Image: A photomicrograph of pleocytosis, which is an increased cell count, particularly an increase in white blood cell (WBC) count, in a bodily fluid such as cerebrospinal fluid (CSF) (Photo courtesy of Shutterstock).
Migration of leukocytes to the cerebrospinal fluid is a cardinal symptom of an infectious condition affecting the meninges or the cerebral parenchyma. Bacterial and viral meningitis cannot reliably be differentiated clinically and requires lumbar puncture to analyze the cerebrospinal fluid.
Lumbar puncture with quantification of leukocytes and differential count of cellular subsets in the cerebrospinal fluid is a standard procedure in cases of suspected neuroinfectious conditions. However, a number of non-infectious causes may result in a low leukocyte number. Pleocytosis is an increased cell count, particularly an increase in white blood cell count, in a bodily fluid, such as cerebrospinal fluid. It is often defined specifically as an increased white blood cell count in cerebrospinal fluid.
Scientists at the Odense University Hospital (Odense, Denmark) and their academic colleagues based their study on data from cerebrospinal fluid (CSF) analyses of all adult patients (15 years or older) admitted to a large university hospital in Denmark during a two-year period (2008–2009). Out of 5,390 unselected cerebrospinal fluid samples, 262 met the inclusion criteria. The neurological department (56.5%), department of emergency admission (14.9%), and the department of intensive care (7.3%) were the main contributors to CSF analyses.
In 141 patients mean CSF/plasma glucose ratio was 0.6 (normal). Significantly lower CSF/plasma glucose ratio was found in the decreased interval (less than 0.46) for CNS infection (mean = 0.2). Significant higher CSF/plasma glucose ratio was found in the decreased interval (less than 0.46) for non-infectious neurological diseases (mean = 0.4). Pleocytosis of greater than five leucocytes/μL was found in samples from 262 patients of which 106 (40.5%) were caused by infection of the central nervous system (CNS), 20 (7.6%) by infection outside CNS, 79 (30.2%) due to non-infectious neurological diseases, 23 (8.8%) by malignancy, and 34 (13.0%) caused by other conditions. Significantly higher mean CSF leukocytes were found in patients suffering from CNS infection (mean = 1,135 cells/μL).
The authors concluded that CNS infection, non-infectious neurological disease, malignancy, and infection outside CNS can cause pleocytosis of the cerebrospinal fluid. Leukocyte counts above 100/μL is mainly caused by CNS infection, whereas the number of differential diagnoses is higher if the CSF leukocyte counts is below 50/μL. These conditions are most commonly caused by non-infectious neurological diseases including seizures.
Odense University Hospital