Neuroscientists have reported making inroads against spinal injury by restoring breathing in lab rats whose key cervical nerves had been severed.

The technique has yet to be tested on humans, but if it works could ease one of the biggest problems for people with catastrophic damage to their spinal cord, they said.

Damage above the fourth cervical vertebra in the neck invariably interrupts breathing. The patient has to be put on a ventilator, and this carries a recurrent danger of respir-atory infection.

Under normal circumstances, the rate and depth of breathing are controlled automatically by nerve cells in the brain stem.

To do this, these neurons in turn control specialised motor cells located from the third to the sixth cervical vertebrae.

These cells develop farther down into the so-called phrenic nerve, which causes the muscles of the diaphram to relax and contract and the lungs to fill and empty.

A team led by Jerry Silver, a professor at Case Western Reserve University School of Medicine in Ohio, report on an experimental way of bridging damage in the key cervical area.

They injured rats’ spinal cords at the second cervical level to paralyse one-half of the diaphragm, and grafted in a tiny section of peripheral nerve from the rodents’ limbs, attaching it both before and after the damage site.

The idea was to use the peripheral nerve as a bridge on which the precursor cells for the phrenic nerve could grow.

After three months tests showed that between 80 and 100 per cent of breathing function had been restored, a performance maintained at the six-month mark.