CNS Infections Flashcards
What is the classification of meningitis?
- Acute pyogenic (bacterial) meningitis
- Acute aseptic (viral) meningitis
- Acute focal suppurative infection (brain abscess, subdural and extradural empyema)
- Chronic bacterial infection (tuberculosis)
- Acute encephalitis is an infection of the brain parenchyma
“a thick layer of suppurative exudate covers the leptomeninges over the surface of the brain.”
What does this describe?
Be more specific about areas the exudate is found
It’s a pyogenic meningitis
Exudate in basal and convexity surface
How does a pyogenic meningitis appear microscopically?
Neurophils in the subarachnoid space
What age group would you expect a pyogenic meningitis to be caused by Neisseria meningitidis?
10-21 y/o
Pt with pyogenic meningitis in 30s with no recent travel.
What’s the most likely bug?
Streptococcus pneumoniae
(in patients over 21 y/o)
What bug should you be worried about for
- >60y/o
- neonates
- immunosuppressed?
Listeria monocytogenes
esp the >60s and immunocompromised groups
What bugs can are most likely to cause a pyogenic meningitis in a neonate?
- E. coli
- Group B streptococcus
- Listeria monocytogenes
Bacterial meningitis in a child (neonate to 10 y/o)
What do you think is the causative organism?
H. influenzae
What are the clinical features of a bacterial meningitis?
- Fever
- Headache
- Photophobia
- Stiff neck
- Altered consciousness
- Petechial rash (non-blanching)
- Potential seizures
- Focal neurological deficits
- Coma
What investigation must be undertaken to diagnose meningitis?
Lumbar puncture
BUT a CT must be done first to exclude SOL
CSF assessment:
- bacterial culture
- fungal staining and culture
- viral PCR
- also look at the colour of it
- and note the pressure as it comes out
Why is it important to always do a CT scan before a lumbar puncture?
Because a lumbar puncture could cause cerebral herniation in the event of a SOL
you’ll be struck off if you forget this!
What empirical treatment are you going to offer to someone between 21yrs and 60yrs with suspected bacterial meningitis?
Ceftriazone IV and dexamethasone IV
What empirical treatment are you going to give a patient >60y/o who has suspected bacterial meningitis?
Ceftriazone IV
Dexamethasone IV
Amoxicillin IV 4 hourly (for Listeria cover)
You are treating a >60y/o patient empirically for bacterial meningitis.
The cultures come back and confirm your suspicion of Listeria.
What do you need to do next?
and how long does the patient require amoxicillin?
Stop dexamethasone
Pt. will require at least 21 days of amoxicillin
You are treating someone between the ages 21 and 60 empirically for suspected bacterial meningitis.
The cultures come back and confirm pneumococcoal meningitis
How long will the patient remain on treatment?
Ceftriaxone IV for 10 days- can extend to 14 days if taking longer to respond
Dexamethasone IV for 4 days
What should be considered after 5 days of IV antibiotic treatment?
Consider outpatient IV therapy if patient has had 5 or more days treatment,
afebrile,
and clinically improving.
You’re treating a patient empirically for bacterial meningitis.
The cultures come back with no organism identified.
What do you?
Continue empirical treatment
Patient can be discharged after 10 days if they’ve clinically recovered
Request Infectious Diseases consult
What would be the best empirical treatment for a child between the ages of 1 and 10 suffering from bacterial meningitis?
What is the likely pathogen?
Ceftriazone IV and Dexamethasone IV
If confirmed on culture stop Dexamethasone and continue Ceftriazone IV for 10 days
H.influenzae
Which countries have high rates of penicillin resistant pneumococci?
(don’t need to learn these countries off but just want you to have read them)
Canada
China
Croatia
Pakistan
Poland
Spain
Mexico
Italy
USA
Greece
Turkey
A patient presents with suspected bacterial meningitis.
In the past 6 months they’ve travelled to a country with high rates of penicillin resistant pneuomococci.
What empirical treatment will you give them while you await the cultures?
Ceftriazone IV
Dexamethasone IV
Vancomycin IV
What are the likely causative organisms of a viral meningitis?
- Enteroviruses
- Coxsackie viruses and echoviruses
- HSV 1/2
- Varicella zoster
What are the clinical features of a viral meningitis?
- Headache
- Photophobia
- Stiff neck
- Altered consciousness
- Potential seizures
- Focal neurological deficits
What investigations do you need to undertake to diagnose a viral meningitis?
Lumbar puncture (CSF PCR)
BUT MUST undertake a CT scan first to rule out SOL
Viral stool culture
Throat swab
What is the treatment for a patient with viral meningitis?
Supportive
Where is N. meningitidis found naturally?
N. meningitidis occurs in the nasopharynx of many people
Usually bacterial meningitis is preceeded by a respiratory or ear infection
What type of infection may precede a bacterial meningitis?
A respiratory or ear infection
What would you prescribe for close contacts of someone with bacterial meningitis caused by N. meningitis?
Cirprofloxacin
Why is Ceftriaxone used instead of penicillin for bacterial meningitis?
Ceftriaxone lasts longer than penicillin in the CSF
(Passtest and PassMed often say penicillin is the right answer)
Why is dexamethasone given initially in bacterial meningitis?
Antibiotics can initially cause a damaging cytokine storm raising ICP which is why dexamethasone is given initially alongside antibiotics
How does encephalitis often present?
an insidious onset
stupor
confusion
What is encephalitis most commonly caused by?
HSV
What do you do in suspected encephalitis?
a CT and LP
EEG and MRI
How do you treat encephalitis?
IV aciclovir
What’s the difference between encephalitis and meningitis?
Encephalitis= global infection, whole brain is inflamed
Meningitis= lining of brain
What is aseptic meningitis?
Non-pyogenic meningitis
a big differential diagnosis
What are the potential causes of an aseptic meningitis?
Infectious
- HSV 1 & 2 (most common)
- Syphilis
- Listeria
- others
Non-infectious
- carcinomatous
- sarcoidosis
- vasculitis drugs
- dural venous sinus thrombosis
What opening pressures would you expect to see in CSF of:
- Bacterial meningitis
- Viral meningitis
- Tuberculous meningitis
- Autoimmune meningitis
- Bacterial= very high
- Viral = slightly increased
- Tuberculous= very high
- Autoimmune = slightly increased
What would you expect to see in the white cell count in the CSF of a bacterial meningitis?
Bacterial= increased neutrophil count
What would you expect to see in the white cell count in the CSF of a viral meningitis?
Increased lymphocyte count
What would you expect to see in the white cell count of a tuberculous meningitis?
Tuberculous= increased lymphocyte count
What would you expect to see in the white cell count of an autoimmune meningitis?
Increased
What would the protein levels be in a:
- bacterial
- viral
- tuberculous
- autoimmune
meningitis?
Protein levels:
- Bacterial= very high
- Viral = slightly increased
- Tuberculous= very high
- Autoimmune = slightly increased to very high
What are the CSF:Serum Glucose ratios in a:
- Bacterial
- Viral
- Tuberculous
- Autoimmune
meningitis?
CSF: Serum Glucose ratio
- <50%
- >50%
- <50%
- >50%
What lactate would you expect in the CSF of a:
- Bacterial
- Viral
- Tuberculous
- Autoimmune
meningitis?
- Bacterial= high
- Viral = normal
- Tuberculous= very high
- Autoimmune= normal
What does CSF look like in a bacterial meningitis?
Bacterial= Turbid/purulent
What does CSF look like in a viral meningitis?
Viral = clear/turbid
What does CSF look like in a tuberculous meningitis?
Tuberculous= turbid/viscous
What does turbid mean?
Not transparent because of stirred up sediment
What is likely to be the causative organism of an immunocompromised patient presenting with bacterial meningitis?
S. pneumoniae
N. meningitidis
Listeria
aerobic GNR (incl. Ps. aeruginosa)
What is likely to be the causative organism of a patient with a previous basilar skull fracture presenting with bacterial meningitis?
S. pneumoniae
H. influenzae
beta-haemolytic strep group A
What is likely to be the causative organism of a patient with previous head trauma or neurosurgery presenting with bacterial meningitis?
S. aureus
S. epidermidis
aerobic GNR
What is likely to be the causative organism in a patient with a CSF shunt presenting with bacterial meningitis?
S. epidermidis
S. aureus
aerobic GNR
Propionibacterium acnes