Electroacupuncture With Two Pulse Patterns for Bell's Palsy Using Surface Electromyography Evaluation

This clinical trial is designed to evaluate the therapeutic effects of two EA parameter settings for Bell's palsy and to investigate the electromyographic characteristics of the disease. The main questions it aims to answer are: * Can continuous pulse pattern and intermittent pulse pattern of EA improve the symptoms of Bell's palsy? * Do continuous pulse pattern and intermittent pulse pattern of EA impact the electromyographic characteristics of facial muscles in patients with Bell's palsy? The researchers will evaluate the effects of continuous pulse pattern and intermittent pulse pattern in treating Bell's palsy by using surface electromyography as an objective indicator of assessment. The trial lasts for 4 weeks and the treatment period lasts for 4 weeks. Participants will: * receive sham EA, EA with a continuous pulse pattern or EA with an intermittent pulse pattern for 3 times weekly for 4 weeks (12 sessions in total). * receive assessment of symptom severity and social functioning on Day 0, end of week 2, end of week 4.

Inclusion Criteria: * diagnosed clinically as BP, with imaging evidence (brain CT and/or MRI) excluding central nervous system lesions associated with facial palsy * the disease duration of 21 days to 6 months, inclusive * age 18-70 years * voluntary participation and provision of written informed consent Exclusion Criteria: * facial paralysis caused by other diseases * have previous history of facial paralysis * present with facial muscle spasm, synkinesis or contracture * diagnosed as Ramsey-Hunt Syndrome * history of surgery on face * with cardiac pacemakers implanted * pregnant or lactating patients * along with other severe uncontrolled diseases, recognition disorder, aphasia or mental disorders * present with bilateral facial paralysis