Nerve cells that control sensation and movement in the hands may exhibit injury-induced changes for decades after patients undergo hand amputation, reattachment or transplantation, according to a press release from the American Physiological Society.
The reportedly first-of-its-kind study to non-invasively examine the health and function of the cortical neurons in hand amputees at the neurochemical level has been published ahead of print in the Journal of Neurophysiology.
“The sensory and motor components of a hand’s nerves are severed during hand amputation, resulting in a dramatic reduction in stimulation in the brain’s cerebral cortex, which controls these functions,” according to the release. “Cortical areas formerly devoted to the missing hand undergo substantial functional reorganization as a result of this nerve loss. Little, however, is known about neurochemical changes at this level and the potential to reverse these changes with reconstructive surgery.”
To study the range of neuronal integrity in amputees, researchers compared a healthy control group to current hand amputees and former amputees who had undergone either hand reattachment or transplantation.
Participants flexed their fingers in both hands — or, for the amputee group, in their existing hand — to activate sensorimotor areas in both sides of the brain, according to the release. Researchers examined levels of N-acetylaspartate (NAA), a chemical associated with neuronal integrity, in those areas.
According to the researchers, the amputees had significantly lower NAA in the areas of the brain formerly involved in processing sensory and motor signals related to the missing hand compared with the control group.
“This result, indicating poor neuronal integrity, was expected and supports evidence that due to lack of stimulation, the neurons in these areas may degenerate,” according to the release.
In addition, NAA values for the reattachment and transplant groups were lower than those of the control group, suggesting these neuronal effects may not be fully reversible through restored sensory and motor activity, the researchers noted.
“This was unexpected and raises the possibility that the effects of nerve injuries on the mature brain may be persistent, even as these patients recover sensory and motor functions to varying degrees,” according to the release. “However, due to the small number of reattachment and transplant patients studied, the researchers urge caution in interpreting these results until more work is completed. This work may have implications for understanding the potential to reverse the effects of injuries to the limbs or spinal cord on the mature brain.”
Cirstea CM, et al. J Neurophysiol. 2017;doi:10.1152/jn.00329.2016.