Phantom pain, which is sometimes experienced after arm amputation, may be caused by disrupted connectivity between different regions of the sensorimoter cortex in the brain. The findings, reported in Nature Communications this week, are in contrast to the commonly held view that phantom pain after arm amputation arises from maladaptive cortical reorganization in the brains of amputees.
Following arm amputation, individuals often perceive pain in their missing limb. It is commonly believed that this pain is caused by loss of sensory input in the deprived hand area representation of the brain known as the primary sensorimotor cortex, which becomes responsive to inputs from other areas of the body such as the face. However, growing evidence suggests that this hypothesis may actually be incorrect. In an attempt to settle this debate, Tamar Makin and colleagues use fMRI to study arm amputees. They find that while loss of sensory input is generally characterized by structural and functional degeneration in the hand area, the experience of persistent pain is actually associated with preserved structure and functional organization in the former hand area representation of the sensorimotor cortex. Furthermore, phantom pain is associated with disrupted connectivity between different regions of the sensorimoter cortex.
The authors propose that these changes in the sensorimotor cortex are due to the loss of nerve input from the former hand area and that the magnitude of these changes correlate with the individual’s level of phantom pain. It is hoped that these findings will be instrumental in furthering our understanding of the complexities of phantom pain.