CNS Infections Flashcards
What is meningitis?
Infection of the meninges
Describe the route of infection for meningitis?
Microorganisms reach the meninges either by direct extension from the ears, nasopharynx, cranial injury or congenital meningeal defect or by blood stream spread
2 most common causes of meningitis?
Strep pneumonia and neisseria meningitidis
strep pneuomnia is most common
Describe neisseria meningitidis?
Gram negative cocci in pairs
Describe how neisseria meningitidis probably causes meningitis?
Can be found in the throats of healthy carriers
The bacteria probably gain access to the meninges through the bloodstream
Symptoms are due to the bacteria endotoxin
Neisseria meningitidis is more common in ________ and can be _________
young children and adults
responsible for outbreaks
Describe the capsular groups of neisseria meningitidis and the vaccine?
There are 12 capsular groups there is currently a vaccine for ACWY
What causes the classic non blanching rash of meningitis?
Neisseria meningitidis infection that gets in the blood
Neisseria meningitidis is also referred to as?
meningococcus
Describe strep pneumonia?
Alpha haemolytic gram positive cocci in chains
Who has a higher risk of developing strep pneumonia meningitis?
Those with diabetes, skull fractures of cochlear implants
Describe haemophilus influenza meningitis?
Now a vaccine for HiB so not as common
Describe listeria moncytogenes?
gram positive bacilli
Who does listeria monocytogenes tend to cause meningitis in?
neonates, elderly, immunosuppressed, particularly those with malignancy
Give an example of an organism that can cause chronic meningitis?
Tuberculosis
Describe some signs and symptoms of meningitis?
headache neck stiffness fever photophobia vomiting intense malaise petechial rash in meningococcal infection
Describe treatment of meningitis?
- ceftriaxone IV 2g bd (if penicillin allergic give chloramphenicol instead) + dexamethasone just before or started with antibiotics
- if listeria is suspected (it should be suspected in those 60 or over or immunocompromised which includes alcoholics and diabetics) should give amoxicillin IV
- if recent travel (within 6 months) to a country on list of high rates of penicillin resistance then add vancomycin too
Who should listeria be suspected then and therefore be treated with amoxicillin as well as ceftriaxone?
those 60 or over
those immunocompromised which includes diabetics and alcoholics
Does ceftriaxone cover listeria?
NO
so if suspected must give amoxicillin
Describe the course of viral meningitis?
This is almost always benign self limiting condition lasting 4-10 days.
Headache may follow for some months.
There are no serious sequelae unless an encephalitis is present.
Describe 4 tests for suspected meningitis?
Blood cultures
Throat swab for culture
CSF sample (although cant do LP / must be careful if high ICP)
Might do PCR
This describes the typical CSF findings for?
10^1-10^3 cell count predominantly lymphocytes
Gram staining neg
Normal or slightly high protein
Normal glucose
Viral meningitis
Describe CSF findings for viral meningitis?
10^1-10^3 cell count predominantly lymphocytes
Gram staining neg
Normal or slightly high protein
Normal glucose
Describe CSF findings for bacterial meningitis?
10^1-10^4 cell count predominantly neutrophils
Positive gram staining
High protein count
Less than 70% of blood glucose (not sure if bacterial influenced or because immune cells using glucose as fuel)
This describes the typical CSF findings for?
10^1-10^4 cell count predominantly neutrophils
Positive gram staining
High protein count
Less than 70% of blood glucose
bacterial meningitis
This describes the typical CSF findings for?
10^1-10^3 cell count predominantly lymphocytes
Positive or negative gram staining
High or very high protein
Less than 60% blood glucose
Tuberculosis meningitis
Describe the typical CSF findings for tuberculosis meningitis?
10^1-10^3 cell count predominantly lymphocytes
Positive or negative gram staining
High or very high protein
Less than 60% blood glucose
What are the public health reporting requirements in terms of meningitis?
Must report every suspected case of bacterial meningitis
May do tracing and give prophylactic treatment to contacts
What is encephalitis?
Acute inflammation of the brain parenchyma usually viral
Describe causes of encephalitis?
Lots of causative viruses, varies depending on countries
Most common in UK is herpes simplex
Other causes now with vaccines includes measles, mumps, rubella
Other common causes include varicella zoster virus, enteroviruses and adenovirus
Describe signs and symptoms of encephalitis?
insidious onset personality and behavioural changes confusion and speech disturbance reduced consciousness coma focal neurological deficits seizures
Describe investigations for encephalitis and what they might show?
MRI shows areas of inflammation and swelling (bright areas), raised ICP and midline shift may occur
EEG shows periodic sharp and slow wave complexes
CSF shows elevated lymphocyte count
Viral detection by CSF PCR can detect HSV or VZV
Describe management of viral encephalitis?
Suspected HSV and VZV encephalitis is treated immediately with IV acyclovir even before investigation results are available
Early treatment significantly reduces both mortality and long term neurological damage in survivors
Seizures are treated with anticonvulsants
Describe complications of encephalitis?
long term complications are common and include memory impairment, personality change and epilepsy
Describe what meningo-encephalitis is?
inflammation of both the brain parenchyma and the meninges
