Julie Hill is paralysed from the waist down. Yet with the aid of researchers from University College London she is cycling with her family again. Tim Perkins describes the work
Eight years ago Julie Hill was involved in a car crash on her way home in Hampshire. Tragically, it broke the middle of her back, leaving her legs totally paralysed. Since then Julie's life has been a long and painful struggle to walk again. Her dream is to ride a bike, to be able to cycle with her family.
Nearly three years ago Julie, a complete paraplegic, stood with the aid of her own leg muscles, stimulated by an electrical device implanted on the roots of her spinal cord and controlled from outside by a close range transmitter. This May she managed to cycle for more than a kilometre, again aided by the implant - and the multi-disciplinary research team of which I am a member.
I am often asked why we bother trying to reactivate the paralysed muscles of people whose spinal cords have been injured. Well, the side effects of paralysis include blood clots and pressure sores. Sometimes just falling out of a wheelchair can break weakened bones and patients are also at risk of heart disease because of their lack of exercise. Having someone manually move the paralysed limbs helps a bit but actually reactivating the disabled muscles helps more. As with able bodied people, it is the exercise that does you good.
There are perhaps five million people with injured spinal cords world wide. The spinal cord contains a huge number of nerves, along which pass signals between the brain and the rest of the body. If the spinal cord is severed, the part of the body below the break is paralysed. If your spinal cord is severed below the neck you end up a paraplegic, with paralysed legs. If the spinal cord is broken in the neck, the result is tetraplegia, involving paralysis in the arms as well.
You can repair nerves outside the spine - with transplants, for instance, to bridge the gap where the natural healing process has failed. But most damage to the spinal cord is permanent. No one has managed to bridge a break in a person's spinal cord, though it has been done in mice.
So, as yet, the only practical method of reactivating paralysed muscles is by electrically stimulating them. Today there are three ways of stimulating muscles: surface stimulation, where electrodes are placed on the skin over the muscle's motor points and connected to a "stimulator" that provides the necessary electrical pulses; percutaneous stimulation, where electrode wires are inserted through the skin into muscles that may be difficult to activate from the surface; and radio frequency coupled implants, where electrodes implanted inside the body are powered and controlled from outside via a close range transmitter. Surface stimulation is used for most patients as it is easier for the research workers to set up. Dozens of paraplegics have stood this way at Salisbury and Stanmore, the hospitals we work with.
I first became involved in getting paraplegics to stand or walk with their own leg muscles in 1977 at the Medical Research Council's Neurological Prostheses Unit in Denmark Hill in London. Although, after 21 years, one of our first patients still uses his peripheral nerve stimulator implant to exercise his paralysed legs daily, progress on standing and walking has been slow.
We had more joy with our bladder and bowel control implant, which stimulates spinal roots, where the nerves leave the spinal cord. It is now used by 1,500 disabled people worldwide. Over time, our team neurologist, David Rushton, had the brainwave of using spinal root stimulation to try to move patients' legs as well as to control their bladders.
After all our difficulties, it was fantastic when Julie walked after having one of our new stimulators implanted in 1994, shortly after we first met her. By implanting Nick's specially designed spinal root stimulator, we were able to reactivate her leg muscles.
With the aid of her implant, powered from outside by a close range transmitter, Julie is now able to get up out of her wheel chair and stand for several minutes, both in the laboratory and in her own home. This has, for instance, allowed her to reach up to take spice jars from the top shelf in her kitchen, without help. But she can only stand for a limited period and her walking is hampered by the fact that her legs tend to cross over at the end of each stride. Assistants stand either side of her to prevent her tripping.
Blocking some nerves with local anaesthetic helps a bit. Julie can then walk better, but only for a few hours till the anaesthetic wears off. With help, Julie has walked for up to 24 steps at a time at Salisbury hospital. But the technique is not good enough to allow her to walk safely outside the lab.
In the last two years, however, we have been using a tricycle in an attempt to allow her to cycle. The trike eliminates the need for Julie to balance (one of our safety concerns). For each leg, alternate lumbar and sacral root stimulation is used to push the corresponding pedal through half a turn.
Of course we feel hugely satisfied with our success. But there is still a long way to go. So, although Julie's achievement so far is outstanding for a complete paraplegic, we still have much to do, not only for her but for many others.
Tim Perkins is a research fellow at University College London and at the Stanmore Spinal Injuries Unit and Salisbury District Hospital. Julie Hill featured in a BBC1 QED documentary earlier this week.