Clinical correlates of painful diabetic neuropathy and relationship of neuropathic pain with sensorimotor and autonomic nerve function

BACKGROUND: This study investigated the clinical correlates of painful diabetic polyneuropathy (PDPN) and the relationship of neuropathic pain with sensorimotor and autonomic nerve function. METHODS: Seventy-eight diabetic patients with PDPN (PDPN(+)), 57 with non-painful diabetic polyneuropathy (DPN(+)), and 56 without diabetic polyneuropathy (DPN(-)) were prospectively studied. Autonomic neuropathy, neuropathic symptoms and signs, vibration perception threshold, and neuropathic pain were assessed using 4 cardiovascular tests, scoring systems for symptoms and signs (Michigan Diabetic Neuropathy Score, MDNS), Biothesiometer, and a numerical rating scale. RESULTS: Compared to DPN(+), PDPN(+) patients displayed higher BMI (P=0.0043), waist circumference (P=0.0057), neuropathy symptom score (P<0.0001), MDNS (P<0.0001), and lower Valsalva ratio (P=0.037). In a multiple logistic regression analysis including PDPN as the dependent variable and age, sex, body mass index (BMI), abdominal obesity, diabetes type, diabetes duration, HbA1c, blood pressure, triglycerides, smoking, peripheral arterial disease, Valsalva ratio and MDNS as the independent variables, BMI (OR 1.22, P=0.0012) and MDNS (OR 1.27, P=0.0005) were significantly and independently associated with PDPN. In a multivariate regression analysis including as independent variables also sex, age, diabetes type, diabetes duration and Valsalva ratio, 24-h pain score was significantly related to neuropathy symptom score (P=0.0011), MDNS (P=0.0158), and 10g monofilament (P=0.018). DISCUSSION: BMI and sensorimotor deficits were the main determinants of PDPN and, as a novel finding, neuropathic pain intensity was related to the degree of neuropathy deficits. Thus, some peculiarity exists in metabolic correlates of diabetic neuropathic pain compared to insensate neuropathy but painfulness can still coexist with insensitivity.