Cerebral fluid examination

At a Cerebral fluid examination Nerve fluid is taken from the spinal canal, usually by means of a lumbar puncture, and then examined. The analysis of the nerve water provides valuable diagnostic information in comparison to the blood values.

What is a brain water test?

In the Cerebral fluid examination, also CSF puncture or Lumbar puncture called, nerve fluid (liquor cerebrospinalis) is taken from the dural sac in the spinal canal.

The puncture of the dural sac is the simplest and most common form of removal of liquor and is performed with the help of an eight to ten centimeter long needle. As a rule, the brain water test is carried out on an outpatient basis and does not require an inpatient stay.

If it is not possible to remove the nerve fluid from the dural sac, for example due to tumors, a cistern puncture can alternatively be performed and the cerebral fluid removed at the level of the first cervical vertebra or a ventricular puncture, in which the liquor enters the cerebral ventricle, a cavity in the brain filled with liquor , is taken directly.

Function, effect & goals

The Cerebral fluid examination is carried out, among other things, to diagnose or exclude diseases of the nervous system or the meninges, such as meningitis, encephalitis, borreliosis, neurosyphilis or multiple sclerosis. In addition, important information about a possible cancer, for example a brain tumor, can be obtained.

Cancer of the meninges in an advanced stage, for example leukemia or lymphoma, can also be detected in the cerebral water. A subarachnoid haemorrhage, a special form of stroke in which blood enters the subarachnoid space, can be detected by a brain water test, since the blood can be detected in the nerve water.

The lumbar puncture is performed while 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 carried out in the laboratory.

An initial diagnosis can often be made with a simple visual inspection. Normally the CSF is clear like water, but in the case of a bacterial infection it is more whitish and cloudy, which is influenced by the high number of leukocytes in the CSF. More recent bleeding can be seen in the nerve water as a reddish cloudiness. A yellowish clouding of the cerebral fluid occurs in older bleeding or in purulent processes, such as purulent meningitis.

Among other things, markers can be determined for:

1. Bacteria

2. mushrooms

3. White blood cells

4. Liquorice

5. Immunoglobulins

6. Enzymes

7. Electrolytes

Since there is almost no exchange between blood and cerebral fluid due to the blood-liquor barrier in the body, components of the blood can pass into the cerebral fluid in some diseases. Therefore, the CSF is usually always compared with the blood values, as this is the only way to make a consistent assessment of the cerebral fluid.

For example, if there are antibodies (immunoglobulins) in the CSF, this can indicate a disruption of the blood-CSF barrier, such as in multiple sclerosis, or it can be caused by the formation of immune cells in the CSF itself. To find out what the cause is a comparison of the immunoglobulins in the blood was used.

Protein in the liquor can also be caused by a disruption of the blood-liquor barrier. However, bleeding into the nerve water or inflammation can also lead to an increased protein concentration.

A comparison between the glucose concentration in the liquor and the blood sugar also provides indications of a disruption of the blood-liquor barrier. Normally the glucose value in the CSF is about half as high as that in the blood. An increased value in the CSF indicates a disruption of the blood-CSF barrier, while a value that is too low indicates inflammatory processes.

The number of cells in the CSF also provides information on a possible disease. Normally the nerve water contains only 4 cells per microliter.However, if there are infections in the nervous system, the number of cells increases. The type of infection, whether bacterial or viral, can also be determined based on the cell type in the CSF.

Risks, side effects & dangers

It doesn't always go Lumbar puncture without complications. The greatest danger with a cerebral fluid test is when the brain pressure is increased, as the cerebrospinal fluid can be squeezed when the liquor drains, which can result in bleeding. Therefore, before a lumbar puncture, increased brain pressure must be ruled out by means of a computer tomography.

Patients with a blood coagulation disorder, even if it is of a medicinal nature, for example by taking aspirin, must also not be punctured.

While the cerebrospinal fluid is being removed, you may experience temporary pain in your buttocks, hips, or legs when the needle touches a nerve root. Usually, however, the pain subsides quickly. In the days after the lumbar puncture, the so-called post-puncture headache often occurs, which can be accompanied by severe nausea and dizziness. In general, this decreases when lying down and subsides after a few days. In rare cases, the headache can persist for up to 4 weeks on a brain water test.