This condition results in the facial muscles on one side suddenly contracting, twitching or jerking (especially around the eye). It results from irritation of the facial nerve within the skull by a loop of a artery which has moved with aging into a position that causes the  pulsations to repeatedly strike the nerve. This eventually creates the situation where spontaneous electrical "sparks" originate and travel down the nerve to activate the muscles on one side of the face to contract. There is a good example posted on youtube at www.youtube.com/watch?v=SvOBThVDmy8. Always be careful though in regard to watching labeled movement disorders on the internet as studies have demonstrated that many actually don't represent what they are claimed to.

Treatment

Medication Options: Medications (Lorazepam, Diazepam, Carbamazepine, Baclofen) can be used to treat this condition  but the success rate is approximately 30%.

Botulinum Toxin Injections: Botulinum Toxin injections will control the spasms > 90% of the time. These provide only temporary relief and need to be repeated every 3-4 months to maintain control. Side effects are minimal usually, and  include dryness, tearing, or drooping of the eye lids. Double vision is rare. These side effects are temporary as they recover as the injection wears off. It may not be possible with this treatment to stop the cheek spasm without some transient facial drooping. Weakness affecting the face may gradually develop over the years, not due to the botulinum toxin injections but due to ongoing damage to the nerve by the pulsating blood vessel.

Surgical Options Information Link https://www.umanitoba.ca/centres/cranial_nerves/hemifacial_spasm/index.html

Surgery can cure this condition. The procedure involves a general  anesthetic. The neurosurgeon through a opening in the skull behind the ear (under microscopic guidance) moves the offending artery away from the facial nerve and/or places protective padding between the nerve and  artery. The success rate and complication rate depend on the expertise and experience of the surgeon. Success rates of  70 - >90% have been reported. Risks include deafness or loss of hearing on the side of the operation in up to  3%, and rarely permanent facial droop, or a stroke due to injuring a blood vessel during the surgery.