The perception threshold to an electric stimulus deeply applied in the lower limbs in normal and diabetic subjects

The loss of sensitivity to nociceptive stimuli is one of the main factors involved in the pathogeny of diabetic gangrene. The aim of this study was to develop a simple and practical method for selecting the cases prone to such a complication. The perception threshold (either voltage, mV or current, microA) was determined in 137 randomly selected diabetic patients and 38 non-diabetic controls, by an original electronic device using sinusoidal waves, delivered through two electrode needles introduced at a depth of 0.5 cm at two points located on the anterior aspect of the shank about 12 cm apart. At each of the eight frequencies studied (10, 20, 50, 100, 200, 500, 1000 and 2000 Hz) three electrical parameters (voltage across the needle electrodes, the resistive and the capacitive current component) were recorded when the subject first perceived the stimulus. A significantly higher perception threshold was found in diabetic patients vs. non-diabetic subjects, at all frequencies studied and with all three electrical parameters recorded. A greater difference in the perception threshold between diabetic and non-diabetic subjects (a ratio higher than 3) was, however, found using the resistive component of the current and at frequencies higher than 200 Hz.