Function Of Spinal Cord

In rats, advances in combatting paralysis

PARIS — Neuroscientists reported on Wednesday they had made 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 respiratory 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.

The technique had been tried before but was hampered by molecules which build up at the site of spinal cord injuries and inhibit regrowth of nerves.

To get around this, the researchers injected an enzyme called chondroitinase ABC at both ends of the graft to degrade the inhibitors and open up avenues in the scar tissue through which the nerves could -- hopefully -- grow.

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

"We've shown for the very first time that robust, long-distance regeneration can restore function of the respiratory system fully," Silver said in a press release, cautioning that further lab work was needed before the technique could be tried on human volunteers.

The study appears in the British journal Nature.

Silver added his lab had also begun preliminary work on restoring bladder function, which is often the top request for help from people who suffer lower spinal cord injuries.

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Any injury to your head or spinal cord is a potentially serious injury. A spinal injury, depending on which part of the cord is injured, could be totally paralyzing, partially paralyzing, and could affect your ability to breathe among other things. Understanding Spinal Cord Injury

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Cellular damage, including bruising and restricted blood flow, can also result in a loss of use.

Incomplete spinal injury is the term used to describe partial damage to the spinal cord. These types of injuries differ depending on the amount of damage caused and the area that has been affected, whether it is the front, centre or back of the spinal cord. The main types of incomplete spinal injury are anterior cord syndrome, central cord syndrome and brown-sequard syndrome. Each of these vary greatly in the symptoms they cause.

Not all injuries to the spine are associated with damage to the spinal cord itself. Some spinal injuries may just require a period of immobilisation or can be repaired with use of a rigid collar, brace or body jacket depending on the location of the fracture.

Many distinctive problems associated with spinal and spinal cord injury vary depending on the type and level of injury, including the disruption of temperature regulation, which causes sweating and shivering. Other processes, which can be affected following a spinal injury, are bowel and bladder management. The communicating nerve impulses that travel along the spine to the brain can be disrupted and can no longer travel normally, which can result in sufferers not being aware that their bladder or bowel is full.

Muscle spasticity can also become affected due to the changes that occur in the nerve cells that control muscle activity. Following a spinal injury, nerves below the injury become disconnected from those above causing muscle spasms to occur. Other common outcomes of spinal injury are blood pressure and respiratory complications. In some cases sufferers require the use of a ventilator to control their breathing pattern.

Lower urinary tract function after spinal cord contusion and transection: Plasticity in the distal spinal cord. by Philberta Yuen-hui Leung

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