Spinal fluid is a substance of great importance for the maintenance of the brain. It is a vital element that keeps the nervous tissue floating , absorbing possible shocks, maintaining the pressure level and electrochemical balance of the nervous system, contributing to keep its cells nourished and eliminating the waste generated by its functioning.

With a life cycle that begins with its synthesis in the lateral ventricles and ends with its reabsorption by the blood system, the cerebrospinal fluid is continuously synthesized, 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 deficient fluid. This is the case of hydrocephalus .

Hydrocephalus: its typical symptoms

Hydrocephalus is a disorder in which, for different reasons, an excess of cerebrospinal fluid appears, swelling 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 the different brain structures.

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

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

In newborn children who do not yet have fully closed skull bones it is typical to observe vomiting, seizures, or a tendency to look down.Occasionally, hydrocephalus can also cause macrocephalus, an exaggerated enlargement of the head in which the meninges and bones are pressed together.

Causes

The causes of excessive spinal fluid may be multiple, but in general, it can be considered to be 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 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 spine does not close before birth (problem known as myelomeningocele), as well as difficulties of a genetic type.

During the course of a person’s life, situations can also arise that lead to this problem. Head injuries that cause internal bleeding (for example in the subarachnoid space) can lead to a blockage in the flow of fluid. Tumors that pinch or press on the pathways through which the cerebrospinal fluid circulates are another possible cause. Certain infections, including meningitis, can also disrupt the normal flow of this substance.

Subtypes of hydrocephalus

Hydrocephalus is a problematic and very dangerous medical condition for both the life and the normative functioning of the human being. This disorder may be congenital, appearing as a result of pre-birth situations such as malformations, genetic predisposition, trauma or poisoning in the fetal phase or acquired during birth or some later time in the life cycle.

The problem itself is in all cases an excess of cerebrospinal fluid that 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 that situation in which a blockage occurs after the cerebrospinal fluid leaves the ventricles . In other words, the problem is not found in the ventricles, through which the cerebrospinal fluid circulates normally, but is caused by a disturbance in the parts of the arachnoid that connect to the blood vessels.

2. Obstructive or non-communicating hydrocephalus

Obstructive is the type of hydrocephalus in which the problem may be found in that the ventricles or the tubes connecting them are disrupted and do not allow proper flow. This type of hydrocephalus is one of the most common , and it is especially common when the cause is found in an excessively narrow Silvio’s aqueduct (the tube that connects the third and fourth ventricles).

3. Ex-vacuum hydrocephalus

Ex-vacuum hydrocephalus occurs when for some reason there has been a loss or decrease in brain mass or density. When faced with such a loss, generally due to the death of neurons from trauma, haemorrhage or neurodegenerative processes such as dementia, the ventricles have more space available within the skull, which eventually causes them to dilate (fill with cerebrospinal fluid) until they occupy the available space. It is therefore a type of passive hydrocephalus , which does not correspond to a disturbance in the normal functioning of the cerebrospinal fluid.

4. Normal pressure hydrocephalus

A subtype that appears especially in the elderly, this type of hydrocephalus appears to occur as a result of poor reabsorption of cerebrospinal fluid, similar to communicating hydrocephalus. However, in this case, although the amount of fluid is excessive, the pressure with which it circulates is practically normal (hence the name).

The fact that it often occurs in older people and that the symptoms it causes are similar to those typical of dementia processes (memory loss, walking problems, urinary incontinence, sluggishness and loss of cognitive functions) means that it is often undetected, making it difficult to treat.

Treatments applied in these cases

Rapid action in the case of hydrocephalus is essential if we are to avoid the problem causing further difficulties. It must be taken into account that the cerebrospinal fluid does not cease to be secreted, and the blockage or disregulation of the flow may cause the areas where the fluid is in excess to continue to swell and lead to ever greater injuries and collateral damage, given the extensive scope of this type of complication.

Although 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 to treat the case), the first thing to do is to remove the excess fluid itself to avoid further damage.

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

Extracranial shunt

One of the most commonly applied treatments in these cases, extracranial shunting, has a relatively easy to understand function: it involves removing 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 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 working for some reason the problem will reappear, so this resolution could be only temporary. That is why even if this intervention is carried out, it is still necessary to investigate the causes that have provoked the hydrocephalus, and treat them as far as possible. Currently it is less and less used, with other treatments being preferred.

Endoscopic third ventriculostomy

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

Cauterization of choroidal plexuses

If the problem of hydrocephalus is caused by excessive spinal fluid synthesis or that the spinal fluid is not reabsorbed quickly enough, one treatment option is cauterization or removal of some of the areas that produce it.

In this way, cauterizing some of the choroid plexuses that secrete the cerebrospinal fluid (not all of them, since the renewal of this fluid is necessary for the correct functioning of the brain) will reduce the rhythm 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.