Pain memories in phantom limbs : a case study

Pain experienced in a limb prior to amputation may influence the course of phantom limb pain many months later. Katz and Melzack (1990) found that 42% of their sample reported a 'somatosensory pain memory' which resembled the quality and location of a painful, or non-painful pre-amputation sensation. For many amputees, pain memories are vivid experiences which incorporate both emotional and sensory aspects of the pre-amputation pain (Katz 1992). Katz and Melzack (1990) suggest that sensory input will 'trigger' somatosensory pain memories while the affective component of a pain memory is generated by the intensity, quality and location of the current experience of phantom limb pain. The present case study used a diary design to examine whether 'triggers' could be identified for somatosensory pain memories. Over a 9-month period, the patient reported daily experience of ongoing phantom limb pain, generally confined to the distal part of the limb, and 5 episodes of injury-related phantom limb pain, primarily experienced in the calf of the missing limb. A 'trigger' was identified for each of the episodes of injury-related phantom limb pain, and a significant finding in this study was that two episodes of injury-related phantom limb pain were associated with cognitive and/or emotional, rather than sensory 'triggers'.