Surg Neurol
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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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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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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.
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A percutaneous technique is described for implanting a dorsal or ventral column stimulator for pain control with minimal surgical trauma. If the patient does not respond to percutaneous on-surface spinal stimulation, a percutaneous cordotomy can be carried out, as the needle is already in the correct position. Stimulation of the cord at the C1-2 level can be used for treatment of trigeminal neuralgia.