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.