Lumbar puncture

Lumbar puncture (lumbar puncture, puncture of the subarachnoid space of the spinal cord, spinal puncture, lumbar puncture)

– insertion of a needle into the subarachnoid space of the spinal cord for diagnostic or therapeutic purposes.

When is a lumbar puncture performed?

Lumbar puncture is performed for diagnostic or therapeutic purposes.

• Diagnostic lumbar puncture – carried out to study the cerebrospinal fluid. When analyzing cerebrospinal fluid, color, transparency, and cellular composition must be determined. It is possible to study the biochemical composition of the cerebrospinal fluid, conduct microbiological tests, including its inoculation on special media. During a lumbar puncture, cerebrospinal fluid pressure is measured and the patency of the subarachnoid space of the spinal cord is examined using compression tests.
• Therapeutic lumbar puncture – performed to remove cerebrospinal fluid and normalize cerebrospinal fluid circulation, control conditions associated with communicating hydrocephalus, as well as to sanitize cerebrospinal fluid in case of meningitis of various etiologies and administer medications (antibiotics, antiseptics, cytostatics).

Absolute and relative indications for lumbar puncture

• Absolute indications for spinal puncture
  • suspected infection of the central nervous system (meningitis, encephalitis, ventriculitis),
  • oncological lesions of the membranes of the brain and spinal cord,
  • normal pressure hydrocephalus,
  • diagnosis of liquorrhea and identification of liquor fistulas by injecting dyes, fluorescent and radiopaque substances into the subarachnoid space,
  • diagnosis of subarachnoid hemorrhage when CT is not possible.
• Relative indications for lumbar puncture
  • fever of unknown origin in children under 2 years of age,
  • septic vascular embolism,
  • demyelinating processes,
  • inflammatory polyneuropathies,
  • paraneoplastic syndromes,
  • systemic lupus erythematosus, etc.

Contraindications for lumbar puncture

In the presence of a brain space-occupying lesion, occlusive hydrocephalus, signs of severe cerebral edema and intracranial hypertension, there is a risk of axial herniation during lumbar puncture. Its likelihood increases when thick needles are used and large amounts of cerebrospinal fluid are removed.

Under these conditions, lumbar puncture is performed only in cases of extreme necessity, and the amount of cerebrospinal fluid removed should be minimal.

If symptoms of herniation appear during puncture (currently this is an extremely rare situation), urgent endolumbar administration of the required amount of fluid is recommended.

Other contraindications to lumbar puncture are not considered so absolute. These include infectious processes in the lumbosacral region, blood clotting disorders, taking anticoagulants and antiplatelet agents (risk of epidural or subdural hemorrhage with secondary compression of the spinal cord).

Caution when performing a lumbar puncture (removal of a minimal amount of cerebrospinal fluid) is necessary if there is a suspicion of hemorrhage from a ruptured cerebral aneurysm (risk of re-rupture) and blockade of the subarachnoid space of the spinal cord (risk of the appearance or worsening of neurological deficit).

How is a lumbar puncture performed?

Lumbar puncture can be performed with the patient lying down or sitting. The latter provision is currently used extremely rarely. Typically, the puncture is performed with the patient lying on his side with the head tilted forward and the legs bent at the hip and knee joints.

The conus of the spinal cord in a healthy adult is in most cases located between the middle sections of the L1 and L2 vertebrae. The thecal sac usually ends at the S2 level.

The line connecting the iliac crests crosses the spinous process of L4, or the space between the spinous processes of L4 and L5 (Jacobi line).

In adults, lumbar puncture is usually performed in the L3-L4 space; in children, an attempt should be made to perform the procedure through the L4-L5 space.

The skin in the area of ​​the puncture is treated with an antiseptic solution, then local anesthesia is administered by introducing an anesthetic intradermally, subcutaneously and along the puncture.

A special needle with a mandrel is used to puncture the subarachnoid space in the sagittal plane parallel to the spinous processes (at a slight angle). The cut of the needle should be oriented parallel to the length of the body.

Bone obstruction usually occurs when there is a deviation from the midline. Often, when passing the needle through the yellow ligaments and dura mater, a sensation of failure is noted.

In the absence of such a landmark, the position of the needle can be checked by the appearance of cerebrospinal fluid in the needle pavilion; to do this, you need to periodically remove the mandrel.

If typical radicular pain appears during needle insertion, the procedure should be stopped immediately, the game should be removed to a sufficient distance and the puncture should be performed with a slight tilt of the needle towards the contralateral leg. If the needle rests on the vertebral body, it is necessary to tighten it by 0,5-1 cm.

Sometimes the lumen of the needle can cover the root of the spinal cord; in this case, slight rotation of the needle around its axis and pulling it up by 2-3 mm can help. Sometimes, even if the needle gets into the dural sac, it is not possible to obtain cerebrospinal fluid due to severe cerebrospinal fluid hypotension. In this case, lifting the head end helps; you can ask the patient to cough and apply compression tests.

With repeated punctures (especially after chemotherapy), a rough adhesive process develops at the puncture site.

If, despite following all the rules, the appearance of cerebrospinal fluid cannot be achieved, it is advisable to attempt to perform a puncture at a different level. Rare reasons for the inability to perform a lumbar puncture are a tumor of the spinal canal and an advanced purulent process.

Liquor pressure. Compression tests

Immediately after the appearance of cerebrospinal fluid in the needle pavilion, it is possible to measure the pressure in the subarachnoid space by connecting a plastic tube or a special system to the needle. The patient should be as relaxed as possible during the blood pressure measurement process.

Normal fluid pressure in a sitting position is 300 mm water column, lying down – 100-200 mm water column. Indirectly, the level of pressure can be assessed by the rate of flow of cerebrospinal fluid (60 drops per minute roughly corresponds to normal pressure).

Pressure increases with inflammatory processes in the meninges and choroid plexuses, and disruption of fluid outflow due to increased pressure in the venous system (venous stagnation). To determine the patency of the subarachnoid spaces, use liquorodynamic tests.

• Queckenstedt sample. After determining the initial pressure of the cerebrospinal fluid, compression of the jugular veins is performed for no longer than 10 s. In this case, normally the pressure increases by an average of 10-20 cm of water column. and returns to normal 10 s after compression stops.
• RџSЂRё Stukey’s test for 10 seconds, press with a fist on the abdomen in the navel area, creating stagnation in the inferior vena cava system, where blood flows from the thoracic and lumbosacral parts of the spinal cord and epidural veins. Normally, the pressure also increases, but more slowly and not as significantly as with the Queckenstedt test.

Blood in the cerebrospinal fluid

An admixture of blood in the cerebrospinal fluid is most typical of subarachnoid hemorrhage.

In some cases, during a lumbar puncture, a vessel may be damaged, and an admixture of “travel blood” appears in the cerebrospinal fluid.

In case of intense bleeding and if it is impossible to obtain cerebrospinal fluid, it is necessary to change the direction or puncture another level. When receiving cerebrospinal fluid with blood, a differential diagnosis should be made between subarachnoid hemorrhage and an admixture of “travel blood”.

For this purpose, the cerebrospinal fluid is collected in three test tubes. With subarachnoid hemorrhage, the cerebrospinal fluid in all three tubes is colored almost identically. In the event of a traumatic puncture, the cerebrospinal fluid from the first to the third tube will gradually clear.

Another way is to evaluate the color of the supernatant: yellow cerebrospinal fluid (xanthochromic) is a reliable sign of hemorrhage. Xanthochromia appears within 2-4 hours after subarachnoid hemorrhage (the result of hemoglobin degradation from broken red blood cells).

Small subarachnoid hemorrhage can be difficult to visually distinguish from inflammatory changes, in which case you should wait for the results of a laboratory test. Rarely, xanthochromia may be a consequence of hyperbilirubinemia.

Study of the composition of cerebrospinal fluid

For a standard study, cerebrospinal fluid is taken into three tubes: for general, biochemical and microbiological analyses.

A standard clinical analysis of cerebrospinal fluid includes an assessment of the density, pH, color and transparency of the cerebrospinal fluid before and after centrifugation, an assessment of total cytosis (normally no more than 5 cells per 1 μl), and determination of protein content. Depending on the need and capabilities of the laboratory, the number of lymphocytes, eosinophils, neutrophils, macrophages, altered cells, polyblasts, plasma cells, arachnoendothelial cells, epidermal cells, granular balls, tumor cells is also examined.

The relative density of cerebrospinal fluid is normally 1,005-1,008; it is increased during inflammatory processes and decreased during excessive fluid formation. Normal pH is 7,35-7,8,

• it decreases with meningitis, encephalitis, paralysis,
• increases with paralysis (before treatment), cerebral syphilis, epilepsy, chronic alcoholism.

A yellow color of the cerebrospinal fluid is possible with a high protein content, in the case of a history of subarachnoid hemorrhage and hyperbilirubinemia.

With melanoma metastases and jaundice, the cerebrospinal fluid may be dark.

Significant neutrophilic cytosis is characteristic of bacterial infection, lymphocytic – for viral and chronic diseases.

Eosinophils are characteristic of parasitic diseases.

If there are 200-300 leukocytes in 1 µl, the cerebrospinal fluid becomes cloudy. To differentiate leukocytosis caused by subarachnoid hemorrhage, it is necessary to count leukocytes, taking into account the fact that in the blood there is approximately 700 leukocyte per 1 red blood cells.

The protein content normally does not exceed 0,45 g/l and increases with meningitis, encephalitis, tumors of the spinal cord and brain, various forms of hydrocephalus, block of the subarachnoid space of the spinal cord, carcinomatosis, neurosyphilis, GBS, and inflammatory diseases. Colloidal reactions also play a significant role – the Lange reaction (“golden reaction”), colloidal mastic reaction, Takata-Ara reaction, etc.

In a biochemical analysis of the cerebrospinal fluid, the content of glucose (normally in the range of 2,2-3,9 mmol/l) and lactate (normally in the range of 1,1-2,4 mmol/l) is assessed. The assessment should be carried out taking into account the fact that the glucose content of the cerebrospinal fluid depends on the concentration of blood glucose (40-60% of this value). A decrease in glucose content is a common sign of meningitis of various etiologies (usually of bacterial origin, including tuberculosis); an increase in the concentration of glucose in the cerebrospinal fluid is possible with ischemic and hemorrhagic stroke.

A reduced content of chlorides in the cerebrospinal fluid is characteristic of meningitis, especially tuberculosis, neurosyphilis, brucellosis, an increase – for brain tumors, brain abscess, echinococcosis.

In a microbiological laboratory, you can stain a smear or sediment of the cerebrospinal fluid, depending on the expected etiology of the pathogen: with Gram stain – if a bacterial infection is suspected, for acid-fast microorganisms – if tuberculosis is suspected, ink – if a fungal infection is suspected. CSF cultures are carried out on special media, including media that absorb antibiotics (in the case of massive antibiotic therapy).

There are a large number of tests to identify specific diseases, for example, the Wasserman reaction, RIF and RIBT to exclude neurosyphilis, tests for various antigens for typing tumor antigens, determination of antibodies to various viruses, etc.

Bacteriological examination can identify meningococci, pneumococci, Haemophilus influenzae, streptococci, staphylococci, listeria, and mycobacterium tuberculosis. Bacteriological studies of cerebrospinal fluid are aimed at identifying the causative agents of various infections: coccal group (meningo-, pneumo-, staphylo- and streptococci) for meningitis and brain abscesses, treponema pallidum – for neurosyphilis, Mycobacterium tuberculosis – for tuberculous meningitis, toxoplasma – for toxoplasmosis, cysticercus vesicles – with cysticercosis.

Virological studies of cerebrospinal fluid are aimed at establishing the viral etiology of the disease (some forms of encephalitis).

After a spinal tap

After a lumbar puncture, it is customary to adhere to bed rest for 2-3 hours to avoid post-puncture syndrome caused by the continued leakage of cerebrospinal fluid through a defect in the dura mater.

Complications of lumbar puncture

The total risk of complications is estimated at 0,1-0,5%. Possible complications include the following.

• Axial wedging:
  • acute herniation during puncture in conditions of intracranial hypertension;
  • chronic herniation as a result of repeated lumbar punctures;
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• Infectious complications.
• Headaches that usually go away when lying down.
• Hemorrhagic complications, usually associated with blood clotting disorders.
• Epidermoid cysts as a result of using low-quality needles or needles without a mandrel.
• Damage to the roots (possible development of persistent pain syndrome).
• Damage to the intervertebral disc with the formation of a disc herniation.

The introduction of contrast agents, anesthetics, chemotherapy drugs, and antibacterial drugs into the subarachnoid space can cause a meningeal reaction. It is characterized by an increase in cytosis to 1000 cells on the first day, an increase in protein content with normal glucose levels and sterile seeding. This reaction usually regresses quickly, but in rare cases can lead to arachnoiditis, radiculitis or myelitis.

At the Prima Medica medical center you can consult with an experienced neurologist. Make an appointment for a consultation by phone +7 495 120-01-07