Cerebrospinal Fluid Analysis

Overview of Cerebrospinal Fluid

Cerebrospinal fluid or CSF is a fluid circulating around the central nervous system, which is composed of the spinal cord and the brain. It is produced in an area of the brain called the choroid plexus. The major functions of the CSF are to carry nutrients, remove waste products, and to act as shock absorber to protect the brain and spinal cord.

In adults, the approximate total volume of cerebrospinal fluid is 140 ml. Its color is normally clear, and it contains very few cells. The normal value for CSF protein is 15 to 45 mg/dl and for glucose, 50 to 80 mg/dl. The normal pressure of CSF is usually between 8 and 15 mmHg.

About Cerebrospinal Fluid Analysis

Cerebrospinal fluid analysis is a series of laboratory tests which measures the amount of protein, sugar or glucose, and several other chemical tests depending on the request of the physician. The number of cells present in the CSF are also counted under the microscope. The CSF analysis is primarily done to detect certain disease conditions or injuries affecting the CNS. These include viral and bacterial infections, neurologic disorders, spinal cord or brain injuries, and for the presence of hemorrhage as well as cancer cells.

To obtain a sample of CSF for laboratory analysis, the common procedure used is the lumbar puncture, also referred to as the spinal tap. In the lumbar puncture method, the patient is often positioned on his side. The procedure is generally done in a sterile environment, having the skin surface surrounding the site to be punctured prepped with antiseptics. After which, the physician determines the specific site and apply a local anesthetic to minimize patient’s pain and discomfort.

The spinal needle is then inserted into the lower back of the patient. As soon as clear fluid flows in the syringe’s barrel, the pressure of the CSF is measured and samples are taken. Having collected an adequate sample of CSF, the needle is then withdrawn and the puncture site covered with a bandage. The patient is often instructed to lie down flat on his back for several minutes to prevent a spinal headache from occurring. The collected CSF samples are then sent to the laboratory for analysis.

Abnormal Cerebrospinal Fluid Analysis Results

Abnormalities in CSF values are usually caused by several factors like cancer, hepatic encephalopathy, encephalitis, meningitis and brain hemorrhage. When values of the patient’s CSF results are not within the normal range, the presence of these central nervous system problems are often considered.

Increased numbers of white blood cells or inflammatory cells, with decreased value of glucose and an elevated protein measurement, are frequently an indication of infection. Cloudiness of the CSF fluid may reflect infection or may be a result of the presence of tumor cells. Changes in CSF color can also indicate infection, or when slightly pinkish or reddish, it may be a result of hemorrhage or bleeding inside the CNS. Several other tests are also done, such as the determination for the presence of specific antigen and antibodies in the CSF.

These tests are specific, and can help physicians determine what organisms are causing the symptoms manifested by patients.

References

LabTestsOnline: CSF Analysis

MedlinePlus: CSF Analysis