During a cerebrospinal fluid examination, nerve fluid is removed from the spinal canal, usually by means of a lumbar puncture, and then examined. Analysis of the cerebrospinal fluid provides valuable diagnostic information compared with blood levels.
What is a cerebrospinal fluid examination?
During a cerebrospinal fluid examination, nerve fluid is removed from the spinal canal, usually by means of a lumbar puncture, and then examined. During a cerebrospinal fluid examination, also called a cerebrospinal fluid puncture or lumbar puncture, nerve fluid (cerebrospinal fluid) is removed from the dural sac in the spinal canal. Puncture of the dural sac is the simplest and also most common form of CSF sampling and is performed using an eight to ten centimeter needle. As a rule, the cerebrospinal fluid examination is performed on an outpatient basis and does not require an inpatient stay. Alternatively, if it is not possible to remove the cerebrospinal fluid from the dural sac, for example because of tumors, a cistern puncture can be performed and the cerebrospinal fluid removed at the level of the first cervical vertebra, or a ventricular puncture, in which the cerebrospinal fluid is removed directly from the cerebral ventricle, a cavity in the brain filled with cerebrospinal fluid.
Function, effect, and goals
Among other things, the cerebrospinal fluid examination is performed to diagnose or rule out diseases of the nervous system or the meninges, such as meningitis, encephalitis , Lyme disease, neurosyphilis or even multiple sclerosis. In addition, important indications of a possible cancer, for example a brain tumor, can also be obtained. Cancer of the meninges in an advanced stage, for example in leukemia or lymphoma, can also be detected in the cerebrospinal fluid. A subarachnoid hemorrhage, a special form of stroke in which blood enters the subarachnoid space, can be detected by a cerebrospinal fluid examination because the blood is detectable in the cerebrospinal fluid. Lumbar puncture is performed while the patient is sitting or lying down, with the upper body bent forward. If desired, the procedure can be performed under local anesthesia. The necessary tests are then performed in the laboratory. A first diagnosis can often be made by a simple visual inspection. Normally, the CSF is clear as water, but in the case of a bacterial infection it is more likely to be cloudy white, which is influenced by the high number of leukocytes in the CSF. Fresher hemorrhages are evident in the cerebrospinal fluid as a reddish turbidity. A yellowish turbidity of the cerebrospinal fluid occurs in older hemorrhages or in purulent processes, such as purulent meningitis. Among other things, markers can be determined for:
1. bacteria
2. fungi
3. leukocytes
4. cerebrospinal fluid sugar
5. immunoglobulins
6. enzymes
7. electrolytes
Since there is virtually no exchange between blood and cerebrospinal fluid due to the blood-cerebrospinal fluid barrier in the body, components of the blood can pass into the cerebrospinal fluid in some diseases. For this reason, the CSF is normally always compared with the blood values, as this is the only way to make a consistent assessment of the cerebrospinal fluid. If, for example, there are antibodies (immunoglobulins) in the CSF, this may indicate a disturbance of the blood-cerebrospinal fluid barrier, as in the case of multiple sclerosis, or it may be due to the formation of immune cells in the CSF itself. To find out where the cause lies, a comparison of the immunoglobulins in the blood is used. Protein in the CSF can also be caused by a disturbance of the blood-cerebrospinal fluid barrier. However, hemorrhage into the cerebrospinal fluid or inflammation can also lead to an elevated protein concentration. A comparison of glucose concentration in CSF with blood glucose also provides evidence of a disturbance of the blood CSF barrier. Normally, the glucose level in CSF is about half that of blood. An elevated value in the CSF indicates a disturbance of the blood CSF barrier, while a value that is too low indicates inflammatory processes. And the number of cells in the CSF also provides information on a possible disease. Normally, the cerebrospinal fluid contains only 4 cells per microliter. However, if there are infections in the area of the nervous system, the number of cells increases. The type of infection, whether bacterial or viral, can also be determined from the cell type in the CSF.
Risks, side effects and dangers
Lumbar puncture does not always proceed without complications. The greatest danger with a cerebrospinal fluid examination is increased intracranial pressure, as the flow of cerebrospinal fluid can cause the brain to be bruised, which can result in bleeding. Therefore, increased intracranial pressure must be ruled out by computed tomography before performing a lumbar puncture. Patients with a blood coagulation disorder, even if this is of a medicinal nature, for example by taking aspirin, must also not be punctured. During the extraction of cerebrospinal fluid, a temporary pain may occur in the buttocks, hip or legs if the needle touches a nerve root. Usually, however, the pain subsides fairly quickly. In the days following lumbar puncture, there is often the so-called postpuncture headache, which may be accompanied by severe nausea and dizziness. Generally, this decreases when the patient is lying down and subsides after a few days. In rare cases, a cerebrospinal fluid headache may last up to 4 weeks.
