Taking the next step: facilitating the process for victims of paralysis

Millions of dollars and countless man-hours have been invested in working to mitigate the damage caused by spinal cord injury. Genetic techniques have allowed research to progress at a steady pace, with knockouts of certain genes exhibiting a greater capacity for axonal growth following spinal cord injury. However, patients with spinal cord injury are largely dismayed by the pace of research. Stroke victims also frequently suffer from paralysis. The journey back to independent movement is arduous.

Warren Dixon, a University of Florida engineer, found that electrical stimulation can help people regain more control of paralyzed limbs. These findings would be relevant for patients suffering from spinal cord injury and for those who have experienced strokes.

In particular, stroke victims can unconsciously drag their toes, causing them to stumble. Dixon and his group have developed a pacemaker-sized device that would deliver the appropriate amount of stimulation to the calf, at the right point in time to prevent this stumble.

The issues which remain to be worked out regarding the technology include calibrating the voltage delivered to the muscle in order to elicit precise and controllable movements in the paralyzed limb. Human movements are exquisitely fine, something that people tend to realize only when something has gone wrong with neurological wiring.

For the approach described here, electrical pads are placed on the skin; the muscle contracts involuntarily when a small current is applied. This stimulation may result in a slight tingling sensation but is not painful. Such stimulation can be used to prevent muscle atrophy and is also used to help athletes build muscle. Unfortunately, the current technology applies a predetermined and rather high voltage to a designated muscle. This shock can result in fatigue, rendering the muscle sore and unable to respond fully to further stimulation. The predetermined voltage dose also elicits rough movements, lacking the precision necessary for common actions like walking.

The group at University of Florida is working to engineer a sort of adaptive learning device. Such a smart machine would adjust to individuals' height, weight and even diet to provide the appropriate level of stimulation to a muscle. With this sort of device, physical therapists could gradually decrease the electrical input, in order to ultimately wean a dependent patient and allow him or her to perform independently controlled movements.

For more, see http://news.ufl.edu/2009/03/18/muscle/

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