Hypoesthesia in the Distal Residual Limb of Amputees

Objective To test the emerging hypothesis that there is polymodal fiber degeneration/loss in distal residual limbs (DRL) of amputees. Design Prospective qualitative and quantitative psychophysical testing. Setting A pain research center at an urban academic rehabilitation hospital. Participants Forty-four amputees (32 with pain, 12 without pain) with a single (upper or lower) limb amputation. Subjects are a clinical "convenience" sample derived from our amputee or prosthetic clinics. Methods Interventions were prospectively acquired psychophysical tests. The primary quantitative test was thermal Quantitative Sensory Testing (tQST) using a Peltier type thermal testing device, assessing sites on the DRL compared with anatomically similar regions on the contralateral "unaffected" extremity. Results Perceptual responses for several qualitative psychophysical stimuli and perceptual thresholds for tQST cold sensation were significantly reduced in the DRL (t(43) = −2.613, P = .012). There were no significant tQST differences in thresholds for warm perception, cold pain, or hot pain ( P > .05). Conclusion These results show a point prevalence of differential hypoesthesia in distal residual limbs. There was a selective loss of cold, but not warm perception or threshold for hot or cold pain by tQST. There are several possible explanations for this polymodal and selective hypoesthesia; specifically, these data may be indicative of a differential "dying back" peripheral neuropathy of the DRL, which may be operational in such clinical features as postamputation pain.