Exploring the Role of Cortical Reorganization in Postamputation Phantom Phenomena Including Phantom Limb Pain in Lower Limb Amputees: A Cross-Sectional Study of the Patterns of Referral of Sensations into the Phantom

Cortical reorganization and pain memory are theories to explain phantom limb pain and other postamputation phantom phenomena. This study was undertaken to identify evidence of cortical reorganization in lower limb amputees and to find evidence for the pain memory theory. This was a qualitative interview study using structured questionnaires with lower limb amputees. Participants were asked to identify body areas and activities that stimulate postamputation phantom phenomena to confirm the cortical reorganization theory. We tested the pain memory theory by comparing traumatic amputees with surgical amputees. A total of 122 participants (response rate 42%) were recruited. Prevalence of postamputation phantom phenomena was similar to previous studies with phantom pain reported as 84%. Twenty (16.3%) identified body regions that could stimulate postamputation phantom phenomena and 32 (26%) identified activities that could stimulate postamputation phantom phenomena. Not all body areas or activities were related to somatotopic regions adjacent to the leg on the sensory homunculus. Overall, 47 (38.2%) exhibited attributes suggestive of cortical reorganization into areas adjacent to the leg. No associations were found between presence of pain or length of time in pain before amputation and the presence of phantom pain (p = .1-1.0). No statistical difference was found between surgical and traumatic amputees for any postamputation phantom phenomena (p = .3-1.0). The cortical reorganization and pain memory theories for the development and maintenance of postamputation phantom phenomena have only limited support from our data. Taking this into account, it may be worth reopening the debate on the mechanism for postamputation phantom phenomena, including phantom limb pain. The cortical reorganization theory and memory theory for the mechanism of phantom limb pain are questioned by these results. Both may play a role, but neither can explain the presence of postamputation phantom phenomena on their own.