Pre-Perceptual Pain Sensory Responses (N1 Component) In Type 1 Diabetes Mellitus (Dm): A Laser Evoked Potentials (LEPs) Study

Background. LEPs may be a useful and sensitive diagnostic tool for assessing the function of small‐myelinated fibers (Aδ) in diabetic neuropathy (DN). This statement is based on recent studies measuring the N2‐P2 vertex potentials. This component is strongly influenced by attention processes and may reflect cognitive processing of nociceptive inputs. It represents a drawback of LEP studies. Recently, it has been demonstrated that a smaller N1 component is not influenced by attention shifts and is thought to be more specific for the sensory‐discriminative aspects of pain. Aim of the study. To evaluate the integrity of Aδ‐fibers in type 1 DM by measuring the N1 component of LEPs. Subjects. 12 healthy volunteers and 20 diabetics divided in two groups: Group 1 included 11 patients staged as N0; group 2 included 9 patients staged as N1 or N2. Methods. N1 component following hand (LEPH) and foot (LEPF) stimulation was measured using a simple fronto‐temporal derivation. Results. A clear N1 component was recorded in 12/12 of controls, 9/11 of patients in group 1 and 6/9 of patients in group 2. No significant difference was found for LEPH. LEPF was significantly prolonged in group 2 patients (controls = 202 ± 10.1 ms; group 1 = 208 ± 12.3 ms; group 2 = 240.4 ± 14.3 ms, p < 0.05). 2 patients in group 1, and 4 patients in group 2 presented abnormal LEPF values. Discussion. N1 component following foot stimulation is abnormally prolonged in type 1 diabetic patients with clinical or electrophysiological evidence of DN. A subclinical hypoalgesia was found in asymptomatic patients as well. These data suggest that LEP abnormalities are secondary to a small fiber dysfunction.