A recent study suggests new insights into how phantom limb pain is caused, and how it can be relieved. These new insights may have therapeutic benefits, according to the researchers.
It was thought that phantom limb pain was caused by abnormal plasticity in the sensorimotor cortex of the brain. With this in mind, rehabilitative therapies have focused on restoring normal motor function to relieve the pain.
In a new study involving 10 patients with phantom limb pain, researchers based at Osaka University used a brain-machine interface (BMI) to investigate the association between changes in pain and the cortical currents during phantom hand movements.
The BMI decodes the cortical signals that instruct the affected hand to move. It then converts this decoded phantom hand movement into movement of the robotic neuroprosthesis, explains a media release from Osaka University.
Patients were asked to either open the robotic hand or grasp with it. The cortical currents activated by hand movements were measured using magnetoencephalography (MEG) signals. Results were compared with movement of the intact hand to check that motor information obtained from the sensorimotor cortex was specific. As expected, training with the prosthesis partially restored functioning of the affected hand and increased motor activity in the cortex. However, unexpectedly, participants reported a significant increase in the sensation of pain, the release continues.
When the patients were asked to move the phantom hand based on MEG signals decoded from movement of the intact hand, cortical sensorimotor activity was disrupted, reducing pain.
The researchers note that contrast to what was previously thought about the cause and treatment of phantom limb pain, their study suggests that pain is not reduced by reconstruction of motor function but by changes in cortical plasticity.
In five study participants, BMI training reduced their pain more than previous therapies did, suggesting that it could be a promising therapy for treating phantom limb pain. In addition, other patients note that BMI training reduced their pain from residual surgery, suggesting that BMI training may be used to treat other chronic pain conditions, per the release.
The study was published recently in Nature Communications.
[Source(s): Osaka University, Science Daily]
[Image courtesy of Osaka University]