SCIENTISTS have shown for the first time that new-born babies have a "unique" nervous system which makes them respond differently to pain from adults.
In research that has far-reaching implications for the medical and surgical treatments of infants, the scientists have found that newborn children feel pain longer and more sensitively. In premature babies, the mechanism that allows older children and adults to "dampen down" the pain messages does not work properly.
Until now it has been presumed that a baby's pain system was too immature to function properly, or that they reacted in a similar way to adults but less efficiently. Researchers at University College London have now discovered that babies' sensory systems have a unique pain-signalling mechanism, which disappears as they grow older. This makes them feel pain sooner than an older child or adult and because of different "wiring" they can react to stimulation as if it is pain - even when it is not.
It is only in the past 10 years that it has even been acknowledged that babies and infants felt pain. Before that, babies born prematurely - after less than 30 weeks of pregnancy - would undergo traumatic or surgical procedures without pain-killing drugs.
Ticky Wright, of the Women and Children's Welfare Fund, set up to promote research into pain relief of the unborn child, last night welcomed the new research. Mrs Wright said: "I call this the 'oops' syndrome. First we were told that infants did not feel pain, then that the new-born baby did not, then that a foetus did not. Each time it is looked at, the boundaries are pushed further and further back. Yet masses more research needs to done."
Maria Fitzgerald, the professor of developmental neurobiology at the Thomas Lewis Pain Research Centre, based at UCL, said the work has shown the importance of adequate pain relief for infants and children. Writing in the Medical Research Council's journal, Prof Fitzgerald said: "Reports in clinical and psychological literature indicate early injury or trauma can have long-term consequences on sensory or pain behaviour that extend into childhood or beyond."
Prof Fitzgerald said that because the spinal sensory nerve cells worked differently in babies, even a simple skin wound at birth could lead to the area becoming hypersensitive to touch long after the wound had healed.
By studying these sensory nerve cells in infants the scientists discovered that their reflex to pain or harm is greater and more prolonged than that of adults. The sensory nerve cells are also linked to larger areas of skin which means they feel pain over a greater area of their body.
While adults produce pain reflexes only when they encounter harmful stimulation, new-born children respond less selectively and produce the same reflex even to a light touch.
The scientists believe that this is because in babies the sensory nerve fibres that communicate non-harmful touch - known as A fibres - end in a different part of the spinal cord from adults. But in adults the cells are connected only to pain-transmitting C fibres.
Prof Fitzgerald said another contributing factor in the new-born child's pain system was that the nerve pathways, which carried pain-inhibiting messages from the brain stem to the spinal cord, matured later than other parts of the system. In the journal, Prof Fitzgerald wrote: "These nerve fibres from the brain stem start to grow down the spinal cord early in foetal life, but they do not extend branches into the spinal cord for some time, and do not function fully until soon after birth.
"This means the premature baby cannot benefit from the natural pain-killing system which in adults dampens down pain messages as they enter the central nervous system. Do these discoveries mean that the new-born infant's spinal cord transmits a different pain signal to the cortex of that of an adult? We think so."
The UCL researchers now aim to investigate the long-term consequences of early injuries which they believe will change the care given to premature and sick new-born babies.
Source: UK News Electronic Telegraph Sunday 2 August 1998
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