Fidelity of dorsal column axon activity in response to clinical spinal cord stimulation paradigms

Many novel spinal cord stimulation (SCS) paradigms have been developed during the last decade. However, understanding of underlying neurophysiological mechanisms is well behind clinical application. Therefore, this study aims to investigate differences between two clinically applied low-frequency SCS paradigms applied at 40Hz and 90Hz. A SCS paddle lead was implanted under the T1 vertebra of seven urethane anesthetized rats. Antidromic action potentials were recorded from the dorsal columns at T13/L1 using a 20MΩ bipolar recording electrode. Spiking fidelity and spike amplitude were investigated during 60s of SCS at 40Hz and 90Hz with active and passive charge balanced (CB) waveforms. Spiking fidelity and spike amplitude decreased significantly with time for 90Hz stimulation with active and passive CB. This was not the case for 40Hz stimulation with active CB. The spike amplitude during 90Hz stimulation with active and passive CB decreased significantly with time and were lower compared to the 40Hz SCS paradigms.Clinical Relevance- The difference in spike fidelity and amplitude between 40Hz and 90Hz SCS is important to consider when designing SCS paradigms.