PHANTOM-LIMB PAIN AS A PERCEPTUAL CORRELATE OF CORTICAL REORGANIZATION FOLLOWING ARM AMPUTATION

ALTHOUGH phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin(1-4). On the basis of the demonstration of substantial plasticity of the somatosensory co rtex after amputation(5) or somatosensory deafferentation in adult mon keys(6), it has been suggested that cortical reorganization could acco unt for some non-painful phantom-limb phenomena in amputees and that c ortical reorganization has an adaptive (that is, pain-preventing) func tion(2,5,7,8). Theoretical and empirical work on chronic back pain(9,1 0) has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical r eorganization and phantom-limb pain should be positively related. Usin g non-invasive neuromagnetic imaging techniques to determine cortical reorganization in humans(11-13), we report a very strong direct relati onship (r = 0.93) between the amount of cortical reorganization and th e magnitude of phantom limb pain (but not non-painful phantom phenomen a) experienced after arm amputation. These data indicate that phantom- limb pain is related to, and may be a consequence of, plastic changes in primary somatosensory cortex.