Microvascular and C-fiber function in diabetic Charcot neuroarthropathy and diabetic peripheral neuropathy

OBJECTIVE - Sympathetic denervation and hyperemia are implicated in the pathogenesis of Charcot neuroarthropathy (CN) but are also features of diabetic peripheral neuropathy (DPN). Differences in these physiological parameters were sought by determining C-fiber function (laser Doppler imager [LDI]flare technique) and maximum microvascular hyperemia (MMH) in 13 subjects with diabetic CN (DCN), 10 subjects with DPN, and 10 healthy control subjects. Additionally, unaffected limbs of the nine DCN subjects with unilateral CN (UCN) were studied to determine whether any observed differences precede CN. RESULTS - LDIflare area was reduced in DPN (mean +/- SD 1.41 +/- 0.51 cm(2)) and DCN (1.42 +/- 0.37) groups compared with the healthy control group (5.24 +/- 1.33; P < 0.0001). MMH was higher in DCN (432 88 PU [perfusion units]) than in DPN (262 +/- 71; P = 0.001) subjects but lower than in the control group (564 112; P < 0.01). LDIflare area and MMH were similar in the UCN and DCN groups. CONCLUSIONS - C-fiber function is equally impaired in neuropathic patients with and without CN; however, a higher MMH distinguishes those with CN. Unaffected and affected limbs of those with unilateral CN have the same neurovascular abnormalities, suggesting that these abnormalities precede CN and are not a result of CN.