Spinal cord stimulation has been talked up as a treatment for severe pain, an agony of a sort that doesn’t respond to painkillers.
It’s effective, but the equipment is so bulky or imprecise, that it’s often called the “solution of last resort”.
There are millions of people worldwide living with intractable pain and spinal cord stimulation (SCS), in theory, should be able to help many of those people.
But complications associated with SCS means there are only 50,000 of these procedures performed worldwide each year.
Tiny device could be a game changer
Cambridge University engineers believe they have a solution: An ultra-thin, inflatable device – about the width of a human hair – that can be inserted into the spinal column without the need for invasive surgery.
Because the device is so thin “it can be rolled up into a tiny cylinder, inserted into a needle, and implanted into the epidural space of the spinal column, the same area where injections are administered to control pain during childbirth”.
This requires only a local anaesthetic.
Once correctly positioned, the device is inflated with water or air so that “it unrolls like a tiny air mattress, covering a large section of the spinal cord”.
When connected to a pulse generator, the ultra-thin electrodes start sending small electrical currents to the spinal cord, which disrupt pain signals.
Inserted under local anaesthetic
According to a statement from the UniversIty of Cambridge, early tests of the device suggest that it could be an effective treatment for many forms of severe pain – including leg and back pain.
The researchers say it could also be adapted into a potential treatment for paralysis or Parkinson’s disease.
Cambridge is working with a manufacturing partner to further develop and scale up their device and are hoping to begin tests in patients within two to three years.
The researchers explain their thinking
“Spinal cord stimulation is a treatment of last resort, for those whose pain has become so severe that it prevents them from carrying out everyday activities,” said Dr Damiano Barone, from Cambridge’s Department of Clinical Neurosciences, one of the paper’s senior authors.
“However, the two main types of SCS devices both have flaws, which may be one reason their use is limited, even though millions struggle with chronic pain every day.”
Dr Barone said the most effective SCS device in clinical use is a paddle-type device, which covers a wide area of the spinal cord, but is bulky and requires invasive surgery under general anaesthetic.
The other type of device can be implanted with a needle and only requires local anaesthetic, but it covers a smaller area and is less clinically effective than a paddle-type device.
“Our goal was to make something that’s the best of both worlds – a device that’s clinically effective but that doesn’t require complex and risky surgery,” said Dr Christopher Proctor, from Cambridge’s Department of Engineering, the paper’s other senior author.
“This could help bring this life-changing treatment option to many more people.”
The researchers used a combination of manufacturing techniques to build their device: Flexible electronics used in the semiconductor industry; tiny microfluidic channels used in drug delivery; and shape-changing materials used in soft robotics.
Microfluidics is both the science that studies the behaviour of fluids through micro-channels, and the technology of manufacturing microminiaturised devices containing chambers and tunnels through which fluids flow or are confined.
The finished device is just 60 microns thick – thin enough that it can be rolled up and placed in a needle for implantation.
However, after implantation, the device expands out to cover a wide area of the spinal cord via the microfluidic channels.
Early versions of the device were so thin that they were invisible to X-rays, which the surgeon would need to use to confirm they’re in the right place before inflating the device.
The researchers added some bismuth particles (a benign metal) to make the device visible without increasing the thickness too much.