The Effectiveness of Various Types of Electrical Stimulation of the Spinal Cord for Chronic Pain in Patients with Postherpetic Neuralgia: A Literature Review.

Introduction: Postherpetic neuralgia (PHN) is a severe condition that remains a challenge to treat. Spinal cord stimulation (SCS) is used in cases of insufficient efficacy of conservative treatment. However, in contrast to many other neuropathic pain syndromes, there is a huge problem in reaching long-term stable pain relief in patients with PHN using conventional tonic SCS. The objective of this article was to present a review of the current management strategies of PHN, their efficacy, and safety. Materials and Methods: We searched for articles containing the keywords "spinal cord stimulation AND postherpetic neuralgia," "high-frequency stimulation AND postherpetic neuralgia," "burst stimulation AND postherpetic neuralgia" and "dorsal root ganglion stimulation AND postherpetic neuralgia" in Pubmed, Web of Science, and Scopus databases. The search was limited to human studies published in the English language. There were no publication period limitations. Bibliographies and references of selected publications on neurostimulation for PHN were further manually screened. The full text of each article was studied once the abstract was analyzed by the searching reviewer and found appropriate. The initial search yielded 115 articles. Initial screening based on abstract and title allowed us to exclude 29 articles (letters, editorials, and conference abstracts). The full-text analysis allowed us to exclude another 74 articles (fundamental research articles, research utilizing animal subjects, and systemic and nonsystemic reviews) and results of PHN treatment presented with other conditions, leaving 12 articles for the final bibliography. Results: 12 articles reporting on the treatment of 134 patients with PHN were analyzed, with a disproportionally large amount of traditional SCS treatment than that to alternative SCS: DRGS (13 patients), burst SCS (1 patient), and high-frequency SCS (2 patients). Long-term pain relief was achieved in 91 patients (67.9%). The mean VAS score improvement was 61.4% with a mean follow-up time of 12.85 months. Although the number of patients in alternative SCS studies was very limited, almost all of them showed good responses to therapy with more than 50% VAS improvement and reduction of analgesic dosage. The article contains a review analysis of 12 articles concerning the current methods of treatment for postherpetic neuralgia including conservative treatment, spinal cord stimulation, and novel neuromodulation strategies. Available information on the pathophysiology of PHN and the effect or stimulation on its course, together with a number of technical nuances concerning various types of neurostimulation are also elucidated in this article. A number of alternative invasive treatments of PHN are also discussed. Conclusions: Spinal cord stimulation is an established treatment option for patients with pharmacologically resistant PHN. High-frequency stimulation, burst stimulation, and dorsal root ganglion stimulation are promising options in the management of PHN due to the absence of paresthesias which can be painful for patients with PHN. But more research is still required to recommend the widespread use of these new methods.

Peripheral Nerve Stimulation on the Brachial Plexus With Ultrasound-guided Percutaneous Technique: A Case Series.

INTRODUCTION: The aim of this case series was to assess the safety and effectiveness of peripheral nerve stimulation (PNS) of the brachial plexus performed using a low invasive percutaneous approach with ultrasound guide. MATERIALS AND METHODS: Patients affected by neuropathic pain with a documented brachial plexus partial avulsion were included in this observational study. A totally implantable PNS system specifically designed for peripheral placement (Neurimpulse, Padua, Italy) was implanted and followed for 18 months, recording the level of pain (Numeric Rating Scale [NRS]), therapy satisfaction (Patient Global Impression of Improvement), quality of life (Short Form Health Survey questionnaire), and change in drug consumption and work status. Descriptive statistic (mean and SD) was used to compare pre- and postimplantation differences. RESULTS: A total of 18 patients were included in the observational study; 16 of them proceeded with the permanent implantation. System infection (N = 1) and lead migrations (N = 2) were recorded during a follow-up mean of 14.8 ± 5.4 months. The average NRS reduction at 18 months was 41%. Average quality-of-life physical and mental indexes increased by 14% and 32%, respectively. Drug intake was stopped in 22% and reduced in 56% of the patients. CONCLUSIONS: PNS systems of the brachial plexus implanted with percutaneous approach appear to be safe and effective in a follow-up period of 18 months. Longer and larger studies are needed to confirm and extend these outcomes.

Psychogenic (nociplastic) pain: Current state of diagnosis, treatment options, and potentials of neurosurgical management.

Classification of pain syndromes is quite multifaceted. However, pathogenetic classification by which chronic pain syndromes are usually divided into nociceptive, neuropathic and psychogenic, is crucial in choosing treatment tactics. In modern classifications, psychogenic pain is distinguished from nociceptive pain (associated with direct tissue injury or damage) and neuropathic pain (in which lesion can only be determined morphologically). Mental disorders play a leading role in psychogenic pain. Here, somatic/neurological disorders, if any, are of no pathogenetic significance in the dynamics of pain syndrome. There are certain algorithms (though not yet fully developed) and even guidelines for diagnosing and treating nociceptive and neuropathic pain, whereas psychogenic pain has been and still is almost out of sight for a long time. Despite its considerable prevalence, attitude towards it is still uncertain. Until now, it has no single classification, nor any strategy with regards to diagnosis, treatment and prevention.

Spinal cord stimulation in chronic pain: technical advances.

Chronic severe pain results in a detrimental effect on the patient's quality of life. Such patients have to take a large number of medications, including opioids, often without satisfactory effect, sometimes leading to medication abuse and the pain worsening. Spinal cord stimulation (SCS) is one of the most effective technologies that, unlike other interventional pain treatment methods, achieves long-term results in patients suffering from chronic neuropathic pain. The first described mode of SCS was a conventional tonic stimulation, but now the novel modalities (high-frequency and burst), techniques (dorsal root ganglia stimulations), and technical development (wireless and implantable pulse generator-free systems) of SCS are becoming more popular. The improvement of SCS systems, their miniaturization, and the appearance of new mechanisms for anchoring electrodes results in a significant reduction in the rate of complications and revision surgeries, and the appearance of new waves of stimulation allows not only to avoid the phenomenon of addiction, but also to improve the long-term results of chronic SCS. The purpose of this review is to describe the current condition of SCS and up-to-date technical advances.

Occipital Nerve Stimulation.

Although the first publications on clinical use of peripheral nerve stimulation for the treatment of chronic pain came out in the mid-1960s, it took 10 years before this approach was used to stimulate the occipital nerves. The future for occipital nerve stimulation is likely to bring new indications, devices, stimulation paradigms, and a decrease in invasiveness. As experience increases, one may expect that occipital nerve stimulation will eventually gain regulatory approval for more indications, most likely for occipital neuralgia, migraines and cluster headaches. This process may require additional studies, at least for approval from the US Food and Drug Administration.