Spinal fluid: composition, functions and disorders
It is popular knowledge that the brain is located inside the skull, being protected by it and by different membranes, such as the meninges.
The correct functioning and protection of this organ is fundamental for survival , so it is necessary to nourish it and avoid possible damage, such as that produced by blows or intracranial pressure. Furthermore, in its necessarily continuous operation, waste is generated, which may be harmful and must therefore be removed from the system.
A very important liquid that circulates through the nervous system, known as cerebrospinal fluid , is involved in all this.
A General Idea of Spinal Fluid
The cerebrospinal fluid is a substance present in the nervous system, both in the brain and the spinal cord , which performs various functions such as protection, maintenance of intracranial pressure and health of the thinking organ.
Its presence in the nervous system is especially in the subarachnoid space (between the arachnoid and the pia mater, two of the meninges that protect the brain) and the cerebral ventricles. It is a transparent liquid of fundamental importance in the preservation and good health of the brain, with a composition similar to that of blood plasma, from which it is derived. In spite of being colourless, different alterations and infections can give it different shades, its colouring being a sign of the presence of a problem.
Spinal fluid life cycle
The cerebrospinal fluid is synthesized in the choroid plexuses, small structures present in the lateral ventricles, the main function of which is the production of this substance. This production occurs in a continuous manner, renewing itself to maintain a constant quantity of this substance .
Once emitted it flows from the lateral ventricles to the third ventricle and then to the fourth ventricle through the Silvio aqueduct. From there it ends up projecting into the subarachnoid space through an orifice known as the Magendie orifice and the Luschka orifices, openings located in the fourth cerebral ventricle that bring the ventricular system and the meningeal system into contact by communicating with the great cistern of the subarachnoid space (located between the arachnoid and pia mater meninges). From that point on, it circulates through the meninges throughout the entire nervous system, exerting various functions in the process.
To culminate its life cycle, it is finally reabsorbed through the arachnoid granulations, which connect with the veins present in the dura mater, so that the liquid ends up reaching the bloodstream.
The average life cycle of this substance is about three hours , between its secretion, circulation, collection and renewal.
Composition
As mentioned above, the composition of the cerebrospinal fluid is very similar to that of blood plasma , the main variations being the comparatively much lower presence of proteins (it is estimated that in blood plasma the presence of proteins is two hundred times higher) and the type of electrolytes that are part of it.
An aqueous-based solution, cerebrospinal fluid has several components of great importance for the maintenance of the nervous system, such as vitamins (especially B-group), electrolytes, leukocytes, amino acids, choline and nucleic acid.
Within this large amount of elements in the cerebrospinal fluid, the presence of albumin as the main protein component stands out, along with others such as prealbumin, alpha-2-macroglobulin or transferrin. Apart from these components, the high presence of glucose stands out, with between 50 and 80% of this solution being so vital for the brain.
Main functions
We have visualized what the cerebrospinal fluid is, where it circulates and what it is made of. However , it is worth asking why this substance is so important for the correct functioning of the whole nervous system. To answer this question it is necessary to see what functions it has.
One of the main functions of the cerebrospinal fluid is that of being the main mechanism for eliminating the waste produced by the continuous functioning of the nervous system , waste that could seriously affect its functioning. Thus, the circulation of cerebrospinal fluid carries away these substances and metabolites, which will end up being excreted from the system. In the absence of this substance, the toxins and surplus particles would remain sedimented in regions of the nervous system and adjacent areas, so that many problems would appear in the state of the living cells: neither could they be freed from these surplus elements, nor could they access the parts of these that can be recycled once they have passed through the appropriate place.
Another of the most important functions of the cerebrospinal fluid is to keep the brain nourished, as well as to ensure the consistency of the environment between the different cells of the brain and the marrow. It is a kind of chemical “buffer” that allows the room for manoeuvre to be increased in the event of certain hormonal imbalances appearing, for example, and when there are problems of homeostasis in general .
The cerebrospinal fluid also allows the brain to stay afloat inside the skull, greatly reducing its weight. Flotation also serves as a buffer against injury, shock, and movement by reducing the possibility of collisions with the skull bones or external elements.
Also, the cerebrospinal fluid is largely involved in maintaining intracranial pressure , making it neither too large nor too small, maintaining a constant balance that allows it to function properly.
Finally, it also participates by acting as an immune system, protecting the nervous system from harmful agents. It also contributes as a means of transporting hormones.
Derived disorders
Thus, the nervous system has in the cerebrospinal fluid an essential tool to function properly.
However, it is possible that there are alterations in the synthesis, circulation or reabsorption of this substance , which can cause different problems, two of them being the following.
1. Hydrocephalus
This concept refers to the excessive presence of cerebrospinal fluid , having such an accumulation that it causes a pressure of the brain against the skull. Some of the elements that may cause it are tumours, infections or traumatisms, but it is also frequent to find congenital hydrocephalus, that is to say, present from birth.
It can cause headache, vomiting, cognitive or coordination impairment or double vision, among other symptoms. In the case of congenital hydrocephalus, it causes severe developmental difficulty and intellectual deficit. Generally it is due to obstructions in the circuit, a common example being the Magendie’s orifice being obstructed. To treat these problems it is possible to perform surgery in order to place an escape route for the liquid to other areas, such as the stomach.
2. Hypertension/Intracranial Hypotension
An excess or deficit of cerebrospinal fluid can cause the pressure on the brain inside the skull to be too high or too low to allow it to function properly. While hypotension would result from the loss or low production of cerebrospinal fluid, hypertension would result from too much cerebrospinal fluid, which can be serious because it puts pressure on areas of the nervous system and prevents them from functioning well (or even kills areas of cell tissue).
In any case, the alterations in the cerebrospinal fluid that may appear in these cases are added to the problems of the heart condition it causes , so that the danger increases. Both groups of symptoms need to be treated to avoid a chain effect resulting from problems in the functioning of the nervous system and the circulatory system.
Bibliographic references:
- RodrÃguez-Segade, S. (2006). Cerebrospinal fluid. Ed Cont Lab Clin;9:49-56.
- Rosenberg, G.A. (2008). Brain edema and disorders of cerebrospinal fluid circulation. In: Bradley, W.G.; Daroff, R.B.; Fenichel, G.M.; Jankovic, J. (eds). Bradley: Neurology in Clinical Practice. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 63.
- Zweckberger, K.; Sakowitz, O.W.; Unterberg, A.W. et al. (2009). Intracranial pressure-volume relationship. Physiology and pathophysiology Anaesthesist. 58:392-7.