The Future of Medicine: Non-Invasive Nerve Repair

neuronsRepairing severed nerves remains one of the most challenging aspects of modern medicine. In addition to being common, due to spinal injuries, pressure or stretching, the severing or damaging of nerves can lead to a loss of mobility as well as sensation. And up until recently, doctors hoping to repair the damage have been heavily reliant on long-term methods that can be expensive and invasive.

However, Professor George Bittner and his colleagues at the University of Texas at Austin Center for Neuroscience have developed a new and inexpensive procedure to quickly repair severed peripheral nerves. Taking advantage of a mechanism similar to that which permits many invertebrates to regenerate and repair damaged nerves, the new procedure involves applying healing compounds directly to the severed nerve ends.

nerveTrauma to peripheral nerves, which connect the central nervous system to the muscles and sensory organs, is quite common, and is usually the result of excessive pressure or stretching. In most cases, this means that the axon of a nerve – the central bundle of cylindrical sheaths that contains individual nerve cells – is separated from the nerve fiber, leaving the nerve intact but disconnected from the muscle.

Afterward, the nerve cell slowly begins to regrow, and can form a twisted ball of nerve fiber at the cut in the axon. Such nerve scars are called neuroma, and in current medical practice, they are repaired by using microsutures to reconnect the cut ends of the axon and provide a continuous axon to guide the regrowth of the nerve fiber. However, this procedure is extremely delicate, and recovery can take months or even years.

george_bittner1Bittner and his colleagues’ new method involve using a natural healing process to aid in repair and recovery. Already, his team discovered that when a plasma membrane in a cell is damaged, a calcium-mediated healing mechanism begins to draw vesicles (small sacks of lipid membranes) towards the site of the injury. These provide the raw material needed to repair the site.

However, when these vesicles are attracted to the site of a severed axon, both ends of the axon are sealed off by this repair mechanism, preventing regrowth of the nerve. To avoid this problem, the first step of the Texas group’s nerve repair procedure is to bathe the area of the severed nerve with a calcium-free saline solution, thus preventing and even reversing premature healing of the axon ends.

nerve_rootThe damaged axons remain open, and can more easily be reattached. This is then done by pulling the severed ends to within a micron of each other, whereupon a small amount of a solution containing polyethylene glycol (PEG) is injected. The PEG removes water from the axonal membranes, allowing the plasma membranes to merge together, thereby healing the axon.

At the same time, the nerve fibers are brought into close enough proximity that they receive chemical messengers from each other, making them believe they are still whole and preventing the death of the disconnected nerve fiber. The severed nerve fibers can then grow together in a short period of time and with relatively good fidelity to the original connectivity of the nerve fibers.

nerves_pinwheeltestThe final step of the procedure is to inject the area with a calcium-rich saline solution, which restarts the vesicle-based repair mechanism, thereby repairing any residual damage to the axonal membrane. At this point, the nerve is structurally repaired, and use of the affected area begins to return within a few hours instead of months.

To test the procedure, Bittner and his colleges experimented on a series of rats that had had their sciatic nerves severed, resulting in paralysis of the affected limb. In each case, once the rats awoke, they were able to move the limbs containing the severed nerves within moments. Normal function was partially restored within a few days,  nd 80-90% of the pre-injury function was restored within two to four weeks.

mouseThe chemicals used in Bittner’s procedure are common and well understood in interaction with the human body. Because of this, there is no clear obstacle to beginning human clinical trials of the procedure, and teams at Harvard Medical School and Vanderbilt Medical School and Hospitals are currently conducting studies aimed at gaining approval for such trials.

While the procedure developed by Bittner’s group will not apply to the central nervous system or spinal cord injuries, the procedure offers hope to people whose futures include accidents involving damaged nerves. In the past, such people would have to undergo surgery, followed by months or years of physiotherapy (often with inconclusive results).

Now they can look forward to a full recovery that could take as little as a few weeks and cost them comparatively very little. And we, as human beings, would be one step closer to eliminating the term “permanent injury” from our vocabulary!


The Future is Here: BCI Stroke Rehabilitation

stroketherapybciIn recent years, rehabilitative systems have been developed that can allow stroke victims to move animated images of their paralyzed limbs, or to activate robotic devices that guide their limbs through the desired movements. Slowly, we are entering an age where machines can turn thoughts into ambulatory ability, allowing people who suffer from paralysis to lead more fuller lives.

But scientists at the University of Wisconsin-Madison have taken it a step further with a device that acts as an intermediary between the brain and a non-responsive hand, receiving signals from the one and transmitting them to the other. Known as the Closed-Loop Neural Activity-Triggered Stroke Rehabilitation Device, it consists of two established technologies.

brain-computer-interfaceThe first of those is a brain control interface (BCI), which interprets electrical signals from the brain and uses them to control an external device. In the past, this has been used to control robotic limbs, usually to assist people dealing with paralysis. But in this case, it activates a functional electrical stimulation (FES) system that’s attached to the paralyzed hand.

Basically, when a patient thinks of tapping their fingers, the BCI reads and recognizes those signals. The computer then passes these signals along to the FES, and it causes the hand to move as desired. The idea is that by repeatedly moving their hand in this fashion, patients will rebuild the neural pathways that previously allowed them to do so unaided.

stroketherapybci-1To test the device, Dr. Vivek Prabhakaran and Dr. Justin Williams, brought together eight stroke patients – all of whom had lost at least partial use of one hand. Over the course of 9 to 15 sessions over a period of three to six weeks, each session lasting from two to three hours, they conducted clinical trials with their machine and recorded the results.

This was conducted using a functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) device. By scanning the patient’s brains before, during and after the trials, they were able to determine that the sessions resulted in a reorganization of the parts of the brain involved in motor function, while the DTI showed a strengthening of fibers in the white matter area of the brain.

brain-computer-interface1Although there was some variation depending on the severity of each person’s stroke, the overall effect ws that patients experienced an improvement in motor function, and reported an improvement in their ability to perform daily activities. Looking long-term, Dr. Vivek Prabhakaran said that:

Our hope is that this device not only shortens rehabilitation time for stroke patients, but also that it brings a higher level of recovery than is achievable with the current standard of care.

Up until recently, the idea of using electrostimulus to send signals directly from the brain to the limbs, bypassing spinal injuries or other impediments to ambulatory ability, has been considered the province of science fiction. However, ongoing research and testing has been pushing the limits of what is possible with this technology.

Using our minds to control machinery is certainly an impressive feat, but using our minds to control machinery to restore or expand our abilities to control our own bodies. Not only is that impressive, its potentially revolutionary, and portends of an age where there is no such thing as permanent injuries or loss of ability anymore.