Bacterial meningitis presenting with a normal cerebrospinal fluid leukocyte count

Area of Science:

• Neurology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Bacterial meningitis typically presents with elevated cerebrospinal fluid (CSF) leukocyte counts.
• A subset of bacterial meningitis cases may exhibit normal CSF leukocyte counts, posing diagnostic challenges.

Purpose of the Study:

• To describe the clinical characteristics and outcomes of adults with bacterial meningitis who present with a normal CSF leukocyte count.
• To identify key diagnostic parameters in bacterial meningitis cases with normal CSF leukocyte counts.

Main Methods:

• Prospective nationwide cohort study of community-acquired bacterial meningitis in adults.
• Analysis of cases with normal CSF leukocyte count (≤ 5 per mm³).
• Evaluation of clinical presentation, CSF protein, Gram staining, and patient outcomes.

Main Results:

• 2% of bacterial meningitis episodes (39 of 2,357) presented with normal CSF leukocyte counts.
• Immunocompromising conditions were more frequent in patients with normal CSF leukocytes (49%) compared to those with elevated counts (30%).
• High CSF protein (68%) and positive CSF Gram stain (95% in severe pneumococcal meningitis) were significant findings. Unfavorable outcomes occurred in 59% of patients, with a 31% mortality rate.

Conclusions:

• Bacterial meningitis can manifest with normal CSF leukocyte counts.
• Elevated CSF protein levels and positive CSF Gram stain are critical diagnostic indicators in these cases.
• Prompt diagnosis and management are essential due to the high rate of unfavorable outcomes.