Hemispherectomy: what is it, and functions of this surgical procedure?

Hemispherectomy is an invasive but very useful surgical procedure. Let's see how it works.

The field of neurology is extremely delicate, and every intervention has to be done knowing that the consequences can be dramatic.

Probably one of the most extreme interventions that exists is the hemispherectomy. We will dedicate this article to talk about this type of operation to know which are its most common effects and in which cases it can be considered to be performed.

What is hemispherectomy?

The hemispherectomy is a surgical intervention consisting of the extirpation or disconnection of one of the two hemispheres of the brain.. Obviously, this is a highly invasive operation, which is only performed in very particular situations, the incidence of which is statistically very low.

In other words, hemispherectomy is a last resort in the face of certain neurological last resort for certain neurological pathologies which, when other methods fail which, given the failure of other less invasive methods, leave as a last resort the aggressive intervention involving the removal of part or even half (a complete hemisphere) of the brain, with all the consequences that this entails.

Hemispherectomy is mainly used to treat the most extreme cases of epilepsy, but we will go into this issue in more detail later on. What must be clear is that, logically, such an aggressive medical intervention is not suitable for all types of patients. In this sense, certain requirements must be met. The first is that of not having achieved any improvement with the rest of the available treatments.

In addition, age is a key factor in deciding whether or not to carry out this operation, age is a key factor in deciding whether or not to carry out this operation.. The younger the patient, the more likely he/she is to experience fewer sequelae. This is due to brain plasticity. Therefore, the best candidates for a successful hemispherectomy are children.

Young children, as they have not yet completed many of the neural connections, start with a certain advantage, as the remaining hemisphere of the brain is not yet fully developed.The remaining hemisphere will be able to take on a large part of the tasks that, in the general population, would be divided between both sides of the brain. Therefore, the general rule will be simple: the younger the patient, the more likely the hemispherectomy will be successful and the less severe the sequelae will be.

What is the purpose of this medical technique?

We were anticipating that hemispherectomy is a neurological operation intended to to improve the situation with very severe epilepsies, in which the origin is a brain dysfunction in a very specific region.. For example, the disease known as Rasmussen's encephalitis would be one of those that would fit this profile.

As a general rule, two thirds of the patients suffering from epilepsy experience an improvement to a greater or lesser extent thanks to pharmacological treatments or other techniques or moderate surgical interventions. But the rest, unfortunately, do not achieve these positive effects.

Within this group of patients who do not improve, some suffer seizures and other symptoms in a moderate way, so they can live with their disease, even suffering the limitations that it generates. But there are others whose epilepsy is so severe that their quality of life is absolutely deteriorated. Hemispherectomy would be a last resort for these specific individuals.

Despite the aggressiveness of this technique, the average success rate is very high.. It is estimated that almost 90% of people treated with this procedure stop suffering from seizures, which is logical, considering that the part of the brain that is causing them is removed.

Likewise, in patients so affected by the severity of epilepsy, it is observed that hemispherectomy also generates a significant improvement in their ability to perform the usual cognitive processes. We note therefore that this is a risky technique, intended only for very severe cases, but which provides a high success rate.

Obviously, removing a part of the brain also has negative consequences, some of them severe.

How a hemispherectomy is performed

Hemispherectomy was first performed in 1928, although it had previously been performed on animals.although it had previously been performed on animals. Its first function was to remove brain tumors, such as glioblastoma multiforme, one of the most aggressive cancers. Even so, the aggressiveness of the technique meant that it was rarely used.

But in the 1980s, neurologists Carson and Freeman, members of the medical team at Johns Hopkins Hospital, revived the use of this procedure, applying it especially to very young patients, since, as mentioned above, the brain plasticity of children resulted in a markedly greater improvement than that of adults.

Initially, the only way to perform a hemispherectomy was to directly remove the damaged hemisphere, thus removing, among other regions, the part of the brain that was causing the seizures. This method is known as anatomical hemispherectomy. But later another technique was developed, the so-called functional hemispherectomy..

This new method, instead of removing the entire hemisphere, the parts of the brain tissue where the origin of the epilepsy is located are sectioned. Therefore, by this modality, the patient's part of the brain associated with the disease is removed, while trying to preserve other regions of the same hemisphere.

Logically, this option has certain advantages, such as not eliminating brain structures that may be performing crucial tasks and that might not be taken over by the other hemisphere in the case of hemispherectomy. Likewise, this method reduces the risk of hydrocephalus by accumulating a smaller amount of fluid in the place where that part of the brain tissue used to be.

But these are not the only ways of performing this procedure. In recent times, a methodology known as periinsular hemispherectomy has been perfected.. This technique involves the removal of a minimal part of the brain, where the seizure focus is located, and sometimes it is not even necessary to remove it as such, since the neurosurgeon tries to disconnect that area from the rest of the brain, sectioning it into different parts.

The most modern way of performing hemispherectomy is by means of surgical procedures with endoscopy and camera. In this way, the incision made is minimal, which drastically reduces the invasiveness of the technique, decreasing the risks and also the possibility of infection. Likewise, the patient's recovery is much faster, logically.

Real case of a person undergoing hemispherectomy

One of the most impressive cases of successful hemispherectomy that science has been able to observe in recent times is that of Nicolas, a patient born in 1989. As a baby, he began to show symptoms of severe epilepsy that caused hemiparesis, i.e., paralysis of half of his body (in this case, the left half). The doctors recommended his parents to perform this intervention.

Nicolas' right hemisphere of his brain was almost completely removed when he was just over three years old. One might think that such an aggressive operation would have marked a person for life, but the truth is that this patient's recovery was extraordinary. Because he was so young and his brain was so underdeveloped, neural plasticity facilitated his recovery, neural plasticity facilitated the creation of networks in the remaining hemisphere..

Thus, with only half of the organ, Nicolás managed to overcome one of the most complicated neurological operations that exist, and to acquire a whole series of skills that until then had been impossible due to the severe epilepsy he had suffered since birth.

In order to have a perspective of the extent to which this patient's life has been normal since then, we should know that he has even been able to develop with remarkable skill such complex hobbies as fencing (even achieving a bronze medal in a national championship) or the art of painting.

One of the sequels of his past illness and of the hemispherectomy is a partial loss of mobility in his left hand.. In addition, as the same hemisphere is responsible for sending motor commands to both sides of the body, when he performs tasks with the right hand, the left hand partially repeats some of the same movements.

In any case, these are relatively mild effects, considering the type of operation he underwent. Even so, it is important to keep in mind that this patient's case is exceptional, and it was thanks to the very favorable conditions and his young age that his recovery from the hemispherectomy and his evolution was so remarkably good.

But each case is particular, so some people will have a prognosis as good as this case, and others on the other hand will suffer different sequelae, depending on the particular conditions of each one.

Bibliographic references:

• Alcalá-Cerra, G., Paternina-Caicedo, Á., Díaz-Becerra, C., Gutiérrez-Paternina, J.J. (2013). Seizure control with cerebral hemispherectomy in adults: systematic review and meta-analysis with individual patient data. Neurosurgery. Elsevier.
• A.M. Ron (2021). My life with half a brain. Voz Pópuli.
• Rodríguez-Osorio, X., López-González, F.J., Eirís-Puñal, J., Frieiro-Dantas, C., Gómez-Lado, C., Peleteiro-Fernández, M., Prieto-González, A. (2018). Functional hemispherectomy: long-term follow-up in a series of five cases. Journal of Neurology.