A Study of Sympathetic Skin Response in Non-Insulin Dependent Diabetic Patients

ABSTRACT

In order to examine the usefulness of the sympathetic skin response(SSR) as an indicator of autonomic dysfunction, we measured the amplitudes and latencies of the SSR in 64 consecutive non-insulin dependent diabetic patients, which were compared with those of 54 normal controls. The SSR on stimulation of median and posterior tibial nerves with EMG electrographer were correlated with nerve conductoin velocity(NCV) findings of median, posterior tibial and sural nerves and with beat-to-beat variation, measured as difference beeen maximum and minimum heart rate during deep breathing. Diabetic patients were also divided into 5 subgroups according to the symptoms of peripheral neuropathy, autonomic neuropathy and NCV findings for further comparisons. The results were as follows 1. The shapes of the SSR were similar in the hand and the foot, but the amplitude was consistently greater in the hand than in the foot(p<0.001). The latency was shorter in the hand than in the foot(P<0.001). 2. The latencies of the foot and hand SSR in the diabetic patients were not significantly different from the normal controls. On the other hands, the amnplitude of the hand and foot SSR was significantly reduced compared to the control(p<0.001). 3. Of the patients with absent foot SSR, 20(59%) had two or more symptoms of autonomic involvement, whereas 14(14%) had no autonomic symptoms. These difference were significant(ppatients with autonomic symptoms, 20(59%) had absent foot SSR, Whereas 12(39%) had normal SSR, which were statistically significant(p<0.01). Absence of the SSR in the foot did not correlated with the patient age, duration of diabetes or peripheral neuropathy, and NCV of limbs except sural nerve. 4. In the PA, PN subgroups, which had compatible NCV findings of peripheral neuropathy, rnean amplitude of the SSR was more decreased than in others(Kruskal-Wallis analysis). 5. Beat-to-Beat variation, rneasured as difference between maximum and minimum heart rates during deep breathing in normal controls showed age-dependent regression{HRD (max-min)=22.63 / s-0.22 age, p<0.05)}. The amplitude of the SSR in the foot correlated with the Beat-to-Beat variation during deep breathing(r=0.27, p<0.05), but not in the hand. The latencies of the SSR did not correlated with the Beat-to-Beat variation. In conclusion, the SSR is probably a good indicator for autonomic dysfunction in non-insulin dependent diabetic patients. With the absence of the foot SSR in diabetic patients we may predict the diabetic autonomic neuropathy in early stage of diabetes mellitus.