Neuropathic pain is nasty. It is baffling and excruciating. It’s also defined as chronic pathological pain that continues after the physiological cause has been eliminated. It can cause even the lightest of feathery touches to produce intolerable pain.
Neuropathy is quite common. It affects 5-10% of the world’s population. No cures or effective treatments are currently available.
The causes of neuropathy include damage to nerve cells and some medicines used to treat cancer. When it’s induced by chemotherapy, neuropathic pain can be so extreme that some cancer patients choose to stop their cancer treatments.
As might be imagined of a symptom with no overt causes, no cures, and no effective treatments, neuropathy can pose significant challenges for pain management practitioners.
What is neuropathic pain?
The “neuro” in neuropathic references neurons, which are cells in our nervous system. They are the core component of our brains, our spinal cords, and our peripheral nerves.
Neuron cells are excitable. Not excitable like your kids at Disneyland. But “excitable” in that they receive, respond to, and transmit information by electrochemical signaling.
Our sensation of pain originates when a neuron in the spinal cord receives sensory information from the body. The information is then relayed on to the brain, where it’s perceived as pain.
A new study signals a new way to treat neuropathic pain
The study was conducted by Boston Children’s Hospital and the National Institute of Mental Health. Its results may provide a pathway to effective treatment of neuropathic pain. The study’s report was published in the journal Nature last week.
Nerve damage can cause a harmless touch to activate a pain sensor
According to Alban Latremoliere, a co-author of the report, the parts of the spinal cord that sense harmless touch and the parts that sense pain are normally insulated from each other by inhibitory neurons. This insulation ordinarily prevents mixed signals from being sent to the brain. However, says Latremoliere, “After nerve injury, this inhibition is lost, leading to touch information activating pain neurons.”
When the brain receives information from spinal neurons that are meant to be used only for reporting pain, it naturally interprets the signals as expressing real pain.
Neurons in the brain respond to a false pain signal
The study shows that neurons that originate in the cerebral cortex (the outer layer of the brain) can amplify touch sensation by sending signals back to the same parts of the spinal cord that receive tactile sensory information from the body.
The researchers believe that this activity sets up a loop of false pain signals.
“We know that mental activities of the higher brain – cognition, memory, fear, anxiety – can cause you to feel more or less pain,” says Clifford Woolf, PhD, another co-author of the study. “Now we’ve confirmed the physiological pathway that may be responsible for the extent of the pain. We have identified a volume control in the brain for pain – now we need to learn how to switch it off.”
The report’s authors see the cortical neurons that they identified in the study as a target. They hope that silencing those neurons will disrupt the feedback loop that occurs when the brain amplifies a false pain response to an innocuous touch.
When those cortical neurons were severed or genetically muted in mice, the mice stopped expressing pain responses to light, harmless touching. But the mice did keep their sensitivity to truly painful stimuli. They reflexively yanked back their paws from heat, cold, or pinpricks.
New functional imaging technologies let researchers see single neurons
- The researchers used brand new imaging technologies to observe and target specific groups of neurons in the mice’s cortexes and spinal cords.
- The new techniques enabled the team to observe what happens when different groups of neurons are artificially activated or muted in mice.
- The team could also observe which circuits were activated when the mice were exposed to actually harmful or truly innocuous stimuli.
Other researchers have experimented with brain stimulation as a way of treating neuropathic pain. The results have been decidedly mixed. With the new functional imaging technologies, investigators can now see what kinds of neural interventions most effectively disrupt the false pain signal loops that underlie neuropathic pain.
“We now have the ability to silence or activate whole groups of neurons and image their patterns of electrical firing with single-neuron resolution, “says Woolf. “None of this was possible 10 years ago.”
Nuvo Spine and Sports specializes in orthopedic pain management
We approach our work armed with regenerative strategies bred from sports medicine and the neurological sciences.
The Nuvo team of medical professionals is solely dedicated to minimizing or eradicating pain by resolving the underlying conditions that cause the pain. We are proud that we consistently achieve that goal and successfully enhance our patient’s overall quality of life.
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Read more about the study here.
Dr. Vahedifar's pain management strategies integrate cutting-edge medical technology with targeted interventions to minimize pain and treat pain’s underlying causes.
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