Hemifacial spasm (HFS), also known as facial muscle twitching, presents as involuntary twitching of one side of the face. The twitching is paroxysmal and irregular, with varying degrees, and can be aggravated by fatigue, stress and voluntary movements. The onset of the twitching mostly starts from the orbicularis oculi muscle and then involves the whole face. The disease tends to occur after middle age and is commonly seen in women. Primary facial spasm mostly occurs after middle age and is more common in women. At the beginning of the disease, it is mostly paroxysmal involuntary twitching of the orbicularis oculi muscle on one side, which gradually and slowly expands to other facial muscles on one side of the face. The degree of twitching varies, and it is paroxysmal, rapid and irregular twitching. The initial twitch is light and lasts for only a few seconds, and then gradually grows for several minutes or longer, while the interval is gradually shortened and the twitches gradually increase in frequency. In severe cases, it is tonic, causing the ipsilateral eye to be unable to open, the corner of the mouth to be skewed to the ipsilateral side and unable to speak, often aggravated by fatigue, mental tension and voluntary movement, but it cannot imitate or control its seizure by itself. A convulsion can last from a few seconds to more than 10 minutes, with intervals of variable length. The patient feels distracted and unable to work or study, which seriously affects the patient’s physical and mental health. Most of the convulsions stop after sleep. Bilateral lateral muscle spasms are rarely seen. If there is, it is often started on both sides successively, and most of the convulsions stop on one side, then the other side has another attack, and the convulsions are light on one side and light on the other side, and the simultaneous onset and convulsions on both sides have not been reported. A few patients have mild facial pain during convulsions, and some cases may have ipsilateral pain. Etiology of the disease Vascular factors It is known that approximately 80% to 90% of HFS is due to vascular compression in the brainstem region of the facial nerve. Clinical data indicate that the anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) are the main vascular factors causing HFS, while the superior cerebellar artery (SCA) is less common. In the past, HFS was thought to be caused by pulsatile compression of the artery, but in recent years, studies have shown that a single venous vessel can also cause HFS when it compresses the facial nerve, and both of these vessels can compress the facial nerve at the same time, which affects the prognosis of HFS surgery to some extent.