The latest news and information about what's going on with SCI science and research. Brought to you by Sam Maddox, author of the Christopher & Dana Reeve Foundation Paralysis Resource Guide.

A Better Bladder Stimulator

Here’s a new research paper from the James Fawcett laboratory in Cambridge, in the journal Science Translational Medicine: “A Microchannel Neuroprosthesis for Bladder Control After Spinal Cord Injury in Rat.” [tp:readmore]

Fawcett, as you know if you are a regular reader here, is a member of the Reeve Foundation International Research Consortium on Spinal Cord Injury. His main interest has been in finding ways to encourage spinal cord axon regeneration around or through the scar formed near the injury site; his work with the bacterial enzyme chondroitinase is widely known.

Daniel J. Chew and Lan Zhu, scientists at the Fawcett lab at the Cambridge Centre for Brain Repair, University of Cambridge, UK, found a way to stimulate sacral nerves and effect a bladder response on command. If you’re thinking this isn’t news, correct, the implanted Bindley bladder device has been around for 30+ years and was approved and marketed in the U.S. 10 years ago as the Vocare system. Vocare could turn the bladder on and off too.

What’s new is that Chew et al don’t have to cut any major dorsal root nerves, as was the case with the Vocare. Dorsal rhyzotomy leads to irreversible sexual function – a risk factor that ultimately doomed sales of the device in the U.S. You can still get a Brindley overseas, from Finetech Medical, but this new one, once it comes around the approval process, also uses ventral stimulation. It looks to be a far superior neuroprosthetic. Chew says it's far from ready to go but what's really left to develop is miniaturization.

From the abstract:
We designed a closed-loop neuroprosthetic interface that measures bladder fullness and prevents spontaneous voiding episodes without the need for dorsal rhizotomy in a rat model. To obtain bladder sensory information, we implanted teased dorsal roots (rootlets) within the rat vertebral column into microchannel electrodes, which provided signal amplification and noise suppression. .

... When the bladder became full enough to initiate spontaneous voiding, high-frequency/amplitude sensory activity was detected. Voiding was abolished using a high-frequency depolarizing block to the ventral roots. A ventral root stimulator initiated bladder emptying at low frequency and prevented unwanted contraction at high frequency. These data suggest that sensory information from the dorsal root together with a ventral root stimulator could form the basis for a closed-loop bladder neuroprosthetic.
The work of Chew and Zhu is featured with good detail by National Geographic.

From Nat Geo:
When the bladder is ready to empty itself, the channels detect a big spike in activity. They react by sending signals to a stimulator that’s hooked up to the nerves leading into the bladder’s muscles. The stimulator hits these nerves with a high-frequency electric pulse that stops them from firing naturally. The bladder’s muscles don’t contract, and no unwanted urine is spilled. When the user actually wants to wee, they just push a button and the stimulator delivers a low-frequency pulse instead. Only then does the bladder contract.

This device does everything that a normal bladder does, but uses electronics to stand in for damaged nerves. It works on a closed loop, so users should be able to go about their day to day lives without worrying about incontinence. And it doesn’t sever the dorsal root, so it carries none of the side effects of the Brindley method.

You can also read about the paper in this BBC report.

Note that Chew says this work isn't the goal. Regeneration of axons to more naturally control the bladder is what they'd all like to achieve. Meanwhile, the cyborg bladder button might be a welcome option for the spinal cord community.
Posted by Sam Maddox on Nov 7, 2013 9:49 PM America/New_York