Cerebrospinal fluid (cerebrospinal fluid, cerebrospinal fluid) is a liquid biological medium of the body that circulates in the ventricles of the brain, cerebrospinal fluid pathways, subarachnoid space of the brain and spinal cord.
The composition of the cerebrospinal fluid includes various proteins, minerals and a small number of cells (leukocytes, lymphocytes). The brain is better than other organs, protected from the effects of chemical factors that are contained in the blood, thanks to the so-called blood-brain barrier. The BBB is a complex mechanism that protects and regulates the tissue environment of the brain. The barrier is formed by:
– capillary endothelium,
glial cells lie between capillaries and neurons
– arachnoid and
-vascular plexuses located in the ventricles of the brain.
Normally, cerebrospinal fluid is formed in the ventricles and absorbed into the blood at the same rate, so that its volume remains relatively constant.
Thus, in terms of its characteristics, cerebrospinal fluid is not only a mechanical protective device for the brain and the vessels lying on its base, but also a special internal environment that is necessary for the proper functioning of the central organs of the nervous system.
The space in which the cerebrospinal fluid is placed is closed. The outflow of fluid from it is accomplished by filtration mainly into the venous system through the granulations of the arachnoid membrane, and partly also into the lymphatic system through the sheaths of the nerves into which the meninges continue.
It is now generally accepted that the space occupied by fluid in the spinal canal represents a direct extension of the extracellular space of the brain. Since these two fluids communicate, all metabolic, inflammatory and degenerative changes that occur in the central nervous system are reflected in the physicochemical parameters of the cerebrospinal fluid.
Normally, cerebrospinal fluid is a crystal clear liquid. The total volume of cerebrospinal fluid in an adult is on average 140 ml. Its renewal occurs approximately 4-8 times a day and depends on nutrition, water regime, physical activity, etc.
Composition and properties of liquor.
The cerebrospinal fluid obtained by spinal puncture, the so-called lumbar cerebrospinal fluid, is normally transparent, colorless, has –
– constant specific gravity 1.006 – 1.007;
The viscosity of cerebrospinal fluid normally ranges from 1.01 to 1.06. Liquor has a slightly alkaline reaction
-pH 7.4 – 7.6;
– temperature of cerebrospinal fluid in the subarachnoid space of the spinal cord 37 – 37.5 °C.
The chemical composition of cerebrospinal fluid is similar to the composition of blood serum:
– 89 – 90% is water;
-dry residue 10 – 11% contains organic and inorganic substances involved in brain metabolism.
The organic substances contained in the cerebrospinal fluid are:
– inorganic phosphorus and
– trace elements.
The protein of normal cerebrospinal fluid is represented by albumins and various fractions of globulins. The content of more than 30 different protein fractions in the cerebrospinal fluid has been established. The Kafka protein coefficient (the ratio of the number of globulins to the number of albumins) has a diagnostic value, which normally ranges from 0.2 to 0.3.
Compared to blood plasma, cerebrospinal fluid has a higher content of chlorides, magnesium, but a lower content of glucose, potassium, calcium, phosphorus and urea. 90% sugar is glucose, 10% dextrose. The concentration of sugar in the cerebrospinal fluid depends on its concentration in the blood.
The number of cells (cytosis) in the cerebrospinal fluid normally does not exceed 3-4 per 1 μl, these are lymphocytes, ependymal cells of the ventricles of the brain, free macrophages.
CSF pressure in the spinal canal when the patient is lying on his side is 100-180 mm of water. Art., in a sitting position, it rises to 250 – 300 mm of water. Art. In children, cerebrospinal fluid pressure is lower than in adults.
With various pathological processes in the central nervous system, changes in fluid pressure, its properties and composition are possible, which reflect a particular disease. For diagnostic and therapeutic purposes, a puncture of the spinal canal is performed, which makes it possible to determine the pressure of the cerebrospinal fluid and extract it for analysis.
The results of the study of cerebrospinal fluid are important, sometimes decisive, for the timely diagnosis of the type of damage to the central nervous system. An analysis of the cerebrospinal fluid over time makes it possible to evaluate the effectiveness of the treatment of inflammatory diseases, tumors of the central nervous system, strokes and other pathological processes, as well as to predict the development of complications in the course of the disease.
With lesions of the central nervous system, the pressure and composition (in particular, the ratio of protein and cells) of the cerebrospinal fluid change. The pressure of the cerebrospinal fluid increases when its outflow is disturbed (trauma to the skull and spine, brain tumors, hemorrhages, etc.). In meningitis, bacteria are found in the cerebrospinal fluid. Biochemical studies of cerebrospinal fluid (determination of sugar, chlorides, free amino acids, enzymes, etc.) – in the diagnosis of neuroinfections, epilepsy, etc.