Hemifacial Spasm (HFS), also known as facial muscle twitching, occurs mostly after middle age and is commonly seen in women. It manifests as involuntary throbbing of one side of the facial muscles. The throbbing is paroxysmal and varies in severity, and can be aggravated by fatigue, stress and voluntary movements. The onset mostly starts from the muscles around the eyes and then expands to the muscles at the corners of the mouth. If the facial muscles are repeatedly throbbing on both sides, it is often not facial muscle spasm and other causes need to be looked for. Facial myoclonus and facial palsy are two different diseases, and the clinical manifestations and causes of both diseases are different. Facial myoclonus can be simply understood as unilateral facial muscle overexcitability, while facial palsy is unilateral facial muscle hypoexcitability or inability to excite, manifested as motor dysfunction of facial expression muscle groups, unable to complete such actions as raising eyebrows, closing eyes, puffing and blowing, etc. It can occur at all ages.