Skeletal muscle is electrically anisotropic, with applied high-frequency electrical current flowing more easily along than across muscle fibers. As an early step in harnessing this characteristic for clinical use, we studied approaches for maximizing the measured anisotropy by varying electrode size and applied current frequency in the tibialis anterior of 10 normal subjects. The results were compared to those from two patients with amyotrophic lateral sclerosis (ALS). Current was applied percutaneously, first parallel and then perpendicular to the major fiber direction of the muscle at frequencies ranging from 20 kHZ to 1 MHZ, using a fixed voltage-electrode length and varying the current-electrode length. The measured anisotropy was most pronounced using the longest length current electrodes and with a 125-kHZ applied frequency for the major outcome parameter phase. In addition, the two ALS patients showed very distinct anisotropic patterns. These results support the belief that, with the appropriate measurement technique, non-invasive assessment of electrical anisotropy of muscle may have useful clinical application.

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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 Ͻ 0.001), reduced maximal temperature (P Ͻ 0.001), increased rate of cooling (P Ͻ 0.001), as well as increased frequency of variation (P ϭ 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.