Description of the condition

Facial paralysis (FP) is a common clinical disease caused by damage to the lower motor neurons of the facial nerve, the clinical symptoms mainly include forehead lines and nasolabial sulcus on the affected side into shallowness or disappearance, additional symptoms include incomplete eyelid closure, taste impairment, ear pain, facial numbness and so on [1, 2]. According to reports, the incidence is described as 11.5 to 40.2 per 100000 people a year [3]. Affected patients may experience facial asymmetries that last for weeks to months. One study indicated that only 71% of patients with FP were able to regain normal facial function with treatment, while 29% of patients still had hemifacial weakness [4]. Usually, it was named intractable facial paralysis (IFP) when the clinical course of FP more than 2 months [5]. IFP is one of the stubborn clinical diseases, which has the characteristics of long course and difficult treatment. From the perspective of social psychology, IFP will produce anxiety and depression, which will seriously affect patients’ life and work [6]. Therefore, to improve the symptoms and life quality of patients, appropriate treatment interventions are needed in the treatment.

Description and function of intervention

To date, there is a wide variety of salvage therapeutical approaches, including antiviral drugs, corticosteroids, vitamin B12, acupuncture or dry needling, botulinum toxin, and rehabilitation [7, 8]. In the last years, a high interest has been growing regarding the use of instrumental physical therapies, such as lower-level laser therapy and electrical stimulation, in improving facial muscle function in patients with facial palsy [9].

Acupuncture is a characteristic therapy of traditional Chinese medicine. Clinically, there are two commonly used acupuncture interventions methods: manual acupuncture (MA) and electric acupuncture (EA). In China, many studies have claimed that these therapies have exact curative effect for IFP [10, 11]. EA is a treatment that combines MA and electric stimulation, which is more suitable for the treatment of IFP due to the stable and continuous stimulus quantity [12]. Studies have found that EA can regulate the relationship between endothelin secreted by vascular endothelial cells and microcirculation, thereby regulating vasoconstriction or hemodynamics, and ultimately treating IFP [13]. In addition, EA can also speed up the facial nerve’s conduction speed, promote the expression of nerve growth factor protein, brain-derived neurotrophic factor protein, BDNF mRNA and its protein in the facial nerve nucleus, thereby enhancing facial nutrition, it also plays a role in nerve regeneration and repair after injury by promoting the growth of facial nerve axons [14].

Why it is important to do this review

Many randomized controlled trials (RCTs) and meta-analyses show that EA treatment has specific benefits for IFP patients [15, 16]. Although the proportion of the application of acupuncture for IFP is also on the rise [16], there has not been a rigorously designed systematic review and meta-analysis to evaluate the curative effect and potential harm of IFP by EA. Therefore, we hope to conduct a systematic review and meta-analysis for the published literature, to explore the status of EA therapy in IFP treatment and the benefits or harm it may bring to patients. The results of this study could resolve the dispute over the benefits or harm of EA in patients with IFP, and to provide concluding evidence for clinical practice.

Study registration

This study has been registered on the International Prospective Register of Systematic Reviews in PROSPERO (registration number is CRD42021278541), and will adhere to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols statement (PRISMA-P) [17]. The PRISMA-P checklist is shown in the S1 Appendix.

Inclusion and exclusion criteria

Data collection

Data synthesis

This study will be conducted with the use of the RevMan5.3 software. Dichotomous data were expressed as relative risk (RR) and continuous variables as standardized mean difference (SMD) with 95% confidence interval (CI). We will use I² to evaluate statistical heterogeneity between trials. The heterogeneity will be regarded as high (I² > 75%), moderate (I² between 50% and 75%), and low (I² < 50%). The random-effects model will be used for the merger analysis when the heterogeneity is moderate, and the fixed-effects model will be used when the heterogeneity is low. If the I² value is higher than 75%, the clinical or methodological heterogeneity will be explored through discussion with the review team. When the meta-analysis is not possible, a narrative analysis will be performed.

Subgroup analysis

If there are a large number of subgroup studies, a subgroup analysis is performed to determine heterogeneity. It may be includes the method of electric acupuncture frequency, the choice of acupoints, the duration and severity of the disease, etc.

Sensitivity analysis

We will conduct a sensitivity analysis to verify the robustness of the preliminary results by a revaluation of risk of bias, methodological quality, missing data or other possible factors. If there is a large difference, sensitivity analysis will be employed careful interpretation.

Publication bias

If more than 10 studies are included in the meta-analysis, we will evaluate the publication bias by EGGER regression test, and the evaluation will be presented in the form of funnel plots.

Grading the quality of evidence

We will evaluate the quality of evidence according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) [18]. It is divided into four grades: high, moderate, low, very low.

Ethics and dissemination

Ethical approval is not necessary because our study is not linked to individual patient data. In addition, the study findings will be published by peer reviewed journals.