The use of intrathecal opioids for pain not due to cancer has burgeoned in recent years in spite of a lack of prospective studies. The most definitive data to date supporting such an increase in use are provided by the survey of physicians in the United States by Paice, Penn, and Shortt,17 cited in connection with cancer-related pain and including data on pain not related to cancer, and in the retrospective study by European authors Winkelmuller and Winkelmuller.34
In the American study, two thirds of the patients were suffering pain of noncancerous origin. The most common pain type was failed back syndrome (42.4%). Other pain syndromes treated included complex regional pain syndrome (5.6%), postherpetic neuralgia (5.1%), and peripheral nerve injury (3.7%). The most common screening technique was continuous epidural infusion (35.3%), followed by bolus intrathecal injection (33.7%). More than half (77.6%) underwent psychological screening. Morphine was by far the most commonly infused drug (95.5%), but a wide variety of medications were used. Doses for neuropathic pain tended to be higher at 6 months than for somatic or visceral pain. Nearly one fifth (19.8%) of patients were treated with a local anesthetic (bupiv-acaine) as an adjuvant to morphine. These patients exhibited a linear increase in dose over time, eventually reaching stable levels by one year at 9.2 mg/24 h. By physician report, 52.4% of the patients had excellent pain relief, 42.9% had good relief, and pain relief was poor in 4.8%, testifying to the considerable efficacy of this technique.17
Specific outcome measures employed by Paice et al. included activities of daily living (ADLs), employment, percent pain relief, a global pain relief score incorporating intensity and pain medication changes, and activity levels.17 In 82% of respondents there was improvement in handling ADLs. Patients with visceral pain showed the greatest improvement in ADLs. Return to work occurred in 24 of the patients with non-cancer-related pain.
In a long-term follow-up of 120 non-cancer-related pain patients in Europe with a mean follow-up of 3.4 years (0.5-5.7 years), 73 patients had mixed neuropathic and nociceptive pain due to multiple back surgeries, while 34 had varying etiologies such as postherpetic neuralgia, stump and phantom limb pain, and various peripheral nerve injuries.34 Six months following implantation the average pain intensity score was 30.5. At the conclusion of follow-up, the score was 39.2. The best initial response was seen in the nociceptive pain group, with a 77% initial reduction in pain intensity that declined to 48% at last follow-up. Deafferentation and neuropathic pain groups benefited from therapy and in fact over the long term showed the best results, with 68 and 62% pain reduction as measured by VAS, respectively.
While these results are impressive in a population of patients unresponsive to more conventional methods, prospective studies comparing this and alternative therapies would more rigorously establish in-trathecal infusion of medication as a treatment of choice. The current acceptance in clinical practice empirically validates the technique but also makes prospective and certainly randomized studies difficult to implement.
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