Infections of the CNS Flashcards
What is the difference between encephalitis, meningitis and myelitis?
encephalitis - inflammation of entire brain parenchyma
meningitis - inflammation of all 3 layers of meninges
myelitis - inflammation of the spinal cord
Would confusion due to SEPSIS be a direct or indirect infection of the brain?
Indirect
- infection started elsewhere
What can be seen macroscopically in pyogenic meningitis?
- thick layer of suppurative exudate (PUS) covers the meninges
over the surface of the brain
What is seen microscopically on lumbar puncture in pyogenic meningitis?
Lots of neutrophils in CSF
During what time of the year does viral meningitis usually present?
Late summer/ autumn
What investigations are used to diagnose viral meningitis?
- viral stool culture
- throat swab
- CSF PCR
How is viral meningitis treated?
generally supportive as self limiting
- e.g anti-emetics for nausea
What questions should you consider asking the patient if they present with symptoms of encephalitis?
- Recent flu-like illness?
- Anybody in the family recently ill?
- Travel?
- Recent vaccinations?
- Insect bites?
- Immunocompromised?
What are the common clinical features of encephalitis?
Insidious onset Stupor, coma Seizures Confusion Speech, memory symptoms
What investigations are useful in encephalitis?
LP
electroencephalogram (EEG - electrodes on head)
MRI
What bacterium is most likely to cause bacterial meningitis in each age group?
Neonates: listeria, group B Streptococci, E. coli Children: H. influenza Ages 10 to 21: Neisseria meningitidis Age over 21: Streptococcus pneumoniae Over 65 : Streptococcus pneumoniae
What bacterium is likely to cause meningitis after neurosurgery or trauma?
Staphylococcus - due to penetration from outside world
What life-altering effects can occur after meningococcal infection?
- limb loss
- deafness
- blindness
- cerebral palsy/quadriplegia
- severe mental impairment
Where do bacteria usually colonise to start a meningococcal infection?
Nasopharyngeal colonization
How is CSF from a lumbar puncture analysed?
Haematology - WCC
Microbiology - Gm stain/culture
Chemistry - glucose/protein
PCR
When is it acceptable to delay a lumbar puncture?
if raised ICP/ seizures
then CT can be completed before lumbar puncture
What findings in the CSF would indicate a bacterial meningitis?
WCC > 2000
Neutrophils > 1180
Protein > 220
Glucose CSF:Serum ratio <0.23
Where is neisseria meningitides usually found in a healthy carrier individual?
Throat
What groups of patients are particularly susceptible to strep pneumo. infections?
CSF skull fractures
diabetics/ alcoholics
young children
Pts with Cochlear implants
What is fulminant septicaemia?
End stage of meningococcal infection likely to increase mortality
Where can Haemophilus Influenzae be found in a healthy person?
part of the normal throat microbiota
What patients are badly infected by strep. pnuemoniae?
Asplenic pts
Describe the gm stain appearance of Listeria?
Gram positive bacilli
Who normally gets listeria?
- Neonatal
- > 55 years
- immuno-suppressed especially malignancy;
WHat antibiotic is used to treat listeria?
Amoxicillin
as listeria is intrinsically resistant to Ceftriaxone
What bacterial infection can reactivate in the elderly and cause meningitis?
TB
How does TB meningitis usually present?
Elderly patient
non specific ill health
Previous TB on CXR
Poor yield from CSF
What is cryptococcal meningitis and in who does it normally present?
- FUNGAL
- present in HIV DISEASE
- CD4< 100
When can bacterial meningitis be culture negative?
If patient was given oral antibiotics prior to their admission
What is an aseptic meningitis?
Non-pyogenic => no pus or bacteria
What antibiotics are given for a suspected meningitis where the patient is NOT penicillin/cephalosporin allergic?
Ceftriaxone (+ dexamethasone)
If >60 years:
Add amoxicillin for listeria cover
If recently travelled to penicillin resistant country:
Add vancomycin
What antibiotics are given for a suspected meningitis where the patient IS penicillin/cephalosporin allergic?
Chloramphenicol (+ dexamethasone)
If >60 years:
Co-trimoxazole for listeria cover
What are the main clinical signs of bacterial meningitis ?
Fever Stiff neck Headache Photophobia Vomiting Lethargy Confusion Non-blanching Rash
What viruses can be cultured on PCR when narrowing the differential of meningitis?
- Enteroviruses
- Herpes Simplex Virus 1, HSV2
- Varicella zoster virus
What infective causes can trigger an aseptic meningitis?
HSV 1 and 2 Syphilis Listeria (occasionally) Tuberculosis Cryptococcus malaria Lyme disease
What non-infective causes can trigger an aseptic meningitis?
- Cancer
- Sarcoid
- Vasculitis
- Dural venous sinus thrombosis
- Drugs
What are the warning signs when admitting a patient with a suspected meningitis?
- Marked depressive conscious level (GCS <12)
- Focal neurology
- Seizure before/at presentation
- Bradycardia and hypertension
- Papilloedema
In what groups of patients would steroids not be given as well as antibiotics in meningitis?
- post-surgical meningitis
- severe immunocompromise
- meningococcal or septic shock
OR if patient is hypersensitive to steroids
How is meningitis prevented?
Public health notified of new cases to allow close contacts of meningitis patients to be aware that they made need prophylaxis
What oral therapies are used for prophylaxis?
Ciprofloxacin
Rifampicin
