OnabotulinumtoxinA in refractory postherpetic neuralgia: a case report

Background Postherpetic neuralgia (PHN) is a chronic neuropathic pain condition following herpes zoster, occurring particularly in elderly or immunosuppressed individuals. It is often difficult to treat and may significantly impair quality of life. Case Report We report the single-blinded treatment of refractory thoracic PHN with onabotulinumtoxinA (BoNT/A). A total of 200 IU was injected into the affected area across 40 injection points (5 IU per site), while one corner of the affected area was injected with saline as an intra-individual blinded comparator. A remaining painful area was treated with a further 100 IU BoNT/A 24 days later. Results Pain intensity decreased progressively from severe pain with attacks up to 10/10 on the numeric rating scale (NRS) to 5/10 in the BoNT/A-treated area, while the saline-injected area showed no noteworthy improvement. Following the second BoNT/A injection, the remaining painful area reduced further to a coin-sized spot. The clinical effect lasted approximately 3 months and repeated treatment stabilised substantial pain reduction for almost 1 year. Conclusion BoNT/A may be an effective treatment option in selected patients with refractory focal PHN, particularly when established first- and second-line treatments are ineffective, poorly tolerated or contraindicated. Further controlled studies are required to clarify efficacy, duration of benefit and repeat-treatment strategies.