Hemifacial Spasm

• The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye.
• The spasm may then gradually spread to involve the muscles of the lower face, which may cause the mouth to be pulled to one side.
• Eventually the spasms involve all of the muscles on one side of the face almost continuously.

• It is a rare condition.
• All races are affected equally.
• The disorder occurs in both men and women, although it is more frequent in middle-aged or elderly women.

• Vascular compression most commonly.¹ Most instances of hemifacial spasm (HFS) previously thought to be idiopathic, were probably caused by aberrant blood vessels compressing the facial nerve within the cerebellopontine angle.
• Idiopathic
• Facial nerve compression by mass or Paget's disease
• Meningitis
• Brainstem lesion such as stroke or multiple sclerosis plaque
• Secondary to trauma or Bell's palsy. 16% of Bell's palsy sufferers are left with hemifacial spasm²
• Secondary to otitis media with effusion³

The disorder presents in the fifth or sixth decade of life:

• Usually unilaterally, although bilateral involvement may occur rarely in severe cases.⁴
• HFS generally begins with brief clonic movements of the orbicularis oculi and spreads over years to other facial muscles. Closing of the eye and drawing up of the corner of the mouth are typical.
• Involuntary facial movement is the only symptom.
• Fatigue, anxiety or reading may precipitate the movements. Stressful life events are also associated with HFS.⁵
• Mild facial weakness and contraction appear without frank facial palsy.
• There is normal facial sensation.
• No other physical signs.

• Facial myokymia appears as vermicular (worm-like) twitching under the skin:⁴
  • Often with a wavelike spread.
  • This is distinguished from other abnormal facial movements by characteristic electromyogram.
  • Facial myokymia may occur with any pathological brainstem process.
  • Most cases are idiopathic and eventually resolve without treatment.
• Myoclonic movements may arise from lesions at the brain or brainstem level.
  • They are distinguished from HFS by the distribution of abnormal movements.
  • They tend to be more generalised, possibly bilateral.
• Oromandibular dystonia (OMD) refers to dystonia affecting the muscles of the lower face.
  • When OMD occurs with blepharospasm, it is called Meige syndrome.
  • Henry Meige first described it in 1910.
• Craniofacial tremor may occur in association with essential tremor, Parkinson's disease, thyroid dysfunction or electrolyte disturbance. It occurs rarely in isolation.
• Focal motor seizures must occasionally be distinguished from other facial movement disorders, particularly HFS. Post-ictal weakness and greater involvement of the lower face are its distinguishing features.
• Facial chorea usually occurs within of a systemic movement disorder e.g. Huntington disease.
• Spontaneous orofacial dyskinesia of the elderly, is observed primarily in the edentulous. It usually responds to proper fitting of dentures.
• Facial tics are brief, repetitive, co-ordinated, semi-purposeful movements of grouped facial and neck muscles:
  • Tics may occur physiologically or in association with diffuse encephalopathy.
  • Tardive dyskinesia - some medications (dopamine agonists) e.g. neuroleptics, anticonvulsants, caffeine, methylphenidate, antiparkinsonian agents are associated with producing tics.

At initial evaluation, consider HFS as a symptom, not a diagnosis:

• An abnormal neurological examination (except for the facial movements) should prompt the search for an underlying cause e.g. compressive lesion, tumour, stroke.
• Needle electromyogram (EMG) shows irregular, brief, high-frequency bursts (150-400 Hz) of motor unit potentials, which correlate with clinically observed facial movements.
• Magnetic resonance imaging is first line imaging study.
• Angiography and/or magnetic resonance angiography may be necessary before a vascular surgical procedure.

Pharmacological treatment

Medications may be used in early HFS:

• This is when spasms are mild and infrequent or in patients who decline BTX injection. Response to medication varies but can be satisfactory in early or mild cases.
• The most helpful agents are carbamazepine and benzodiazepines e.g. baclofen, clonazepam. Topiramate has also been used successfully.⁶
• Often, medication effects attenuate over time, necessitating more aggressive treatment.

In most patients, the treatment of choice is injection of Botulinum toxin type A (BOTOX®) under EMG guidance:^7,8

• This is a chemical denervation that safely treats most patients. Especially those with sustained contractions.
• It works by binding to receptor sites on the motor nerve terminals and after uptake inhibits release of acetylcholine, blocking transmission of impulses in neuromuscular tissue.
• The spasms usually relax 3-5 days after injection and the effect lasts approximately 6 months.
• Potential side effects of Botulinum injection are facial asymmetry, ptosis and facial weakness. These are usually transient.
• Most patients are very satisfied with their response to treatment.
• Patients should be warned that although Botulinum toxin stops the spasm, the sensation of spasm often persists.
• It is now far more commonly used than surgical intervention.⁹

Surgical treatment

• This usually consists of exploration of the posterior fossa to separate blood vessels from the VIIth cranial nerve.
• Microvascular decompression of the facial nerve can provide long-term symptom control in approximately 90% of patients with hemifacial spasm.¹⁰
• Post-operative complications have been noted in 35% patients e.g. facial palsy, hearing deficit and low cranial nerve palsies. The more immediate and severe the facial palsy was, the more permanent it remained.¹¹
• Myectomy is rarely ever required.

HFS is a progressive, but non-fatal illness. It usually responds favourably to treatment.