'Bionic spine' could pave the way for new paralysis treatments

"'Bionic spine' could enable paralysed patients to walk using subconscious thought," reports The Guardian.

In a study using sheep, Australian researchers have developed a device that can record movement signals from the brain. It's hoped this will eventually lead to these signals being transmitted to other parts of the body.

The spine – specifically, the spinal cord – is essentially a signal cable. It transmits electrical impulses from the brain to other parts of the body. Damage to the spine can result in paralysis.

Restoring this signal process in humans has been described as the "Holy Grail" of bionic medicine, which uses technology and engineering to improve or restore bodily functions.

The researchers implanted the device, called a stentrode, via a blood vessel in the neck and guided it into position in a blood vessel overlying the part of the sheep's brain responsible for movement.

They found the device was able to record signals as the sheep moved around for a period of up to 190 days. These recordings were comparable to the recordings taken from electrodes implanted directly on to the brain.

Accurate recordings may mean this device can be used for people with paralysis to control bionic limbs and exoskeletons in the future.

While this technology is exciting, the usual caveats about early-stage research apply.

The first tests in humans are planned for 2017, and the results will give more of an indication about whether the device could be effective if implanted in humans – and, importantly, whether it would be safe.  

Where did the story come from?

The study was carried out by researchers from a number of institutions, including the University of Melbourne and the University of Florida, and was funded by grants from the US Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office, the Office of Naval Research (ONR) Global, and a National Health and Medical Research Council of Australia (NHMRC) Project Grant and Development Grant.

It was published in the peer-reviewed Nature Biotechnology.

The UK media has not reported the technical details and findings of this animal study at length, but the implications of the findings and the direction for future research has been discussed appropriately.   

What kind of research was this?

This was an animal study where a type of device or stent able to record brain activity (stentrode) was positioned in a blood vessel overlying the motor cortex. This is the part of the brain responsible for muscular activity.

This type of study is useful for the first testing stages of new devices or technologies, but it is not certain these findings will be replicated in humans.

However, the researchers did look for an animal model with blood vessel structures in the brain similar – but not identical – to humans, eventually settling on sheep.   

What did the research involve?

The researchers used human samples to investigate blood vessel structures in the human brain, and chose an animal model considered to have a comparable structure to human vessels. 

The stentrode, or "bionic spine", is a small device fitted with electrodes that can detect signals coming from the motor cortex.

Usually, inserting a device into the brain would require advanced brain surgery to open the skull, which carries the obvious risks of complications, such as postoperative infection.

However, in this study the device was inserted via a blood vessel in the sheep's neck, and was then guided under imaging through a thin tube called a catheter to its target position in a blood vessel overlying the motor cortex in the brain.

This could then record signals for movement. The movement signals coming from the device were validated by comparing them with electrodes implanted on to the brain surgically. 

What were the basic results?

In brief, the researchers were able to successfully position the stentrode within a blood vessel overlying the motor cortex of the brain, and record brain signals coming from freely moving sheep for a period of up to 190 days.

The content of these recordings was comparable to the recordings taken from electrodes implanted directly into the brain.  

How did the researchers interpret the results?

The researchers concluded that stentrodes may have wide-ranging applications in the treatment of a range of brain conditions. 

Conclusion

This early-stage study was conducted in sheep, and aimed to test whether a stentrode could be inserted into a blood vessel overlying the brain using a non-surgical method. Researchers then wanted to see whether the device was able to accurately record movement signals.

Overall, the results were promising. Implanting devices into the brain normally requires surgery to open the skull, which carries the associated risks of trauma, infection and inflammation. Also, devices positioned in brain tissue can be rejected by the immune system.

However, this device could be inserted through a blood vessel in the neck, and was successfully guided into the correct position in a blood vessel overlying the brain. As the results demonstrated, it was then able to record brain signals. 

The hope is this device could be used in the future for people with a spinal cord injury – such as those with paralysis – to control bionic limbs and exoskeletons with thought alone.

These signals are still present in the brain, but cannot be transmitted to the limbs. The stentrode would in effect bypass this problem, which is why it has been referred to as the "bionic spine".

A sheep model was used to replicate the structures found in humans as closely as possible. The stentrode technology used is currently in clinical use, which should allow easy transfer from animal models to humans.

However, the sheep used in this study weren't paralysed, so the big test now is whether these signals can actually be transferred into movement instructions.

The Guardian reported the researchers are now set to trial this device in humans at the Austin Health spinal cord unit. The device will similarly be inserted via one of the neck veins and, once implanted, will feed brain signals to another device positioned at the person's shoulder.

This will then translate signals into commands, which will be fed to the bionic limbs using Bluetooth wireless technology to tell them to move.

This technology is exciting and could provide hope for people with a spinal cord injury. But the research is still in its very early stages, and it is too soon to know when, or if, it will become available.

The researchers have planned the first tests in humans next year, and the results will give more of an indication about whether the device could be effective – and safe – in humans.