Interventional Treatments for Postherpetic Neuralgia: A Systematic Review.

Background: Postherpetic neuralgia, a persistent pain condition often characterized by allodynia and hyperalgesia, is a deleterious consequence experienced by patients after an acute herpes zoster vesicular eruption has healed. The pain associated with postherpetic neuralgia can severely affect a patient's quality of life, quality of sleep, and ability to participate in activities of daily living. Currently, first-line treatments for this condition include the administration of medication therapies such as tricyclic antidepressants, pregabalin, gabapentin, and lidocaine patches, followed by the application of tramadol and capsaicin creams and patches as second- or third-line therapies. As not all patients respond to such conservative options, however, interventional therapies are valuable for those who continue to experience pain.

Objective: This review focuses on interventional therapies that have been subjected to randomized controlled trials for the treatment of postherpetic neuralgia, including transcutaneous electrical nerve stimulation; local botulinum toxin A, cobalamin, and triamcinolone injection; intrathecal methylprednisolone and midazolam injection; stellate ganglion block; dorsal root ganglion destruction; and pulsed radiofrequency therapy.

Study Design: Systematic review.

Setting: Hospital department in Taiwan.

Methods: Search of PubMed database for all randomized controlled trials regarding postherpetic neuralgia that were published before the end of May 2017.

Results: The current evidence is insufficient for determining the single best interventional treatment. Considering invasiveness, price, and safety, the subcutaneous injection of botulinum toxin A or triamcinolone, transcutaneous electrical nerve stimulation, peripheral nerve stimulation, and stellate ganglion block are recommended first, followed by paravertebral block and pulsed radiofrequency. If severe pain persists, spinal cord stimulation could be considered. Given the destructiveness of dorsal root ganglion and adverse events of intrathecal methylprednisolone injection, these interventions should be carried out with great care and only following comprehensive discussion.

Limitations: Although few adverse effects were reported, these procedures are invasive, and a careful assessment of the risk-benefit ratio should be conducted prior to administration.

Conclusion: With the exception of intrathecal methylprednisolone injection for postherpetic neuralgia, the evidence for most interventional procedures used to treat postherpetic neuralgia is Level 2, according to "The Oxford Levels of Evidence 2". Therefore, these modalities have received only grade B recommendations. Despite the lack of a high level of evidence, spinal cord stimulation and peripheral nerve stimulation are possibly useful for the treatment of postherpetic neuralgia.

Key Words: Interventional treatment, postherpetic neuralgia, botulinum toxin, steroid, stellate ganglion block, peripheral nerve stimulation, paravertebral block, radiofrequency, spinal cord stimulation.