Neurostimulation for Chronic Pain: A Systematic Review of High-Quality Randomized Controlled Trials With Long-Term Follow-Up

OBJECTIVE

This study aimed to review the best evidence on the long-term efficacy of neurostimulation for chronic pain.

MATERIALS AND METHODS

We systematically reviewed PubMed, CENTRAL, and WikiStim for studies published between the inception of the data bases and July 21, 2022. Randomized controlled trials (RCTs) with a minimum of one-year follow-up that were of high methodologic quality as ascertained using the Delphi list criteria were included in the evidence synthesis. The primary outcome was long-term reduction in pain intensity, and the secondary outcomes were all other reported outcomes. Level of recommendation was graded from I to III, with level I being the highest level of recommendation.

RESULTS

Of the 7119 records screened, 24 RCTs were included in the evidence synthesis. Therapies with recommendations for their usage include pulsed radiofrequency (PRF) for postherpetic neuralgia, transcutaneous electrical nerve stimulation for trigeminal neuralgia, motor cortex stimulation for neuropathic pain and poststroke pain, deep brain stimulation for cluster headache, sphenopalatine ganglion stimulation for cluster headache, occipital nerve stimulation for migraine, peripheral nerve field stimulation for back pain, and spinal cord stimulation (SCS) for back and leg pain, nonsurgical back pain, persistent spinal pain syndrome, and painful diabetic neuropathy. Closed-loop SCS is recommended over open-loop SCS for back and leg pain. SCS is recommended over PRF for postherpetic neuralgia. Dorsal root ganglion stimulation is recommended over SCS for complex regional pain syndrome.

CONCLUSIONS

Neurostimulation is generally effective in the long term as an adjunctive treatment for chronic pain. Future studies should evaluate whether the multidisciplinary management of the physical perception of pain, affect, and social stressors is superior to their management alone.

Recent advances in dyspnea

Dyspnea is the most prevalent symptom among patients with cardiac and respiratory diseases. It is an independent predictor of mortality in patients with heart disease, COPD, and the elderly. Studies using naloxone to block opioid-receptor signaling demonstrate that endogenous opioids modulate dyspnea in patients with COPD. Neuroimaging studies support a cortical-limbic network for dyspnea perception. A 2012 American Thoracic Society statement recommended that dyspnea be considered across three different constructs: sensory (intensity), affective (distress), and impact on daily activities. The 2013 GOLD (Global Initiative for Chronic Obstructive Lung Disease) executive summary recommended a treatment paradigm for patients with COPD based on the modified Medical Research Council dyspnea score. The intensity and quality of dyspnea during exercise in patients with COPD is influenced by the time to onset of critical mechanical volume constraints that are ultimately dictated by the magnitude of resting inspiratory capacity. Long-acting bronchodilators, either singly or in combination, provide sustained bronchodilation and lung deflation that contribute to relief of dyspnea in those with COPD. Opioid medications reduce breathing discomfort by decreasing respiratory drive (and associated corollary discharge), altering central perception, and/or decreasing anxiety. For individuals suffering from refractory dyspnea, a low dose of an opioid is recommended initially, and then titrated to achieve the lowest effective dose based on patient ratings. Acupuncture, bronchoscopic volume reduction, and noninvasive open ventilation are experimental approaches shown to ameliorate dyspnea in patients with COPD, but require confirmatory evidence before clinical use.