Relationship between sympathetic skin response and power spectral analysis of heart rate variation in patients with type 2 diabetes

Augmentation of the sympathetic skin response after electrical train stimuli

It is well known that the size of the sympathetic skin response (SSR) depends on the stimulus strength. In the present investigation train stimuli (TS) were employed to study the behavior of the SSR when recruited above the usual level. The SSR was obtained in healthy human subjects over the palm of the hand after supramaximal single stimuli (SS) and trains of three (TS; interstimulus interval 3 ms) over the ipsilateral superficial radial nerve in 15 healthy volunteers. Ipsilateral to the stimulus site SSR amplitudes were 5.7 ± 5.3 (SS) and 7.7 ± 5.9 mV (TS; p < 0.001), and contralateral 6.3 ± 6.3 (SS) and 7.2 ± 4.9 mV (TS; not significant). The relative gain in amplitude after TS vs. SS was negatively correlated with the SSR amplitude after SS ipsilateral (p < 0.0005) and contralateral to the stimulus site (p < 0.01). The increase in SSR amplitudes after TS compared with SS is in line with temporal summation of the excitatory synaptic input in neurons generating the SSR. Driving the SSR with TS is of possible relevance for the investigation of disorders of the peripheral or central autonomic nervous system.

COMPARATIVE NEUROPHYSIOLOGICAL STUDY FOR THE DIAGNOSIS OF MILD POLYNEUROPATHY IN PATIENTS WITH DIABETES MELLITUS AND GLUCOSE INTOLERANCE

This article evaluates diagnostic sensitivity of minimal F-wave latency, sural/radial amplitude ratio (SRAR), dorsal sural/radial amplitude ratio (DSRAR), sympathetic skin response (SSR), and R-R interval variability (RRIV) for detecting early polyneuropathy in patients with glucose intolerance and diabetic patients. F-wave latencies were more prolonged in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). SRAR was lower, SSR latency was more prolonged, and RRIV was lower in diabetic patients with abnormal nerve conduction studies than healty controls (p < .001). SSR latency was more prolonged and RRIV was lower in diabetic patients with normal nerve conduction studies than healty controls (p < .01, p < .05, respectively). DSRAR was lower in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). DSRAR was also lower in patients with glucose intolerance than control subjects (p < .01). DSRAR was the most sensitive and specific test in either of diabetic patients with normal nerve conduction studies (sensitivity 66%, specificity 90%) and diabetic patients with abnormal nerve conduction studies (sensitivity 100%, specificity 90%). DSRAR is the most reliable method for detection of early nerve pathology. Patients with glucose intolerance might have subclinical neuropathy that can be demonstrated with DSRAR analysis.

Relationship between skin resistance level and static balance in type II diabetic subjects

Diabetes mellitus is major cause leading to pathological changes in skin foot plantar area (SFPA) and affected the static standing balance duration (SSBD). Skin resistance level (SRL) is related to skin conductance which changes in the presence of sweat. This study aims to find out the relationship between the SRL and SSBD in type II diabetic patients. Sixty-eight voluntary students, 30 type II diabetic patients and 30 healthy non-diabetic subjects, were participated to the study. The SSBD was measured on dominant and non-dominant legs. SRLs were recorded with two surface electrodes over the metatarsus heads and heel. The SSBD of the healthy young group was found to be higher than the other groups (P<0.001). The SRL values of the non-dominant leg in the diabetic group was found to be lower than the others (P=0.014). For dominant and non-dominant legs within each group, only the healthy young group has statistically difference (P=0.012). A significant correlation was seen to be between the SRL and SSBD for only healthy non-diabetic group for the non-dominant leg. The relation between the SRL and SSBD is poor but very promising. Measurement of the SRL can be used in evaluating the inflammation of the diabetic foot.

Evaluation of peripheral and autonomic neuropathy among patients with newly diagnosed impaired glucose tolerance

BACKGROUND

We have aimed to investigate the presence of peripheral and autonomic neuropathy in individuals who had been diagnosed with impaired glucose tolerance (IGT) on the basis of an oral glucose tolerance test, by comparing with age-matched healthy subjects with an oral glucose tolerance test (OGTT) in normoglycemic ranges.

MATERIAL AND METHODS

Conventional nerve conduction studies, heart rate variation variability, heart rate response to deep breathing, heart rate response to valsalva maneuvre, blood pressure response to standing up quickly, hand grip test and sympathetic skin response tests were used to evaluate the IGT and the control subjects.

RESULTS

No obvious statistical difference indicating peripheral neuropathy and/or cardiac autonomic neuropathy was detected between patient group and controls. Amplitudes of sympathetic skin response of two limbs (right upper and lower extremities) were lower in the IGT patient group when compared to healthy controls (p < 0.05) indicating the presence of sudomotor autonomic neuropathy.

CONCLUSION

Complaints and neurological examinations of patients with IGT were thought to be consistent with small-fiber neuropathy in the early phase of glucose intolerance. Not detecting any neuropathic findings in conventional electroneurography should be attributed to insufficient time allowed for settling down of large-fiber neuropathy. Obtaining no response in some of the patients in addition to general decrease in the amplitudes of sympathetic skin responses indicates that sudomotor fibers tend to be affected earlier in autonomic neuropathy in the group with IGT when compared with healthy controls. Newly diagnosed IGT patients take receive priority in primary protection since the time for settling down of cardiac autonomic neuropathy was short.

The effect of rosiglitazone on orthostatic tolerance during heat exposure in individuals with type II diabetes

BACKGROUND AND METHODS

Twenty-two subjects with type II diabetes and 30 control subjects participated in a 1-year study to examine the effect of rosiglitazone on heart rate variability at rest and the blood pressure, heart rate, and blood flow changes during a change in body position from horizontal to the 45 degrees head up position. To assess nerve damage, latency was measured for sensory nerves in the foot.

RESULTS

The results of the experiments showed that subjects with diabetes had an approximate 50% impairment in sural, medial, and lateral plantar nerve latency. After 1 year of administration of rosiglitazone, there was improvement by about 50% in sural, medial, and lateral nerve plantar latency. The changes in blood flow in the subject with diabetes was less than half that of control subjects, during tilting from the horizontal to the vertical position. Heart rate variability was less during tilt, and the blood pressure change was significantly greater in subjects with diabetes than control subjects (P < 0.01). After administration of rosiglitazone for 1 year, the changes in blood flow, blood pressure, and heart rate, while improving by about half, were not equal to those of age matched controls (P < 0.01).

CONCLUSIONS

The results of the experiments indicate that the insulin sensitizer rosiglitazone cannot reverse all of the damage associated with diabetes to the autonomic nervous system, but much can be reversed.

Changing cerebral blood flow velocity by transcranial Doppler during head up tilt in patients with diabetes mellitus

OBJECTIVE

Diabetes mellitus is an independent risk factor for poor prognosis in patients with ischemic stroke. It is known that diabetes mellitus directly affects cerebral vasculature as a secondary, long-term complication of cerebral circulation, and causes cerebral blood flow abnormalities. The abnormalities of cerebral autoregulation also poorly affects the prognosis of ischemic stroke. In this study, we aimed to show the cerebral autoregulation with transcranial Doppler (TCD) ultrasound in diabetic patients with autonomic nervous system abnormalities, determined with electrophysiological studies.

MATERIAL AND METHOD

Twenty healthy controls and 39 patients, who had at least 2 years of diabetes mellitus, were evaluated (age ranges: 42-75 years). The patients were divided into two groups according to sympathetic skin response and R--R interval variation studies: (1) patients with autonomic neuropathy; (2) patients without autonomic neuropathy. Blood flow velocities were measured during supine position and after the patients were raised upright position on head up tilt table. Arterial blood pressures and heart rates were also evaluated.

RESULTS

Mean blood flow velocities of diabetic patients with autonomic neuropathy were found more decreased at 90s after the patients were raised upright position.

DISCUSSION

Autonomic neuropathy due to diabetes mellitus affects cerebral autoregulation, and by this way cerebral perfusion loses protection against hemodynamical changes.

New developments in diabetic neuropathy

PURPOSE OF REVIEW

Diabetic neuropathy is a debilitating consequence of type 1 and 2 diabetes. Hyperglycemia disrupts the normal function of neurons and their supporting glia at multiple levels. The complexity of this complication, combined with difficulties of delivering therapy to sensory, sympathetic and parasympathetic neurons, contributes to the intractability of this serious diabetic complication. This review summarizes recent reviews examining the state of research on and treatment of diabetic neuropathy and highlights areas of clinical and basic research that may yield new diagnostic and treatment options.

RECENT FINDINGS

Recent reviews summarize the effects of hyperglycemia on the peripheral nervous system as well as diagnosis and treatment of patients with diabetic neuropathy. Advances in the analysis of intraepidermal fiber densities could shorten the time course of clinical trials and extend data analyses to include sympathetic as well as sensory information. Unchecked glucose-mediated oxidative stress and advanced glycation endproduct signaling through receptors for advanced glycation endproducts are implicated in diabetic neuropathy and may serve as new therapeutic targets.

SUMMARY

The best efforts of countless investigators have yet to find effective treatments either to stop the progression of axonal degeneration and cell death or regrow damaged axons. Basic research into the prevention of oxidative stress caused by excess glucose as well as the prevention of advanced glycation endproduct/receptor for advanced glycation endproduct signaling may offer new therapeutic targets. The use of skin biopsies may aid in early detection of both sensory and autonomic neuropathy, and perhaps in the case of patients with type 2 diabetes, diagnose neuropathy prior to the onset of symptoms.

Significance of nueroelectrophysiological tests in the early diagnosis of sub-clinical neuropathay with diabetes mellitus

To evaluate the application of nueroelectrophysiological tests in early diagnosis of sub-clinical neuropathy in diabetes mellitus (DM), The routine nerve conductive velocity (NCV), F-wave and sympathetic skin response (SSR) were detected in 27 patients with diabetes mellitus but without symptoms and signs of lesions of nerve system. Our results showed that 48.1%, 44.4%, 51.9% of the patients were found to have abnormal NCV, F-wave and SSR respectively. The abnormalities were mainly characterized by prolonged latency, reduced velocity and absence of wave-form. There were significant differences between the controls and the DM group (P < 0.05). Both the distal and proximal segments of nerves were affected and the distal lesions took place earlier than proximal ones and the changes in low extremities were more severe than those of upper extremities. F-wave can be used as a sensitive indicator for the early diagnosis of peripheral neuropathy and it can help to detect the subclincial lesions. SSR can be used for the evaluation of functional status of autonomic nerves in DM patients.