Etiology of Hemifacial Spasm

The initial symptom of hemifacial spasm is eyelid twitching. In folk belief, “left-eye twitching signifies wealth, while right-eye twitching foretells misfortune,” so it is often overlooked. Over time, the condition may progress to hemifacial spasm, spreading to the corner of the mouth and, in severe cases, even involving the neck. So, what are the underlying causes of hemifacial spasm? Below, we provide an explanation.

Causes of Hemifacial Spasm

1. Cold Exposure

A major contributing factor to hemifacial spasm involves neurological dysfunction—for instance, invasion of wind-cold pathogens into facial meridians, leading to compression of these meridians, impaired tissue circulation, and consequent muscular laxity, ultimately resulting in hemifacial spasm. During deep sleep, skeletal muscles relax and pores dilate; if air conditioning temperature is set too low or if one sleeps directly under a fan or in a draft, cold exposure may trigger vasoconstriction of facial nerves—potentially progressing to hemifacial spasm.

2. Facial Neuritis

Some patients with hemifacial spasm have idiopathic facial nerve palsy. Following recovery from the initial paralysis, secondary hemifacial spasm may develop on the affected side. This may result from incomplete resolution of demyelination caused by facial neuritis—persistent partial demyelination renders facial nerve conduction susceptible to aberrant signal propagation. Alternatively, facial neuritis may involve brainstem nuclei, creating epileptiform foci that provoke paroxysmal facial muscle contractions.

3. Focal Epilepsy

Focal motor seizures may involve extensive regions—including the neck, upper limbs, or even an entire unilateral limb—and typically spread sequentially along the motor cortex’s somatotopic map. Isolated involvement of facial muscles is rare; however, electroencephalography (EEG) may reveal epileptiform discharges. If left untreated, hemifacial spasm may predispose individuals to other neurological complications; thus, timely diagnosis and management are essential.

The above outlines the primary etiologies of hemifacial spasm. We hope this information proves helpful.