Repetitive Transcranial Magnetic Stimulation at Different Frequencies for Postherpetic Neuralgia: A Double-Blind, Sham-Controlled, Randomized Trial

Abstract

Background: Repetitive transcranial magnetic stimulation (rTMS) at 5 Hz and 10 Hz is effective in improving pain, sleep quality, and anxiety among patients with postherpetic neuralgia (PHN). But it has not been reported which frequency is more effective and which frequency is safer. Objectives: This study aimed to observe the efficacy and safety of rTMS at different high frequencies (5 Hz, 10 Hz) for PHN. Study Design: The design of the study was a prospective randomized, controlled clinical trial. Setting: The research was conducted within a department of pain management at a university hospital in China. Methods: Sixty patients with PHN who were treated at the Department of Pain Management at Xuanwu Hospital of Capital Medical University were recruited. Using a computer-created number list, the cases were equally divided into 3 groups (n = 20), namely, the sham rTMS group, 5-Hz rTMS group, and 10-Hz rTMS group. The sham rTMS group received sham stimulation, and the other 2 groups received high-frequency (5-Hz and 10-Hz) rTMS, respectively. The primary motor cortex (M1) on the healthy side was stimulated with an intensity of 80% transcranial magnetic stimulation (RMT). For the 5-Hz rTMS group, each stimulation session consisted of a series of 300 one-second pulses with a frequency of 5 Hz and an interval of 2.5 seconds between each train, giving a total of 1500 pulses per session. For the 10-Hz rTMS group, each stimulation session consisted of a series of 300 0.5-second pulses with a frequency of 10 Hz and an interval of 3 seconds between each train, giving a total of 1500 pulses per session; the total time of stimulations was 17.5 minutes. rTMS was performed once daily for 10 days. The 3 groups received conventional medication therapy. Baseline data (gender, age, course of disease, affected side) were recorded in the 3 groups. At different time points (before treatment, T0; during treatment, T1-T10; 1 month after treatment, T11; and 3 months after treatment, T12), the patients were evaluated on the following scales: Visual Analog Scale (VAS), short-form McGill Pain Questionnaire (SF-MPQ), Quality of Life (QOL) scale, sleep quality (SQ) scale, Self-Rating Depression Scale (SDS), Patient Global Impression of Change (PGIC), and incidence of adverse events. Results: Compared with the sham rTMS group, there was a significant reduction in VAS scores in the 5-Hz rTMS group and 10-Hz rTMS group at T2-T12 (P < .05). VAS scores in the 10-Hz rTMS group at T7-T12 were significantly lower compared with the 5-Hz rTMS group (P < .05). The average VAS reduction was significantly different between the 5-Hz and 10-Hz rTMS groups; 28.3% (95% confidence interval [CI],19.48%-49.35%), compared to 39.89% (95% CI, 22.47%- 58.64%), with (F = 5.289, P = .022). The 3 groups did not differ significantly in general SF-MPQ, QOL, SQ, SDS, and PGIC scores. However, the QQL, SQ, and PGIC scores of the 5-Hz rTMS group and the 10-HZ rTMS group at T12 were significantly higher than that of the sham rTMS group. Limitations: The study’s follow-up period was limited to 3 months. Conclusions: rTMS at either frequency, 5 Hz or 10 Hz, relieved PHN and improved the patients’ quality of life. rTMS at 10 Hz was superior to rTMS at 5 Hz in terms of pain relief, quality of life, and improvement in sleep quality, though the latter had higher safety. rTMS at either 5 Hz or 10 Hz can be used as an adjuvant therapy for PHN. Key words: Repetitive transcranial magnetic stimulation, postherpetic neuralgia, pain evaluation