Optimal Utility of H-Reflex RDD as a Biomarker of Spinal Disinhibition in Painful and Painless Diabetic Neuropathy

Impaired rate-dependent depression of the Hoffman reflex (HRDD) is a potential biomarker of impaired spinal inhibition in patients with painful diabetic neuropathy. However, the optimum stimulus-response parameters that identify patients with spinal disinhibition are currently unknown. We systematically compared HRDD, performed using trains of 10 stimuli at five stimulation frequencies (0.3, 0.5, 1, 2 and 3 Hz), in 42 subjects with painful and 62 subjects with painless diabetic neuropathy with comparable neuropathy severity, and 34 healthy controls. HRDD was calculated using individual and mean responses compared to the initial response. At stimulation frequencies of 1, 2 and 3 Hz, HRDD was significantly impaired in patients with painful diabetic neuropathy compared to patients with painless diabetic neuropathy for all parameters and for most parameters when compared to healthy controls. HRDD was significantly enhanced in patients with painless diabetic neuropathy compared to controls for responses towards the end of the 1 Hz stimulation train. Receiver operating characteristic curve analysis in patients with and without pain showed that the area under the curve was greatest for response averages of stimuli 2–4 and 2–5 at 1 Hz, AUC = 0.84 (95%CI 0.76–0.92). Trains of 5 stimuli delivered at 1 Hz can segregate patients with painful diabetic neuropathy and spinal disinhibition, whereas longer stimulus trains are required to segregate patients with painless diabetic neuropathy and enhanced spinal inhibition.

Patterns of formation of spinal inhibition in humans

The monograph is devoted to the study of age-related features of presynaptic, recurrent, non-reciprocal and reciprocal inhibition of the human spinal cord. New data on the formation of structures and functions of the spinal cord, peripheral nervous system, skeletal muscles in pre - and postnatal ontogenesis are summarized. Modern data on presynaptic, recurrent, nonreciprocal and reciprocal inhibition in the Central nervous system are presented. The original methodological techniques adapted by the authors for the study of various types of inhibition in the human spinal cord are presented. The age stages of formation and formation of different types of spinal inhibition in humans are described, age-related features of inhibitory processes in the implementation of arbitrary motor activity are analyzed. The monograph is intended for neurophysiologists, pediatricians, specialists in the field of age physiology, teachers of pedagogical, sports and medical universities.