CNS Infections — DCE Clinical Case

Systematic examination routine

1. General inspection first: conscious state and engagement (the single most important observation — confusion redirects you from meningitis toward encephalitis), photophobia behaviour, rash on the trunk and limbs (press for blanching — a non-blanching purpuric rash is meningococcaemia until proven otherwise) [1].
2. Vital signs: temperature, heart rate, blood pressure, respiratory rate, oxygen saturation — sepsis physiology changes the urgency, not the examination [1].
3. Higher function screen: orientation to person/place/time, attention (serial sevens or months reversed), and a brief language screen — dysphasia localises, confusion globalises.
4. Meningeal signs: neck stiffness on passive flexion, Kernig sign (hip flexed to 90°, pain on knee extension), Brudzinski sign (hips flex on neck flexion) — then state their limitation aloud: these signs are traditional but insensitive, and their absence does not exclude meningitis [1].
5. Fundi: papilloedema — the finding that gates the LP decision via the Hasbun criteria [2].
6. Cranial nerves and a rapid motor screen: focal signs (again Hasbun-relevant), and ears/throat for a contiguous source [2].

Presentation template (deliver this to the examiner)

"This febrile 26-year-old with 2 days of headache is alert and orientated with intact attention. He has neck stiffness with positive Kernig sign, no rash, no papilloedema and no focal neurological signs. My working diagnosis is meningitis, and my immediate actions are blood cultures, empirical ceftriaxone plus vancomycin, dexamethasone with the first dose, and a lumbar puncture without CT — because none of the Hasbun criteria apply" [1] [2].

Discussion questions

"Your neck stiffness examination was negative. Does that reassure you?" — "No. Meningeal signs are insensitive, particularly early, in the elderly, the immunosuppressed and the partially treated. They shift probability when present; they do not exclude when absent. The features that change management are the conscious state, the fundi and any focal deficit" [1].

"When would you image before the LP?" — "When any Hasbun criterion is present: immunocompromise, known CNS disease, seizure in the past week, papilloedema, abnormal consciousness or focal deficit — and always after antibiotics, because a normal CT does not exclude raised pressure and the organism does not wait" [2].

"The CSF shows 300 lymphocytes, normal glucose, protein 0.9 g/L. What changed?" — "That is a viral pattern — clinically compatible with enteroviral or HSV meningitis rather than bacterial disease. I would stop the dexamethasone, review the empirical antibiotics against cultures and PCR, and consider HSV PCR if there is any encephalopathic feature, because that changes the drug and the duration" [1].