Noninvasive Evaluation of Neural Impairment in Subjects With Impaired Glucose Tolerance

Abstract

OBJECTIVE -To evaluate neural dysfunction in subjects with impaired glucose tolerance (IGT).RESEARCH DESIGN AND METHODS -For this study, 46 subjects with IGT and 45 healthy volunteers underwent detailed neurological assessment. Cardiovascular autonomic function was assessed by standard cardiovascular reflex tests, and heart rate variability was characterized by the triangle index. Sensory nerve function was assessed using Neurometer (for current perception threshold) and Medoc devices. Peak plantar pressure was measured by dynamic pedobarography, and symptoms were graded using the neuropathy total symptom score.RESULTS -Subjects with IGT had significantly greater abnormalities detected by four of five cardiovascular reflex tests and greater heart rate variability characterized by the triangle index. They had a higher frequency of both hyperesthesia and hypoesthesia as detected by current perception threshold testing at 5 Hz, as well as increased heat detection thresholds.CONCLUSIONS -This study provides evidence that subclinical neural dysfunction is present in subjects with IGT and can be detected noninvasively. Cardiovascular autonomic neuropathy may contribute to increased cardiovascular risk in IGT subjects.

Why Not to Use the Handgrip Test in the Assessment of Cardiovascular Autonomic Neuropathy Among Patients with Diabetes Mellitus?

“…Its prevalence varies between 7 and 65% depending on the diagnostic criteria and the studied population increasing with age and DM duration [1]. Moreover, it may be present in newly diagnosed patients with type 1 and type 2 DM and in patients with impaired glucose tolerance [2]. A meta-analysis of 15 longitudinal studies with a follow-up of 1-16 years showed that the definite diagnosis of CAN based on at least 2 abnormal test results is accompanied by a relative risk of mortality of 3.65 [3].…”

Assessing autonomic dysfunction in early diabetic neuropathy

“…8 In contrast, another study examined patients with newly diagnosed IGT with a battery of autonomic tests including heart rate variation variability, heart rate response to deep breathing, heart rate response to Valsalva maneuver, blood pressure response to standing up quickly, and skin sympathetic skin response (SSR) that evaluates postganglionic sympathetic sudomotor function but is less precise than the QSART. 7 They found no difference compared to controls in measures of CAN.…”

“…1,2 The neuropathy associated with IGR and early diabetes is a small-fiber neuropathy that is often accompanied by mild autonomic symptoms and abnormalities. [3][4][5][6][7][8] A recent consensus statement by the American Diabetes Association recognizes that glycemic burden is a strong predictor of adverse outcomes and that IGR represents a continuum of risk. 9 Thus, for the purposes of this study, subjects with neuropathy and prediabetes or newly diagnosed diabetes are described as having IGR or early diabetic neuropathy.…”

Polyneuropathy in Impaired Glucose Tolerance: Is Postprandial Hyperglycemia the Main Culprit? A Mini-Review

“…The diagnosis of neuropathy in IGT is based on careful clinical examination [2,16]. As in diabetes, this should include both motor and sensory modalities, both small- and large-fiber function tests.…”