Chronic pain | New study raises hope

Objectively identify patients with chronic pain through brain recording. And even treat them. This is the promise of a new American study on the neurology of chronic pain.

“Episodes of chronic pain are predicted by certain changes in the brain, which we have recorded with electrodes implanted in the brains of patients,” explained during a press conference call earlier this week, Prasad Shirvalkar, neurologist at the University of California, San Francisco (UCSF) and lead author of the study published in the journal Nature Neuroscience. ” It’s a first. »

Chronic pain is one of the most common chronic diseases. Nearly one in five American adults have it, according to a study published last winter in JAMA Network Open.

This is higher than the prevalence of diabetes.

The study of D^r Shirvalkar involved only four patients, followed for three to six months. “On the other hand, we have measurements of their pain episodes and recordings of their brain activity several times a day,” says the Californian researcher. And the signals that we observe in the two areas of the brain studied are relatively similar from one patient to another, even if they did not have the same types of pain. One of the patients had had a leg amputated and suffered from phantom pain. The others had had a stroke.

The study of Nature Neuroscience is one of a kind, according to Yves de Koninck, neurobiologist specializing in pain at Laval University. “If this is confirmed with more patients, it could allow us to make an objective diagnosis of chronic pain. And perhaps even to detect the disease before it appears and to prevent it. »

One of the big problems with chronic pain is its subjective nature. “Often patients aren’t taken seriously because their doctor can’t detect anything physical,” says Dr.^r by Koninck. Besides, we shouldn’t fall into the trap of saying “if you don’t have these brain biomarkers, you don’t have chronic pain”. Pain of different origin may have different neurological biomarkers. »

Anticipation

The two regions studied are the anterior cingulate cortex (ACC) and the orbitofrontal cortex (COF). “Previous studies have mostly looked at regions of the brain associated with physical perception,” says Dr.^r Shirvalkar. But pain also has an affective and cognitive dimension. CCA is related to emotions and COF to decision-making, therefore also to predicting the future. We believe that COF is related to the apprehension of pain. Our approach is based on the fact that the neurology of chronic pain has been studied since the 1950s without finding a biomarker. Animal research has shown the importance of CCA for pain.

The brain electrode is the same that is used for “deep brain stimulation” (DBS). “DBS has been used for Parkinson’s since the 1990s. We believe that if the biomarkers are confirmed, DBS could be used for chronic pain as well,” says Dr.^r Shirvalkar.

Are there any risks at SCP? “Very rarely,” says the D.^r Shirvalkar. And it seems to be related to the amount of electricity administered. We believe that if DBS is only administered episodically, when biomarkers predict an episode of pain, the risks will be minimal. »

It is all the same a “last chance” treatment, “not even second or third line”.

The next step is to study 20 to 30 chronic pain patients.

Optogenetics

In Europe, magnetic stimulation external to the brain is used for pain, but its effects last a maximum of a month, notes the D^r Shirvalkar. “You then have to come back for two weeks of magnetic stimulation. »

The laboratory of D^r de Koninck is working on optogenetic neurostimulation to counter chronic pain. “With light, we activate certain populations of nerve cells without affecting others,” says the Quebec City researcher. With an electrode, we touch all the cells.

“Quebec is one of the cradles of research on chronic pain. The pioneers of the mental representation of pain by brain imaging, in the 1990s, are from here. »