One of our primary goals at SBM is to advocate for high standards of science in medicine. This means that we spend a lot of our time discussing claims and practices that fall short of this standard. This is very useful – exploring exactly why a claim falls short is a great way to understand what the standard should be and why.
An unfortunate consequence of this approach, however, is that many of our articles tend to be negative. We focus on what doesn’t work, on what needs to be fixed, and on why people fail.
But there is a positive side to the story as well that we should not neglect – science is powerful and it works. That is why we are such enthusiastic advocates of science in medicine and why it is so important to get it right. We shy away from overhyping scientific advances in medicine, because the mainstream media does that so well, but every now and then it’s good to acknowledge awesome medical and scientific advances.
Hacking the nervous system
A new report marks a notable advance in using both robotics technology and electrical stimulation to help a paralyzed man walk. Mark Pollock, described as a blind adventurer, broke his back four years ago after falling out of a window. He was completely paralyzed below the waist, with no voluntary movement. He has been working with the Edgerton Neuromuscular Research Laboratory at the University of California, Los Angeles. Dr. Reggie Edgerton has been working on spinal cord injury research for the past 30 years.
The new research combines two techniques. The first is electrical stimulation of the spinal cord. This is nothing short of a new paradigm in medical intervention for spinal injuries.
There are several broad approaches to intervening in biological function. We can alter problematic anatomy and repair trauma through surgery or compensate with braces, prosthetics, and devices. We can alter physiology and biochemistry through pharmacological intervention. We can adjust physical activity, nutrition, and environmental exposures.
Added to this list is the use of electrical or magnetic stimulation to directly alter nervous system function. Electricity has been used to alter cardiac function, such as with a pacemaker. It has also been used to alter brain function for decades, going back to the beginning of electroconvulsive therapy. But that is a fairly crude and limited application of electrical stimulation. Electrical stimulation has also been used to modulate pain.
The last couple of decades have seen an increase in the sophistication and potential applications for electrical or magnetic stimulation. Combining this technology with computers and robotics has the potential to dramatically increase those applications.
Approaches to paralysis
There are a number of ways we could potentially hack the nervous system in order to repair or replace function lost through injury. Several research teams are working on implanting electrodes onto the surface of the brain, or using scalp surface electrodes, in order to translate thought into computer control. Software interprets the brain signals, which the subject learns to control, enabling them to move a cursor on a screen, or control a robotic arm. This approach has the potential of bypassing any injury or paralysis and giving direct mental control to robotic limbs and devices.
Another approach is to attach electrodes to proximal muscles that are still under voluntary control and then connecting them to more distal muscles that have been paralyzed, or to robotic prosthetic limbs.
The robotics themselves can either take the form of a limb (such as a robotic arm) or an exoskeleton that fits over a patient’s arm or leg.
Edgerton’s team has been working on another approach entirely, specific to spinal cord injury. They use continuous low levels of electrical stimulation below the spinal cord injury to “wake up” the injured spinal network. The theory is that even with complete paralysis, there still may be some surviving connections and if they can be activated that can restore some voluntary control, even after years of total paralysis.
They have been using two methods. The first involves surgically implanting electrodes epidurally – over the membrane that covers the spinal cord. The second is to use transdermal electrical stimulation, which stimulates across the skin and has the advantage of being noninvasive.
A couple years ago they reported on four subjects who were completely paralyzed after spinal cord injury who were able to have some voluntary control of their legs restored. The “holy grail” of spinal cord injury and recovery is voluntary walking, but any movement was a proof of concept.
The new advance
The latest report from Edgerton’s team is the result of a combination of transdermal electrical spinal cord stimulation and a robotic exoskeleton in Mark Polock. The exoskeleton is capable of supporting the patient’s weight and walking. The exoskeleton is also able to monitor any voluntary contribution to movement from the patient.
They were able to demonstrate that Pollock was voluntarily flexing his left knee and hips, contributing a little to the exoskeleton’s movement. He still needed assistance to walk, but this was a significant advance.
The reason it is beneficial for Pollock to contribute to the walking, rather than letting the exoskeleton do all the work, is that there are other health benefits. Paralysis can lead to lack of physical activity and cardiovascular disability. Voluntarily contracting muscles can improve muscle tone and function and improve cardiovascular health.
Combining robots, computer control, and electrically hacking the nervous system is still relatively new. This is often referred to as brain-machine or brain-machine-brain interface. There are also muscle/nerve-machine interfaces, and now we also have spinal cord-machine interface.
Obviously this is all a very new technology and we need to have realistic expectations of how long it will take for this technology to mature. There is a tendency to overestimate short term technological advances, and then become disappointed when the promised benefits do not manifest quickly. However, there is also a tendency to underestimate longer term advances. Then one day, the world changes rather quickly.
We are still years away from this technology going mainstream – getting it out of the research centers and into hospitals and regular practices. There are still technical issues to be worked out in terms of interfacing with the nervous system. But all of the proofs of concept are now in place. We really just need incremental technological advances.
It may take 10-20 years or even 30-40 years, but it seems likely that in something like that time frame we will see robotics and machine-nervous system interfaces essentially solve the problem of paralysis.