Prompt Implantation May Improve Efficacy of Spinal Cord Stimulation
The success rate was 75% for patients with chronic pain who waited less than two years for implantation of a spinal cord stimulator (SCS), compared with 15% for patients whose implants occurred 20 years after the onset of pain, according to a retrospective analysis. The length of time that patients waited for a referral also varied by specialty, researchers said.
Fewer than 50% of patients report long-term success with SCS in the treatment of chronic pain. Improving wait times could significantly increase success rates, said Krishna Kumar, MD, a neurosurgeon at Regina General Hospital in Regina, Canada. “The success of SCS is time-sensitive, in that as wait times decline, long-term outcomes with SCS are enhanced,” he added.
Barriers to referral may include lack of uptake and awareness among healthcare providers, patients, and payers; reimbursement concerns; and fragmentation of pain-care delivery, said Dr. Kumar. Judging the value of SCS according to whether patients return to employment may have the effects of curtailing access to SCS and downplaying the treatment’s benefits for quality of life, pain, and depression, he continued.
Dr. Kumar and colleagues studied 443 patients who received SCS. Beginning with the initial pain diagnosis, investigators examined points of delay to referral for implantation by primary care physicians and specialists. The effects on pain duration of gender, age, referring specialty, and their interactions were analyzed using a two-way analysis of variance. The investigators developed a multiple linear regression model that incorporated patient demographic characteristics and components of wait times to predict factors responsible for delays in SCS implantation.
Patients first saw a physician at an average of 3.4 months after developing a pain syndrome. Family physicians managed patients for 11.9 months. Specialists subsequently managed patients for an additional 39.8 months on average.
The mean time to implantation from symptom onset was 5.12 years. Neurosurgeons were quickest to make a referral, whereas nonimplanting anesthetists were most likely to delay implantation. Referral for SCS treatment took 2.15 years longer if a nonimplanting anesthetist, compared with a neurosurgeon, referred the patient.
Successful SCS outcomes depend on appropriate candidate selection, and examining underlying pain pathology helps determine who might benefit from treatment, said Dr. Kumar. For example, patients who have failed back surgery syndrome, complex regional pain syndrome, refractory angina pectoris, pain due to peripheral vascular disease, postherpetic neuralgia, chronic migraine, or postsurgical neuropathy are considered good candidates for SCS. Patients with secondary gain from litigation, persistent uncontrolled or undiagnosed psychiatric disorder, unwillingness to curb inappropriate drug use, or cognitive issues that could interfere with the operation of SCS equipment generally are not good candidates.
Superior Conditioned Pain Modulation May Predict Better Response to NSAIDs
Neuropathic pain symptoms are common in knee osteoarthritis, and researchers can predict who will respond to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) by assessing the nervous system’s capacity to regulate pain, according to researchers. Data suggest that patients whose tests indicate superior conditioned pain modulation (CPM) have less pain and fewer neuropathic symptoms.
“Patients with neuropathic pain symptoms in osteoarthritis respond equally as well to topical NSAIDS as those who do not have neuropathic pain symptoms,” said Ajay D. Wasan, MD, Vice Chair for Pain Medicine at the University of Pittsburgh Medical Center.
Investigators conducted a five-week effectiveness study of diclofenac topical gel in 44 patients with knee osteoarthritis. Patients were extensively tested to identify their genetically and environmentally influenced physical characteristics. Methods included the Neuropathic Pain Questionnaire, the Knee Injury and Osteoarthritis Outcome Score, an exercise performance task, and quantitative sensory testing (QST), which uses brief computer-applied painful stimuli as well as sophisticated manually applied pain sensitivity testing (such as heat, cold, pressure, and pinpricks) to assess how the nervous system responds to painful stimuli.
Of 38 subjects who completed the study, 40% had significant neuropathic symptoms, with a mean of 35 on a 100-point pain scale, which included burning or shooting sensations and sensitivity to touch. Pain sensitivity at baseline, as measured by QST, had a modest correlation to symptoms.
After four weeks of treatment with diclofenac gel, patients had an average improvement in pain of 30%. Participants also had significant response for neuropathic symptoms and improved function (ie, self-rated and measured).
Using CPM, an index of endogenous pain-inhibitory capacity that was calculated from QST measurements, investigators correctly predicted changes in pain intensity and in neuropathic symptoms. Subjects with higher CPM at baseline, which indicated better functioning endogenous pain-inhibitory systems, reported lower pain intensity and neuropathic pain symptoms at the study’s end.