Paradoxical blood flow responses in the diabetic neuropathic foot: an assessment of the contribution of vascular denervation and microangiopathy.

Blood flow is abnormal in the diabetic neuropathic foot, and this may be of importance in the pathogenesis of complications. Arteriovenous shunting is increased, and blood flow through these channels may paradoxically decrease in response to local heating. Peak skin blood flow is also reduced in these patients. It is not known whether these blood flow abnormalities may reflect diabetic microangiopathy, or whether they simply reflect vascular denervation. The skin blood flow response to a local thermal stimulus was studied in four non-diabetic patients with a unilateral traumatic neuropathy and foot ulceration. All showed a decrease in skin blood flow (to 68% of basal) at the great toe during local heating in the neuropathic limb, in contrast to the normal limb, in which blood flow increased to 180% of basal. Peak skin blood flow was also greatly reduced in the neuropathic limb, being only 29% of the normal limb. Neuropathy alone can be responsible for abnormal skin blood flow responses in the neuropathic foot.