Our program has transplanted nine hands in eight recipients over the last 15 years. Prior to surgery, six of our recipients reported a history of significant phantom limb pain (PLP)--a form of neuropathic pain that is experienced as arising from the absent limb. Up to 85% of amputees experience moderate to severe PLP, which can adversely impact health and quality of life (Jensen et al 1985). Further, evidence-based treatments are lacking (Weeks et al 2010), and there is no FDA-approved pharmacological intervention (Zanni & Wick, 2008). Remarkably, all six patients experienced complete resolution of PLP or discomfort post-transplant. Some of the patients experienced immediate relief of pain, while in others pain subsided, returned and then resolved within the first year. We hypothesize this is attributable to the re-establishment of afferent and efferent activity within regions of sensory and motor cortex formerly devoted to the amputated hand.
Deafferenting injuries, including limb amputation, precipitate large-scale functional reorganization in cortical maps (Garraghty & Kaas, 1991; Merzenich et al., 1984), and there is evidence to suggest that the extent of these changes is associated with PLP severity(Flor, Diers, & Andoh, 2013). However, what role (if any) these cortical changes play in the generation and maintenance of this PLP remains unknown.
We describe functional magnetic resonance imaging (fMRI) data showing that sensory and motor cortex can recover grossly typical map organization post-transplant (see also Frey et al 2008; Giraux et al 2001). Sensory stimulation of the transplanted hand evoke robust responses within the former hand territory. The resolution of PLP following these changes supports the view that injury-related cortical reorganization may be causally related to PLP. If so, then this suggests new therapeutic approaches to PLP that seek to increase activity in the former sensorimotor hand territory. This may also help patients who exhibit both cortical reorganization and neuropathic pain including spinal cord injury (Wrigley et al., 2009) and complex regional pain syndrome (Maihofner et al., 2007; Maihofner et al, 2003). Importantly this data suggests that an additional benefit of hand transplantation is the alleviation of phantom pain, a syndrome that is difficult to treat with conventional methods.