Transcranial Direct Current Stimulation Is Safe and Relieves Post-Herpetic Neuralgia in Patient with Dermatomyositis: A Case Report

To the best of our knowledge, this is the first report in the literature showing the efficacy of transcranial direct current stimulation (tDCS) in treating refractory post-herpetic neuralgia in a patient with dermatomyositis. In addition, our results showed that tDCS sessions are safe and do not lead to disease relapse. Therefore, despite the limitations of being a case report, this study provides encouraging results that need to be widely explored in studies with a representative number of patients and with an appropriate design for patients with this systemic rheumatic autoimmune disease.


Introduction
Transcranial direct current electrical stimulation (tDCS) is a non-invasive brain stimulation technique that has been widely studied for the treatment of chronic pain, including neuropathic pain [1] [2] [3] [4]. In general, this technique is well tolerated, safe, without significant adverse effects, and is capable of inducing neuroplasticity and modulating cortical excitability to modulate the pain [1] [2] [3] [4].
Dermatomyositis is a rare systemic autoimmune myopathy characterized by symmetrical and predominantly proximal muscle weakness in the limbs and classical cutaneous lesions [5]. nique is also safe in these autoimmune diseases, without disease relapse [6].
To the best of our knowledge, no studies have assessed the safety and potential effects of tDCS in treating refractory post-herpetic neuralgia in a patient with dermatomyositis.

Case Report
The patient was a 49-year-old white woman with definite dermatomyositis (European League against Rheumatism/American College of Rheumatology classification criteria [5]) since 2016. The patient was promptly treated with methylprednisolone and intravenous human immunoglobulin pulse therapies multiple times, in addition to several immunosuppressive drugs (azathioprine, methotrexate, and/or leflunomide), and immunobiological therapy (rituximab and abatacept) in our tertiary center. The disease was controlled within three weeks with tofacitinib (5 mg every 12 h, orally). In 2019, she presented with a herpes zoster infection (5 th right thoracic dermatome) that was treated orally with acyclovir, and tofacitinib was temporarily suspended. Owing to new cutaneous disease relapse, tofacitinib was reintroduced immediately, with sustained remission thereafter. However, the patient had refractory post-herpetic neuralgia, despite the use of gabapentin, duloxetine, and pregabalin. Concerning post-herpetic neuralgia, we found improvement in pain and general health in the SF-36 (Figure 1(a)) and a significant reduction in sensory,   (Figure 1(b)), based on the McGill questionnaire. Moreover, a reduction in pain and its variants was observed on the basis of the PQAS questionnaire (Figure 1(c)). Finally, the patient reported no differences in relation to her physical activity, and she performed no structured exercise program during the post-intervention period.

Discussion
Our results showed that tDCS sessions were safe and did not lead to disease relapses. The patient also experienced notable pain reduction, as assessed by multidimensional pain questionnaires and, in particular, a significant improvement in post-herpetic neuralgia.
Studies have demonstrated the impact of pain on the quality of life of patients with dermatomyositis. tDCS is commonly used for pain management in patients with fibromyalgia [12] and neuropathic pain [1] [2] [3]. Currently, few studies have assessed tDCS in dermatomyositis [6] [7]. In general, tDCS appears to be safe, without disease relapse [6] [7].
To corroborate these studies, our data showed that tDCS was safe and effective in the control of pain in refractory post-herpetic neuralgia in a patient with dermatomyositis. In addition, we included physical training simultaneously with tDCS. The aim was to increase the integration between the central and peripheral stimuli, increase the connectivity of the neural network, and improve the patient's symptoms. In addition, as shown by the results, there was significant improvement in the patient's quality of life.
Despite the limitations of being a case report, this study provides encouraging results that need to be widely explored in studies with a representative number of patients and with an appropriate design for patients with dermatomyositis.
In conclusion, this study showed that tDCS is safe and effective on post-herpetic neuralgia in a patient with dermatomyositis.

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.