Lymphocytic pleocytosis

Lymphocytic pleocytosis is an abnormal increase in the amount of lymphocytes in the cerebrospinal fluid (CSF). It is usually considered to be a sign of infection or inflammation within the nervous system, and is encountered in a number of neurological diseases, such as pseudomigraine, Susac's syndrome, and encephalitis. While lymphocytes make up roughly a quarter of all white blood cells (WBC) in the body, they are generally rare in the CSF. Under normal conditions, there are usually less than 5 white blood cells per µL of CSF. In a pleocytic setting, the number of lymphocytes can jump to more than 1,000 cells per µL. Increases in lymphocyte count are often accompanied by an increase in cerebrospinal protein concentrations in addition to pleocytosis of other types of white blood cells. Lymphocytic pleocytosis is an abnormal increase in the amount of lymphocytes in the cerebrospinal fluid (CSF). It is usually considered to be a sign of infection or inflammation within the nervous system, and is encountered in a number of neurological diseases, such as pseudomigraine, Susac's syndrome, and encephalitis. While lymphocytes make up roughly a quarter of all white blood cells (WBC) in the body, they are generally rare in the CSF. Under normal conditions, there are usually less than 5 white blood cells per µL of CSF. In a pleocytic setting, the number of lymphocytes can jump to more than 1,000 cells per µL. Increases in lymphocyte count are often accompanied by an increase in cerebrospinal protein concentrations in addition to pleocytosis of other types of white blood cells. Determination of lymphocytic pleocytosis became possible with the advent of the diagnostic lumbar puncture and the technology necessary to analyze the cerebrospinal fluid via microbiological, biochemical, and immunological tests. While the first lumbar punctures were performed in the late 19th century, the tests revealing elevated lymphocyte levels within the CSF were not available until much later. Modern lumbar punctures testing for lymphocyte counts are commonly used to diagnose or rule out certain diseases such as meningitis and determine whether an infection is present within the CSF. Though exact concentrations differ based on the specific disease, mild cases of lymphocytic pleocytosis are considered to begin when lymphocyte counts enter the range of 10-100 cells per mm3. In healthy individuals, only 0-5 white blood cells per µL are normally present in the CSF. In patients suffering from pseudomigraines, studies have shown concentrations ranging from 10-760 cells per mm3, with a mean concentration of 199 ± 174 cells per mm3. Increases in white blood cell count to more than 500 cells per mm3 can cause the CSF to appear cloudy when observed during diagnostic tests. The rise in concentration corresponds to an inflammatory immune response typically seen during viral infections. Despite their diversity, diseases featuring lymphocytic pleocytosis share a number of symptoms, most notably headaches and neurological deficits. Cerebral spinal fluid lymphocytic pleocytosis is generally the result of an immune response to neurovascular inflammation. Many cases point to a viral infection as the root cause of pleocytosis, in which the immune system produces antibodies against neuronal and vascular antigens. This evidence possibly connects it to viral meningitis and Mollaret’s disease. Certain non-viral infections, such as Lyme disease have also been considered possible causes. In some diseases, an infection precipitates an autoimmune response, leading to increased lymphocyte levels. The presence of lymphocytic pleocytosis is generally detected through a lumbar puncture followed by clinical analysis of cerebrospinal fluid. When combined with analysis of the appearance and pressure of the tested CSF, along with measurements for the amount of glucose and proteins present, white blood cell counts can be used to detect or diagnose a number of diseases. Among these are subarachnoid hemorrhage, multiple sclerosis, and the various types of meningitis. While a lumbar puncture may return a WBC count within the normal range of 0-5 cells per µL, this does not rule out the possibility of a disease.