Lumbar puncture( LP) - Causes, symptoms and treatment. MF.
Lumbar puncture is performed for various purposes: obtaining cerebrospinal fluid for its analysis, determining intracranial pressure and patency of subarachnoid spaces, performing myelography, with a therapeutic purpose( for extracting cerebrospinal fluid and thus reducing intracranial pressure, for the administration of medications).
Puncture is usually performed by a special needle between the spinous processes of the LIII-LIV-LV vertebrae. The patient is laid on his side with legs bent and lowered to the abdomen. The head of the patient is also somewhat bent and is located in the same horizontal plane with the trunk. The interval between the spinous processes of the LIV-LV vertebrae is located at the level of the line connecting the crests of the ileum. After treatment of the skin at the puncture site with a disinfectant solution( alcohol, gebitane), skin and soft tissues are anesthetized( 2-3 ml of 0.5% solution of novocaine).
For needle puncture, a special needle with a diameter of 0.5-1 mm and a length of 9-12 cm is used. The needle with the mandrel inserted in it is advanced strictly in the sagittal plane and slightly upward, respectively, the gap between the spinous processes. The moment of puncture of the dura mater is determined by the surgeon after a sensation of the needle "falling through".The needle moves a few millimeters deeper, then the mandrel is removed, and the cerebrospinal fluid flows from the needle. When the needle moves to the subarachnoid space, severe pain may occur if the needle touches the horse's tail. In this case, you must carefully change the position of the needle. A pressure measuring tube is connected to the needle. Normally, when lying, it varies from 100 to 180 mm of water. If there are indications, liquorodynamic tests are carried out. After that, 2-3 ml of cerebrospinal fluid is extracted for laboratory tests( determination of the amount of protein, cell composition, Wasserman reaction, etc.).
With the medical purpose, especially after neurosurgical operations, a different amount of liquid can be extracted( up to 10-15 ml).
Liquorodynamic tests are performed to determine the patency of the subarachnoid space of the spinal cord.
Quakenstedt's test consists in compression of the veins of the neck, resulting in increased intracranial pressure. In the absence of a block of liquor spaces above the puncture level, there is a simultaneous increase in pressure in a manometric tube connected to a puncture needle( a negative test of Quecenstedt).
If there is difficulty in circulating the cerebrospinal fluid, there is a slow, slight increase in pressure at the lumbar level. With a full block of the subarachnoid space, pressure changes in the manometric tube in response to the compression of the veins of the neck do not occur at all( a positive test of Quéquenstedt).A similar result can be obtained by flexing the patient's head, which also leads to difficulty in the flow of cerebrospinal fluid from the cranial cavity and an increase in intracranial pressure.
Additional information on the permeability of the subarachnoid space of the spinal cord can be obtained by pressing on the abdominal wall of the patient - the Stukkei test, which also leads to an increase in cerebrospinal pressure due to obstruction of outflow from the vestibular cavity and spinal canal. With a block of cerebrospinal fluid at the cervical or thoracic level with a Stukka sample, cerebrospinal fluid pressure at the lumbar level will increase, while in the neck veins( Quéquenstedt test) it will remain unchanged.