Friday May 20 2011
The technique is promising but needs testing in more people
A man paralysed from the chest down “is now able to stand with electrical stimulation of his spinal cord,” BBC News has reported.
Ron Summers, 23, had been paralysed in a road traffic accident five years ago, but after two years of intensive physical training and the implantation of spinal electrodes, he can now perform short bursts of limited movement. After 80 sessions of electrical stimulation, Summers was able to stand for over four minutes and activate certain leg muscles, allowing him to step while being assisted.
The treatment did not provide a cure as such, because the injured spinal cord has not been healed and Summers is not able to walk without assistance and electrical stimulation.
This initial trial of electronic spinal stimulation provides highly promising results, although the findings must be interpreted in the correct context, being derived from only one patient. It will require further study of this technique in other people with spinal injury to determine if the same results are experienced, particularly in those people with different types of injuries.
An appropriate concluding remark comes from Professor Geoffrey Raisman, of the Institute of Neurology at UCL, who is quoted by the BBC as saying, ‘To what extent this procedure could in the future provide a further and sustained improvement cannot be judged on the basis of one patient […] It is not and does not claim to be a cure.’
Where did the story come from?
The study was carried out by researchers from the Universities of Louisville and California, and other institutions in the US and Italy. Funding was provided by the US National Institutes of Health, and the Christopher and Dana Reeve Foundation. The study was published in the peer-reviewed medical journal The Lancet.
BBC News provided clear coverage of this story, with a personal recorded account of the treatment from the patient himself. The other news stories also provided accurate coverage of this study, and made it clear that it is a case report trialling this technique in only one man.
What kind of research was this?
This was a single case report on the use of electrical stimulation to treat an individual who had paraplegia as the result of a traffic accident. This accident had caused displacement of two vertebrae - the last of the neck (cervical) vertebrae and the first of the upper back (thoracic) vertebrae - from their normal position, causing damage to the spinal cord. Paraplegia means that there is a loss of movement and sensation in the legs. There may also be a variable degree of involvement of the body up to the chest, but arm movements will be normal.
Previous animal models of spinal cord injury have found that repeated electrical stimulation of the spinal cord can increase the ability to control movements, with the spinal cord itself providing the muscles with necessary motor signals without the need for input from the brain. For example, it has been demonstrated that providing lower spinal stimulation to cats with completely severed spinal cords can allow them to stand and support their hindquarters.
The researchers believed that the use of implanted electrodes in humans to stimulate the spinal cord at the base of the back (lumbosacral spine) could allow sensory signals to come from the legs when standing and stepping. This could allow some nervous control of these movements.
What did the research involve?
The 23-year-old man from the US had been paralysed for five years following the accident in July 2006. MRI scans revealed that he had wasting of the spinal cord where it had been damaged. This man had lost all voluntary control of movement in his trunk and legs but had partial preservation of sensation below this level.
Over a period of 26 months the man received 170 locomotor training sessions where he had support of his bodyweight and received manual help to move his legs on a treadmill – a total of 108 hours of step training and 54 hours of standing.
Measurement of the electrical activity that usually occurs in muscles when they are stimulated by nerves (electromyography) revealed no change in the electrical activity in his leg muscles during this training.
After this training in December 2009, 3.4 years after the accident, 16 electrodes were surgically placed on the outer dura (the outermost layer of the three layers covering the spinal cord) at the site where the lower back meets the pelvis. Spinal cord stimulation was carried out during sessions that each lasted up to 250 minutes (average 54 minutes of stimulation), during which time the man once again received help to move his legs on the treadmill and had electromyographic analysis of his muscle activity. The man reported experiencing a tingling sensation from the site of the electrodes during stimulation.
The researchers carried out 29 experiments and tested different electrical stimulation levels with the aim of trying to help the man to stand and step by himself, with the researchers providing support where necessary.
What were the basic results?
Spinal cord stimulation enabled the man to stand and fully bear his weight for a maximum of 4.25 minutes, with assistance provided for balance only. Electromyography revealed muscle activity on both sides of his body. Electromyography showed that after this time the signal changed, and the man needed help to remain standing. The researchers reported that this sequence occurred repeatedly during each 60-minute standing session.
When the researchers attempted to optimise stimulation parameters for stepping, they observed different electromyographic activity depending on the position of the legs and load at the hip, knee and ankle during manually assisted simulation of stepping.
After 80 stand-training sessions, seven months after electrode implantation, the man was observed to gain some control over the extension of his toes and ankle and leg flexion. However, this only occurred during spinal stimulation, and with different stimulation parameters used for each leg.
After training and spinal stimulation the man experienced improvements in control of bladder function, sexual response and sexual performance, as well as an increase in body weight. The man was reported to gain a sense of wellbeing and better self-esteem.
How did the researchers interpret the results?
The researchers conclude that a combination of task-specific training and spinal cord stimulation might reactivate nervous pathways that were spared following the injury. They say that these interventions ‘could be a viable clinical approach for functional recovery after severe paralysis’.
These are promising results from the treatment of one young man with paraplegia following a car accident. They demonstrate that, following assisted standing and stepping training for a two-year period, surgical implantation of electrodes below the site of his spinal injury allowed him to regain some muscle control during sessions of electrical stimulation.
This stimulation allowed some activation of the nervous pathways in the lower spinal cord that were spared following the injury, activating the muscles sufficiently enough to let him stand for a brief period and regain some leg movements.
Given that improvements in movement only occurred while stimulation was switched on this technique should not be considered to be a cure for paralysis. It should also be highlighted that it did not heal the damage to the participant’s upper spinal cord. However, the research has demonstrated that with the assistance of implanted electrodes, the lumbosacral spinal nerves are able to generate movement without input from the brain.
These are encouraging results but it is important they are interpreted in the correct context. The case report is of one patient only and we cannot assume the results seen in this first patient will represent what will happen in future tests. In particular, the results cannot be generalised to all people with spinal cord injury, who may have variable causes, different levels of severity and different preservation of nervous function.
It will take much further study of electrical stimulation in other people with spinal injury. Researchers need to see whether similar results could be achieved, if this type of stimulation and movement could be achieved outside of a laboratory, and ultimately, if this treatment could provide a viable way of assisting people with paraplegia due to spinal cord injury.