World-first MRI study shows babies experience pain ‘like adults’

21 Apr

For the first time, researchers have examined the brains of infants to discover how they experience pain. They found that babies experience pain in much the same way as fully-grown adults.

Older man about to enter a CT scanner.
Previously, researchers believed that it would not be possible to study babies in MRI scanners on account of their inability to remain still.

With the help of a Magnetic Resonance Imaging (MRI) scanner, researchers from Oxford University in the UK demonstrated that many of the same regions of the brain that activate in adults in response to pain are also active in the brains of babies.

Their findings also indicate that infants are more sensitive to pain than adults, suggesting that pain relief procedures for babies are in need of a review.

“Thousands of babies across the UK undergo painful procedures every day but there are often no local pain management guidelines to help clinicians. Our study suggests that not only do babies experience pain but they may be more sensitive to it than adults,” explains lead author Dr. Rebeccah Slater.

“We have to think that if we would provide pain relief for an older child undergoing a procedure then we should look at giving pain relief to an infant undergoing a similar procedure.”

The researchers examined the brains of 10 healthy infants aged 1-6 days old and 10 healthy adults aged 23-36 years. While accompanied by their parents and staff, the babies were placed inside an MRI scanner where the bottoms of their feet were poked with a special retracting rod. The sensation was described as “like being poked with a pencil.”

When inside the scanner, many of the babies would fall asleep. The poking sensation was mild enough so that the infants were not woken up by the stimulus.

Study provides ‘first strong evidence’ that infants really ‘feel’ pain

Rachel Edwards gave permission for her son Alex to participate in the study, curious as to why babies react in the way they do to a painful stimulus. She explains the process of the scanning:

“I fed him and put him down on this special bean bag that they suck all the air out of to help keep the babies’ heads still. Then they put on earphones that cut out some of the sound but I think the noise actually soothed him. He was out for the count, he didn’t wake up during the scanning and seemed really content afterwards.”

“Up until recently people didn’t think it was possible to study pain in babies using MRI because, unlike adults, they don’t keep still in the scanner!” says Dr. Slater. The researchers discovered, however, that the parents of the infants could often get them to fall asleep inside the scanner, enabling them to study their brains for the first time.

The researchers observed significant brain activity in 18 of the 20 brain regions that are active in adults when experiencing pain. The babies’ brains responded in the same way to a poke (force 128 mN) as adults did to a stimulus that was four times stronger (512 mN).

Dr. Slater states that their findings stand in contrast with previous understandings of infant pain. “In fact, some people have argued that babies’ brains are not developed enough for them to really ‘feel’ pain, any reaction being just a reflex,” she says. “Our study provides the first really strong evidence that this is not the case.”

Last year, a review of neonatal pain management practice in intensive care units showed that despite infants experiencing an average of 11 painful procedures per day, around 60% of infants do not receive any form of pain-relieving medication for them.

Other research has demonstrated that the neurological signature of pain can be detected in the brains of adults by MRI. Dr. Slater says that, in the future, they hope to develop similar systems to do the same in the brains of babies.

“This could enable us to test different pain relief treatments and see what would be most effective for this vulnerable population who can’t speak for themselves,” she explains.

The study is published in the journal eLife and funded by the Wellcome Trust. Raliza Stoyanova, Science Portfolio Advisor for the Wellcome Trust, states the result means “we may need to re-think clinical guidelines for infants undergoing potentially painful procedures.”