Hemispherectomy: what it is, and functions of this surgical intervention

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

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

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What is a hemispherectomy?

Hemispherectomy is a surgical intervention consisting of the removal or disconnection of one of the two hemispheres of the brain. Obviously, it is a highly invasive operation, which is only carried out in very particular situations, the incidence of which is really low in statistical terms.

In other words, the hemispherectomy involves a last resort for certain neurological pathologies that, given the failure of other less invasive methods, leave as a last option the aggressive intervention that involves removing a part and even half (a complete hemisphere) of the brain, with the consequences that this it implies.

The hemispherectomy is mainly used to treat the most extreme cases of epilepsy, but we will delve into this issue later. What must be clear is that, logically, a medical intervention as aggressive as this is not suitable for all types of patients. In that sense, certain requirements have to be met. The first is that of not having achieved any type of improvement with the rest of the available treatments.

What's more, age is key to deciding whether or not to carry out this operation. And the fact is that the younger the patient, the more likely they are to experience fewer sequelae. This is due to brain plasticity. Therefore, the best candidates for a successful hemispherectomy are children.

Young children, having not yet completed many of the neural connections, start with some advantage, since the remaining hemisphere will be able to assume a large part of the tasks that, in the general population, would be distributed between both sides of the brain. Therefore, the general rule of thumb will be simple: the younger the patient, the more likely the hemispherectomy will be successful and the less severe the sequelae.

What is this medical technique for?

We anticipated that the hemispherectomy is a neurological operation aimed at improve the situation with very serious epilepsies, in which the origin is in a cerebral dysfunction in a very specific region. For example, the disease known as Rasmussen encephalitis would be one of those that would fit that profile.

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

Within this group of patients who do not improve, some suffer seizures and other symptoms, of a moderately, so they can live with their disease, even suffering the limitations that it generate. But there are other people whose epilepsy is so serious that their quality of life is absolutely deteriorated. The hemispherectomy would be a last resort thought for these people in particular.

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

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

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

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How a hemispherectomy is done

The hemispherectomy was performed for the first time in 1928, although previously it had been carried out in animals. Its first function was to eliminate brain tumors, such as glioblastoma multiforme, one of the most aggressive cancers. Even so, the aggressiveness of the technique made its use very scarce.

But in the 1980s, neurologists Carson and Freeman, members of the Johns Hopkins hospital medical team, recovered the use of this intervention, applying it especially in very young patients, since, as mentioned above, children's brain plasticity resulted in a markedly greater improvement than that of children. Adults.

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

This new method, instead of removing the entire hemisphere, sections of the brain tissue where the origin of the epilepsy is found. Therefore, through this modality, the part of the brain associated with his disease is removed from the patient, trying to preserve other regions of that same hemisphere.

Logically, this option has some advantages, such as not eliminating brain structures that can be fulfilling crucial tasks and that perhaps could not be assumed by the other hemisphere in case of hemispherectomy. Likewise, this method reduces the risk of hydrocephalus, by accumulating less fluid in the place where that part of the brain tissue used to be.

But those are not the only ways to perform such an intervention. 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 focus of the seizures is located, and sometimes it is not even necessary to remove as such, since the neurosurgeon tries to disconnect that area from the rest of the brain, sectioning in different parts.

The most modern way to perform the hemispherectomy is through surgical procedures with endoscopy and camera. In this way, the incision that is made is minimal, so the invasive level of the technique is drastically reduced, reducing the risks and also the possibility of an infection. Likewise, the recovery of the patient is much faster, logically.

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Real case of a person with hemispherectomy

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

Nicolás had almost completely removed the right hemisphere of his brain, when he was just over three years old. We 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. Being so young and having such an underdeveloped brain, neural plasticity facilitated the creation of networks in the remaining hemisphere.

In this way, with only half the organ, Nicolás managed to overcome one of the most complicated neurological operations that exist, and acquire a whole series of skills that until then had been impossible because of the severe epilepsy that he suffered from since he he was born.

To have perspective on how normal this patient's life has been since then, we must know that he has even been able to develop with remarkable he masters such complex hobbies as the sport of fencing (even achieving a bronze medal in a national championship) or the art of painting.

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

In any case, these are relatively minor effects, taking into account the type of operation to which it was subjected. Even so, it is important to keep in mind that this patient's case is exceptional, and it was thanks to the conditions so propitious and at his young age, so 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 one. case, and others will suffer different consequences, depending on the particular conditions of each one.

Bibliographic references:

• Alcalá-Cerra, G., Paternina-Caicedo, Á., Díaz-Becerra, C., Gutiérrez-Paternina, J.J. (2013). Control of epileptic seizures with cerebral hemispherectomy in adults: systematic review and meta-analysis with data from individual patients. Neurosurgery. Elsevier.
• A.M. Ron (2021). My life with half a brain. Populi voice.
• 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.