Nerve damage in the forearm from crush injuries or cuts by glass, knife, or saw can lead to significant disability. But nerves do heal even if at a very slow rate. In fact, studies show that with nerve repair, improvement can continue up to five years after the surgery. The keys to best outcomes are age at the time of injury and time between injury and surgery. Younger patients who have surgery soon after the injury have the best results.
Now with this new study from Sweden, we find out what happens 30 years after nerve injury and repair in childhood or adolescence. They followed 45 patients who had a complete (nerve cut clear through) nerve injury of the median and/or ulnar nerves in the forearm. They measured outcomes in terms of sensory and motor function, level of pain or discomfort, and impact on the patient’s life (education, work, recreation).
They found that children who were younger at the time of the injury and repair (younger than 12 years old) had significantly better results. Complete recovery occurred in 87 per cent of the younger children compared with only 67 per cent of the teens (12 or older). Which nerve was cut (median or ulnar) didn’t seem to matter; age was the main prognostic factor.
The cut-off age between the two groups (12 years old) wasn’t arbitrary but rather based on the knowledge that this time period is when growth reaches a peak. Maximal growth acceleration in girls is around 11 years and 13 years of age for boys. It was expected that the growth spurt might make a difference in recovery (and it did).
Other factors assessed in the long-term period after surgery included sensitivity to cold, motor function, and difference in size of the two hands (injured versus uninjured). The patients (now adults) were asked if the nerve injury affected their choice of work or career. And they were tested for locognosia, a sign of misdirection.
Locognosia is the ability to tell where on the skin the injured person was touched. This sign is referred to as “misdirection” because when nerve cells regrow (regenerate), they are misdirected at the site of the cut. The nerve ends try to reach across to each other but end up going in all different directions. The end-result is a change in the signal pattern from the nerve to the spinal cord and up to the brain. The brain then remaps the location of sensation from the hand based on these signals.
Surgery was done in all cases to either repair (stitch the two ends of the cut nerve together) or reconstruct (use a grafted nerve to help the two ends meet) the injured nerves. In some cases, reconstruction had to be done right from the start because of the extent of the damage. In other patients, enough time had passed (up to 15 months in some cases) that the two nerve endings had retracted (pulled away) enough that stretching the nerve ends to meet was no longer possible.
When nerve grafting (reconstruction) was done in both age groups, the younger children still had better results. That was true regardless of whether one nerve (either one) or both were injured. Fortunately, motor function was preserved in all the patients no matter what age they were or which nerve was injured. Locognosia was significantly better among those who were injured at an earlier age.
Cold sensitivity wasn’t a big problem. A few patients still had less tolerance to cold. The older group was affected the most and they reported that this problem gradually got better over time. Hand size was not different among any of the participants. The older group also said the injury influenced their leisure activities and choice of career but not how far they went in school (high school versus college).
The authors concluded that children who sustain nerve injuries at a younger age have a better chance for full recovery and function. Which nerve was injured doesn’t seem to make a difference in long-term results. But when both nerves were cut, patients reported a greater impact on education and recreation.
Return of normal sensation is less likely than return of normal motor function. Pain and cold sensitivity were reported but difficulty with locognosia was not a problem. It seems that motor recovery is not dependent on age like sensory function is. Better brain capacity and ability to adapt at a younger age may account for the differences in results based on age.
The authors mention that today’s patients facing similar nerve injuries may have even better long-term results compared with children and teens treated 30 years ago. It is now recognized that associated injuries (e.g., tendons, arteries) must be repaired as well.
Newer surgical techniques and tools may also aid in better outcomes. We also now know that participation and motivation in the rehab process make a difference. And we have better strategies to help patients relearn sensory function based on new information about brain plasticity (ability of the brain to adapt and recover).