Lumbar puncture and cerebrospinal fluid (liquor) diagnostics
The brain and spinal cord are very well protected, enveloped in the cerebral membranes (meninges) and immersed in a clear fluid, the Liquor cerebrospinalis. The cerebrospinal fluid for the central nervous system is produced in the ventricles of the brain. The subarachnoid spaces of the brain are also in direct contact with the structures surrounding the spinal cord. The cerebrospinal fluid is in constant circulation, and its constitution provides important signs of neurological disorders.
Lumbar puncture is a simple way to collect cerebrospinal fluid for testing or to introduce medications directly into the spinal canal. The procedure involves puncturing the spinal canal in the lower region of the lumbar spine. While collecting the fluid, the pressure of the cerebrospinal fluid system can be measured as well. Performing tests on the cerebrospinal fluid can provide indications of diseases of the nervous system.
When is lumbar puncture used?
Lumbar puncture is mainly performed when the following disorders are suspected:
- Certain cerebral hemorrhages (subarachnoid hemorrhage)
- Multiple Sclerosis (MS)
- Overproduction of cerebrospinal fluid (hydrocephalus)
- Suspected inflammatory neuropathy
- Guillain-Barre syndrome
- Lyme disease
- Brain tumors, spinal cord tumors, metastases
How is lumbar puncture performed?
The examination is carried out under local anesthesia while the patient is sitting or lying on their side. After a thoroughly disinfecting the site, a thin, long hollow needle is inserted between the two vertebrae of the lumbar spine and into the nerve canal. To prevent injury, this is performed between the fourth and fifth lumbar vertebrae, well below the spinal cord.
Once cerebrospinal fluid begins to drip from the needle, a manometer can be attached to measure the pressure. Next, a small amount of the cerebrospinal fluid is collected – as much as 50 ml in the case of certain disorders that produce excessive amounts of cerebrospinal fluid. The needle is then removed and the puncture site dressed with a bandage. After the procedure, the patient should lie with a straight back for about 30 minutes before going home.
Side effects of lumbar puncture
In general, lumbar puncture is a low-risk procedure and is not very painful. Occasionally, however, the stimulation of the nerve fibers in the spinal canal can cause electrifying sensations in the legs. These symptoms go away once the needle is removed. In rare cases, a highly abnormal spine can make the puncture procedure difficult.
Some patients experience headache and nausea a few hours later or on the day after the lumbar puncture (post-puncture syndrome). Negative pressure resulting from the collection of cerebrospinal fluid becomes noticeable mainly in the form of headaches when the person changes positions. Bed rest, adequate fluid intake and caffeine help in such cases. In most cases, these symptoms quickly go away again.
Cerebrospinal fluid diagnostics
The cerebrospinal fluid is tested in the laboratory for the number of cells, type of cells, proteins, sugar, bacteria and fungi and, depending on the clinical problem, other parameters as well. Normal cerebrospinal fluid is colorless and contains very few cellular constituents.
How long does it take for the results from cerebrospinal fluid tests?
Initial results from tests needed to diagnose acute meningitis, for example, take no more than a few hours. Results from several more specialized tests can take several days, however.