Articles: pain.
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Twenty-three patients underwent implantation of a stimulator system and were followed for 6-20 months. Twenty patients estimated between 50% and 100% pain relief. ⋯ Reduced drug intake and improved social performance were associated with subjective improvement. The surgical technique is given, complications are analyzed and parameters are discussed.
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Electrical stimulation of the nervous system has been advocated as a means of alleviating pain in situations in which more conventional methods have been ineffective. A chronically implanted electrode on the dorsal surface of the spinal cord may prove to be a valuable adjunct to the neurosurgeon's armamentarium for pain control in selected individuals. The physiologic basis for this action is unclear but has been related to Melzack and Wall's gate control theory. This preliminary report deals with a series of patients treated with implanted dorsal cord stimulators.
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The long-term (three-year) effect of dorsal column electrical stimulation for chronic pain in a group of 30 patients was generally decreased effectiveness with time, and increased stimulation thresholds. Further animal and human studies of this technique are recommended.
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Twenty-seven patients with chronic pain had dorsal column stimulators implanted for pain control over a period of three years. Technical factors of electrode placement and type of unit were not found to correlate with the degree of pain relief. The preoperative psychological attitude of the patient correlated highly with the degree of pain relief and was the single most important factor in patient selection and evaluation. Theoretical concepts of pain psychophysiology in relation to the gate theory and areas for more extensive investigation of pain are discussed.
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Comparative Study
A comparison between anterior and posterior spinal implant systems.
In four patients with intractable pain from metastatic cancer, application of current through electrodes placed on the anterior surface of the cord produced analgesia and pain relief below the level of implant without the development of paresthesias. Application of current through electrodes placed on the dorsal columns in these patients also relieved pain, but to a lesser degree and with the development of associated paresthesias. In one patient, application of current from anterior electrodes to posterior electrodes produced a zone of dissociated sensory loss. While it is simpler to implant electrodes over the dorsal columns, the anterior location may be superior when currents are to be applied for the pain relief in the lower lumbar and sacral dermatomes.