Implanted microelectrodes used for side-effect-free pain relief
Living with chronic pain can be very difficult, especially since heavy-duty pain relievers typically have unwanted side effects, and can be habit-forming. An experimental new treatment, however, gets around those limitations by using implanted electrodes.
First of all, it should be noted that previous studies have explored the use of brain-implanted electrodes for pain-relieving deep brain stimulation. Unfortunately, according to scientists at Sweden's Lund University, such trials have met with limited success.
The researchers state that the large size of the electrodes relative to the target neurons may have resulted in nearby neurons also being stimulated, producing side effects such as anxiety, vertigo and gaze problems. It has also been difficult to get the electrodes into the proper locations, and to subsequently keep them in place.
Additionally, because the electrodes have been considerably stiffer than the surrounding brain tissue, the recipients' immune systems have sometimes identified them as foreign objects, coating them in a layer of scar tissue that impeded their performance.
With such problems in mind, the Lund team created three-dimensional clusters of highly soft, flexible "ultrathin microelectrodes." Each cluster was encased in a needle-shaped piece of biocompatible gelatine that was initially hard – allowing it to be surgically inserted into the brain tissue – but that later expanded and dissolved.
In rat studies, the scientists were subsequently able to see which specific sub-groups of electrodes within each cluster ended up in the brain's pain control centers. By only sending an electrical current to those electrodes, it was possible to activate only those centers, without any "collateral damage." As a result, it was possible to block pain signals from reaching the cerebral cortex, so they couldn't be processed.
"We have achieved an almost total blockade of pain without affecting any other sensory system or motor skill, which is a major breakthrough in pain research," says doctoral student Matilde Forni, first author of the study. "Our results show that it is actually possible to develop powerful and side effect-free pain relief, something that has been a major challenge up to now."
The team hopes that within five to eight years, the technology may be scaled up to the point that it could be utilized on humans. It should work on all types of pain that are conveyed by the spinal cord – which is most of them.
A paper on the research, led by Prof. Jens Schouenborg, was recently published in the journal Science Advances.
Source: Lund University