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By: Nikhita Dogra and Naima Kotadia
This is a summary of a paper published by a research group from Zurich, Switzerland in the journal Science.
Original article: Rubia van den Brand et al. Restoring Voluntary Control of Locomotion after Paralyzing Spinal Cord Injury. Science 336, 1182 (2012); DOI: 10.1126/science.1217416
A recently published study that has gained significant attention from the media explored the benefits of a combination therapy after a functionally complete spinal cord injury (SCI). Some controversies have also emerged regarding the research methods used and the claims made in this study. This latest research shows the potential of combining activity-based rehabilitation with electrical and chemical stimulation of regions of the spinal cord below the injury.
The extent of potential recovery depends on the type of SCI sustained. Clinically incomplete SCIs, in which some sensation or movement is retained, are more common. A clinically complete SCI, on the other hand, results in a total loss of motor control or sensation, despite the possibility that the spinal cord may not be completely severed.
During electro-chemical stimulation, the spinal cord is excited both electrically and with neurotransmitters — small molecules that excite neurons. The researchers determined that by using electro-chemical stimulation in combination with physical training, the tissue surviving an SCI can form new connections between the brain and the spinal cord below the level of the injury. These new pathways allowed rats with clinically complete SCIs to regain voluntary movement of their hind limbs. Thus the combination of electro-chemical stimulation and long-term physiotherapy may yield an improved functional outcome for patients with SCI, when compared to activity-based therapy alone.
What was the most important finding?
According to the authors, given the proper training conditions — activity-based rehabilitation and electro-chemical stimulation — it is possible to stimulate the formation of new connections between the brain and the injured spinal cord. These new connections are able to restore voluntary control of muscle movement below the level of the injury. In this study, the injury sustained by the rats mimicked a clinically complete SCI with some tissue spared. The authors claim that their intervention was able to restore voluntary hind-limb movement in these cases.
What are some things we need to consider?
An important consideration is that this study was conducted on rodents. One major difference between rodents and humans is that rodents’ muscle movements can be produced without input from the brain, whereas in humans input from the brain is required. This work has therefore created some controversy, since the authors use a methodology that has produced similar hind limb movements in rats without any input from the brain. Additionally, the authors do not report several gold-standard behavioural measures of functional recovery. These findings are still promising, but the study shortcomings require that more research be conducted before considering this therapy for clinical trials in patients with SCI.
What does this mean for people with SCI?
Once these findings are comprehensively established, the question of whether this type of intervention can be translated into a human therapy can be addressed. It should be noted that the invasiveness of such a treatment may make it unsuitable for some people with SCI.
The training and rehabilitation conditions used in this study allowed for the brain to regain access to the spinal cord not only by altering the remaining neurons, but also by creating new connections through the spared tissue. The positive results of this study do indeed provide insight into potential enhancements for existing physiotherapy treatments. If confirmed, this electro-chemical neuro-prosthesis could provide an exciting new tool for rehabilitation therapists.
