Cerebrospinal fluid, or cerebrospinal fluid, is a substance circulating in the cavities of the brain. These cavities are called ventricles. Liquor is synthesized by the lateral ventricles located in the cerebral hemispheres. Further, through the system of all cavities, he “washes” the brain. This fluid is a kind of indicator of the pathological processes that occur in the brain. Therefore, if you suspect damage to the membranes and brain matter, a cerebrospinal fluid test is taken.
Cerebrospinal fluid function
The role of cerebrospinal fluid in the body is to protect the organs of the central nervous system from pathological processes in the body. This function is implemented as follows:
- the cerebrospinal fluid acts as a shock absorber in case of head blows or with sudden movements;
- provides constant pressure inside the cranium;
- It is in constant interaction with blood, due to which it supplies oxygen to the nerve cells and removes carbon dioxide from them;
- is a component of the barrier between the brain and blood vessels;
- prevents the penetration of microorganisms into the organs of the central nervous system.
Analysis of the cerebrospinal fluid will almost unmistakably show a violation of its function, if any.
Normal cerebrospinal fluid
The study of cerebrospinal fluid is carried out in order to determine its exact composition. The volume of cerebrospinal fluid taken for analysis and the level of intracranial pressure are also measured.
Normally, the amount of cerebrospinal fluid is between 140 and 160 ml. Most of the cerebrospinal fluid (90%) is water. The remaining 10% includes:
- proteins, some of which are in the form of amino acids;
- glucose;
- fats in the form of lipids;
- urea;
- lactate, or lactic acid;
- ammonia;
- minimum amount of nitrogenous compounds;
- destroyed cell elements.
In a normal analysis of cerebrospinal fluid, blood cells (red blood cells, white blood cells, and platelets) should not be. If they are determined, then there is an inflammatory process or hemorrhage.
The composition of the cerebrospinal fluid is constantly updated due to its synthesis in the lateral ventricles of the brain and the sweating of plasma through the blood vessels.
Normal cerebrospinal fluid
The main indicators of this biological fluid can be found in the general analysis of cerebrospinal fluid (see table).
| Indicator | Normal value |
| Color | Colorless |
| Transparency | Completely transparent |
| Pressure | 155-405 mm. water Art. |
| Acidity (the lower the pH, the more acidic the environment) | pH = 7.39-7.87 |
| Density | 1003-1008 g / l |
| Number of cells | 1-10 cells in a microliter of cerebrospinal fluid |
| Protein level | 0.12-0.34 g / l |
| Glucose level | 2.8-3.85 mmol / L |
| Chlorine level | 120-135 mmol / L |
Such a wide variation in pressure indices is the physiological norm of the general analysis of cerebrospinal fluid. It is due to the difference in pressure in a sitting and lying position. In the supine position, it is 155-205 mm. water Art. When a person sits down, the cerebrospinal fluid pressure increases to 310-405 mm. water Art.
The concentration of glucose in the cerebrospinal fluid, as well as the concentration in the blood, is variable. It depends on the characteristics of nutrition, the functional activity of the pancreas and many other factors. There is a simple rule: the glucose level in the cerebrospinal fluid is 2 times less than in the blood at the time of the examination.
When do the analysis
Since collecting cerebrospinal fluid is a serious procedure, it cannot be done simply at the request of the patient. There are a number of conditions in which the doctor will refer the patient to a cerebrospinal fluid analysis. All these indications are divided into two groups: relative and absolute.
With absolute readings, an analysis is done urgently. These include pathological conditions such as:
- infectious processes affecting the central nervous system (viral or bacterial encephalitis and meningitis);
- malignant neoplasms in the central nervous system;
- subarachnoid hemorrhage (accumulation of blood under the arachnoid meninges).
In processes belonging to the group of relative indications, the analysis of cerebrospinal fluid is optional:
- multiple sclerosis - a chronic autoimmune process with damage to the membranes of the processes of neurons;
- multiple lesions of nerves of inflammatory genesis;
- fever in young children with an unexplained cause;
- systemic autoimmune diseases of the connective tissue (systemic lupus erythematosus, rheumatoid arthritis and others).
Contraindications to the analysis
Despite all the informativeness of this method, in some cases, taking liquor can only do harm. Situations in which the analysis of cerebrospinal fluid is contraindicated are presented below:
- cerebral edema;
- extremely high intracranial pressure;
- accumulation of fluid around the brain (hydrocephalus);
- large volume formation in the brain.
Analysis in these conditions can lead to brain dislocation. This is a life-threatening process that is characterized by displacement of brain tissue into the openings of the skull and damage to vital brain centers.
There are also a number of conditions in which it is not recommended to carry out any intervention, accompanied by damage to the skin. These diseases are also called relative contraindications, that is, cerebrospinal fluid analysis is possible if the intended benefit exceeds the possible risk. These include:
- inflammatory processes on the skin in the lumbar region;
- diseases that are accompanied by a bleeding disorder (hemophilia, idiopathic thrombocytopenic purpura);
- taking medications that thin the blood (Aspirin, Heparin, Warfarin);
- period of pregnancy.
Cerebrospinal fluid sampling procedure
CSF analysis is an invasive intervention that requires a violation of the integrity of the skin. Since this fluid is in close proximity to the brain and spinal cord, there are a number of rules for its collection.
The fence procedure was called lumbar puncture. Literally, this name can be deciphered as a puncture in the lumbar region. All stages are carried out under sterile conditions to prevent the development of an infectious process. Tools should be disposable, the doctor puts on gloves, a mask, a hat and a dressing gown.
The patient lies on his side and bends his legs in the knee and hip joints, pressing them to the body as much as possible. The patient's head is tilted forward, hands are hugging his knees. The puncture site is between the 3rd and 4th lumbar vertebrae for adults and the 4th and 5th vertebrae for children. The difference in localization is due to the fact that in children the spinal cord is longer relative to the spinal canal.
Before the puncture, the skin is treated several times with cotton soaked in alcohol. Puncture is carried out with a special needle, which is inserted not absolutely perpendicularly, but under a slight inclination from top to bottom. The needle must be inserted until the specialist feels a "failure". This means that the needle is in the spinal canal. With the correct insertion of the needle, the cerebrospinal fluid flows freely. If he does not appear, the patient is asked to raise his head and cough, which will increase cerebrospinal fluid pressure and provoke his exit.
To determine the pressure level, a special tube is attached to the needle. If there are no special devices for measuring pressure, it can be calculated approximately. At normal pressure, 60 drops of cerebrospinal fluid should flow out per minute.
Types of cerebrospinal fluid analysis
The process of diagnosing diseases using cerebrospinal fluid research consists of two stages: fluid intake and the analytical stage. The sampling procedure is described in the previous section. After the puncture, the cerebrospinal fluid is collected in a sterile tube and go to the stage of fluid analysis. There are several ways to do this:
- macroscopic;
- biochemical;
- determination of the level of cytosis (number of cells);
- microbiological (seeding cerebrospinal fluid on nutrient media to determine the number of bacteria).
In some cases, an immunological study is also used. Its purpose is to find out the presence of certain antibodies in the cerebrospinal fluid.
Biochemical analysis of cerebrospinal fluid will show the level of protein, glucose, electrolytes. A change in the concentration of these substances is possible with infections and neoplasms of the central nervous system.
Color and transparency changes
Now it's time to consider the pathological changes in the clinical analysis of cerebrospinal fluid.
Already without additional analysis of cerebrospinal fluid, only by color can a possible pathology be determined:
- pink or red - indicates an impurity of blood, which is typical for subarachnoid hemorrhage;
- yellow-green - this color occurs with an infectious bacterial lesion of the organs of the central nervous system (meningitis, brain abscess);
- opalescent (glowing) - in oncological processes, meningitis of tuberculous etiology.
Liquor becomes cloudy with infections of the brain and spinal cord of both viral and bacterial etiology.
Cell number changes
When deciphering the analysis of cerebrospinal fluid, pay attention to the number of cells (cytosis). Diagnostic value is the increase in their concentration. It occurs during the following processes:
- infectious inflammation of the meninges (meningitis);
- allergic reactions;
- subarachnoid hemorrhage;
- brain tumors.
The laboratory assistant must not only count the number of cells, but also establish their type. This is very important for a more accurate diagnosis of diseases. If the high cytosis in the cerebrospinal fluid analysis is due to an increase in the concentration of leukocytes, an infectious process takes place. With an increase in the neutrophilic fraction, a bacterial infection is observed, and a lymphocytic infection is a viral infection.
If a large number of red blood cells is determined, then hemorrhage under the membrane of the brain occurs. For allergic reactions, an increase in the level of eosinophils is characteristic.
Changes in protein, glucose and chloride concentrations
For diagnosis, it is important to increase the concentration of protein. This may occur in the following situations:
- meningitis of various etiologies;
- encephalitis;
- herniated discs;
- tumors.
Reducing the level of protein does not pay much attention, since this condition is the physiological norm in the analysis of cerebrospinal fluid.
But the glucose level in the cerebrospinal fluid can be both increased and decreased. Both options are pathologies for the body.
An increase in sugar level occurs with traumatic brain injuries (concussion), diabetes mellitus (due to its increased penetration from blood vessels), and oncological processes in the brain and spinal cord. A periodic increase in glucose levels in patients with epilepsy during an attack is also possible. Between attacks this is not observed.
A decrease in glucose is possible with inflammation of the brain, tuberculous meningitis.
The concentration of chlorides and other electrolytes can both increase and decrease. Their increase is observed in renal and heart failure, the appearance of neoplasms. The level of chlorine decreases with meningitis or tumors. This component of the biochemical analysis of cerebrospinal fluid does not have high diagnostic value, therefore it is rarely determined by laboratory assistants.
Cerebrospinal fluid for meningitis
Analysis of cerebrospinal fluid with meningitis is the main examination for making this diagnosis. If during the examination of the patient a neurologist revealed that he had specific symptoms of meningitis, he immediately sends him to a lumbar puncture.
Regardless of the causes of inflammation of the meninges, such changes in cerebrospinal fluid analysis are characteristic:
- the color becomes yellowish (with a bacterial nature) or milky (with a viral nature);
- the liquid becomes cloudy;
- high cytosis: due to neutrophils (with bacterial inflammation) or due to lymphocytes (with viral);
- glucose lowering;
- increased protein concentration;
- reduction in the number of electrolytes.
Timely appointed analysis of cerebrospinal fluid allows effective treatment of the disease.
Analysis of cerebrospinal fluid in veterinary medicine
The study of cerebrospinal fluid is effective in the diagnosis of diseases of not only people but also animals. So, the analysis of cerebrospinal fluid of a dog or cat will help diagnose diseases of the brain and spinal cord of various origins. It can also be used to control the effectiveness of the treatment of diseases of the central nervous system.
The main indication for the analysis of cerebrospinal fluid in animals is soreness in the neck and head. As a rule, it is combined with other examination methods: analysis of blood, urine, magnetic resonance imaging.
During the diagnosis, the animal is under general anesthesia. This is a necessary measure so that the pet does not move during the procedure.
Thus, cerebrospinal fluid analysis is an informative method for diagnosing diseases of the central nervous system not only for people, but also for animals. Its low cost, high availability, lack of need for special devices have made it so common in modern medicine.