RR interval variation, sympathetic skin reflex and QT dispersion in the assessment of autonomic function in peripheral neuropathy

In recent years, two simple non-invasive tests, sympathetic skin response (SSR) and RR interval variation (RRIV) have been used to assess autonomic function (Wang et al., 1994; Drory et al., 1995; Chassande et al., 1996; Bordet et al., 1996; Spitzer et al., 1997). Their easy performance by an electromyographic (EMG) machine and successful clinical correlation (Shahani et al., 1990) have made them routine in autonomic assessment in several EMG laboratories. More recently QT dispersion on electrocardiogram (ECG) has been shown to have increased in patients with diabetic neuropathy and several autonomic dysfunctions (Wei et al., 1995; Lengyel et al., 1997; Langen et al., 1997; Axelrod et al., 1997). In order to evaluate the diagnostic value of the RR interval variation, sympathetic skin response and QT dispersion combined, we performed the three tests on a group of 37 patients with several peripheral neuropathies with and without clinical signs of dysautonomia. All patients were studied using an electromyograph (EMG). The results of the SSR, RRIV and QT dispersion combined have shown abnormal values in all patients with neuropathy and clinical dysautonomia and in some patients without clinical signs of dysautonomia, suggesting a subclinical autonomic dysfunction. The principal finding of this study is that the evaluation of the RRIV, SSR and QT dispersion combined may contribute to the assessment of dysautonomia in patients with somatic neuropathy and that they may be currently performed by an electromyograph.