Background: Many amputees experience referred sensations described as sensations from the phantom fingers elicited by stimulation of specific skin areas on, eg, the residual limb—a phantom hand map (PHM). Some amputees have a very detailed PHM with a mapping of all fingers, while others have a more “simple” map containing 1 or 2 fingers and others do not have a map at all. The anatomical and physiological substrate behind the PHM is not completely understood. Here, we evaluated the sensory qualities of the PHM. Methods: Touch thresholds and discriminative touch of the PHM were assessed in 10 traumatic forearm amputees. They were assessed for ability to localize touch in the PHM areas, and they were also asked to grade how distinct and similar to normal touch the referred feeling was. Corresponding areas on the contralateral, intact forearm were used as controls. Results: Similar touch thresholds were seen in the PHM and the control site at the contralateral forearm. Tactile discrimination, requiring both detection of stimulus and interpretation, was significantly better in the PHM. The quality of touch in PHM areas compared with normal touch experience was rated as mean 7.4 (range, 3-10) on a visual analogue scale (0-10). Conclusions: This study provides initial data supporting the hypothesis that the PHM and the superior tactile discrimination in the PHM may be based on adaptation in brain function. Further investigations of the neural basis for the PHM are, however, needed to better understand its origin.
