What types of CNS infection are there?
- Acute pyogenic (bacterial) meningitis
- Acute aseptic (viral) meningitis
- acute focal suppurative infection (brain abscess, subdural/extradural empyema)
- Chronic bacterial infection (TB)
- Acute encephalitis (infection of brain parenchyma)
What viruses tend to cause viral meningitis?
Enteroviruses e.g. ECHO virus
How is viral meningitis managed?
Usually supportive treatment as illness is self-limiting
Give 2 common causes of viral encephalitis, and how they are treated.
Herpes simplex
Varicella zoster
Both treated with high dose aciclovir (IV for HSV) - this should be given asap (give empirically if delay of >6 hours for investigations is expected)
What are the clinical features of encephalitis?
- Usually insidious onset
- Meningismus
- stupor, coma
- seizures
- partial paralysis
- Confusion, psychosis
- speech, memory symptoms
What are the common causes of bacterial meningitis in neonates?
Group B strep - if within 24 hours of birth this is most likely cause (from maternal vaginal flora)
Listeria
E.coli
What are the common causes of bacterial meningitis in adults?
10-21: meningococcal
>21: pneumococcal > meningococcal
Elderly: pneumococcal > listeria
What are the clinical contraindications to lumbar puncture without neuro-imaging?
- Moderate - severe impairment of consciousness (reduced or fluctuating GCS 2)
- Focal neurological signs (e.g. poorly responsive pupils)
- Abnormal posture/posturing
- Papilloedema
- After seizures, until stabilised
- Relative bradycardia with hypertension
- immunocompromise
- systemic shock
- Coagulation abnormalities (low platelets or anticoagulant drugs)
- local infection at lumbar puncture site
- suspected meningococcal septicaemia
- respiratory insufficiency
Name a source of listeria infection in meningitis.
Eating soft cheese
A patient presents with fever, confusion and meningism. They have been in hospital due to a fractured cribriform plate. You suspect meningitis. What are the most likely infective organisms?
Pneumococcus
Haemophilus influenzae
Group A beta-haemolytic strep
In bacterial meningitis, what organisms are associated with neurosurgery or open head trauma?
Staph aureus
Staph epidermidis
Gram negative rods
You suspect bacterial meningitis in a patient with a CSF shunt. What are the most likely infective organisms?
Staph epidermidis
staph aureus
aerobic gram negative rods
proprionobacterium acnes
What are the 3 mechanisms associated with the pathogenesis of bacterial meningitis?
- Nasopharyngeal colonisation
- direct extension of bacteria
- mastoiditis, sinusitis, brain abscess
- across skull fracture/defect - from remote foci of infection e.g. endocarditis, pneumonia
What causes the symptoms in meningococcal meningitis?
endotoxin production
Name 3 causes of bacterial meningitis that commonly colonise the throat/nasopharynx of healthy individuals.
Neisseria meningitidis
Haemophilus influenzae
Strep pneumoniae
What organism causing meningitis are hospitalised patients, CSF skull fractures, diabetics, alcoholics, and young children most susceptible to?
Strep pneumoniae
What does Listeria monocytogenes look like on Gram stain?
Gram positive bacilli
What antibiotic treats Listeria meningitis?
IV amoxicillin (or ampicillin)
What are the clinical signs and symptoms of bacterial meningitis?
Fever Neck stiffness Altered consciousness Headache Vomiting Pyrexia Photophobia Lethargy Confusion Rash
What are the investigations for diagnosing bacterial meningitis?
Blood cultures CSF: - culture and microscopy - biochemistry for glucose and protein - blood count and antigen detection - PCR Throat swab
What are the CSF findings in aseptic (non-pyogenic) meningitis?
Low WCC
Minimally elevated protein
Normal glucose
How should patient with acute bacterial meningitis be managed?
- Blood cultures and throat swab
- If no contraindications - LP
- Start empirical abx: Ceftriaxone 2g IV (cefataxime) - DO NOT WAIT FOR LP RESULTS
- If delay in LP >30 minutes, start empirical abs first
- steroids: dexamethasone with or just before first dose of abx
- tailor abx treatment once you get LP results
- If signs of raised ICP, do not do lumbar puncture
- Start empirical abx: Ceftriaxone 2g IV
- steroids
- CT head
- manage in critical care unit
For all patients - notify public health and give abx prophylaxis to patient contacts
What is the empiric antibiotic therapy used in bacterial meningitis?
IV Ceftriaxone 2g bd
Add IV amoxicillin 2g ads if listeria suspected (age >55)
If penicillin allergy:
- IV chloramphenicol and IV vancomycin
- Co-trimoxazole if listeria suspected
What antibiotics are used in the contact prophylaxis regimen for bacterial meningitis?
Adults and children >12: - Rifampicin - oral, 600mg, 4 doses - Ciprofloxacin - oral, 500mg, single dose - Ceftriaxone - IM, 250mg, single dose Children
