Ultra-low Frequency Neuromodulation and Traditional SCS Alter Thalamic Firing Patterns in a Rat Neuropathic Pain Model

OBJECTIVE: Short-pulse low-frequency spinal cord stimulation (LF-SCS) is a standard treatment for managing chronic intractable pain. Action potential conduction in nerves can be inhibited by long pulses, but this approach has not been used clinically because application through traditional electrode materials causes tissue damage. We have developed an ultra-low frequency system that combines long-duration pulses with novel electrode material to safely produce pain-inhibiting effects. Here, we directly compared the effect of ultra-low frequency neuromodulation with traditional LF-SCS on spontaneous firing of thalamic neurons in a rat model of neuropathic pain. MATERIALS AND METHODS: We recorded spontaneous activity of thalamic neurons, which was elevated by injury, and compared the ability of spinal ultra-low frequency neuromodulation and LF-SCS to normalize this firing in neuropathic rats. RESULTS: In male rats with neuropathic injury, ultra-low frequency neuromodulation applied at the thoracic spinal level significantly reduced the ongoing activity of 8% to 56% (1/12‒9/16) of thalamic neurons in a dose-dependent manner. LF-SCS also reduced thalamic neuron activity but in only 11% of neurons (2/18). CONCLUSION: We conclude that both ultra-low frequency current and traditional LF-SCS can reversibly suppress aberrant neuropathic neural activity in the brain. Ultra-low frequency may therefore represent a novel viable treatment for chronic neuropathic pain.