Definition
Definition
Cerebrospinal fluid (CSF) is a fluid contained within the spaces between two meningeal membranes, called the pia mater and arachnoid mater (protective and covering membranes of the central nervous system). It is extremely clear and composed of 99% water. The spinal cord and brain are located within the CSF.
Symptoms
physiology
Cerebrospinal fluid in the central nervous system is contained in two distinct anatomical areas:
- Le internal system also called training system consisting of the lateral cerebral ventricles in communication by le Magendie hole with the middle cerebral ventricle, and through theSylvius aqueduct with the fourth ventricle. These are the choroid plexus contained in the cerebral ventricles, which secrete cerebrospinal fluid.
- Le external systemalso called resorptive systemn. These are the cavities, located below thearachnoid which is one of the three brain protection, and covering of the central nervous system. This cavity is more precisely located between the pia mater (very thin membrane which covers the nerve substance itself), and thearachnoid (for specialists the visceral leaflet).
Cerebrospinal fluid is collected by a specific area of the arachnoid membrane called the arachnoid villi . The granulations of Pacchion also contribute to the collection of cerebrospinal fluid. This fluid then mixes with the blood in the veins.
The circulatory system containing cerebrospinal fluid is not a typical circulatory system, unlike the venous , arterial , or lymphatic systems . Indeed, it contains no valves, and any blockage to the flow of cerebrospinal fluid is considered an abnormal (pathological) phenomenon. Cerebrospinal fluid appears to circulate within the nervous system by simple eddying rather than through a pulsatile fluid flow like arterial blood , venous blood , or lymph.
Cerebrospinal fluid, when cloudy, indicates the presence of at least 200 to 300 cellular elements per microliter.
The yellow discoloration, called xanthochrony , results from the presence of bilirubin originating from a previous blood collection (hemorrhage). In cases of spinal cord compression , the cerebrospinal fluid is likely to become xanthochromic ( Froin's syndrome ).
When normal, it has the appearance of clear water. It contains proteins, in smaller quantities, in the upper part ( brain ) than in the lower part ( lumbar spine ). Overall, the amount of protein in cerebrospinal fluid is between 15 and 45 mg per deciliter.
Pathophysiology
Certain pathologies, and more specifically meningitis, are accompanied by an increase in the amount of protein.
Cerebrospinal fluid also contains immunoglobulins ( antibodies ), or gamma globulins , representing approximately 7 to 13% of the total protein. This amount is increased in the presence of acute inflammatory conditions of the central nervous system. Brain tumors and certain neurological conditions characterized by myelin damage are also accompanied by an increase in the amount of immunoglobulins in the cerebrospinal fluid.
Bloody cerebrospinal fluid (CSF) raises questions about its origin. Is it due to a traumatic lumbar puncture or a lumbar puncture related to a meningeal hemorrhage ? To determine the cause, it is necessary to collect the fluid in at least three separate tubes. The collection technique is performed by a neurology specialist. It requires slowing the flow using a stylet for two minutes per tube, and two minutes between each tube. Each tube is then analyzed for cell pigments and the total protein content of the CSF.
When there is an injury to the blood vessels , such as during a lumbar puncture , the cerebrospinal fluid is clearer in the third tube, and the red blood cell count is lower. The protein level is also lower than in the first tube. Furthermore, a blood clot is often observed , most frequently when there are more than 250,000 red blood cells per cubic millimeter of cerebrospinal fluid.
In cases of vascular injury (damage to blood vessels), gentle and immediate centrifugation may show that the floating portion contains no pigments, indicating the absence of hemolysis (rupture of red blood cells). However, this does not appear to be entirely accurate. Indeed, below 12,000 red blood cells per cubic millimeter, this technique is not completely reliable.
If we examine the red blood cells under a microscope, we notice that the erythrocytes are intact, and that the ratio between red blood cells and white blood cells is identical to that which we would obtain if we performed the same cytological examination on blood from a vein.
In cases of meningeal hemorrhage , the color, cell analysis, and protein analysis of the cerebrospinal fluid are identical in all three tubes. The red blood cells appear crenulated (due to the hypertonic, or more concentrated, medium) and are generally damaged. Macrophages (a type of white blood cell) are also present. Furthermore, the cerebrospinal fluid does not clot, unlike in the first experiment. If centrifugation is performed, the concentration of blood pigments is identical in all three tubes. Most often, laboratory results show traces of pigment. Yellowing of the cerebrospinal fluid can occur following a hemorrhage.
Sometimes the cerebrospinal fluid is either very cloudy (frankly purulent), as is seen in bacterial meningitis , or simply opaque (specialists speak of rice water), because of pleocytosis (a large variety and number of white blood cells) corresponding to more than 400 elements per cubic millimeter.
Cerebrospinal fluid can also be fatty, for example when a contrast agent has been injected into the spine and has not been absorbed.
Intrathecal immunoglobulin synthesis is the local production, within the membranes of the meninges, of immunoglobulin-like proteins (a type of antibody). The cerebrospinal fluid electrophoresis profile suggests, or does not suggest, the presence of intrathecal immunoglobulin G synthesis . Some bacterial meningitis cases are accompanied by a drop in cerebrospinal fluid glucose and chloride levels (presence of chloride in the cerebrospinal fluid). The prognosis for this type of infection is favorable.
Tuberculous meningitis is accompanied by intrathecal synthesis of immunoglobulin G, and moderate hyperproteinorachia of 0,6 to 0,8 g per liter.
Syphilis is always characterized by the presence of intrathecal synthesis of immunoglobulin G, and intrathecal synthesis of immunoglobulin M in the acute phase.
Viral meningoencephalitis is characterized by a significant intrathecal synthesis of immunoglobulin M.
Multiple sclerosis is characterized by intrathecal synthesis of immunoglobulin G (48 mg per liter on average) in the majority of patients.
In Guillain-Barré syndrome, intrathecal synthesis of immunoglobulin G is observed, averaging 41 mg per liter, comparable to that of multiple sclerosis. This intrathecal synthesis is linked to the extent of the disease; that is, it is higher in cases involving the brainstem.
During lupus and connective tissue diseases , the cerebrospinal fluid is inflammatory, and the intrathecal synthesis of nucleic antibodies is diverse.
In Alzheimer's disease , the cerebrospinal fluid is normal.
During amyloid angiopathy , intrathecal synthesis of immunoglobulins has an oligoclonal appearance.
Medical exam
Physical examination
Examination of cerebrospinal fluid is possible, thanks to a sample taken by lumbar puncture.
Labo
- Alpha 1 globulins are between 1 and 3%.
- Alpha 2 globulins are between two and five percent.
- Beta globulins are between 10 and 15%.
- Gamma globulins are between 5 and 10%.
Cerebrospinal fluid (CSF) glucose : This fluid also contains glucose . The normal CSF glucose level is between 45 and 80 mg per deciliter, or 0,45 to 0,80 g per liter. This level varies depending on blood glucose (blood sugar) levels. There is a ratio between the blood sugar level and the cerebrospinal fluid level. This ratio is approximately 0,6. CSF glucose levels increase during certain encephalitides and meningitis related to viral infections , and during diabetic coma . They decrease during meningitis accompanied by pus , and in acute tuberculous meningitis.
It usually contains 120 to 130 millimoles of chloride in the form of sodium chloride.
During tuberculous meningitis, the sodium chloride levels in the cerebrospinal fluid decrease. This level also decreases, but later, in purulent meningitis.
The pH (acidity and alkalinity) of the cerebrospinal fluid is between 7,35 and 7,40.
Cerebrospinal fluid normally contains cells ( lymphocytes , monocytes ) that originate from the arachnoid mater (located beneath it). Certain parasites are tested for in the cerebrospinal fluid:
- Parasites of the malaria
- Toxoplasm
- Acanthamoeba
- Aegleria fowleri
- entamoeba histolytica
- Trypanosome
Technical
The analysis of intrathecal immunity (of the cerebrospinal fluid) involves three successive stages:
- Calculation of intrathecal syntheses.
- The study of specific activities of intrathecal antibodies.
- The study of intrathecal complement variations.
To understand what intrathecal synthesis ( ITS) calculation represents , it is necessary to know that two processes, either in isolation or in combination, modify the protein composition of cerebrospinal fluid. The protein composition of cerebrospinal fluid is directly related to its immune defenses.
- The first mechanism is called transudation. This is the passage of proteins from the blood plasma (liquid part of the blood), through the walls of the vessels, whether at arteries, or some veins, and this in the direction of the central nervous system, contained in the spinal column and the skull: the neuraxis.
- The second mechanism is called intrathecal synthesisThis is the production that takes place locally, that is to say inside the envelopes, in other words the meninges, of the proteinThese are immunoglobulins (antibodies), complement components, and fibronectinThe latter (Latin fibra: filament and nectere: to unite, in English fibronectin), is a glycoprotein (sugar associated with a protein), of high molecular weight of which a form is described present inside the plasma, and possessing the ability to behave in opsonin non-specific. The other form is located on the surface of many cells, particularly platelets, But also connective tissue and the walls making up the vessels. The role of the fibronectin is to intervene by adhering the cells together. Healing involves fibronectin. Coagulation and stabilization of the blood clot, at the time of coagulation, also involve it.
Additional examination
Cerebrospinal fluid (CSF) is the third internal fluid of the body . Part of the nervous system , it is a fluid that is continuously secreted and then reabsorbed (recovered). It is renewed three times every 24 hours. CSF originates from the bloodstream (80%) and from the brain, specifically the cerebral interstitial fluid ( 20% ).
Given the similarity in composition between cerebrospinal fluid and the patient's blood, the former cannot be studied separately from the latter in the same patient.
First, the cerebrospinal fluid pressure is checked, which is 6 to 18 cm of water in a healthy patient. Between 10 and 15 milliliters of cerebrospinal fluid are collected (via lumbar puncture), which is normally clear, transparent, and colorless. The total volume of cerebrospinal fluid varies from 100 to 150 ml, which corresponds to approximately one-sixtieth of the individual's total body weight.
The first step is to look for the presence of dyes, which medical specialists call pigments , using a spectrophotometer (spectrophotometric examination at 450 nm). During this examination, the cerebrospinal fluid appears normal in a 1 cm cuvette and shows slight absorption of the optical density, which is less than 0,025.
A cytological study is then performed , that is, an examination of the cells contained in the cerebrospinal fluid. This is achieved through the examination of the Nageotte cell . Abnormal cells are always sought after concentrating the cerebrospinal fluid by performing what neurology specialists call sedimentation, or centrifugation. The cells are visualized using a light or electron microscope. Usually, fewer than two leukocytes (a type of white blood cell) are found per cubic millimeter of fluid in the cerebrospinal fluid. The composition of these white blood cells is as follows:
- Monocytes : 16%.
- Lymphocytes : 17%.
- Large lymphocytes: 63%.
- Misidentified cells: 4%.
- Red blood cells (RBCs) less than 100 per milliliter.
Cerebrospinal fluid (CSF) electrophoresis is a technique similar to blood protein electrophoresis. Its purpose is to identify the different proteins contained in the CSF. For specialists, it is necessary to concentrate a volume of CSF containing approximately 400 mg of protein onto the ultrafilter (such as a Minicon), which corresponds to 1 ml of normal CSF.
The term cerebrospinal fluid protein refers to the protein content of abnormal cerebrospinal fluid. Cerebrospinal fluid electrophoresis is performed on a cellulose cassette over two hours. A staining process is carried out, allowing for the evaluation of the densitometry and percentage.
We obtain these main fractions which are:
- The prealbumin : 6.
- The albumins : 58,5.
- Alpha-1-globulin 4,5.
- Alpha-globulin number: 4,5.
- Beta-1-globulin: 10.
- Beta-globulin number: 6.
- The gamma globulins : 9,5.
Increasingly, in neurology , electrofocusing is being used to provide a more detailed analysis of cerebrospinal fluid proteins. This technique is used to study the gamma region, corresponding to gamma globulins, more precisely, particularly the oligoclonal aspect (from the Greek oligos: few). It is a technique that is not yet routinely used and, moreover, is relatively lengthy and expensive.
In some cases, specific immunochemical assays are also performed . These methods use either radial immunodiffusion or electroimmunodiffusion , which is much more sensitive, faster, and even more economical.
The normal cerebrospinal fluid (CSF) glucose level is 0,60 g per liter, which corresponds to 3,3 millimoles. These variations depend on the blood sugar level ( glucose ). CSF glucose is usually equal to 60% of the blood glucose level.
Hypoglycorrhachia is a decrease in the sugar level in the cerebrospinal fluid. It is defined as a value below 0,40 g per liter.
It is encountered during the following pathologies (non-exhaustive list):
- La tuberculous meningitis.
- Some meningitis linked to infection by a bacterium, such as a meningococcus or a pneumococcus.
- The mycoses (yeast).
- La meningeal sarcoidosis which is sometimes confused with tuberculous meningitis.
- The you die malignant.
- Excess secretion, or use of the insulin (hyperinsulinism), which results in organic hypoglycemia.
Hyperglycorrhachia is almost always linked to hyperglycemia (elevated blood sugar levels). Electrolytes are measured in the same way as in blood, that is, by flame photometry , colorimetry , and complexometry . This is how the chloride level in the cerebrospinal fluid is determined; it is 125 millimoles per liter.