Abstract
Punctate midline myelotomy (PMM) has been successfully applied clinically in humans for the relief of intractable visceral pain. The operation is thought to work by interrupting the postsynaptic dorsal column pathway (PSDC) of the spinal cord. In fact, PMM was developed specifically for that purpose after it was demonstrated in rats that the PSDC conveyed about 90% of the visceral pain information to the thalamus. The application of PMM also to the problem of severe intractable back or spine pain was never tested, and it has never been established whether the PSDC pathway relates only to visceral pain or whether there may be a broader involvement with pain affecting structures of embryological midline origin, perhaps including the spine. Retrospective analyses of decades of results from various attempted myelotomy procedures in man for the relief of pain are consistent with the notion that the common element crucial to the successful midline or visceral pain relief was the interruption--even incomplete--of the PSDC pathway. Herein, we present evidence from a rat model of lumbar facet pain that interruption of the PSDC significantly reduces pain responses. The implications for the possible treatment of severe intractable spine pain in man are discussed.
Highlights
The purpose of this study is to clarify how pain signals originating in the spine, from lumbar facet joint inflammation, ascend in the spinal cord to reach higher levels of the nervous system
Until the discovery of the postsynaptic dorsal column (PSDC) pathway [1], the answer to this question was presumed to be trivial because it was believed that all pain signals reach the thalamus in some component of the classical spinothalamic tract (STT) system, ascending bilaterally crossed in the anterolateral quadrants of the spinal cord
This study was intended to probe the question, "Does the postsynaptic dorsal column pathway (PSDC) play a role in conveying pain signals from the axial spine to more rostral levels of the nervous system?" If so, spine pain signals should be reduced by Punctate midline myelotomy (PMM)
Summary
The purpose of this study is to clarify how pain signals originating in the spine, from lumbar facet joint inflammation, ascend in the spinal cord to reach higher levels of the nervous system. Until the discovery of the postsynaptic dorsal column (PSDC) pathway [1], the answer to this question was presumed to be trivial because it was believed that all pain signals reach the thalamus in some component of the classical spinothalamic tract (STT) system, ascending bilaterally crossed in the anterolateral quadrants of the spinal cord. The major role of the dorsal column midline in visceral pain conduction went unrecognized. The view that there is only one major pain tract system ( subdivided) has been superseded, and it is abundantly clear from both clinical and laboratory studies that there is a robust pain pathway that ascends in the dorsal. Retrospective analyses of clinical patient outcomes following various older myelotomy procedures affecting the dorsal columns were consistent with this view [2, 5]
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