a new non -invasive tool to treat the brain with precision

a new non -invasive tool to treat the brain with precision


Depression, chronic pain, Parkinson and Alzheimer’s diseases, obsessive compulsive disorders … So many pathologies that could, in the more or less close future, benefit from focused ultrasonic treatments. Back on an approach that is on the rise thanks to technological progress made in recent decades.


Imagine: suffering from depression, you no longer feel anything other than incomprehension, despair and suffering, even in the face of the most beautiful things of existence. Drug treatments are heavy and can last for months, without a systematic guarantee of results, since up to a third of depressive people do not respond to commonly prescribed treatments.

Imagine again: suffering from Parkinson’s disease, it is difficult for you to move. Drug treatments may exist, the more you take it, the more you risk increasing the extent of the side effects, which result in particular by abnormal and often jerky (dyskinais) involuntary movements characteristic of this condition.

These situations are representative of what many people with brain diseases experience. Currently, the treatments are of two kinds, drugs or surgicals per (implantation of electrodes).

The former flood the brain and most often cause many undesirable effects, such as insomnia, digestive disorders (nausea, vomiting) or cognitive disorders (memory loss or executive functions). The latter are, like any surgery, and all the more so, particularly risky brain surgeries.

Other approaches to modify the activity of the brain without surgery are also explored. Grouped under the term neuromodulation, they are either electric (diffusion of a weak current between two electrodes, or magnetic (in short change of the magnetic field inducing a neuronal activity). Unfortunately, these techniques are only able to reach the surface part brain, with low specificity.

On the other hand, the use of ultrasound could change the situation. This method makes it possible to precisely target deep areas of the brain. Explanations.

Concentrate ultrasound

The sounds correspond to vibrations spreading in air or water. Our ear is able to perceive them when their frequency remains weak, between 100 Hz and 150 Hz for a male voice and between 200 Hz and 300 Hz for a female voice. The ultrasound, which correspond to vibrations whose frequency exceeds 20 kHz, are however no longer perceptible by the human ear.

On the medical level, ultrasound has been used for decades to make imaging of different parts of the body. One of their best known uses is ultrasound, used for example to verify the state of health of the fetus and allow future parents to distinguish the traits and movements of their child to be born.

The ultrasounds generated by imaging devices propagate in the body, and are variably resonated with the different tissues, depending on their density. These resonances are captured by the instruments, then converted into images. We then speak of diagnostic ultrasound.


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The novelty of focused ultrasound is based on the orientation and temporal concentration of acoustic vibrations and the amount of energy deposited in the same place. The goal here is to distribute them to the same point. We can compare this approach to that which consists in focusing the rays of the sun with a magnifying glass: the energy accumulates at the focal point where they meet. This approach opens up new perspectives.

Scientists have thus noticed that it was possible, using high intensity focused ultrasound, to coagulate the tissues and to eliminate tumors throughout the body. This approach, called “echo therapy” is used for example to treat thyroid nodules or certain prostate or breast tumors.

The rebirth of ultrasonic neuromodulation

In the 1960s, some researchers discovered that low-intensity focused ultrasounds-that is to say with intensities close to diagnostic ultrasound-could modulate brain activity.

By entering into relation to the brain fabric, acoustic waves increase the local pressure (acoustic pressure due to acoustic waves), which temporarily modifies the behavior of neurons. If this process is repeated, communication between certain neurons (circuit) changes more permanently and allows the brain to reorganize.

The implementation of this approach in the 1960s came up against a major obstacle: the skull, by its density and its shape, absorbs or dissipates the majority of acoustic energy. Implementing ultrasound neuromodulation required at the time to practice a surgical operation to remove part of the skull (craniotomy). This intervention being particularly invasive, the use of ultrasound focused to act on the brain has been abandoned.

But the technological progress of recent decades has made it possible to exceed this limitation. On the one hand, medical imaging now makes it possible to obtain high resolution shots of the skull, and therefore to know its density. On the other hand, the development of so -called computational tools makes it possible to estimate the share of acoustic energy lost due to the bone, and therefore to compensate.

Young woman receiving transcranial ultrasound treatment
Technological progress has enabled the return of transcranial ultrasounds to the forefront of the scientific scene.
Elsa Fouragnan, Author provided (no reuse)

These advances make possible the precise and safe use of transcranian ultrasound in humans, which explains the renewed exponential interest that this technique has known for a few years. But, despite these advances, many limitations remain.

Limitations to exceed

The first limitation is linked to the fact that focused ultrasounds do not produce directly observable effects, which makes their dosage difficult. As a safety measure (to avoid heating the fabric, or having coagulation risks), very low intensities are chosen, which probably limits the extent of the observable effects.

In addition, the positioning of the devices requires high precision, which requires many stages of preparation, making this approach complex to set up. There is also a very important interindividual variability in terms of skull geometry and brain organization (configuration and size of certain regions, organization of the neural circuit to this region, etc.).

Thus, the stimulation of the same part of the brain in two individuals, with the same parameters, leads to different results, by the acoustic intensity that will cross the skull, but also of the way the brain will react.

There is also an intraindidividual variability. Depending on the state of the participant (for example, depending on their state of fatigue or stress), stimulation is likely to induce variable effects. Finally, and as for all treatments, research work must be carried out to determine the share of the placebo effect in the results obtained.

Nevertheless, once the limits have been overwhelmed, stimulation by focused ultrasound has important potential to help people with brain diseases.

Considerable potential

Recent studies in many clinical contexts have made it possible to obtain promising results, whether it is to use ultrasound to reduce the symptoms related to depression, reduce the intensity of chronic pain, mitigate certain motor disorders Associated with Parkinson’s disease or improve the cognitive functioning of patients suffering from Alzheimer’s disease. In addition, preliminary results suggest that people with obsessive compulsive disorders can also benefit from it.

However, these descriptions of clinical cases or these studies carried out on small samples have still not made it possible to access a precise understanding of the dose required to reach a biological effect or to develop precise protocols.

Despite the many uncertainties that remain and technical challenges that still remain to be met to optimize this technology, the potential of neuromodulation by focused ultrasound arouses real scientific and medical enthusiasm. This sector is in full development, and the culmination of current research could improve the situation of many patients with brain disorders.

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