What is a lumbar puncture used for?

Lumbar puncture

Puncture of the dural sac for CSF diagnostics

It is a puncture of the dural sac in the lumbar area. This low-risk examination is mainly carried out if there is a suspicion of inflammatory or malignant diseases of the meninges or the brain

But a lumbar puncture is also used for other pathological changes such as a lymph gland tumor. It is a fast and, above all, painless method with a high diagnostic value.

In this guide we provide you with comprehensive information on the subject of lumbar puncture, such as how it works, the areas of application or the possible risks.

Table of Contents

What is a lumbar puncture?

If the doctor decides to perform a lumbar puncture, the majority of patients are very unsettled. After all, a long needle is inserted into the spinal canal and cerebrospinal fluid is taken from there.

But the all-clear can be given, because this is a very safe, fast and, above all, painless procedure that provides a lot of information about the patient's clinical picture and the further course of action.

As already mentioned, this type of puncture is a very safe procedure, in which a hollow needle is inserted into the lower lumbar vertebral area in order to obtain cerebrospinal fluid (Latin: liquor cerebrospinalis). With the help of the liquor, a distinction can be made between bacterial, viral and autoimmune diseases in the laboratory within a very short time.

This method is not only used to make a diagnosis, but also to overcome the so-called blood-brain barrier, the purpose of which is to protect the brain from certain substances. This is particularly important when special chemotherapeutic agents are given to treat certain types of cancer.

Liquor is formed in the so-called choroid plexus in the four chambers of the brain (Latin: ventricle). This is a vein network with a shaggy surface. The blood is filtered in these braids and the liquor is created from this. The cerebral fluid surrounds the brain as well as the entire spinal cord in the so-called subarachnoid space and thus offers protection for the most sensitive regions of the human body.

The functions of this clear liquid primarily serve the metabolism of the nerve cells of the central nervous system. The breakdown products of the nervous system are transported away by constant circulation and excreted from the body via the lymph.

The lumbar puncture is still known under the more common name of spinal anesthesia. The procedure is the same as with the lumbar puncture, only no liquor is removed, but an anesthetic is injected into the spinal canal so that the lower extremities no longer feel pain. This procedure is mainly used for caesarean sections and hip operations.

Origin & Development

This examination method was established as early as 1891 and embedded in everyday medical practice. This method was invented by the Kiel physician Heinrich Irenäus Quincke. Quincke was a very dedicated doctor who started his career at the age of 16.

In his career he set important milestones that are still of use to internists today. Quincke's preliminary scientific work enabled a great number of research methods to be further developed and improved.

Process, impact & goals

Execution, indications & goals of the puncture

Before a lumbar puncture is performed, there should be some check-ups. On the one hand, the coagulation and thrombocyte count (blood platelets) must be examined for pathological changes and the fundus of the eye (increased intracranial pressure must be excluded). If there are no abnormalities, a puncture is carried out by a doctor.

To do this, the patient either lies on his side or sits upright on the examination table. It is important here that the patient lies or sits in a curved position, because this creates a greater distance between the spinous processes of the individual lumbar vertebrae and the doctor performing the procedure can more easily reach the spinal canal.

Before the puncture, the puncture site is precisely marked and then disinfected and the area around the puncture is covered with a sterile drape. The puncture is usually painless, so local anesthesia is only available in exceptional cases or if the patient requests it.

The puncture is usually carried out between the 3rd and 4th or 5th and 6th lumbar vertebrae, because at this level there is no longer any spinal cord in the spinal canal, only liquor. In this way, an injury to the spinal cord can be excluded. When the doctor has reached the spinal canal, it will feel a slight resistance.

In rare cases, an electrifying sensation can occur in the patient's legs when the needle touches a nerve cord. This feeling disappears again by changing the position of the needle slightly. Once the doctor has reached the correct position, he removes the inside of the needle so that only the outer hollow needle remains in the puncture site.

The liquor now drips from this hollow needle into a sterile vessel. Approximately 3-5 ml are collected and then examined in the laboratory according to the medical question. The duration of the puncture is approximately 5-10 minutes. The patient should then lie down for 24 hours to avoid or relieve post-puncture headaches.

Indication in case of suspicion

  • inflammatory or malignant diseases of the meninges or brain
  • Autoimmune diseases
  • multiple sclerosis
  • Lyme disease
  • Tumors
  • Cerebral hemorrhage

The most common indication to perform a lumbar puncture is the suspicion of inflammatory (meningitis or encephalitis) or malignant diseases of the meninges or the brain. Since it is a non-invasive and low-risk procedure, it is the gold standard for diagnosing the diseases mentioned.

Autoimmune diseases, multiple sclerosis and Lyme borreliosis can also be diagnosed in this way. If it is a brain tumor, the corresponding tumor cells can be detected in the liquor. If there is a suspicion of cerebral haemorrhage, the color of the liquor provides information.

If the liquor is bright red, it is fresh bleeding, but if it is yellow, the bleeding is old and no longer acute. As is clear, the collection and examination of the liquor has a great use in medicine.

Objectives of treatment and analysis of the CSF:

  • Diagnosis
  • Crossing the blood-brain barrier.

This effect is particularly desirable in the case of specific cancers, since the blood-brain barrier normally only allows very few substances into the brain. However, if a chemotherapeutic agent is injected directly into the spinal canal, it can act directly and unfiltered on tumors in the brain.

  • Treatment of hydrocephalus malresorptivus after subarachnoid hemorrhage to relieve pressure

Diagnosis & examination

Diagnostics & examination methods

The components of the liquor and, above all, their composition are analyzed in the laboratory. The main components are proteins, antibodies, glucose, lymphocytes and, in rare cases, monocytes.

The components of the liquor and their composition are analyzed in the laboratory

Diseases can be excluded or diagnosed from the ratio of the components mentioned. If you take the protein albumin as an example, if you increase it it can be determined that the blood-brain barrier is not working properly.

Albumin is produced exclusively in the liver and is normally not allowed to cross the blood-brain barrier. Therefore, the presence of albumin in the CSF is a sure sign that the blood-brain barrier is disrupted. So does glucose. Normally, the glucose level in the CSF is between 50-60% of the serum level.

If the glucose is increased this speaks for a virus-caused meningitis, if it is significantly reduced it can be assumed that it is a bacterially caused meningitis which must therefore be treated differently.

Risks & side effects

frequent side effects

(> 3%):

  • Post-puncture headache: a common side effect, as even a slight difference in pressure, which is caused by the removal of the CSF, leads to these typical headaches. The pain is reduced in the lying position. The pain subsides on its own within a few days
  • Hip pain: Sometimes there may be mild hip pain caused by the puncture when the needle hits the nerve roots
  • Slight feeling of pressure at the puncture site
  • Nausea and dizziness
  • Injury to smaller blood vessels, which can lead to light bleeding, but without functional failure

Rare side effects

  • local inflammation
  • Circulatory reactions
  • temporary impairment of consciousness

Extremely rare side effects

(only described as individual cases in the literature):

  • Infection through transmission of germs: this is an extremely rare side effect because the puncture is performed in a sterile environment.
  • Injury to the spinal cord: if the puncture site is too high, the doctor can use the needle to injure the spinal cord
  • Injury to the spinal canal and nerve tracts
  • Brain damage if the intracranial pressure is too high (the puncture must not be performed if the intracranial pressure is increased)

Contraindications & Dangers

  • increased intracranial pressure
  • Coagulation disorder
  • Thrombocytopenia
  • Infections
  • critical cardiopulmonary condition
  • Brain edema

If the intracranial pressure is increased, no lumbar puncture is performed, as the sudden drop in pressure can cause contusions in the brain. This can lead to cardiovascular arrest or respiratory failure, which in most cases is fatal.

Another contraindication is a coagulation disorder such as absolute thrombocytopenia. If patients have fewer platelets than 50,000 / µl, a puncture could in principle still be performed, but if fewer than 20,000 / µl are present, the puncture must not take place under any circumstances (normal values ​​are between 150,000-350,000 / µl).

In this case, platelets must be substituted in advance. Patients who take Marcumar if they have a tendency to bleed are switched to heparin. Low molecular weight heparin may be given for the last time no later than 8-12 hours before the procedure and no earlier than 2 hours after the puncture.

Who treats?

Which doctors do a lumbar puncture?

  • doctor
  • Assistance from trained medical staff

The treatment is carried out exclusively by doctors. Since it is a minor surgical procedure, the procedure is sterile. Doctors and staff involved wear sterile disposable gloves and face masks.

The puncture site is thoroughly disinfected before the procedure and the rest of the body is covered with a sterile drape. As a result, the risk of getting an infection through the puncture is extremely unlikely.

Our conclusion on the procedure

The lumbar puncture is a low-risk and quick examination method that provides information about certain clinical pictures such as meningitis or autoimmune diseases and thus accelerates the recovery of the affected patient.
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