Meningitis Examination for NAC OSCE Canada
Immediate Management Approach
In a Canadian OSCE scenario for suspected acute bacterial meningitis, you must obtain blood cultures immediately, perform lumbar puncture without delay (unless contraindications exist), and initiate empiric antibiotics within one hour—specifically vancomycin plus ceftriaxone (or cefotaxime) plus ampicillin, along with dexamethasone given before or with the first antibiotic dose 1, 2, 3.
Focused Clinical Examination
Cardinal Symptoms to Assess
Look specifically for the classic triad (though absence doesn't exclude diagnosis):
- Fever (present in most cases)
- Nuchal rigidity/meningismus (neck stiffness on passive flexion)
- Altered mental status (confusion, lethargy, decreased GCS)
- Severe headache 4, 5
Critical Meningeal Signs
- Kernig's sign: Resistance/pain with knee extension when hip is flexed at 90°
- Brudzinski's sign: Involuntary hip/knee flexion when neck is passively flexed
Neurological Red Flags Requiring CT Before LP
Examine specifically for these contraindications to immediate lumbar puncture 1, 2, 3:
- Severely impaired consciousness (GCS ≤10 or deteriorating)
- New focal neurological deficits (hemiparesis, cranial nerve palsies, aphasia)
- New-onset seizures
- Papilledema on fundoscopy
If ANY of these are present: Start antibiotics immediately after blood cultures, then obtain CT head before LP 1.
Additional Risk Factors to Document
- Age ≥60 years
- Immunocompromised state (HIV, immunosuppressive therapy)
- History of CNS disease (mass lesion, stroke, prior infection)
These factors increase risk of abnormal CT findings and guide empiric therapy choices 1.
Immediate Investigations
Blood Work (Before Antibiotics)
- Two sets of blood cultures (mandatory before antibiotics) 2, 3
- Complete blood count
- Serum glucose (for CSF-serum glucose ratio calculation)
- Electrolytes, renal function
- Coagulation studies (if LP planned)
Lumbar Puncture - CSF Analysis
Perform immediately if no contraindications present 1, 2:
CSF Studies to Order:
- Opening pressure (elevated in bacterial meningitis)
- Cell count with differential (elevated WBC, neutrophil predominance)
- Protein (elevated, often >100 mg/dL)
- Glucose (decreased, CSF:serum ratio <0.4)
- Gram stain (positive in 60-90% of untreated cases)
- Bacterial culture (gold standard)
- Consider PCR/molecular testing if available (FilmArray panel) 6
Key Point: Even if antibiotics are given before LP, CSF findings (elevated WBC, low glucose, high protein) will still support the diagnosis, though culture yield decreases 1.
Empiric Antibiotic Therapy
Standard Regimen for Adults in Canada
Initiate within 1 hour of presentation 2, 3, 6:
- Vancomycin (covers resistant S. pneumoniae)
- Ceftriaxone or Cefotaxime (third-generation cephalosporin)
- Ampicillin (covers Listeria monocytogenes, especially if age ≥50 years) 4, 2
Dosing 1:
- Vancomycin: 15-20 mg/kg IV every 8-12 hours
- Ceftriaxone: 2 g IV every 12 hours
- Ampicillin: 2 g IV every 4 hours
For Children >1 Month
Vancomycin plus ceftriaxone (or cefotaxime) pending culture results 1, 7
Critical Caveat: In regions with high pneumococcal resistance to third-generation cephalosporins, vancomycin or rifampicin must be added 3. This is standard practice in Canada.
Adjunctive Dexamethasone Therapy
Give dexamethasone 10 mg IV before or with the first antibiotic dose 1, 2:
- Reduces mortality and neurologic sequelae, particularly in pneumococcal meningitis
- Must be given before or simultaneously with antibiotics to be effective
- Continue for 2-4 days
Rationale: Attenuates subarachnoid inflammatory response that contributes to cerebral edema, increased intracranial pressure, and neuronal injury 1.
Algorithm Summary for OSCE
If NO Red Flags Present:
- Obtain blood cultures immediately
- Perform lumbar puncture without delay
- Start vancomycin + ceftriaxone + ampicillin + dexamethasone immediately after LP
- Send CSF for cell count, protein, glucose, Gram stain, culture
If Red Flags Present (Altered Consciousness/Focal Deficits/Seizures):
- Obtain blood cultures immediately
- Start vancomycin + ceftriaxone + ampicillin + dexamethasone BEFORE imaging
- Obtain CT head emergently
- Perform lumbar puncture after imaging if safe 1, 3
Common OSCE Pitfalls to Avoid
- Never delay antibiotics waiting for LP or imaging—bacterial meningitis is a neurological emergency with time-dependent outcomes 1
- Don't forget ampicillin in adults, especially age ≥50 (Listeria coverage) 4, 2
- Don't skip dexamethasone—it must be given before/with antibiotics, not after 1
- Don't perform LP if patient has severely decreased consciousness (GCS ≤10), focal deficits, or seizures without CT first 1, 2
- Always obtain blood cultures before antibiotics—this may be the only positive culture if antibiotics are given pre-LP 2, 3
Monitoring and Complications
Patients require ICU-level monitoring in the initial phase 2:
- Neurologic deterioration occurs in up to 50% of adults
- Watch for seizures, focal deficits, decreased consciousness
- Common complications: cerebral infarction, hydrocephalus, subdural empyema, hearing loss 8
- If deterioration occurs, obtain MRI or CT and consider neurosurgical consultation 8
Follow-up: All patients need audiology testing post-discharge due to high risk of hearing loss (34% in children) 8, 7.