Lumbar puncture

Lumbar puncture (lumbar puncture, puncture of the subarachnoid space of the spinal cord, spinal puncture, lumbar puncture) - insertion of the needle into the subarachnoid space of the spinal cord for diagnostic or therapeutic purposes.

Lumbar puncture is one of the widely used methods of research in neurology. In some cases (infectious diseases of the central nervous system, subarachnoid hemorrhage) the diagnosis is entirely based on the results of lumbar puncture. Her data complement the clinical picture and confirm the diagnosis for polyneuropathies, multiple sclerosis and neiroleukemia. It should be noted that the widespread introduction of neuroimaging methods has dramatically reduced the number of diagnostic lumbar punctures. Puncture can sometimes be used for therapeutic purposes for the intrathecal administration of antibiotics and chemotherapeutic drugs, as well as for reducing intracranial pressure in benign intracranial hypertension and in normotensive hydrocephalus.

The total volume of cerebrospinal fluid is about 120 ml in adults. Speaking about the extraction of small volumes of it (from 10 to 20 ml) for diagnostic purposes, it should be borne in mind that the daily volume of secretion is 500 ml. Thus, a full update of the cerebro-spinal fluid occurs 5 times a day.

[1], [2], [3], [4], [5]

Indications for the procedure

Lumbar puncture is performed for diagnostic or therapeutic purposes.

• With a diagnostic purpose, the puncture is performed for the investigation of the cerebrospinal fluid. When analyzing CSF, it is necessary to determine the color, transparency, cellular composition. It is possible to study the biochemical composition of the liquor, conduct microbiological tests, including its sowing on special media. During the lumbar puncture, the liquor pressure is measured, the patency of the subarachnoid space of the spinal cord is examined with the help of compression tests.
• With a therapeutic purpose, the lumbar puncture is performed to remove the liquor and normalize the liquor circulation, to control the conditions associated with the communicating hydrocephalus, as well as to sanitize the liquor with meningitis of various etiologies and the administration of medications (antibiotics, antiseptics, cytostatics).

Allocate absolute and relative indications for lumbar puncture.

• Absolute indications: suspicion of CNS infection ( meningitis, encephalitis, ventriculitis), oncological damage to the membranes of the brain and spinal cord, normotensive hydrocephalus; diagnostics of liquorrhea and detection of cerebrospinal fistulas by introducing dyes, fluorescing and radiocontrast agents into the subarachnoid space; Diagnosis of subarachnoid hemorrhage when CT is impossible.
• Relative indications: fever of unknown origin in children under 2 years, septic embolism of vessels, demyelinating processes, inflammatory polyneuropathies, paraneoplastic syndromes, systemic lupus erythematosus, etc.

[6], [7], [8],

Technique of the lumbar puncture

Lumbar puncture can be performed in the position of the patient lying or sitting. The latter provision is currently used extremely rarely. Usually puncture is performed in the position of the patient lying on his side with the head tilted forward and bent in the hip and knee joints with his legs. The cone of the spinal cord in a healthy adult is in most cases located between the middle parts of the vertebrae L ₁  and L ₂. The dural bag usually ends at the level of S ₂. The line connecting the crests of the iliac bones intersects the spinous process L ₄  or the interval between the spinous processes L ₄  and L ₅  (the Jacobi line).

Adult lumbar puncture is usually performed in the L ₃ -L ₄ interval , children should try to conduct the procedure through the gap L ₄ -L ₅. Carry out the treatment of skin in the area of puncture with antiseptic solution, then local anesthesia by injecting an anesthetic intradermally, subcutaneously and along the puncture. A special needle with a mandrel is performed by puncturing the subarachnoid space in the sagittal plane parallel to the spinous processes (at a slight angle). The needle cut must be parallel to the body length. Bone obstruction, as a rule, occurs when the deviation from the midline. Often when the needle passes through the yellow ligaments and the solid medulla, a sense of failure is noted. In the absence of such a guideline, the position of the needle can be checked by the appearance of the cerebrospinal fluid in the needle pavilion, for this it is necessary to periodically remove the mandril. If typical root pain occurs during the introduction of the needle, the procedure should be stopped immediately, the game should be taken a sufficient distance and a puncture with a certain inclination of the needle towards the contralateral leg should be performed. If the needle rests against the body of the vertebra, 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 the light rotation of the needle around its axis and its pulling by 2-3 mm can help. Sometimes even when a needle enters the dural sac, the cerebrospinal fluid can not be obtained due to the pronounced cerebrospinal fluid hypotension. In this case, helps lift the head end, you can ask the patient to cough, apply compression tests. With multiple punctures (especially after chemotherapy ), a coarse adhesive process develops at the puncture site. If, if all the rules for the emergence of CSF were not met, it would be advisable to attempt a puncture at a different level. Rare causes of the inability to perform a lumbar puncture include a spinal canal tumor and a far purulent process.

Measurement of liquor pressure and compression tests

Immediately after the appearance of the liquor in the pavilion of the needle, 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 in the process of measuring the pressure. Normal fluid pressure in the sitting position is 300 mm of water, lying - 100-200 mm of water. Indirectly, the level of pressure can be estimated from the rate of leakage of CSF (60 drops per minute conditionally corresponds to normal pressure). The pressure increases with inflammatory processes of the meninges and vascular plexuses, a violation of the outflow of fluid due to increased pressure in the venous system (venous congestion). Liquidity tests are used to determine the patency of subarachnoid spaces.

• The Québecstedt test. After determining the initial pressure of the cerebrospinal fluid, jugular veins are compressed for no longer than 10 s. At the same time, normal pressure increases on average by 10-20 cm of water. And it is normalized after 10 seconds after the termination of compression.
• With a stool sample for 10 with a fist, press on the abdomen in the navel, creating stasis in the system of the inferior vena cava, where the blood flows from the thoracic and lumbosacral spinal cord, epidural veins. Normally, the pressure also increases, but slower and not as much as in the Quéquenstedt test.

The admixture of blood in the liquor

The admixture of blood in the cerebrospinal fluid is most typical for  subarachnoid hemorrhage. In some cases, with a lumbar puncture, the vessel may be damaged, and an admixture of "ground blood" appears in the cerebrospinal fluid. In case of intensive bleeding and if it is impossible to get the cerebrospinal fluid, it is necessary to change the direction or puncture another level. When receiving a cerebrospinal fluid with blood, a differential diagnosis should be made between subarachnoid hemorrhage and an admixture of "ground blood". For this purpose, the liquor is collected in three test tubes. With subarachnoid hemorrhage, the liquor in all three test tubes is almost the same color. In case of a traumatic puncture, the liquor from the first to the third test tube will be gradually cleared. Another method is to evaluate the color of the supernatant: yellow liquor (xanthochromic) is a reliable sign of hemorrhage. Xanthochromia appears only 2-4 hours after subarachnoid hemorrhage (the result of the degradation of hemoglobin from decomposed red blood cells). A small subarachnoid hemorrhage can be difficult to visually distinguish from inflammatory changes, in this case, you should wait for the results of a laboratory study. Rarely, xanthrochromia can be a consequence of hyperbilirubinemia.

Contraindications to the procedure

In the presence of volumetric formation of the brain, occlusive hydrocephalus, signs of severe brain edema and intracranial hypertension, there is a risk of axial wedging during lumbar puncture, its probability increases with the use of thick needles and the removal of a large amount of liquor. In these conditions, lumbar puncture is performed only in cases of extreme necessity, and the amount of CSF withdrawn should be minimal. If there are symptoms of wedging during the puncture (at present this is an extremely rare situation), urgent endolumbal administration of the required amount of fluid is recommended. Other contraindications to the lumbar puncture are not considered so absolute. These include infectious processes in the lumbosacral region, blood clotting disorders, the use of anticoagulants and antiaggregants (risk of epidural or subdural hemorrhage with secondary compression of the spinal cord). Caution when conducting a lumbar puncture (the withdrawal of a minimum amount of CSF) is necessary if there is a suspicion of a hemorrhage from an exploded aneurysm of the cerebral vessels (risk of a rupture) and blockade of the subarachnoid space of the spinal cord (risk of appearance or strengthening of neurological deficit).

[9]

Normal performance

For a standard study, the liquor is taken in three test tubes: for general, biochemical and microbiological analyzes.

Standard clinical analysis of CSF includes assessment of density, pH, color and clarity of the CSF before and after centrifugation, assessment of total cytosis (normally not more than 5 cells per 1 μl), determination of protein content. Depending on the need and capabilities of the laboratory, the number of lymphocytes, eosinophils, neutrophils, macrophages, altered cells, polyblasts, plasmocytes, arachnoendothelium cells, epidermal cells, granular spheres, and tumor cells are also examined.

The relative density of the cerebrospinal fluid is normally 1.005-1.008, it is increased in inflammatory processes, reduced with excess fluid formation. Normally, the pH is 7.35-7.8, it decreases with meningitis, encephalitis, paralysis, increases with paralysis (before treatment), syphilis of the brain, epilepsy, chronic alcoholism.

Yellow color of the CSF is possible with high protein content, in case of subarachnoid hemorrhage and with hyperbilirubinemia. With metastases of melanoma and jaundice, the cerebrospinal fluid can be dark. Significant neutrophilic cytosis is characteristic for bacterial infection, lymphocytic - for viral and chronic diseases. Eosinophils are characteristic of parasitic diseases. If there are 200-300 leukocytes in 1 μl, the CSF becomes turbid. To differentiate the leukocytosis caused by subarachnoid hemorrhage, it is necessary to count leukocytes taking into account that in the blood for 700 erythrocytes there is approximately 1 leukocyte. 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, a block of the subarachnoid space of the spinal cord, carcinomatosis, neurosyphilis, SGB, inflammatory diseases. An important role is played also by colloid reactions - the Lange reaction (the "golden reaction"), the colloidal mastic reaction, the Takata-Ara reaction, and others.

In the biochemical analysis of the cerebrospinal fluid, the glucose content (normally within the range of 2.2-3.9 mmol / l) and lactate (within the range of 1.1-2.4 mmol / l) is evaluated. The evaluation should be carried out taking into account that the content of glucose glucose depends on the concentration of blood glucose (40-60% of this value). Reducing glucose - a frequent sign of meningitis of various etiologies (more often of bacterial origin, including tuberculosis), an increase in the concentration of glucose of cerebrospinal fluid is possible with ischemic and hemorrhagic stroke.

Reduced chloride content in cerebrospinal fluid is characteristic of meningitis, especially tuberculosis, for neurosyphilis, brucellosis, increase - for brain tumors, brain abscess, echinococcosis.

In the microbiological laboratory, it is possible to stain a smear or sediment of the cerebrospinal fluid depending on the alleged causative etiology of the pathogen: according to Gram - if there is a suspicion of a bacterial infection, on acid-fast microorganisms - if suspected of tuberculosis, ink - if a fungal infection is suspected. Cereals of cerebrospinal fluid are carried out on special media, including on media, sorbing antibiotics (in case of massive antibiotic therapy).

There are a large number of tests for the detection of specific diseases, for example, Wasserman's reaction, RIF and RIBT to exclude neurosyphilis, tests for various antigens for typing tumor antigens, detection of antibodies to various viruses, etc. At bacteriological research it is possible to allocate meningococci, pneumococci, hemophilic rods, streptococci, staphylococcus, listeria, mycobacterium tuberculosis. Bacteriological studies of cerebrospinal fluid are aimed at identifying the causative agents of various infections: the cocco group (meningo-, pneumo-, staphylo- and streptococci) with meningitis and abscesses of the brain, pale treponema - with neurosyphilis, mycobacterium tuberculosis - with tuberculosis meningitis, toxoplasm - with toxoplasmosis, cysticercic vesicles - with cysticercosis. Virological studies of cerebrospinal fluid are aimed at establishing a viral etiology of the disease (some forms of encephalitis).

[10], [11], [12], [13], [14],

Complications after the procedure

The total risk of complications is estimated at 0.1-0.5%. Possible complications include the following.

• Axial wedge:
  • acute wedging with puncture in conditions of intracranial hypertension;
  • chronic injection as a consequence of repeated lumbar punctures;
• Meningism.
• Infectious complications.
• Headaches, usually passing in the lying position.
• Hemorrhagic complications, usually associated with blood clotting disorders.
• Epidermoid cysts as a result of the use of substandard needles or needles without mandril.
• Damage to roots (possible development of persistent pain syndrome).
• Damage to the intervertebral disc with the formation of herniated disc.

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

[15]

Care after the procedure

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

[16], [17], [18]