Neural changes associated with spinal cord and external peripheral nerve stimulation for the treatment of neuropathic lower limb pain

Danielle Hewitt
Spinal cord stimulation (SCS) and external low-frequency peripheral nerve stimulation (LFS) are palliative neurostimulation interventions for intractable neuropathic pain. However, understanding of the neural mechanisms underlying SCS and LFS is limited. Neurostimulation parameters such as waveform type and intensity modulate peripheral and central nociceptive pathways, which influence their therapeutic effects. The current thesis aimed to investigate the effects of varying intensities of burst
more » ... and tonic SCS on resting cortical oscillations and somatosensory processing, and the temporal dynamics of LFS on somatosensory processing. Effects of SCS on oscillatory dynamics were assessed in patients using burst and tonic SCS for neuropathic leg pain. Spontaneous resting oscillations and event-related desynchronisation during brushing of a pain-free leg were examined at four SCS intensities. Temporal effects of LFS applied to the radial nerve were examined using source dipole modelling in healthy volunteers at varying intensities. Change in resting EEG and nociceptive processing were investigated after LFS. Results of four empirical studies pointed towards intensity-related changes in cortical activation during both SCS and LFS. Greater intensities of SCS and LFS were associated with decreased cortical excitability primarily in central and parietal scalp regions. Facilitatory effects of stimulation intensity were also identified in sensorimotor sources. Cortical activation changes during processing of somatosensory input were found between burst and tonic SCS. Intensity-related changes in cortical excitability during SCS and LFS may be partially explained by the Gate Control Theory and long-term depression, respectively. Coexistence of attenuated cortical excitability and sensorimotor facilitation suggests that these neurostimulation interventions do not have simple gating effects. Results support different underlying mechanisms between burst and tonic SCS which are engaged during somatosensory input. Findings have imp [...]
doi:10.17638/03156227 fatcat:vqi3bpjviffkdooerlneyb6fdu