Study of the cutaneous electric potentials and the perception threshold to an electric stimulus in diabetic patients with and without clinical neuropathy.

Clinical heterogeneity of diabetic peripheral neuropathy could express a neurophysiological and electrophysiological heterogeneity possibly related with the dissociated metabolic susceptibility of the difference types of nerve fibres and endings. To evaluate the functional status of the skin autonomous nervous system and of the deep pain sensitivity system in diabetics we studied two electrophysiological parameters skin electrical potential (using Digital Multimeter 3466 Hewlet Packard, USA) and the perception threshold (microA) at an electrical stimulus (spike wave, 0.5 m sec duration) 1 cm deeply applied through 2 acupuncture needles placed 30 cm distance each other, in 3 groups: Ia-18 diabetic patients with clinical signs of neuropathy (12 M, 6 F, aged 55 +/- 17 yrs); Ib - 17 diabetic patients without clinical signs of diabetic neuropathy (12 M, 5 F, aged 57 +/- 16 yrs); I1 - 10 age and sex matched non-diabetic controls. Our data show: a higher mean value of the potential in the acupuncture points as against neighbour areas, both in non-diabetic control (- 111 +/- 25 mV v.s. -81 +/- 29 mV, p less than 0.05) and in diabetics (-85 +/- 43 mV v.s. -58 +/- 25 mV, p less than 0.01); a lower mean value of the electrical potentials in diabetic with clinical signs of neuropathy as against in those without clinical signs of neuropathy (-66 +/- 29 mV v.s. -108 +/- 43 mV, p less than 0.01): a higher mean value of the perception threshold in diabetics with clinical signs of neuropathy as against in diabetics without clinical signs of neuropathy (213 +/- 82 microA. v.s. 102 +/- 40 microA, p less than 0.01); a significant correlation (r = -0.81) between the perception threshold and the electrical potentials of the studied points.