Cerebrospinal fluid, or cerebrospinal fluid, is a substance that circulates 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 systems of all cavities, it "washes" the brain. This fluid is a kind of indicator of pathological processes that occur in the brain. Therefore, if there is a suspicion of damage to the membranes and substances of the brain, they take an analysis of the cerebrospinal fluid.
Cerebrospinal Fluid Functions
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 carried out in this way:
- liquor acts as a shock absorber when hitting the head or during sudden movements;
- provides constant pressure inside the cranium;
- is in constant interaction with the blood, due to which it supplies oxygen to nerve cells and removes carbon dioxide from them;
- is part of the barrier between the brain and blood vessels;
- prevents the penetration of microorganisms into the organs of the central nervous system.
An analysis of CSF will almost infallibly show a violation of its function, if any.
Normal composition of cerebrospinal fluid
Study of cerebrospinal fluid is carried out in order to determine its exact composition. They also measure the volume of CSF taken for analysis and the level of intracranial pressure.
Normal amount of cerebrospinal fluid is from 140 to 160 ml. Most of the liquor (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 (erythrocytes, leukocytes and platelets) should not be present. If they are determined, then there is an inflammatory process or hemorrhage.
The composition of CSF is constantly updated due to its synthesis in the lateral ventricles of the brain and the sweating of plasma through the blood vessels.
Normal CSF values
The main indicators of this biological fluid can be found from the general analysis of the cerebrospinal fluid (see table).
| Indicator | Normal value |
| Color | Colorless |
| Transparency | Totally transparent |
| Pressure | 155-405mm. water. st. |
| Acidity (the lower the pH, the more acidic) | pH=7, 39-7, 87 |
| Density | 1003-1008 g/l |
| Number of cells | 1-10 cells per microliter of CSF |
| Protein levels | 0, 12-0, 34g/l |
| Glucose levels | 2, 8-3, 85 mmol/L |
| Chlorine levels | 120-135 mmol/L |
Such a large variation in pressure indicators is the physiological norm of the general analysis of cerebrospinal fluid. It is due to the difference in pressure in the sitting and lying position. In the supine position, it is 155-205 mm. water. Art. When a person sits down, the CSF pressure increases to 310-405 mm. water. st.
The concentration of glucose in the cerebrospinal fluid, like the concentration in the blood, is not constant. It depends on the characteristics of nutrition, the functional activity of the pancreas and many other factors. There is a simple rule: the level of glucose in the cerebrospinal fluid is 2 times less than in the blood at the time of the examination.
When analysis is done
Since the collection of CSF 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 for a CSF analysis. All these indications are divided into twogroups: relative and absolute.
In case of absolute indications, the 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 mater).
Cerebrospinal fluid analysis is optional for relative indications:
- multiple sclerosis - a chronic autoimmune process with damage to the membranes of the processes of neurons;
- multiple nerve damage of inflammatory origin;
- fever in young children with unexplained cause;
- systemic autoimmune connective tissue diseases (systemic lupus erythematosus, rheumatoid arthritis and others).
Contraindications for analysis
Despite all the informativeness of this method, in some cases, taking CSF can only bring harm. Situations in which CSF testing is contraindicated are listed below:
- cerebral edema;
- extremely high intracranial pressure;
- fluid accumulation around the brain (hydrocephalus);
- large volumetric formation in the brain.
Performing analysis under these conditions can lead to dislocation of the brain. This is a life-threatening process that is characterized by a shiftbrain 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, CSF analysis is possible if the expected benefit outweighs the possible risk. These include:
- inflammatory processes on the skin in the lumbar region;
- diseases that are accompanied by bleeding disorders (hemophilia, idiopathic thrombocytopenic purpura);
- taking drugs that thin the blood ("Aspirin", "Heparin", "Warfarin");
- pregnancy period.
CSF collection procedure
CSF analysis is an invasive intervention that requires breaking 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 taking it.
The sampling procedure was called a 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. The instruments must be disposable, the doctor puts on gloves, a mask, a cap and a gown.
The patient lies on his side and bends his legs at the knee and hip joints, pressing them to the body as much as possible. The patient's head is tilted forward, hands hugging the knees. Puncture site -between the 3rd and 4th lumbar vertebrae in adults and the 4th and 5th vertebrae in 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 wool soaked in alcohol. The puncture is carried out with a special needle, which is inserted not absolutely perpendicular, but at 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 CSF flows freely. If it does not appear, the patient is asked to raise his head and cough, which will increase the CSF pressure and provoke his exit.
To determine the level of pressure, 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 CSF per minute should flow.
Types of cerebrospinal fluid analysis
The process of diagnosing diseases using the study of cerebrospinal fluid consists of two stages: fluid sampling and an analytical stage. The sampling procedure is described in the previous section. After puncture, the liquor is collected in a sterile tube and proceed to the stage of fluid analysis. This can be done in several ways:
- macroscopic;
- biochemical;
- determining the level of cytosis (number of cells);
- microbiological (sowing 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 CSF 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 CSF.
Already without additional analysis of cerebrospinal fluid, a possible pathology can be determined only by color:
- pink or red - indicates an admixture of blood, which is typical for subarachnoid hemorrhage;
- yellow-green - this color occurs when an infectious bacterial lesion of the organs of the central nervous system (meningitis, brain abscess);
- opalescent (luminous) - in oncological processes, meningitis of tuberculous etiology.
CSF becomes cloudy in infections of the brain and spinal cord of both viral and bacterial etiology.
Changes in the number of cells
When deciphering the analysis of CSF, be sure to pay attention to the number of cells (cytosis). Diagnostic value has an increase in their concentration. It occurs during the following processes:
- infectious inflammation of the membranes of the brain (meningitis);
- allergic reactions;
- subarachnoid hemorrhage;
- brain tumors.
The laboratory assistant must not only count the number of cells, but also determine their appearance. This is very important for a more accurate diagnosis of diseases. If a high cytosis in the CSF 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, while in the lymphocytic fraction, a viral one.
If a large number of erythrocytes is determined, then there is a hemorrhage under the membranes of the brain. Allergic reactions are characterized by an increase in the level of eosinophils.
Changes in protein, glucose and chloride concentrations
For the diagnosis is important to increase the concentration of protein. This can happen in the following situations:
- meningitis of various etiologies;
- encephalitis;
- herniated discs;
- tumors.
The decrease in protein levels is not given much attention, since this condition is a physiological norm in the analysis of cerebrospinal fluid.
But the level of glucose in the cerebrospinal fluid can be both increased and decreased. Both options are a pathology for the body.
An increase in sugar levels occurs with traumatic brain injuries (concussion), diabetes mellitus (due to its increased penetration from blood vessels), oncological processes in the brain and spinal cord. It is also possible to periodically increase the level of glucose in patients with epilepsy during an attack. This is not observed between attacks.
Reducing the amount of 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. Reduced chlorine levels in meningitis or tumors. This component of the biochemical analysis of CSF does not have a high diagnostic value, therefore it is rarely determined by laboratory assistants.
Cerebrospinal fluid for meningitis
CSF analysis for meningitis is the main examination for making this diagnosis. If, during the examination of a patient, a neurologist reveals that he has specific symptoms of meningitis, he immediately sends him for a lumbar puncture.
Regardless of the causes of inflammation of the meninges, the following changes in the analysis of cerebrospinal fluid are typical:
- color becomes yellowish (with bacterial nature) or milky (with viral nature);
- fluid becomes cloudy;
- high cytosis: due to neutrophils (with bacterial inflammation) or due to lymphocytes (with viral inflammation);
- lower glucose levels;
- increased protein concentration;
- decrease in electrolytes.
Timely appointed CSF analysis allows for effective treatment of the disease.
Analysis of cerebrospinal fluid in veterinary medicine
The study of CSF is effective in diagnosing diseases not only in humans, but also in animals. So, the analysis of the cerebrospinal fluid of a dog or cat will help diagnose diseases of the brain and spinal cord of various origins. Also with his helpit is possible to control the effectiveness of therapy for diseases of the central nervous system.
The main indication for the analysis of cerebrospinal fluid in animals is pain in the neck and head. As a rule, it is combined with other examination methods: blood tests, urine tests, 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, CSF analysis is an informative method for diagnosing diseases of the central nervous system not only for humans, but also for animals. Its low cost, high availability, and no need for special devices have made it so common in modern medicine.
