Hemifacial spasms (HFS) are irregular and involuntary muscle spasms on one side of the face. The contractions may be tonic (one intense contraction) or clonic (repeated rhythmic contractions). HFS commonly begins from the age of 40 onwards and is more common in women than in men.

Causes

The most common cause of HFS is a compression of the blood vessels around the root of the facial nerve, which irritates the nerve and causes muscles in the face to contract involuntarily. Other causes include cholesteatoma (a growth in the middle ear), acoustic neuroma (a growth on the nerve connecting the ear to the brain), facial nerve neuroma (a growth on the facial nerve), and adenoid cystic tumors (a growth at the back of the nasal cavity). When diagnosing HFS, it is first necessary to exclude other facial movement disorders, such as blepharospasm (eyelid twitches), facial myokimia (shivering), oromandibular dystonia (contractions of the mouth, jaw and tongue muscles), facial tics, and post Bell’s palsy synkinesis (quivering). 

Treatment 

• Medication 
• Botulinum toxin (BoNT): Resulting in improvements in between 75% and 100% of patients, BoNT injections have been reported to improve patients’ quality of life. The benefits of Botulinum toxin serotype A (BoNT/A) appear within 1-3 days after treatment, although they can take up to 2-3 weeks in some patients.  In most cases, however, the effects peak within 2 weeks of treatment and are maintained for a further 6-8 weeks. Repeated injections are usually required for 3-6 months. 
• Surgical treatment: The most likely form of surgery is microvascular decompression, which requires an incision to be made behind the ear on the affected side.