A 20 year old presents with a 72 hour history of headache, photophobia and fever. On examination he is alert and orientated and has mild neck stiffness. There are no focal neurological signs. He has no significant past medical history. He has no risk factors for HIV nor does he have any history of travel to tropical areas.
A CT scan of his head is normal.
A lumbar puncture is performed and a CSF sample is taken.
The initial CSF results are as follows:
- Clear and colourless macroscopically
- White cell count: 85 x 10^6/l, Differential 99% lymphocytes.
- Red cell count: 14 x 10^6/l
- Protein 0.7 g/l
- Glucose 4.2 mmol/l (serum glucose 6.5 mmol/l)
- Gram Stain: No organisms seen
The following morning he is feeling a bit better, with supportive and symptomatic treatment alone.
1) What is the likely cause of this young man’s illness?
Common things are common, and this presentation is most likely to represent a viral meningitis caused by an enterovirus. In most parts of the world, enteroviruses cause approximately 75% of all cases of “lymphocytic meningitis”. In our laboratory this profile above would easily be the most “typical” CSF picture that we see.
2) What further testing should be undertaken on the CSF sample?
There is NO right or wrong answer to this question. The answer depends on many factors. e.g. duration and persistence of symptoms, severity of symptoms, risk factors for particular diseases, whether treatment is available, turnaround time and cost of testing.
In our institution, such patients often end up getting Enterovirus and Herpes Simplex Virus (HSV) PCR testing. Given that in this particular case, the patient is getting better within 24 hours (as they most often do…) there is an argument for doing no further testing at all. I can imagine it would be frustrating sweating over a CSF PCR on a patient, only to come across the patient later that day going about their normal business, having fully recovered from his illness and discharged from hospital. (These tests need to be real-time to have any significant impact)
If the patient is not getting better, could consider testing the CSF for CMV, EBV, VZV, HHV6, mumps, measles, influenza, LCMV (Lymphocytic Chorio-Meningitis Virus). Consider testing for arboviruses depending on what part of the world you live in. Consider a serum HIV test. Consider spirochaetes such as Lyme disease and leptospirosis. Consider other non-viral pathogens such as mycobacteria, fungi and rickettsia. The list is endless! (and these are only the main infectious causes that are being considered, not to mention non-infectious causes of CSF lymphocytosis. This is where the CSF volume comes into play and often more CSF is required from the patient for extended testing. Clinical Microbiologists like myself can also occasionally be useful for rationalising extended testing!
Click here for a nice article on viral meningitis. It is getting a little old (2005) but not too much has changed I think. It packs a lot of information into what is a 10-15 minute read.