New Brain Study Offers Hope for Treating Phantom Limb Pain
Reading Time: 4 minutes
___
Summary:
-
Brain study overturns belief about post-amputation rewiring
-
Amputees’ brain activity remains unchanged years after limb loss
-
Research may transform treatment for phantom limb pain
-
Could support future brain-computer interface advances
___
In a groundbreaking study, researchers discovered that the brain’s control center for a missing limb can remain active long after surgical amputation. This finding challenges the traditional understanding of the brain’s plasticity, or its ability to rewire itself. However, this opens new avenues for treating phantom limb pain.
Researchers at the National Institutes of Health (NIH) and their colleagues investigated how the human brain reacts to limb loss. Their findings reveal that losing a limb does not cause a widespread reorganization of brain activity. Published in Nature Neuroscience, this study sheds light on phantom limb syndrome and may inform future advances in neuroprosthetics and pain management.
Losing a limb does not cause a widespread reorganization of brain activity. This finding challenges the prevailing understanding of the brain’s ability to reorganize itself after amputation.
The team from NIH and University College London conducted MRI scans on three individuals before their planned amputations—performed for medical reasons—and continued monitoring them for up to five years afterward.
In a news release, the researchers emphasized the rarity of conducting such a study. Chris Baker, Ph.D., co-author and affiliated with NIH’s National Institute of Mental Health (NIMH), explained that they examined their data from multiple angles, and all results consistently supported their findings.
The brain still remembers your limb
Different regions of the brain’s outer layer, called the cortex, are tasked with controlling specific body parts. A common theory among neuroscientists is that when a body part is damaged or lost, the cortex reorganizes itself, with neighboring areas related to intact body parts expanding into the vacated space. This rewiring is also known as ‘brain plasticity.’
However, this theory has faced challenges. One issue is the widespread phantom limb syndrome, where patients feel vivid, sometimes painful sensations in a missing limb. Baker and his colleagues saw this as evidence that the brain might remember what was lost. To confirm this, they needed to do something unprecedented: compare brain activity before and after amputation.
After years of identifying and screening patients already scheduled for amputation, the researchers selected three participants to help answer their questions.
Before each planned arm amputation, they used functional MRI to visualize brain activity associated with individual finger tapping. Following the surgeries, they conducted three additional scans as participants attempted to move their phantom limbs. Comparing the brain activity before and after amputation, they found little to no difference—so subtle that, without knowing when the data was collected, it would be hard to tell the maps apart.
Interestingly, their analysis extended beyond human observation. A machine learning model trained on pre-amputation finger movements could successfully identify which phantom finger was being moved post-amputation.
Why the brain map matters
The researchers also discovered that brain circuits linked to lip and foot movements did not shift into the area associated with the phantom limb. Further analyses comparing their findings with scans of able-bodied individuals and other studies reinforced their primary conclusion—that the brain’s map of the missing limb persists.
These findings could enhance the medical community’s understanding of how phantom limb pain occurs. They also suggest that current treatments for phantom limb pain, many of which are based on the concept of brain reorganization following limb loss, may need reconsideration.
Hunter Schone, a Ph.D. researcher and the main author of the study, explained that even after someone loses a limb, the brain still remembers the body's connection to that limb, almost as if it’s waiting to reconnect. He pointed out that new brain-computer interfaces can work based on the idea that the brain’s map of the body stays the same over time.
Next steps and future research
The NIH team emphasized that while these findings are promising, more work is required. Further research is needed to determine which amputees will benefit most (factors such as time since amputation, age, level of activity, and prosthetic usage may all be relevant) and which therapies are scalable in clinical practice.
Related Reading:
General Principles of Revision Surgery
