Abnormal function of C-fibers in patients with diabetic neuropathy

K Ørstavik, B Namer, R Schmidt… - Journal of …, 2006 - Soc Neuroscience
K Ørstavik, B Namer, R Schmidt, M Schmelz, M Hilliges, C Weidner, RW Carr, H Handwerker…
Journal of Neuroscience, 2006Soc Neuroscience
The mechanisms underlying the development of painful and nonpainful neuropathy
associated with diabetes mellitus are unclear. We have obtained microneurographic
recordings from unmyelinated fibers in eight patients with diabetes mellitus, five with painful
neuropathy, and three with neuropathy without pain. All eight patients had large-fiber
neuropathy, and seven patients had pathological thermal thresholds in their feet, indicating
the involvement of small-caliber nerve fibers. A total of 163 C-fibers were recorded at knee …
The mechanisms underlying the development of painful and nonpainful neuropathy associated with diabetes mellitus are unclear. We have obtained microneurographic recordings from unmyelinated fibers in eight patients with diabetes mellitus, five with painful neuropathy, and three with neuropathy without pain. All eight patients had large-fiber neuropathy, and seven patients had pathological thermal thresholds in their feet, indicating the involvement of small-caliber nerve fibers. A total of 163 C-fibers were recorded at knee level from the common peroneal nerve in the patients (36–67 years old), and these were compared with 77 C-fibers from healthy controls (41–64 years old). The ratio of mechano-responsive to mechano-insensitive nociceptors was ∼2:1 in the healthy controls, whereas in the patients, it was 1:2. In patients, a fairly large percentage of characterized fibers (12.5% in nonpainful and 18.9% in painful neuropathy) resembled mechano-responsive nociceptors that had lost their mechanical and heat responsiveness. Such fibers were rarely encountered in age-matched controls (3.2%). Afferent fibers with spontaneous activity or mechanical sensitization were found in both patient groups. We conclude that small-fiber neuropathy in diabetes affects receptive properties of nociceptors that leads to an impairment of mechano-responsive nociceptors.
Soc Neuroscience