Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation

Abstract

ALTHOUGH phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin l -4.On the basis of the demonstration of substantial plasticity of the somatosensory cortex after amputationS or somatosensory deafferentation in adult monkeys6, it has been suggested that cortical reorganization could account for some non-painful phantom-limb phenomena in amputees and that cortical reorganization has an adaptive (that is, pain-preventing) function 2 ,s,7,8. Theoretical and empirical work on chronic back pain 9 ,lo has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical reorganization and phantom-limb pain should be positively related. Using non-invasive neuromagnetic imaging techniques to determine cortical reorganization in humans ll -13, we report a very strong direct relationship (r = 0.93) between the amount of cortical reorganization and the magnitude of phantom limb pain (but not non-painful phantom phenomena) 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.A brief telephone interview was used to obtain information about the amount of phantom-limb pain in 65 upper-limb ampu-482 tees. This information served as the sole basis for the selection of a representative sample of 13 subjects with widely varying degrees of phantom-limb pain. The mean age of the 13 subjects was 50.1 years (s.d. = 17,2, range 27-73 yr), mean post-amputation time was 24.3 years (s.d. = 19.8, range I to 51 yr). Twelve men and one woman participated in the study, Traumatic injury in ten cases and osteosarcoma in three cases had made the amputation necessary. Cortical reorganization was determined by magnetic source imaging' , using the method illustrated in Fig. 1. The subjects underwent a comprehensive neurological and psychological investigation which included detailed assessments of phantom pain and phantom sensations, stump pain and stump sensations, pre-amputation pain, telescoping (the subjective experience of the phantom limb retracting towards and often disappearing in the stump), and facial remapping (the appearance of phantom sensations upon non-painful stimulation of the face with isomorphism between facial stimulation sites and the location of phantom sensations) (Fig. 2 legend).A large significant positive linear relationship was found between the amount of phantom-limb pain, as measured on the standardized pain-intensity scale, and the amount of cortical reorganization (r=0.93, P<O.OOOI; Fig. 2); phantom-limb pain explained almost 85'Yo (adjusted r 2 =0.83; F(l,11)=66.89, P < 0.0001) of the variance in cortical reorganization. A similar correlation was obtained for the visual analogue phantom pain scale (r=0.85, P<O.OOI) and the adjective phantom pain scale (r=0,86, P<O.OOI).The mean shift in the focus of cortical responsivity to facial stimulation was 0.43 cm (s.d. =0.40, range 0.01-1.0...

Enhancing Rehabilitative Therapies with Vagus Nerve Stimulation

“…Maladaptive plasticity in the CNS is believed to contribute to the percept phantom limb pain and some forms of chronic pain. In amputees, cortical reorganization can be accompanied by phantom limb pain, which is correlated with the degree of overrepresentation [48]. Some forms of chronic pain unrelated to limb loss display a similar manifestation of aberrant cortical plasticity [49,50].…”

Cortical reorganization in human amputees and mislocalization of painful stimuli to the phantom limb

“…We had earlier found a nearly perfect correlation between cortical reorganization and phantom limb pain, indicating the importance of the nociceptive system for cortical reorganization [6]. In this study, we employed painful stimulation (pinprick) as well as stimulation in three other somesthetic modalities (touch by a cotton applicator, vibration by a tuning fork and heat by a 40°C thermode), in order to compare the capacity of the different modalities to produce mislocalization to the phantom limb.…”

“…The mean age of was 54 years (range 24-70 years) and the mean interval since amputation 22 years. Cortical reorganization was assessed with magnetic source imaging by a method described previously [6,7]. Briefly, it was based on the source localization of the cortical representation of the lip on the amputated side.…”

“…This relationship was not significant for non-painful stimuli. To date, in most experiments concerning cortical reorganization after amputation or dorsal rhizotomy [1,2, 5,6,8], only unilateral effects in the primary somatosensory cortex contralateral to the lesion were studied. The bilaterality of the sites eliciting mislocalization in this study, however, cannot be explained solely on the basis of the generally known invasion of cortical projections from neighbouring areas into the 'amputation' zone.…”

Massive cortical reorganization is reversible following bilateral transplants of the hands: evidence from the first successful bilateral pediatric hand transplant patient

“…Following deafferentation of the upper limb in adult primates, the area of somatosensory cortex deprived of afferent signals begins to respond to tactile stimulation of the face, a massive cortical reorganization (MCR) mediated subcortically through the cuneate nucleus 4. Similar demonstrations of MCR have also been reported in human adults with unilateral upper limb amputations using MEG 5, 6, 7. MCR has not been demonstrated in children previously, and the cortical adaptation to restoration of sensory inputs in children is unknown.…”