Hydrocephalus: causes, types and treatments

The cerebrospinal fluid It is a substance of great importance for the maintenance of the brain. It is a vital element by keeping the nervous tissue floating, cushioning possible shocks, maintaining the pressure level and electrochemical balance of the system nervous system, helping to keep your cells nourished and eliminating the waste generated by your functioning.

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 due to excess or lack of liquid. This is the case of hydrocephalus.

Hydrocephalus: its typical symptoms

Hydrocephalus is a disorder in which an excess of cerebrospinal fluid appears for different reasons, swelling of the cerebral ventricles and / or subarachnoid space

and producing a high level of pressure in the rest of the brain matter against the skull or between the different brain structures.

Hydrocephalus is a problem that without treatment can be fatal, especially if the areas of the brainstem that regulate vital signs are put under pressure. The pressure exerted on the different parts of the brain will produce a series of symptoms that can vary depending on which parts are pressed. In addition, the subject's age and tolerance to CSF ​​also influence the appearance of certain symptoms.

However, some of the most common symptoms are headaches, nausea and vomiting, blurred or double vision, balance and coordination problems when moving and walking, drowsiness, irritability, growth retardation, and disability intellectual if it occurs in the period of neurodevelopment, alterations of consciousness or changes of personality or memory.

In newborn children who have not yet fully closed the bones of the skull, vomiting, seizures or a tendency to look down is typical. Sometimes, in addition, hydrocephalus can cause macrocephaly, that is, an exaggerated enlargement of the head in which the meninges and the bones are pressed.

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 brokenEither because too much is secreted or because it cannot be reabsorbed through the blood.

But these assumptions can be reached in very different ways, whether we are dealing with congenital or acquired hydrocephalus. Some of the causes may be malformations such as spina bifida or that the spinal column does not finish closing before birth (a problem known as myelomeningocele), as well as genetic difficulties.

Throughout life development, situations can also occur that end up causing this problem. Head injuries causing internal bleeding (for example in the subarachnoid space) can cause a blockage in the flow of the fluid. Tumors that pinch or press on the pathways through which cerebrospinal fluid circulates are another possible cause. Also certain infections, including meningitis, can alter the normal flow rate of this substance.

Subtypes of hydrocephalus

Hydrocephalus is a problematic medical condition and very dangerous both for life and for the normative functioning of the human being. This disorder can be congenital, in which it appears as a consequence of pre-birth situations such as malformations, Genetic predisposition, trauma or poisoning in the fetal phase or acquired during childbirth or at some point later in the cycle vital.

The problem itself is in all cases an excess of cerebrospinal fluid which 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 there is a blockage after cerebrospinal fluid leaves the ventricles. In other words, the problem is not in the ventricles, through which cerebrospinal fluid circulates normally, but the cause is an alteration of the parts of the arachnoid that connect with the vessels blood.

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 tubes that connect between them are altered and do not allow proper flow. This type of hydrocephalus is one of the most common, being especially frequent that the reason is in an aqueduct of Silvio (conduit that communicates the third and fourth ventricles) excessively narrow.

3. Ex-vacuous hydrocephalus

Ex-vacuo hydrocephalus occurs when, for some reason, a loss or decrease in brain mass or density has been caused. Faced with this loss, generally due to the death of neurons due to trauma, hemorrhage or neurodegenerative processes such as dementias, ventricles have more space available within the skull, which in the long run causes them to dilate (filling with cerebrospinal fluid) until they occupy the space available. It is therefore a type of passive hydrocephalus, which does not correspond to an alteration of the normal functioning of the cerebrospinal fluid.

4. Normal pressure hydrocephalus

A subtype that occurs especially in the elderly, this type of hydrocephalus appears to occur as consequence of poor reabsorption of cerebrospinal fluid, similar to hydrocephalus caller. However, in this case even though the amount of liquid is excessive, the pressure with which it circulates is practically normal (hence its name).

The fact that it usually occurs in elderly people and that the symptoms it causes are similar to those typical of dementia processes (memory loss, gait problems, urinary incontinence, sluggishness and loss of cognitive functions) often goes undetected, making it difficult to treatment.

Treatments applied in these cases 

Quick action in the event of hydrocephalus is essential if we want to prevent the problem from causing more difficulties. It must be taken into account that the cerebrospinal fluid does not stop secreting, and the blockage or dysregulation of the flow can cause the areas in which the fluid is presented in excess, do not stop swelling and cause increasing injuries and collateral damage, given the extensive scope of this class 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 to do is to remove the excess fluid itself to avoid damage greater.

The treatments used in these cases are surgical in nature, the following being the most applied.

Extracranial shunt

One of the most applied treatments in these cases, the extracranial bypass, has a relatively easy to understand operation: it involves removing the excess of fluid from the cranial cavity and send it to another part of the body where it does not produce alterations, usually one of the cerebral ventricles or the blood. The basic procedure is to place a catheter between the area from which the transfer is to be made to the area where the flow is to 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 taken into account that the drainage stops work for some reason the problem will reappear, so this resolution could be just temporary. For this reason, even when this intervention is carried out, it is still necessary to investigate the causes that have caused the hydrocephalus, and treat them as much as possible. Currently it is less and less used, preferring other treatments.

Endoscopic third ventriculostomy

This intervention is based, like the previous one, on creating a drainage path that allows the excess fluid to be eliminated. However in this case it would be an internal and endogenous drainage path, producing a small opening in the third ventricle that allows excess fluid to flow into the blood (where it would end up naturally). It is usually one of the most successful and reliable types of intervention.

Choroid plexus cauterization

If the problem of hydrocephalus is caused because the synthesis of cerebrospinal fluid is excessive or that it is not reabsorbed quickly enough, a treatment option is cauterization or removal of some of the areas that they manufacture.

In this way, cauterizing some of the choroid 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.