Hydrocephalus: causes, types and treatments
Cerebrospinal fluid is a substance of great importance for the maintenance of the brain. It is a vital element in keeping nervous tissue floating , cushioning possible blows, maintaining the level of pressure and electrochemical balance of the nervous system, helping to maintain nourished their cells and eliminating the waste generated by their operation.
With a life cycle that begins with its synthesis in the lateral ventricles and ends in its reabsorption by the blood system, the cerebrospinal fluid is synthesized continuously, generally maintaining a constant balance between the amount of this liquid substance that is synthesized and that which is absorbed . However, this balance can be altered, causing serious problems either by excess or defect of liquid. It is the case of hydrocephalus .
Hydrocephalus: your typical symptoms
Hydrocephalus is a disorder in which, for different reasons, there is an excess of cerebrospinal fluid, swelling of the cerebral ventricles and / or the subarachnoid space and producing a high level of pressure in the rest of the brain matter against the skull or between different brain structures.
Hydrocephalus is a problem that without treatment can be fatal, especially if the brainstem areas that regulate vital signs are pressed. The pressure exerted in the different parts of the brain will produce a series of symptoms that can vary according to which parts are pressed . In addition, the age of the subject and CSF tolerance also affect the appearance of certain symptoms.
However, some of the most frequent symptoms are headache, nausea and vomiting, double or blurred vision, problems of balance and coordination When moving and walking, drowsiness, irritability, slow growth and intellectual disability if it occurs in the period of neurodevelopment, changes in consciousness or changes in personality or memory.
In newborn infants who do not yet have fully closed skull bones, it is typical to observe vomiting, seizures or a tendency to look down. Sometimes, in addition, hydrocephalus can cause macrocephaly, that is, an exaggerated enlargement of the head in which the meninges and bones are under pressure.
Causes
The causes of the excessive presence of cerebrospinal fluid can be multiple, but in general it can be considered that it is usually due to two possible groups of causes. Hydrocephalus usually occurs either when the normal flow of cerebrospinal fluid is blocked at some point, or when the balance between synthesis and absorption of this substance is broken , either because too much is secreted or because it is not reabsorbed by blood.
But these assumptions can be reached in very different ways, whether we are dealing with congenital or acquired hydrocephalus. Some of the causes can be malformations such as spina bifida or that the vertebral column does not close before birth (problem known as myelomeningocele), as well as genetic difficulties.
Throughout life development situations can also occur that end up causing this problem. Cranioencephalic traumas causing internal bleeding (for example in the subarachnoid space) can cause a blockage in the flow of fluid. Tumors that pinch or press the pathways through which cerebrospinal fluid circulates are other possible causes. Also certain infections, including meningitis, can alter the normal flow rate of this substance.
Subtypes of hydrocephalus
Hydrocephalus is a problematic and very dangerous medical condition both for life and for normative functioning of the human being. This disorder can be congenital, in which it appears as a consequence of situations prior to birth such as malformations, genetic predisposition, trauma or intoxication in the fetal phase or acquired during childbirth or at some later time in the life cycle.
The problem itself is in all cases an excess of cerebrospinal fluid It induces different problems due to the pressure caused to the brain, but depending on the cause, different types of hydrocephalus can be found.
1. Communicating hydrocephalus
We call communicating hydrocephalus to that situation in which it occurs a blockage after the cerebrospinal fluid leaves the ventricles . In other words, the problem is not in the ventricles, whereby the cerebrospinal fluid circulates normally, but the cause is an alteration of the parts of the arachnoid that connect with the blood vessels.
2. Obstructive or non-communicating hydrocephalus
It is called obstructive the type of hydrocephalus in which the problem can be found in that the ventricles or the conduits that connect between them are altered and do not allow a correct flow. This type of hydrocephalus is one of the most common , being especially frequent that the motive is in an aqueduct of Silvio (conduit that communicates the third and fourth ventricles) excessively narrow.
3. Ex-vacuo hydrocephalus
Hydrocephalus ex-vacuo occurs when for some reason it has caused a loss or decrease in brain mass or density. Faced with this loss, usually due to the death of neurons due to trauma, hemorrhage or neurodegenerative processes such as dementia, the ventricles have more space available inside the skull, which eventually causes them to dilate (filling with cerebrospinal fluid) to occupy the Available space. It is therefore a type of passive hydrocephalus , which does not correspond to an alteration in the normal functioning of the cerebrospinal fluid.
4. Normotensive hydrocephalus
A subtype that appears especially in the elderly, this type of hydrocephalus seems to occur as a result of poor reabsorption of cerebrospinal fluid, in a similar way to communicating hydrocephalus. However, in this case although the amount of liquid is excessive, the pressure with which this circulates is practically normal (hence its name).
The fact that it usually occurs in elderly people and that the symptoms they cause are similar to those typical of demential processes (loss of memory, gait problems, urinary incontinence, slowing down and loss of cognitive functions) means that they often do not be detected, making it difficult to treat.
Treatments applied in these cases
The quick action before in case of hydrocephalus is fundamental if we want to avoid that the problem causes more difficulties. It must be borne in mind that the cerebrospinal fluid does not stop segregating, and the blockage or disregulation of the flow can cause the areas in which the fluid is present in excess do not stop swelling and cause more and more injuries and collateral damage, given the extensive scope of this kind of complications.
While treating the cause of hydrocephalus is necessary and the treatment of this factor will depend on the cause itself (if it is due to an infection, an inflammatory process or a tumor there will be different ways of treating the case), the first thing that must be done is to eliminate the excess fluid itself to Avoid major damage.
The treatments used in these cases they are surgical , being the most applied the following.
Extracranial bypass
One of the most applied treatments in these cases, extracranial shunt, has a relatively easy to understand operation: it involves removing the excess fluid from the cranial cavity and sending it to another part of the body where it does not produce alterations, generally one of the cerebral ventricles or the blood system. The basic procedure is to place a catheter between the area from which you want to make the transfer to the area where the flow will be redirected, placing a valve that regulates that the drainage is neither insufficient nor excessive.
Although it is the most common and used treatment, it must be borne in mind that drainage stops working for some reason, the problem will reappear, so this resolution could only be temporary. That is why even if this intervention is carried out, it is still necessary to investigate the causes that have caused hydrocephalus, and treat them as far as possible. Currently it is less and less used, preferring other treatments.
Endoscopic ventriculostomy of the third ventricle
This intervention is based, like the previous one, on creating a drainage path that allows to eliminate the excess of liquid. However in this case it would be an internal and endogenous drainage pathway , producing a small opening in the third ventricle that would allow excess fluid to flow into the blood (where it would end naturally). It is usually one of the most successful and reliable types of intervention.
Cautery of choroidal plexus
If the problem of hydrocephalus is caused because the synthesis of cerebrospinal fluid is excessive or it is not reabsorbed quickly enough, a treatment option is the cauterization or elimination of some of the areas that manufacture it.
In this way, cauterizing some of the choroidal plexuses that secrete cerebrospinal fluid (Not all, since the renewal of this is necessary for the proper functioning of the brain) will reduce the rate at which the flow circulates. It is usually used in conjunction with ventriculostomy. However, it is one of the most invasive forms of intervention.
Bibliographic references:
- Kinsman, S.L .; Johnston, M.V. (2016), Congenital anomalies of the central nervous system. In: Kliegman, R.M .; Stanton, B.F .; St.Geme, J.W .; Schor, N.F. (eds) Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier;: chap 591.
- Rosenberg, G.A. (2016). Brain edema and disorders of cerebrospinal fluid circulation.In: Bradley, W.G .; Daroff, R.B .; Pomeroy, S.L .; Mazziotta, J.C .; Jankovic, J. (eds). Bradley: Neurology in Clinical Practice. 7th ed. Philadelphia, Pa: Elsevier Saunders; 88
- Zweckberger, K .; Sakowitz, O.W .; Unterberg, A.W. et al. (2009). Intracranial pressure-volume relationship. Physiology and pathophysiology Anaesthesist. 58: 392-7.
