Articles: pain.
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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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A systematic, strict appraisal was made of 100 patients, after preliminary clinical trials suggested that some patients with pain could be helped by peripheral nerve stimulation. Transcutaneous stimulation of different nerve trunks was done with a special electrical stimulation device with various selected electrical parameters. More than half of the patients experienced some relief; in many, this effect was obtained by stimulating nerves distant from the area of referred pain. ⋯ A few patients had response decay, gain or worsening. Results differ to some degree from previous reports. The results seem encouraging for the treatment of certain forms of intractable pain.
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Sixty-nine patients with chronically incapacitating pain were treated with an implantable stimulator over the posterior columns of the spinal cord. Evaluations at 24, 30 and 34 months showed a progressive decrease in the number of patients considered to have an excellent result. Evaluation of 60 patients with pain of benign origin after implantation of the stimulating device showed only ten patients who could be considered to have an excellent result on the basis of their own report of pain relief. The most common failure of the stimulating devices was failure of stimulation into a painful part.
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Serious questions are raised as to whether electrical control of pain is related to stimulation of the dorsal columns per se or the conduction of the electrical impulse via the cerebrospinal fluid to the ventrolateral columns. Percutaneous on-surface spinal cord stimulation is advocated as an accurate screening method before implantation. Of 27 patients who underwent dorsal column stimulator implants, the last three patients also underwent ventral column stimulator implants. Results in the patients with both implants tend to predict much better results with the possibility that ventral column stimulation alone is sufficient.
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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.