Electrical signals help paraplegic man stand, move legs voluntarily



London, May 20: A Caltech research has helped a paraplegic man to stand and move legs voluntarily.


A team of researchers from the University of California, Los Angeles (UCLA), the California Institute of Technology (Caltech), and the University of Louisville have used a stimulating electrode array to assist a paralyzed man to stand, step on a treadmill with assistance, and, over time, to regain voluntary movements of his limbs.

The electrical signals provided by the array, the researchers have found, stimulate the spinal cord's own neural network so that it can use the sensory input derived from the legs to direct muscle and joint movements.

Starting eight years ago, Joel Burdick, a professor of mechanical engineering and bioengineering at Caltech, teamed with the Edgerton lab to study how robotically guided physical therapy and pharmacology could be coupled to better recover locomotion in animals with spinal-cord injuries

Building upon these studies and the earlier work of Edgerton and Gerasimenko, Burdick and Yu-Chong Tai, a Caltech professor of electrical engineering and mechanical engineering, introduced the concept of high-density epidural spinal stimulation, which uses sheet-like arrays of numerous electrodes to stimulate neurons.

The goal of the system, Burdick said, "is to stimulate the native standing and stepping control circuitry in the lower spinal cord so as to coordinate sensory-motor activity and partially replace the missing signals from above"-that is, from the brain-"and shout 'get going!' to the nerves."

The subject in the new work is a 25-year-old former athlete who was completely paralyzed below the chest in a hit-and-run accident in July 2006. He suffered a complete motor injury at the C7/T1 level of the spinal cord, but retained some sensation in his legs.

After implantation with the device, however, the patient could-while receiving electrical stimulation, and after a few weeks of locomotor training-push himself into a standing position and bear weight on his own. He can now remain standing, and bearing weight, for 20 minutes at a time. With the aid of a harness support and some therapist assistance, he can make repeated stepping motions on a treadmill. With repeated daily training and electrical stimulation, the patient regained the ability to voluntarily move his toes, ankles, knees, and hips on command.

The scientists aren't yet fully sure how these functions were regained-or, indeed, how the control of voluntary function was returned through the procedure.

"Somehow, stimulation by the electrodes may have reactivated connections that were dormant or stimulated the growth of new connections," said Burdick.

The study is detailed in the British medical journal The Lancet.


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