Current perception threshold through sinusoidal electrical stimulation at different frequencies in a comparative assessment for subjects affected and non-affected by diabetes mellitus

Evidence of Current Perception Threshold (CPT) to assess neural fiber function in healthy subjects suggests greater discrimination for stimuli at 1, 250 and 3000 Hz than at 5, 250 and 2000 Hz. Similar data are not yet described for subjects affected by diabetes mellitus. This study proposes to provide a comparative database of parameters obtained with sinusoidal electrical stimulation applied at 1, 5, 250, 2000 and 3000 Hz in subjects affected and non-affected by the diabetes. Ninety subjects were recruited to compose the control (n=45) and diabetic (n=45) groups. The CPT intensities and the reaction times obtained for left and right feet stimulation show responses characterized by weaker intensities (533 to 1671 μA) and longer delays (1.24 to 1.42 s) at low frequencies (1 and 5 Hz) than the intensities (3965 to 5685 μA) and delays (0.96 to 1.12 s) obtained at high frequencies (2000 and 3000 Hz). Moreover, the low frequency stimulation trials evoked up to 73% of the self-reports corresponding to C-fiber sensations while high frequencies evoked up to 60% of the self-reports related to Aβ-fiber sensations. Moreover, the subjects affected by diabetes needed a stronger intensity of stimulation current in order to perceive consistently the sensations evoked by Aβ-fibers (hypoesthesia). In addition, the findings reinforce the suggestion that the discrimination between sensations related to different neural fibers is increased for stimuli at 1, 250 and 3000 Hz for both groups.