Nociceptive two-point discrimination acuity and body representation failure in polyneuropathy

Abstract

Abstract Objectives Although patients’ complaints suggest polyneuropathy (PNP) and neuropathic pain, routine investigations do not always support the diagnosis. Assessing two-point-pain discrimination thresholds (2ptDT) and quantify body representation disturbances might be useful to close this diagnostic gap. Methods Pinprick pain and laser-heat pain perception thresholds and 2ptDT on hands, forearms, lower legs and feet were obtained in 20 PNP patients (mean age: 57.6 ± 13.9) and 20 healthy subjects (mean age: 50.6 ± 4.7 years). Body representation disturbances were assessed by self-estimating feet size and the Bath CRPS body perception disturbances questionnaire adapted for PNP. Results Pain perception thresholds and laser-heat pain 2ptDT were unaltered, but patients had higher pinprick pain 2ptDT then the healthy subjects. The 2ptDT for pinprick at the hands discriminate best between groups (U-test; p=0.001). Furthermore, patients estimated their feet longer than they are. In subsequent multivariate discriminant analyses, 2ptDT for pinprick pain at the hands, 2ptDT for laser-heat pain and the perception thresholds for laser-heat pain at the feet classified 85% of PNP vs. HC correctly. The combination of 2ptDT for pinprick pain at the hands, pinprick pain perception thresholds at the calves and foot length estimation differentiates painful vs. non-painful PNPs correctly in 90% of the cases. Conclusions Testing 2ptDT for painful pinprick stimuli at the hands and asking for foot length estimation might add to diagnostic accuracy in painful PNP.