteroides)
Chronic: TB, syphillus, Lymes disease. Fungal, parasitic e.g. toxoplasmosis
What organism causes syphillus?
Treponema pallidum
What organism causes lyme disease?
Borrelia burgdorefri
What is meningitis?
Inflammation of the lining of the brain due to infection
100% fatal in bacterial infections if not treated
What is the most common organism in meningitis to affect the age group:
Group B strep
What is the most common organism in meningitis to affect the age group: >3mth
Streptococcus pneumoniae (45%) N. Meningitidis (34%)
What is the most common organism in meningitis to affect the age group: >10years
N. meningitidis
What are the clinical features of meningism?
Headache, neck stiffness and photophobia
also: fever, N&V and general malaise
What is a petechial non-blanching rash a sign of in meningitis?
bacteraemia
What is brudzinskis sign?
neck rigidity - involuntary flexion of the hips when the neck is flexed
sign of meningitis
What is kernigs sign?
pain and resistance on passive knee extension with full hip flexion
sign of meningitis
What are the common causes of viral meningitis?
> 85% is enteroviruses
some echoviruses, cocksackie A&B and poliovirus
What is the CSF profile of a bacterial infection?
turbid, increased neutrophils, increased protein, low or absent glucose
What is a gram +ve cause of meningitis likely to be?
strep pneumonia
What is a gram -ve cause of meningitis likely to be?
neisseria meningitidis
What is a normal CSF profile?
clear, soem neutrophils and lymphoctues, 150-450mg/L protein, some glucose
What is a viral CSF infection profile?
clear, increased lymphocytes, normal protein and glucose
What stain would you use to look for a fungal infection in CSF?
Indian ink
What stain would you use to look for a mycobacterial infection in CSF?
AFB
When is a lumbar puncture contraindicated?
if suspected raised ICP, local skin infection
How do you manage a suspected case of meningitis?
Immediate care!
1st contact: 999 and IM penicillin/ cefotaxime in allergy
What antibiotics should be given to an infant
Ampicillin + aminoglycoside/cefotaxime
What antibiotics should be given to an adult with meningitis?
cefatriaxone/cefotaxime
What extra drug can be given to adults with their abx and what is the benefit -in meningitis?
Corticosteroids have been shown to reduce morbiditiy and mortality and long term neurological sequelae - no benefit in children
What prophylaxis is given to direct contacts of those with meningitis?
rifampicin/ciprofloxacin
isnt treatment but erradicates the possible source!
What is encephalitis?
acute inflammation of the brain parenchyma -often not pure but mixed as meningo-encephalitis
What is the most common cause of encephalitis in the UK? What is it characterised by?
herpes simplex 1 - extensive necrosis of the temporal lobes
