Sunday Explainer: how a paralysed man walked again

FIRST STEPS: Darek Fidyka walks with the aid of leg-braces and a walking frame at the Akron Neuro-Rehabilitation Center in Wroclaw, Poland. Photo: AFP

A paralysed man has begun to walk again after pioneering surgery injected cells from his nasal cavity into his spine. How was this possible - and what does it mean for others with spinal injury? Kate Hagan stitches together the evidence.

Darek Fidyka sounds as though he has been through a lot. How did he lose his ability to walk?

A Bulgarian firefighter, Mr Fidyka's spinal cord was severed after he was repeatedly stabbed in the back during a knife attack in 2010. It left the 40-year-old paralysed from the chest down. Despite two years of intensive physiotherapy he had showed no sign of recovery.

Why did scientists think he might be able to walk again?

Scientists have long recognised the potential of particular cells in the olfactory bulb, at the top of the nasal cavity, to stimulate growth of nerve fibres. Called olfactory ensheathing cells, they act as pathway cells to enable nerve fibres in the olfactory system to be constantly renewed throughout a person's life, preserving the senses of smell and taste.

The role of the cells in the olfactory bulb has led scientists to explore their potential in the spinal cord, where regeneration of nerve fibres fails after spinal injury.

Mr Fidyka had two operations. In the first, Polish surgeons removed one of his olfactory bulbs and grew the olfactory cells in culture in a laboratory. Two weeks later they injected the cells above and below Mr Fidyka's spinal injury. They also transplanted nerve tissue from his ankle into his injured spinal cord to form a bridge for nerve fibres to grow.

How has the operation changed his life?

Three months after the treatment Mr Fidyka noticed that he was developing muscle on his left thigh. After six months, he took steps along parallel bars using leg braces. Two years later he can walk with a frame and drive a car. He has also recovered some bladder, bowel and sexual function.

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Sunday Explainer: how a paralysed man walked again