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• CSF:plasma glucose
  oscar,m jolobe
  Published on: 16 March 2011

• Published on: 16 March 2011

  CSF:plasma glucose

  • oscar,m jolobe, retired geriatrician

  Although it is true that, in patients with suspected meningitis, a CSF:plasma glucose of >0.5 suggests a viral aetiology(1), underrecognition of the fact that the ratio may sometimes fall below 0.5 has led to inclusion of a CSF:plasma ratio > 0.5 among the "clinical case definitions" of aseptic meningitis(2), notwithstanding the fact that CSF:plasma glucose ratios below 0.5(and even as low as 0.26) may be encounte...

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  Although it is true that, in patients with suspected meningitis, a CSF:plasma glucose of >0.5 suggests a viral aetiology(1), underrecognition of the fact that the ratio may sometimes fall below 0.5 has led to inclusion of a CSF:plasma ratio > 0.5 among the "clinical case definitions" of aseptic meningitis(2), notwithstanding the fact that CSF:plasma glucose ratios below 0.5(and even as low as 0.26) may be encountered in viral meningitis(3), and in viral encephalitis(4). In one study, among 22 patients with enterovirus meningitis, the CSF:plasma glucose ratio fell within the range 0.26-0.76. In the same study, among 8 patients with varicella zoster virus meningitis the ratio fell within the range 0.4-0.73, and within the range 0.47-0.57 among 8 patients with herpes simplex type 2 meningitis(3). Even in viral encephalitis, patients have been encountered with CSF:plasma glucose ratios < 0.5, as was the case in a multicentre population-based prospective study of patients in England(4). In that study among 18 subjects with herpes simplex virus encephalitis in whom the CSF;plasma ratio was evaluated , there were five with a ratio < 0.5. Among 6 with varicella zoster virus encephalitis in whom the ratio was evaluated there were two in whom the ratio fell below 0.5(4). Given the fact that some subtypes of viral meningitis are amenable to treatment(3), and the fact that management of this disorder may be suboptimal, in part due to its underrecognition(5), it is important to stress to frontline medical staff that the diagnosis should be entertained even when the CSF:plasma glucose ratio falls within the range where the differential diagnosis includes tuberculous meningitis.

  References (1)Davies N ., Thwaites G Infections of the nervous system Practical Neurology 2011:11:121-131 (2) Michael BD., Sidhu M., Stoeter D et al Acute central nervous system infections in adults-a retrospective cohort study in the NHS Northwest region QJ Med 2010;103:749-758 (3)Ihekwaba UK., Kudesia G., McKendrick MW Clinical features of viral meningitis in adults: significant differences in cerebrospinal fluid findings among herpes simplex virus, varicvella zoster virus, and enterovirus infections Clinical Infectious Diseases 2008;47:783-789 (4) Granerod J., Ambrose HE., Davies NWS et al Causes of encephalitis and differences in their clinical presentations in England: a multicentre, population-based prosepctive study Lancet Infectious diseases 2010;10:835-844 (5)Landrey ML., Greenwold J., Vikram HR Herpes simplex type-2 meningitis: presentation and lack of standardised therapy American Journal of Medicine 2009;122:688-691

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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