Abnormal function of C-fibers in patients with diabetic neuropathy.
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 approximately 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.
Ørstavik
Kristin
K
Faculty of Medicine, University of Oslo, 0027 Oslo, Norway. kristin.orstavik@medisin.uio.no
Namer
Barbara
B
Schmidt
Roland
R
Schmelz
Martin
M
Hilliges
Marita
M
Weidner
Christian
C
Carr
Richard W
RW
Handwerker
Hermann
H
Jørum
Ellen
E
Torebjörk
H Erik
HE
D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology* / Q000502:physiology; D010147:Pain Measurement / Q000379:methods; D014110:Touch / Q000502:physiology