SAQ 418 – Infectious Diseases – meningitis and CSF interpretation
Model Answer
Infectious Diseases – meningitis and CSF interpretation.
a. Contraindications to lumbar puncture
- Suspected raised intracranial pressure, such as reduced consciousness, papilloedema, focal signs, or Cushing response.
- Focal neurological deficit.
- Coagulopathy, thrombocytopaenia, anticoagulation, or purpuric rash suggesting bleeding risk.
- Seizure or unstable patient requiring resuscitation first.
- Local infection or abnormal anatomy at the puncture site.
- Patient refusal or inability to cooperate safely.
b. Most likely diagnoses
- Viral meningitis.
- Partially treated bacterial meningitis.
c. Supporting CSF features
- Raised lymphocytes with a predominantly lymphocytic CSF supports viral meningitis.
- Raised protein supports meningitis.
- Some polymorphs and glucose at the low end of normal keep partially treated bacterial meningitis in the differential.
- Very low red cell count makes traumatic tap or SAH less likely.
d. IV antibiotics
| Pros | Cons |
|---|---|
| Treats partially treated bacterial meningitis, which carries high morbidity and mortality if missed. | Risk of adverse drug effects including allergy or anaphylaxis. |
| Can be stopped if cultures/PCR and clinical course exclude bacterial infection. | May require admission and can contribute to antimicrobial resistance or complications of inpatient care. |
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