CNS infections in the absence of CSF pleocytosis

Int J Inf Dis 2017; 65:107-109

Courtesy - Dr Balavinoth

  • CSF pleocytosis is important in establishing the diagnosis of central nervous system (CNS) infections such as meningitis, encephalitis, and meningoencephalitis.
  • The absence of pleocytosis represents a diagnostic challenge to clinicians when suspecting a CNS infection.
  • The Infectious Diseases International Research Initiative (IDIRI) study group analysed ID-IRI studies to identify patients without CSF pleocytosis (WBC count of <=5 x 106 cells/l).
  • Clinical presentations, laboratory findings, and outcomes were assessed to provide an insight into this particular condition for the treating clinician.
  • 32 of 141 patients (18%) with neurosyphilis, 39 of 496 patients (7.9%) with herpetic meningoencephalitis, 19 of 507 patients (3%) with tuberculous meningitis, five of 294 patients (1.7%) with Brucella meningitis, and one of 306 patients (0.2%) with pneumococcal meningitis did not present with CSF pleocytosis.

The authors concluded that the absence of pleocytosis was relatively infrequent but not rare in these CNS infections; such patients have a high rate of unfavorable outcomes, including sequelae and death. The examining clinician should not underestimate the presence of a CNS infection despite the lack of CSF pleocytosis for a patient with a suspicion of meningitis or encephalitis. The mean values of protein and CSF/blood glucose suggested the probable presence of a CNS infection in these patients and stresses the importance of considering the total CSF profile when ruling out a CNS infection.