The Clinical journal of pain
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The choice of an appropriate control group has been recognized as one of the most difficult problems in the methodology of case/control studies, both in theory and in practice. In the study of chronic pain, a "well control group" has frequently been employed. ⋯ Second, controls should be selected independently of exposure to the putative risk factors under investigation. To illustrate the nature of this problem we present two numerical examples, using a chronic pain disorder.
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This study used a radionuclide imaging technique to map the spread and density contours of phenol in glycerin injected into the epidural space of cancer patients. Correlations were made between phenol injectate volume, sequence of injection, position of patient, and resultant epidural spread and analgesic outcome. Fifteen patients with cancer pain (average age of 61 years) were treated with serial epidural phenol in glycerin injections. ⋯ Good analgesia was obtained in 14 patients (93%). Epidural neurolysis using serial injections of small volumes of phenol in glycerin is an effective, safe technique for cancer pain relief. Injectate volumes larger than 3 ml may be unnecessary and potentially dangerous.