EFFECTIVENESS OF SPINAL-CORD STIMULATION IN THE MANAGEMENT OF CHRONICPAIN - ANALYSIS OF TECHNICAL DRAWBACKS AND SOLUTIONS

OBJECTIVE: A major drawback of currently available spinal cord stimula tion (SCS) systems for the management of chronic intractable pain, esp ecially of widespread pain patterns as in reflex sympathetic dystrophy , is the generally limited paresthesia coverage. The aim of this study is to analyze the origin of this problem and to provide solutions. ME THODS: Results from theoretical studies, in which a computer model was used to mimic the effects of SCS on spinal nerve fibers, were used to analyze which factors may limit paresthesia coverage. Model predictio ns were verified by empirical data from clinical literature. RESULTS: When using common SCS electrodes, both perception threshold and motor/ discomfort threshold are generally related to dorsal root stimulation, Because these thresholds have a small ratio (similar to 1:1.4), stimu lation of dorsal column fibers and paresthesia coverage is limited by this small range of stimulation. When the distance between the epidura l electrode and spinal cord is large (midthoracically), the threshold for dorsal column stimulation exceeds discomfort threshold, resulting only in segmental paresthesia. The range of dorsal column stimulation and paresthesia coverage can be improved when using either an optimall y dimensioned rostrocaudal bi-/tripole or a transverse tripole (''guar ded cathode''). When applying the latter in combination with a dual ch annel pulse generator providing simultaneous pulses, paresthesias can simply be changed to optimally cover the painful area. CONCLUSION: Par esthesia coverage and pain management by SCS can be improved when usin g electrodes as proposed.