What is paralysis? Video: Doctors’ Circle
Patients suffering from paralysis can at last look forward to a time when their condition is cured, and they can walk, run or move their damaged limbs again, as recent advancements show the possibility of reversal.
‘The environment has never been better for exploring ways to restore neurological function, including paralysis – in fact, there has been a dramatic escalation of the entire research spectrum aimed at functional neurorestoration,’ says Charles Liu, Director of the University of Southern California Neurorestoration Center.
Paralysis comes in many forms: the paralysis of one limb (monoplegia), one side of the body (hemiplegia), below the waist (paraplegia), and all four limbs below the neck (tetraplegia, or also referred to as quadriplegia).
There are many classifications of paralysis. It can be localised or generalised, and can affect most areas of the body. Image: Pixabay
In an able-bodied person, the brain sends a signal as an electrical impulse, known as an action potential, down the spinal cord to the peripheral nerves, which instruct the muscles to contract and move, whereupon sensors in the muscles and skin send signals back to the brain.
In most paralysis cases, the condition occurs as a result of damage to nerves rather than an injury to the affected area. Strokes are the most common cause of paralysis, followed by spinal cord injuries. Multiple sclerosis, cerebral palsy, polio, head injuries and several other rare diseases can also cause paralysis.
‘Long term, we hope to cure paralysis and make the injured walk,’ explains William Sikkema, a graduate student at Rice University, Houston. The challenge is not only to repair cells but to restore connectivity, too. In collaboration with researchers at Konkuk University in South Korea, the team has already made a paralysed rat walk again.
The addition of graphene nanoribbons restored motor and sensory neuronal signals across the previous nerve gap after 24 hours, with almost perfect motor control recovery after a period of healing. ‘Two weeks later, the rat could walk without losing balance, stand up on his hind limbs and use his forelimbs to feed himself with pellets. No recovery was observed in controls,’ the team reported.
‘After a neuron is cut, it doesn’t know where to grow. So, it either doesn’t grow, or grows in the wrong direction,’ says Sikkema. ‘Our graphene nanoribbons act as a scaffolding track, and it tells the neurons where to grow.’
Rats are a common animal model in paralysis studies, as they share similar structure and functions with humans. Image: Pexels
Spinal cord stimulation
Electrical stimulation of the spinal cord could also provide a big breakthrough, says Chet Moritz, Co-Director of the Center for Sensorimotor Neural Engineering at the University of Washington, US.
‘We’re seeing some really impressive results with spinal cord stimulation where people with complete paralysis, who have been unable to function, have regained control of their limbs. We didn’t expect this. It’s the most exciting thing we’ve seen in the last 20 years,’ he says.
Last year, a team led by Grégoire Courtine at the Swiss Federal Institute of Technology inserted an implant in the brains of paralysed monkeys and another over the spinal cord below the injury. The brain-spine interface worked by capturing leg-moving brain signals, decoded by a computer and sent – bypassing the damaged region – to the second implant, which delivered the signals as electrical impulses to the nerves, causing the leg to move.
Grégoire Courtine talks about his pioneering work on paralysis using electrical stimulation. Video: TED
Within six days, the monkeys had regained the use of their lower limbs and improved even more over time. The success of the experiment has led Courtine to launch a human trial of a spinal implant system.
We may be a long way still from restoring full function, as prior to paralysis, but Moritz is optimistic. Even a modest change, such as the movement of a single finger, can have a dramatic effect on quality of life and independence. ‘In five years, we’ve had dramatic improvement in function,’ he says. ‘It’s an exciting trajectory with tremendous potential.’