Hemifacial spasm (HFS) is a peripherally-induced movement disorder characterized by the involuntary, unilateral, intermittent, irregular, tonic or clonic contractions of muscles innervated by the ipsilateral facial nerve.
● intermittent unilateral painless contractions of facial muscles
● typically caused by compression of VII nerve by AICA
● along with palatal myoclonus: the only movement disorder that persists in sleep
● responds well to microvascular decompression, but risk of hearing loss is ≈ 20%
Hemifacial spasm (HFS) is a condition of intermittent, painless, involuntary, spasmodic contractions of muscles innervated by the facial nerve in one side of the face only. May be limited to the upper or lower half of the face only, and excess lacrimation may be present. HFS usually begins with rare contractions of the orbicularis oculi, and slowly progresses to involve the entire half of the face and increases in frequency until the ability to see out of the affected eye is impaired.
HFS is more common in women, is seen more often on the left, and usually presents after the teenage years. Auditory function testing reveals abnormal acoustic middle ear reflex in almost half of patients, indicating some degree of VIII compromise.
Meige’s syndrome: hemifacial spasm with oral movements.
▶ Note. HFS and palatal myoclonus are the only involuntary movement disorders that persist during sleep.
The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons.
This disorder occurs in both men and women, although it affects middle-aged or elderly women more frequently.
Hemifacial spasm is much more common in some Asian populations.
The purpose of a study was to characterize the natural history and clinical outcome in patients with HFS.
The initial visits of all 2,155 patients and the diagnosis of HFS took place between 2001 and 2010. In 1,775 of the patients, compressing vessels were identified on magnetic resonance imaging. Of these, we excluded 1,469 patients (82.8%) who received microvascular decompression, 101 (5.7%) who continued to visit the clinic for botulinum toxin injections, and 9 (0.5%) who died or suffered from other diseases. Ninety-two (5.2%) of the patients were lost to follow-up; the remaining 104 were followed up for 5-42 years (mean 12 years) after the onset of the symptoms of HFS.
The condition was aggravated in 11 (10.6%) of the 104 patients and stationary in 40 (38.5%) for 6-42 years (mean 13 years). Ten (9.6%) improved partially for 7-18 years (mean 11 years). Forty-three (41.3%) were in remission for between 2 months and 23 years (mean 6.4 years) after onset and required no further treatment for 5 months to 13 years (mean 5.7 years) 1).
Tu et al. used resting state functional magnetic resonance imaging with regional homogeneity (ReHo) analysis to investigate changes in spontaneous brain activity of patients with hemifacial spasm HFS and to determine the relationship of these functional changes with clinical features. Thirty patients with HFS and 33 age-, sex-, and education-matched healthy controls were included in this study. Compared with controls, HFS patients had significantly decreased ReHo values in left middle frontal gyrus (MFG), left medial cingulate cortex (MCC), left lingual gyrus, right superior temporal gyrus (STG) and right precuneus; and increased ReHo values in left precentral gyrus, anterior cingulate cortex (ACC), right brainstem, and right cerebellum. Furthermore, the mean ReHo value in brainstem showed a positive correlation with the spasm severity (r = 0.404, p = 0.027), and the mean ReHo value in MFG was inversely related with spasm severity in HFS group (r = -0.398, p = 0.028). This study reveals that HFS is associated with abnormal spontaneous brain activity in brain regions most involved in motor control and blinking movement. The disturbances of spontaneous brain activity reflected by ReHo measurements may provide insights into the neurological pathophysiology of HFS. 2).
This disease takes two forms: typical and atypical. In typical form, the twitching usually starts in the lower eyelid in orbicularis oculi muscle. As time progresses, it spreads to the whole lid, then to the orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area.
The reverse process of twitching occurs in atypical hemifacial spasm; twitching starts in orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area in the lower face, then progresses up to the orbicularis oculi muscle in the eyelid as time progresses.
The most common form is the typical form, and atypical form is only seen in about 2–3% of patients with hemifacial spasm.
In typical cases of HFS, the diagnostic work-up is negative.
Most patients should have MRI of the posterior fossa (CT scan is less sensitive here) to R/O tumors or AVMs.
Vertebral angiography is usually not performed if imaging is normal. The neurovascular compression responsible for HFS usually cannot be identified on angiography.
Abnormal lateral spread response (LSR) is a typical finding in facial electromyography (EMG) in patients with hemifacial spasm (HFS). Although intraoperative monitoring of LSR has been widely used during microvascular decompression (MVD), the prognostic value of this monitoring is still debated.
Although intraoperative EMG monitoring during Microvascular decompression for hemifacial spasm was beneficial for identifying the offending vessel and suggesting the most appropriate surgical end point, loss of LSR did not always correlate with long-term HFS treatment outcome. Because the HFS cure rate improved over time, revision might be considered for persistent LSR when follow-up has been performed for more than 1 year and the spasm remains despite adequate decompression 3).