Spinal Cord Stimulation Modulates Visceral Nociception and Hyperalgesia via the Spinothalamic Tracts and the Postsynaptic Dorsal Column Pathways: A Literature Review and Hypothesis

Abstract

Introduction. Early animal and human evidence existed for a postsynaptic dorsal column (PSDC) pathway for visceral nociception that, when lesioned, decreased pain of terminal illness. There have been recent anecdotal reports in the literature that spinal cord stimulation (SCS) reduces pain of visceral nociception. We present here a review of the literature supporting a hypothesis that SCS might work by modulating information through the spinothalamic tracts (STT) and PSDC. Methods. A review of the relevant literature regarding nociception, nociceptive transmission, visceral sensitization, and the "brain-gut" axis; and SCS was performed as a foundation for this hypothesis. Key words used for this review of databases and nonindexed relevant journals included visceral pain, visceral nociception, visceral hyperalgesia, visceral neuropathic pain, visceral sensitization, "brain-gut" axis, SCS, PSDC pathway, and STTs. Results. An abundance of both clinical and scientific literature suggests the neuropathic and sensitized nature of chronic visceral nociception. There is also evidence that there may be an interaction between the PSDC pathway and lateral spinothalamic tracts (LSTT) that might be operant in the preclinical and anecdotal clinical evidence that SCS ameliorates the pain of visceral nociception. Conclusions. Chronic visceral nociception may be secondary to visceral sensitization and hyperalgesia and can be affected by the spinal cord and brain, the "brain-gut" axis. There is preclinical evidence and clinical anecdotes that this nociceptive information is transmitted in the central nervous system through the PSDC pathway and LSTT and that SCS decreases pain of visceral nociception. It may be that SCS works by modulation of the above pathways.