To repair the brain after a stroke, towhat not to go electrically stimulate the so-called vagus nerve, this nerve connecting the brain to most organs? 500,000 people in France today live with after-effects that cause a visible disability. (paralysis, muscle weakness, speech and comprehension disorders) or invisible (cognitive, behavioral and mood disorders).
Why stimulate the vagus nerve?
Because unfortunately, the brain's spontaneous recovery capacities mobilized from the first days and for about six months after the stroke do not always allow complete recovery, even if they are associated with classic rehabilitation techniques (physiotherapy, speech therapy, neuropsychology, etc.), posing serious problems of reintegration, not to mention the socio-economic costs, which are often considerable.
"In 2024, we still do not have an effective and standardized treatment to amplify the reconstruction of destroyed brain circuits", recalls Julien Chuquet, researcher at the GRHVN (Research Group on Ventilatory and Neurological Disabilities) at the University of Rouen.
This is why the Rouen team hopes to be able to start the first clinical trials as soon as the necessary authorizations are obtained. Because on the other side of the Atlantic, around twenty clinical trials evaluating the benefits of vagus nerve stimulation (VNS in French) have already started.
Stroke conceptual image. Colored angiogram (x-ray of blood vessels) of the cerebral arteries. SAMUNELLA / SCIENCE PHOTO LIBRARY / SPD / Science Photo Library by AFP
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The acceleration of research in 2021
It all actually started 20 years ago, after encouraging work on animals, but the research accelerated in 2021, with the results of a study published in the journal The Lancet.
Menee In about a hundred patients, it demonstrated a clear improvement in motor functions in half of the patients. Surprisingly, sending painless electrical impulses through this easily accessible cranial nerve can actually boost patients' functional recovery without causing any side effects.", specifies Julien Chuquet. Who continues: " However, we still don't understand why some patients respond and others don't and "We also do not know the mechanism of action by which the nerve can modify the course of the reconstruction of neuronal circuits".
The hopes raised by the study have in any case quickly convinced the American drug agency, the Federal Drug Administration, to give in 2021, and after resistant epilepsy and depression, its green light in this new indication of So-called ischemic strokes (a clot blocks a cerebral artery, the most frequent, different from hemorrhagic strokes, when an artery ruptures).
“ The original hypothesis that we are following with the help of the Gueules Cassees foundation and the Stroke Research Foundation, is to demonstrate that SNV normalizes the excitability of the repairing cortex, details the researcher. Our first results have already demonstrated that SNV favorably modulates the power of gamma oscillations in rodent brains.".
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“Finding a consensus to no longer practice empirically”
His work ultimately plans to optimize the use of SNV in terms of pulse frequency, dose intensity and by associating or not SNV with a learning task, in this case the use of the front paw of rodents this time suffering from stroke.
To better understand the real therapeutic potential of SNV, "It is essential to decipher the cellular and neurophysiological mechanisms at the origin of its beneficial effects and to find a consensus to no longer practice it empirically", concludes the researcher.
Two different approaches have already been developed: one by surgical means (implantation of the stimulator around the nerve, Vivistim), the other, non-invasive but still experimental, by simple application at the ear (Nemos), the stimulation then being exerted transcutaneously at the level of the terminal branches of the nerve.
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