Burst & High-Frequency Spinal Cord Stimulation Differentially Effect Spinal Neuronal Activity After Radiculopathy

Although burst and high-frequency (HF) spinal cord stimulation (SCS) relieve neuropathic pain, their effects on neuronal hyperexcitability have not been compared. Specifically, it is unknown how the recharge components of burst SCS-either actively balanced or allowed to passively return-and/or different frequencies of HF SCS compare in altering neuronal activity. Neuronal firing rates were measured in the spinal dorsal horn on day 7 after painful cervical nerve root compression in the rat. Motor thresholds (MTs) and evoked neuronal recordings were collected during noxious stimuli before (baseline) and after delivery of SCS using different SCS modes: 10 kHz HF, 1.2 kHz HF, burst with active recharge, or burst with passive recharge. Spontaneous firing rates were also evaluated at baseline and after SCS. The average MT for 10 kHz SCS was significantly higher (p < 0.033) than any other mode. Burst with passive recharge was the only SCS mode to significantly reduce evoked (p = 0.019) and spontaneous (p = 0.0076) firing rates after noxious pinch. This study demonstrates that HF and burst SCS have different MTs and effects on both evoked and spontaneous firing rates, indicating they have different mechanisms of providing pain relief. Since burst with passive recharge was the only waveform to reduce firing, that waveform may be important in the neurophysiological response to stimulation.