Depending on the cause, hemilic spasm can be primary or secondary. In 97% of cases of primary hemilic spasm, the cause is a nearby artery, which pulsates, periodically irritating the nerve, which causes spasm of facial muscles. Secondary hemilic spasm develops due to other diseases or conditions, such as:
- Bell's palsy or idiopathic (of unknown origin) facial paralysis
- brainstem lesions, such as multiple sclerosis, stroke
- arteriovenous anomalies, intracranial arterial aneurysms, arterio-venous fistula, angiomas
- infections of the mammary gland and ear (otitis media, cholesteatoma)
- parotid tumors
- Arnold-Chiari anomaly and other structural anomalies of the posterior cranial fossa.