Person:

Rutkove, Seward

Objective: To determine how thermoregulation of the feet is affected by diabetes and diabetic polyneuropathy in both wakefulness and sleep. Research Design and Methods: Normal subjects, diabetic subjects without neuropathy, diabetic subjects with small-fiber diabetic polyneuropathy, and those with advanced diabetic polyneuropathy were categorized based on neurological examination, nerve conduction studies, and quantitative sensory testing. Subjects underwent foot temperature monitoring using an iButton device attached to the foot and a second iButton for recording of ambient temperature. Socks and footwear were standardized, and subjects maintained an activity diary. Data were collected over a 32-h period and analyzed. Results: A total of 39 normal subjects, 28 patients with diabetes but without diabetic polyneuropathy, 14 patients with isolated small-fiber diabetic polyneuropathy, and 27 patients with more advanced diabetic polyneuropathy participated. No consistent differences in foot temperature regulation between the four groups were identified during wakefulness. During sleep, however, multiple metrics revealed significant abnormalities in the diabetic patients. These included reduced mean foot temperature (P < 0.001), reduced maximal temperature (P < 0.001), increased rate of cooling (P < 0.001), as well as increased frequency of variation (P = 0.005), supporting that patients with diabetic polyneuropathy and even those with only diabetes but no diabetic polyneuropathy have impaired nocturnal thermoregulation. Conclusions: Nocturnal foot thermoregulation is impaired in patients with diabetes and diabetic polyneuropathy. Because neurons are highly temperature sensitive and because foot warming is part of the normal biology of sleep onset and maintenance, these findings suggest new potentially treatable mechanisms of diabetes-associated nocturnal pain and sleep disturbance.

Localized impedance methods can provide useful approaches for assessing neuromuscular disease. The mechanism of these impedance changes remains, however, uncertain. In order to begin to understand the relation of muscle pathology to surface impedance values, 8 immature rats, 12 mature rats, and 8 mature rats that had undergone sciatic crush were killed. Tissue from the gastrocnemius muscle from each animal was measured in an impedance cell, and the conductivity and relative permittivity of the tissue calculated in both the longitudinal and transverse directions for frequencies of 2 kHz to 1 MHz. In addition, quantitative histological analysis was performed on the tissue. Significant elevations in transverse conductivity and transverse relative permittivity were found with animal growth, but longitudinal values showed no difference. After sciatic crush, both transverse and longitudinal conductivity increased significantly, with no change in the relative permittivity in either direction. The frequency dependence of the values also changed after nerve injury. In the healthy animals, there was a strong linear relation between measured conductivity and relative permittivity with cell area, but not for the sciatic crush animals. These results provide a first step toward developing a comprehensive understanding of how the electrical properties of muscle alter in neuromuscular disease states.

Nerve conduction studies and electromyograms (EMGs) are most often performed in the outpatient setting in patients with suspected neuromuscular diseases, where they help the physician confirm the clinical diagnosis, assess the localization and severity of the disease, and plan further evaluation and treat- ment. Not infrequently, EMGs are requested on a relatively urgent basis for patients who are admitted to the hospital. Inpatient electrodiagnostic studies are usually requested in two situations: (1) as part of the diagnostic evaluation of patients who present with symptoms of a neuromuscular disorder; or (2) in patients who are admitted to the hospital with non-neuromuscular illnesses but develop symptoms suggestive of a neuromuscular disorder during the course of their illness. The second scenario com- monly occurs in patients who are in the intensive care unit and are unable to be weaned from the ven- tilator. This raises the possibility of a neuromuscular disorder as a cause of respiratory muscle weakness and ventilator dependence. The role of EMG in the evaluation of neuro- muscular disorders in the inpatient setting has not been studied previously. In this study, we evaluated the contribution of EMG to the diagnosis and man- agement of hospital inpatients. We hypothesized that inpatient EMGs (IP-EMGs) would frequently find clinically meaningful diagnoses that would affect the subsequent management of patients. The aims of this study were to compare the results of IP-EMGs with the referring physicians’ clinical diag- noses and to assess how often results of IP-EMGs changed the clinical diagnosis and altered further diagnostic evaluation and treatment.