Bell palsy (BP) is the most common cause of acute facial palsy, which leads to functional and esthetic disturbances for patients and results in a lowered quality of life. Electroacupuncture (EA) received attention as an alternative and complementary treatment method. The low-frequency continuous wave EA and the intermittent wave EA have been used in the management of BP. The aim of this study is to compare the efficacy and safety of these two electroacupuncture waveforms for different severity groups of BP.

The investigators will recruit 60 patients with BP whose ENoG test indicate a mild to moderate facial nerve damage, as indicated by the ratio of amplitude of the compound muscle action potential (CMAP) of the affected side comparing to normal side is 20% or higher. And the investigators will recruit 60 patients with BP whose ENoG test indicate a severe damage, as indicated by the ratio of amplitude of the CMAP of the affected side comparing to normal side is less than 20%. Both the two types of patients will be randomly divided into either the low-frequency continuous wave group, or the intermittent wave group, and receive 4 weeks treatment. The primary outcomes is change from baseline score of the Facial Nerve Grading System 2.0. The secondary outcomes are change from baseline score of the Sunnybrook grading scale, and change from baseline value of the amplitude of the CMAP of the affected side in the ENoG test.

Inclusion Criteria:

1. Diagnosed as BP by specialist.
2. The score of FNGS 2.0 ≥ 15 at the day 21 since the onset of BP.
3. 18 years ≤ age ≤ 65 years.
4. Received prednisolone within 72 hours since initial symptoms of BP, the prednisolone dose used was 60 mg per day for 5 days and then reduced by 10 mg per day.
5. Signed informed consent and volunteered to participate in this study.

Exclusion Criteria:

1. Facial palsy caused by other diseases or injury.
2. Ramsey-Hunt syndrome.
3. Bilateral facial palsy.
4. History of previous facial palsy.
5. Manifesting facial spasm, facial synkinesis or contracture at day 21 since the onset of BP.
6. History of surgery on face.
7. Combined with uncontrolled diabetes mellitus, uncontrolled hypertension, serious heart, liver, kidney damage or cognitive impairment, aphasia, mental disorders.
8. Installing pacemakers.
9. Pregnant and lactating patients.