It is the most reliable technique for removing a brain tumor: a neurosurgeon at Nice University Hospital deciphers awake surgery

Remove as large a tumor volume as possible, without affecting the patient’s brain functions. A real challenge when we know that low-grade gliomas in particular – the most frequent indication for awake surgery – infiltrate the brain and therefore potentially the so-called functional brain regions, dedicated to motor skills, sensitivity, language, cognition etc.

The D^r Fabien Almairac, neurosurgeon at Nice University Hospital, and his team specialize in this unusual surgery during which the patient is an active and central partner.

Only practiced in certain hospitals, it relies on perfect coordination between the different stakeholders: neurosurgeon, anesthetist, speech therapist, neuropsychologist.

What difficulty does the neurosurgeon face when he has to remove a lesion in the brain?

For primary brain tumors (gliomas), it is mainly a matter of being able to differentiate between the infiltrated (and therefore diseased) brain and the healthy, functional brain. For metastases located deep in the brain, the challenge is above all to find the right “path” through the brain tissue to access it without creating irreversible damage. It is imperative to respect the areas identified as essential for “normal” functioning of the brain, and therefore to be as least harmful as possible when removing the lesion.

Are these essential areas not known?

Each brain is unique, so there is no universal map to determine the usefulness of this or that area. We must therefore carry out, with the help of the patient, a personalized map of their brain (cortex and white matter), by applying low-intensity bipolar electrical stimulation in a directed manner. If the stimulation concerns an area essential for function, the task that the patient is carrying out is disrupted independently of his or her will. An example: if we stimulate cortical areas involved in language processing, we cause specific language errors, such as blocking, which are reported by the speech therapist. This is valid for a certain number of neurocognitive functions. The tumor is then resected, avoiding areas identified as functional.

What are the risks for the patient if these areas are injured?

By damaging the cortex and especially by cutting white matter tracts, we can cause neurological and cognitive deficits that are potentially extensive and, for the most part, irreversible.

Is awake surgery applicable to all patients?

It is only with the help and participation of the patient that the surgeon can demarcate the area to be removed. Also, this surgery can only be performed on patients who are able to cooperate by carrying out tests to assess language and other cognitive functions during the operation. In fact, it is mainly used to treat low-grade gliomas, tumors which affect often young people who generally do not present neurological or cognitive deficit when the disease is discovered. It is more difficult to consider in the case of glioblastoma, a more aggressive tumor which affects older people, often already suffering from neurocognitive disorders at the time of diagnosis. Also, and even if there is no real age limit, the technique is less well supported beyond 65-70 years; waking up is more difficult, longer, patients tire more quickly, and there is a tendency to go less far in tumor resection, with suboptimal results.

Concretely, how does awake surgery take place?

We first open the skull under general anesthesia, then we wake the patient. After 10-15 minutes, it is fully operational (and feels no pain). There, we can begin the tests under the control of the speech therapist or the specialized neuropsychologist in order to establish the personalized map of the patient’s brain. Even after having identified the functional areas of the cortex, we continue, during the resection of the tumor, to control its neurocognitive functions. We thus remove the invaded area of ​​the brain little by little until the patient begins to make errors on tests. We then know that it is not possible to continue the procedure otherwise it would cause irreversible brain damage.

How long does this type of intervention last?

Mapping the cortex takes around fifteen minutes knowing that we only explore the area where the tumor is located. Then, the tumor resection phase does not last longer than during “classic” surgery, if you are experienced in this practice. Or 1h30 to 2 hours at most, depending on the location of the tumor and the patient himself. In any case, after 2 hours, the patient becomes tired and his responses are less reliable.

The following?

When we have reached the so-called functional limits of the brain, we put the patient back to sleep, and we finish the surgery as usual.

Is Awake Surgery the Panacea for Removing Brain Tumors?

Without a doubt! Unfortunately, not all patients, and in particular those with cognitive disorders, can benefit from it, which can represent a loss of opportunity for them. Without this personalized mapping, we tend to be more careful during resection, at the risk of removing fewer tumors.

The future?

We are trying to develop other mapping methods, perhaps less efficient than awake surgery, but which would improve the care of patients who cannot benefit from them. And this is the purpose of the research that we are carrying out in partnership with INRIA.