A 17 year old man was referred with a 12 hour history of generalised headache, mild photophobia, and a rash on his body that was macular and blanching. The rash, though not classic for bacterial meningitis, was developing “in front of my eyes.” The patient had a temperature of 37.4°C, no neck stiffness, and a negative Kernig's sign. There were no focal neurological signs. He seemed clinically well, talking and smiling with no great discomfort. His white cell count was a clinically significant 24×109/l (predominantly neutrophils), and blood cultures were taken.
As the admitting senior house officer, I decided to proceed to lumbar puncture on the basis of the high white cell count and developing signs. I felt that the most likely diagnosis was meningitis, although, apart from the white cell count, the clinical signs favoured a viral rather than a bacterial infection. Bacterial meningitis was simply my “hunch,” and intravenous benzylpenicillin was started (after lumbar puncture in this case). Within an hour of having the antibiotic, the patient's temperature settled and the rash completely disappeared. His cerebrospinal fluid was reported as a clear and colourless specimen with two red cells, no white cells, and a negative Gram stain. Biochemical analysis was also completely normal. He was admitted for overnight observation.
On the post-take ward round his intravenous antibiotics were stopped and his prescription written for discharge. Shortly before he left, however, a call from an excited microbiologist confirmed the presence of Gram negative diplococci in both blood and cerebrospinal fluid culture. These were meningococci. Intravenous antibiotics were recommenced, and the patient made an uneventful recovery.
A negative result from cerebrospinal fluid microscopy clearly doesn't exclude bacterial meningitis, and I learnt a valuable lesson that clinical findings and hunches are sometimes more important than test results.
Footnotes
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