October 24, 2012

Spinal cord damage repaired

New Scientist - Paralysis may no longer mean life in a wheelchair. A man who is paralysed from the trunk down has recovered the ability to stand and move his legs unaided thanks to training with an electrical implant.

A 16-electrode array implanted into the lower region of his spinal cord, which stimulated spinal nerves with continuous electrical activity and training helped to restore function.

Andrew Meas of Louisville, Kentucky, says it has changed his life (see "I suddenly noticed I can move my pinkie", below). The stimulus provided by the implant is thought to have either strengthened persistent "silent" connections across his damaged spinal cord or even created new ones, allowing him to move even when the implant is switched off.

The results are potentially revolutionary, as they indicate that the spinal cord is able to recover its function years after becoming damaged.

Previous studies in animals with lower limb paralysis have shown that continuous electrical stimulation of the spinal cord below the area of damage allows an animal to stand and perform locomotion-like movements. That's because the stimulation allows information about proprioception – the perception of body position and muscle effort – to be received from the lower limbs by the spinal cord. The spinal cord, in turn, allows lower limb muscles to react and support the body without any information being received from the brain

The Journal of Neuroscience - Novel and Direct Access to the Human Locomotor Spinal Circuitry (2010)

Lancet (2011) - Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study



Last year, Susan Harkema and Claudia Angeli at the Frazier Rehab Institute and University of Louisville in Kentucky and colleagues tested what had been learned on animals in a man who was paralysed after being hit by a car in 2006. He was diagnosed with a "motor complete" spinal lesion in his neck, which means that no motor activity can be recorded below the lesion.

First, the man had extensive training in which his legs were moved by physiotherapists while his weight was supported by a harness. During this time no improvement was observed.

He then had a 16-electrode array implanted into the lower region of his spinal cord, which stimulated spinal nerves with continuous electrical activity. When the implant was switched on and he was helped into the correct position, he succeeded in holding his own body weight and standing on his first attempt.

Then something unexpected happened. Seven months into training on how to stand using the implant, he tried to move his toe while the stimulation was on. "He just started trying to move his toe," says Angeli. "He was like, 'look it's wiggling!' Further testing showed that he was able to move his leg and ankle, too – indicating that voluntary signals from the brain were crossing the lesion.

Over time, the volunteer also gained increased bladder control and sexual function, and had better temperature regulation. All of these abilities involve input from the brain, confirming information could now be sent across the damaged area of the spine, as long as the stimulation was on.

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