Researchers have recorded for the first-time the brain's firing pattern while a person feels chronic pain. This opens the door for implanted devices that can one day predict or short-circuit pain signals.
Scientists recorded four patients with unremitting pain in the nerves for over a year using a pacemaker device that was surgically implanted inside the brain. The devices recorded up to six month's worth of data, several times per day. This provided clues as to where chronic pain is located in the brain.
The study published in Nature Neuroscience on Monday reported that pain was linked to electrical fluctuations in orbitofrontal cortex, an area responsible for emotion regulation, self evaluation and decision-making. This research suggests that patterns of brain activity can be used as biomarkers for diagnosis and treatment of millions of people who suffer from chronic shooting or burning pain due to damage to the nervous system.
The study advances a generation of research which has shown the importance of brain functioning in processing and perceiving the pain. Dr. Ajay wasan, a specialist in pain medicine at the University of Pittsburgh School of Medicine who wasn't part of the study, said.
Around one-fifth of American adults suffer from chronic pain. This is persistent pain or recurrent discomfort that lasts more than three months. Doctors rely on their patients to rate the pain they are experiencing, either using a numerical or visual scale based on emojis. Self-reported measures of pain are subjective, and they can change throughout the day. Some patients, such as children or those with disabilities, have difficulty communicating or scoring their pain.
Kenneth Weber is a Stanford University neuroscientist who wasn't involved in the study. He said that there's been a lot of movement in the field of pain to develop objective markers for pain. Dr. Weber said that such markers could help us better understand the neural mechanisms behind pain. They can also validate pain felt by patients who are not being fully understood or ignored by their doctors.
In previous studies, patients with chronic pain were scanned to measure changes in blood flow. This was an indirect way of measuring brain activity. This type of research, however, is limited to laboratories and requires that patients visit the hospital or lab several times.
In a new study, Dr. Prasad Shirvalkar and his colleagues, who are neurologists at the University of California in San Francisco, used electrodes instead to measure the collective firing patterns of thousands of neurones near the electrodes.
Researchers surgically implanted recording devices in four patients who were suffering from pain for over a year, and found no relief with medications. Three of the four patients experienced pain after having a stroke. The fourth patient had phantom leg pain after losing their leg.
Patients would rate their pain at least three times per day and then press a key that would trigger their implant to record brain signals. This would last for 30 seconds. 'This is the first time chronic pain has ever been measured in real life,' said Dr. Shirvalkar.
Researchers placed electrodes on two brain regions: the orbitofrontal cortex, which is not well studied in pain research and the anterior cortex, an area involved in processing emotions. Numerous studies have shown that the anterior cortex is crucial for detecting both acute and chronic levels of pain.
Scientists fed data from the electrical signals and pain scores of patients into machine-learning models that could predict chronic pain levels based solely on brain signals.
Researchers found that orbitofrontal cortex frequency fluctuations were the best predictors for chronic pain. Dr. Shirvalkar stated that although this brain signature is common to all patients, each one also shows unique brain activity. He said that 'each patient had a unique fingerprint of their pain.
Tor Wager (a Dartmouth College neuroscientist who was not part of the study) cautioned against referring to these signatures in the orbitofrontal cortex as biomarkers yet, given that there were so many variations in each person's profile and only four participants in this study.
He said: 'We want to confirm this study with other studies that use other methodologies which can cover the entire brain in a systematic way.'
Authors of the study also pointed out that other brain areas may be involved. Dr. Edward Chang is a neurosurgeon from the University of California San Francisco. This is only chapter one.
The implants also serve a second purpose: deep-brain stimulation. Dr. Shirvalkar, along with his colleagues, are using mild electric currents as part of a clinical trial that aims to treat chronic pain. They stimulate brain regions located near the electrodes. Researchers hope to expand the study beyond the four patients who receive this experimental treatment to include 20-30 people. Researchers hope to relieve lingering pain in patients by sending pulses via electrodes that correct any abnormal brain activity.