Week 3- CNS infections Flashcards
What can untreated infection in the brain lead too?
Brain herniation and death.
Cord compression and necrosis with subsequent paralysis.
Which organisms can cause community acquired bacterial meningitis?
Pneumonoccus
Menigicoccus
H- influenza.
Listeria spp (over 60’s or immunocompromised)
What is the treatment for community acquired bacterial meningitis?
Ceftriaxone IV plus dexamethasone IV.
1) Treatment for community acquired meningitis if its listeria ?
2) If its listeria and penicillin allergic?
Amoxicillin IV plus normal community acquired treatment (ceftriaxone IV plus dexamethasone IV)
Chloramphenical IV plus dexamethasone
When would you stop dexamethasone in a community acquired meningitis?
If you find out the causative organism is- meningococcus Listeria (common in 60+ years) H influenza Other gram neg
What treatment would you add if you found out the causative organism for a community acquired meningitis is Listeria?
Add amoxicillin.
Which pathogen commonly causes viral meningitis?
Enterovirus e.g. ECHO
How would you diagnose a viral meningitis?
Stool culture
CSF PCR
Throat swab
Treatment of a viral meningitis?
Generally supportive because its self limiting.
Clinical features of encephalitis?
Insidious (gradual) onset
Meningismus (triad of headache, photophobia and nuchal rigidity (impaired neck flexion))
Stupor (state of near unconsciousness), coma
Siezures, partial paralysis
Confusion, psychosis
Speech, memory symptoms
Investigations into encephalitis? What are they likely to show?
Bloods- blood cultures, serum for viral PCR
Lumbar puncture- likely to show increased CSF protein and lymphocytes and decreased glucose.
EEG (electrocephalogram- test detecting brain activity)- diffuse abnormalities.
Contrast enhanced CT- will show focal bilateral temporal lobe involvement. MRI if allergic to contrast.
When should you start treatment for encephalitis?
If delay in tests, start pre-emptive aciclovir due to it drastically improving outcomes when started early.
Symptoms of meningitis (and septicaemia- blood poisoning)
Early symptoms
- headache
- leg pain
- neck stiffness
- cold hands and feet
Later symptoms -reduced conscious level and confusion -Meningism- sore neck, photophobia and Kernigs sign (pain and resistance on passive knee extension with hip fully flexed) Non blanching petechial rash ever Possibly seizures
Which bacterial meningitis (community acquired) are neonates likely to get?
Listeria (occurs in extremes of age)
Group B streptococci
E.coli
Which bacterial meningitis (community acquired) are children likely to get?
H influenza
Which bacterial meningitis (community acquired) are age 10-21 likely to get?
Neisseria Meningitidis
Which bacterial meningitis (community acquired) are age over 21’s likely to get?
Strep pneumoniae (most likely) Neisseria meningitidis
Which bacterial meningitis (community acquired) are age over 65s likely to get?
Strep pneumoniae (most likely) Listeria.
Which bacterial meningitis (community acquired) are immunocompromised patients likely to get?
Listeria
Which bacterial meningitis (community acquired) are patients who have recently had neurosurgery likely to get?
Staphylococcus
Gram neg bacilli
Which bacterial meningitis (community acquired) are patients who have fractured their cribriform plate likely to get?
Strep pneumoniae.
Meningitis can leave you with life altering after affects, what can these be?
Limb loss, deafness, blindness, cerebral palsy, quadriplegia, severe mental impairment.
Complications of meningitis
Purulence (pus)- can compress cranial nerves (esp III and IV). Can cluster at the base of the brain.
Abscesses- if it invades the Pia mater.
Cerebral oedema
Ventriculitis/hydrocephalus
Describe the pathogenesis of bacterial meningitis?
The nasopharynx becomes colonised. Direct extension of bacteria (through fractures in the skull or parameningeal foci (sinusitis, mastoiditis, brain abscess).
Which pathogen causes mengiococcal meningitis?
N. Meningitidis
Pathogenesis of N meningitidis?
Found in the throats of healthy carriers. Bacteria probably gain access to the meninges via the bloodstream. The bacteria may also be found in leukocytes in the CSF.
What causes N meningitidis to have symptoms?
The endotoxin released.
H influenza is part of the normal throat microbiota? True or false
True- it requires blood factors for growth and to become pathogenic.
Which type of H influenza most commonly affects children under 4?
Type b.
Who is most susceptible to S pneumoniae meningitis?
Hospitalised patients, patients with CSF skull fractures, diabetics/alcoholics and young children.
What might S pneumoniae be linked too?
CNS devices e.g. cochlear implant. Rare but high mortality rate.
Which drug has no value against listeria monocytes
Ceftriaxome- they are intrinsically resistant. Use IV ampicillin or amoxicillin.
Who is likely to get tuberculosis meningitis?
Reactivation in the elderly
What signs is someone with tuberculosis meningitis likely to show?
Need a very high level of suspicion to diagnose. Previous TB infection with poor yield on CSF, fairly non-specific ill health.
Treatment of tuberculosis meningitis?
Rifampicin plus isoniazid
You can add pyrazinamide and ethambutol
What fungal infection can cause meningitis?
Cryptococcal (crytococcal meningitis)
Signs to point you towards a diagnosis of cryptococcal meningitis?
HIV disease Subtle neurological signs Aseptic CSF CD4<100 Disseminated infection
Treatment of cryptococcal meningitis?
IV Amphotericin B/ Flucytosine Fluconazole
When should lumbar puncture be delayed in suspected bacterial meningitis?
Signs of severe sepsis or rapidly evolving rash. Respiratory or cardiac compromise Anticoagulant therapy/known thrombocytopenia Infection at the site of LP Focal neurological signs Presence of papilloedema Continuous or uncontrolled seizures GCS<12
Principles of lumbar puncture in meningitis?
If flow fast- measure pressure
Be cautious if there is increased ICP
Be careful with delirium
TREAT WITH ANTIBIOTICS FIRST.
What things are you looking for in a lumbar puncture?
Haematology- WCC, RBC, differential
Microbiology- gram stain, cultures
Chemistry- glucose, protein
NOTE
Bacterial meningitis can be culture negative on LP
Could be due to already treating with antibiotics.
Typical CSF findings in a viral meningitis
Lymphocytes 10^1-10^3 Gram stain- negative Bacterial antigen detection- negative Glucose- normal (2.3-4.5) Protein-normal (0.1-0.4)
Typical CSF findings in bacterial meningitis
Lymphocytes 10^1-10^4 (predominantly polymorphs e.g. neutrophils) Gram stain- positive Bacterial antigen detection- positive Protein- high Glucose-less than 70% of blood glucose.
Typical CSF findings in tuberculosis meningitis
Lymphocytes- 10^1-10^3- predominantly lymphocytes Gram stain- positive or negative Bacterial antigen detection-negative Protein- high or very high Glucose-less than 60% of blood glucose
When is the CSF 99% predictive of bacterial meningitis?
When the WCC >2000, Neutrophils >1180, Protein >220
Glucose< 34 and glucose CSF/serum <0.23
What else can cause low CSF glucose and high neutrophils (apart from bacterial meningitis)?
Early phase viral meningitis Some parameningeal foci Leakage of brain abscess into ventricle Amebic meningoencephalitis Drug induced (NSAIDS) Chemical meningitis Behcet syndrome
What is aseptic meningitis?
Non-pyogenic (non-pus producing) bacterial meningitis
What will the spinal fluid of aseptic meningitis be like?
Low number of WBC
Minimally elevated protein
Normal glucose
What infections can cause aseptic meningitis?
HSV 1 and 2 Syphilis Listeria (occasionally) TB Cryptococcus Leptospirosis Cerebral malaria African tick typhus Lyme disease (ALL TREATABLE)
What non-infectious agents can cause aseptic meningitis?
Carcinomatous Sarcoidosis Vasculitis Dural venous sinus thrombosis Migraine Drug- co-trimoxazole, IVIG, NSAIDs
Indications for hospital admission in adult bacterial meningitis?
Signs of meningeal irritation Reduced conscious level A petechial rash Febrile, unwell or recent fit Any illness, esp headache.
On arrival in hospital, the doctor should do the following to deal with bacterial meningitis
Blood culture and coag screen
Give treatment as outlined.
Throat swab
Aspirate and swab any petechial or purpuric skin lesions
Who should undergo a CT prior to lumbar puncture?
Immunocompromised patients History of CNS disease New onset siezure Papilloedema Abnormal level of consciousness Focal neurological deficit
When should you give steroids to patients with bacterial meningitis?
Should give to all patients with suspected bacterial meningitis with the antibiotics.
When should you not give steroids to patients with bacterial meningitis?
Do not give in post-surgical meningitis, severe immunocompromised, meningococcal or septic shock or those that are hypersensitive to steroids.
When should you report meningitis to public health?
ASAP- to minimise secondary infections.
