Transcutaneous Auricular Vagus Nerve Stimulation on Post-Herpetic Neuralgia

Post-herpetic neuralgia (PHN) is a chronic neuropathic pain condition that persists for months or years following the resolution of herpes zoster (HZ) infection. It is characterized by persistent burning, stabbing, or shooting pain, often accompanied by allodynia and hyperalgesia, which can significantly impair quality of life. Current treatment options for PHN, including pharmacological therapies, often provide incomplete pain relief and are associated with side effects, creating a need for novel, non-invasive interventions.

This randomized controlled trial aims to evaluate the therapeutic efficacy of transcutaneous auricular vagus nerve stimulation (taVNS) as an adjunct to standard medical treatment for patients with PHN. The vagus nerve plays a crucial role in modulating pain perception and inflammatory processes, and its non-invasive stimulation through the auricular branch has shown promising analgesic effects in various chronic pain syndromes.

A total of 34 male and female participants, aged 35-65 years, diagnosed with PHN will be randomly allocated into two equal groups (17 participants per group). Group A (Experimental) will receive taVNS in addition to conventional pharmacological management, while Group B (Control) will receive conventional pharmacological management alone. The taVNS intervention will be delivered using the EV-906 device with TENS ear clips, applied according to the study protocol and safety standards (ISO 13485, FDA QSR, and CE compliance).

Pain intensity and quality will be assessed at baseline, after two weeks, and after four weeks using validated outcome measures: the Brief Pain Inventory (BPI) short form and the Short-form McGill Pain Questionnaire-2 (SF-MPQ-2). The primary outcome is the change in pain severity scores, and the secondary outcome is the change in pain interference with daily activities.

The results of this study will provide evidence regarding the clinical utility of taVNS as a safe, non-invasive, and effective adjunct therapy for PHN, with the potential to improve patient outcomes and quality of life

Inclusion criteria

Adults aged 35-65 years diagnosed with PHN. Persistent pain for at least 3 months after herpes zoster infection. Only patients who sign the informed consent form will be included.

Exclusion criteria

Contraindications to taVNS such as:

• pregnancy;
• active implants (e.g., pacemakers, cochlear implants) or brain shunts;
• previous neurological or psychiatric diagnoses;
• history of addiction or substance abuse;
• history of trauma and/or brain surgery;
• cardiac disease;
• acute or chronic use of medications and/or illicit drugs;
• susceptibility to headaches and seizures. Severe cognitive impairment. Other chronic pain conditions.