Cambridge Team Develops Inflatable Neurostimulator

by James Cavuoto, editor

June 2021 issue

Since the first spinal cord stimulation devices emerged more than 50 years ago, neuromodulation vendors and research institutions, have sought to improve the performance and decrease the size of the devices. One challenge confronting them is that larger electrodes, with greater surface area, provide better therapeutic benefit but more invasive implantation procedures.

Several vendors, including MicroLeads and WISE, have addressed this problem with flexible or expandable paddle leads that can be implanted percutaneously. Recently, a research team at Cambridge University in the U.K. developed an ultra-thin, inflatable stimulation device to optimize both coverage and ease of implantation. The device is so thin that it can be rolled up into a tiny cylinder, inserted into a needle, and implanted into the epidural space of the spinal column.

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.

Early tests of the device suggest that it could be an effective treatment for many forms of severe pain—including leg and back pain—which are not remedied by painkillers. It could also be adapted into a potential treatment for paralysis or Parkinson’s disease. However, extensive tests and clinical trials will be required before the device can be used on patients.

Although other types of SCS devices are currently used to treat severe pain, the most effective of these devices are bulky and require invasive surgery, while current keyhole devices are far less effective at treating pain. By combining the clinical effectiveness of the surgical devices and the ease of implantation of the keyhole devices, the Cambridge-developed device could be an effective, long-term solution to intractable pain, which affects millions worldwide. The results are reported in the journal Science Advances.

“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,” said Damiano Barone from Cambridge’s department of clinical neurosciences, one of the paper’s senior authors. 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 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. Their 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, thanks to the microfluidic channels.

“Thin-film electronics aren’t new, but incorporating fluid chambers is what makes our device unique—this allows it to be inflated into a paddle-type shape once it is inside the patient,” said Proctor.

The researchers validated their device in vitro and on a human cadaver model. They are currently 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 technology is being commercialized by Cambridge Enterprise, the University’s commercialization arm.


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