10 kHz spinal cord stimulation improves metrics of spinal sensory processing in a male STZ rat model of diabetes

To explore why clinical 10 kHz spinal cord stimulation (10 kHz SCS) might improve neurological function in a model of painful diabetic neuropathy (PDN), the short-term behavioral, electrophysiological, and histological effects of 10 kHz SCS were studied using adult male streptozotocin (STZ)-induced diabetic Sprague-Dawley rats. Four testing groups were established: Naïve controls (N = 8), STZ controls (N = 7), STZ+Sham SCS (N = 9), and STZ+10 kHz SCS (N = 11). After intraperitoneal injection (60 mg/kg) of STZ caused the rats to become hyperglycemic, SCS electrodes were implanted in the dorsal epidural space over the L5-L6 spinal segments in the STZ+Sham SCS and STZ+10 kHz SCS groups and were stimulated for 14 days. The von Frey filament paw withdrawal threshold was measured weekly. At termination, animals were anesthetized and the electrophysiologic response of dorsal horn neurons (receptive field size, vibration, radiant warmth) of the ipsilateral foot was measured. Tissue from the plantar paw surface was obtained post-euthanization for intraepidermal nerve fiber density measurements. In comparison to other control groups, while no significant effect of 10 kHz SCS on peripheral intraepidermal nerve fiber density was observed, 10 kHz SCS 'normalized' the central neural response to vibration, receptive field, and paw withdrawal threshold, and elevated the neural response to tissue recovery from warm stimuli. These results suggest that short-term, low intensity 10 kHz SCS operates in the spinal cord to ameliorate compromised sensory processing, and may compensate for reduced peripheral sensory functionality from chronic hyperglycemia, thereby treating a broader spectrum of the sensory symptoms in diabetic neuropathy.