Etiology

• Vascular compression of the facial nerve at the brainstem
• Less common: pontine glioma or other mass compressing facial nerve
• Autosomal dominant pattern of inheritance apparent in three males in successive generations who developed left-sided acquired hemifacial spam, with a pontine vertebral anomaly demonstrated on MRI in the proband (Carter, Arch Ophthalmol 1990).
• Can present in infancy (Fleuler, Arch Ophthalmol 1990).
• A 3-year-old was found to have occlusion of the straight sinus and vein of Galen
• Onset at age 10 months was associated with a glioma of the superior and middle cerebellar peduncles in one patient
• Pontine tumor found in another infant
• Parotid gland tumor can also be the cause (Behbehani, OPRS 2009)

Epidemiology

• Usually occurs in older patients, usually as a result of dolichoectatic basilar artery
• Suspect tumor in young patient with hemifacial spasm

History

• Uncontrolled spasm on one side of the face, present for a variable period of time

Clinical features

• Begins with unilateral fasciculations of the orbicularis oculi muscle and later involves the lower facial muscles
• Intermittent synchronous gross contractures of the unilateral face
• Spasms continue during sleep.
• Rarely bilateral, but spasms are not synchronous

Testing

• The diagnosis is made based on clinical findings.
• In a survey of 1,676 patients with hemifacial spasm, 9 tumors were identified as the cause for an incidence of 0.54% of patients (Sprik, Ophthalmology 1987).
• Magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA) can demonstrate compression of the facial nerve at the brainstem, from vascular ectasia, pontine glioma, or posterior fossa masses (Port, OPRS 2002)
• Scan might be appropriate in the initial evaluation of new onset hemifacial spasm, or when intervention is being contemplated for vascular ectasia.

Not known

Benign essential blepharospasm: The hallmark is that it affects both eyes.

Meige syndrome: When blepharospasm affects the lower face, it can be difficult to differentiate from bilateral blepharospasm.

Aberrant regeneration following facial nerve palsy, with a history of Bell palsy or trauma, creates a clinical condition that is similar to hemifacial spasm and is treated similarly.

Parkinson disease can be associated with unilateral apraxia of lid opening, which can appear similar to hemifacial spasm.

Orbicularis myokymia affects only the eye, is usually self-limiting, and is believed to be caused by a number of factors including

• Caffeine
• Stress
• Physical exertion
• Fatigue

Corneal irritation can cause voluntary and/or involuntary contraction of the orbicularis muscle, which can rarely be unilateral and can rarely include the lower face.

Facial tics can be unilateral and can mimic hemifacial spasm but do not respond as well to botulinum injections.

Natural history

• Interestingly, although it has a vascular etiology, it does not tend to get worse or become more resistant to treatment with time.
• Rarely resolves spontaneously; patients typically require the same or similar levels of treatment for a prolonged period of time.

Medical therapy

• Botulinum toxin is the hallmark of treatment.
• The optimal location of injections can be different for hemifacial spasm compared with blepharospasm.
• Injection above the brow and in the lower lid had equal effect to injection directly in the upper lid, with less eye irritation (Price, Ophthalmology 1997).
• The location should be individualized and maximized for each patient but alternate treatment patterns should be considered.
• The interval for treatment of hemifacial spasm is usually longer than for blepharospasm
• Repeat injections are often at intervals of 4 to 6 months, or even up to a year, while more regular injections every 3 months or shorter are typical for blepharospasm.
• Treatment of the lower face can cause symptoms of facial weakness, which can be more troubling than the spasms.
• Limited treatment with botulinum toxin in the lower face can bring some relief and is individualized to the patient.
• No oral medications with proven efficacy for hemifacial spasm

Radiation

• None

Surgery

• Neurosurgical decompression of the facial nerve at the brainstem is helpful in some patients
• The risk reward ratio of craniotomy for relief of facial spasms is not favorable
• Given the effectiveness of alternative treatments, neurosurgical intervention is rarely recommended.
• In a series of 194 patients, results of decompression were defined as "excellent" in 79.9%, "good" in 4.6%, and "bad" in 15.5%. Paresis occurred in 34 patients, hearing loss developed in 29 patients, and tinnitus ensued in four patients.  (Soriano-Baron, Surg Neurol Int 2015).
• Orbicularis oculi hemi-myectomy is another surgical alternative, for patients who are not responding adequately to botulinum injections.
• Correction of concurrent eyelid ptosis can improve the primary complaint, which is difficulty keeping the eye open.
• Correction of ptosis can exacerbate otherwise subclinical or well managed dry eye symptoms

Other management considerations

• Facial fillers can be used as adjunctive treatment in the lower face bringing support that buffers the effect of muscle contraction (Borodic, OPRS 2013).
• 18 patients were injected with 1–2 ml of hyaluronic acid filler over the lower cheek, nasolabial fold, marionette region and chin.
• Repeat injection was needed at 3-8 months, depending on duration of effect and the filler material used.
• Aggressive treatment of dry eye symptoms with artificial tears and punctal plugs is an important adjunct for hemifacial spasm.
• Botulinum injections can exacerbate dry eye symptoms.
• Dry eye can be exacerbating the spasms.

Common treatment responses, follow-up strategies

• Once the interval of treatment is established these patients typically do well with regular botulinum injections. (Chundury, OPRS, 2015)
• Regular reassessment is appropriate to determine if additional or alternative treatment is indicated.

Botulinum toxin injections can cause

• Ptosis from injection close to the center of the upper lid.
• Diplopia from tracking of the toxin posteriorly, especially when given near the origin of the inferior oblique. These can occur randomly, or some patients can be more prone which requires an individualized treatment plan.
• When weakness of a muscle occurs after injection reassure the patient that it will diminish and resolve as the medication effect subsides
• Ectropion after botulinum injection might be an indication for horizontal lid tightening.
• Lagophthalmos and worsening of dry eye symptoms might limit the effectiveness of botulinum injections.
• If cheek or perioral muscles are injected, transient oral incompetence and difficulty speaking might occur.
• Treatment of the lower face requires far more individualized treatment than the upper face

Unilateral orbicularis myectomy:

• Transient lymphedema and forehead anesthesia were the most common post-operative sequelae after unilateral myectomy in 21 patients (Garland, Ophthalmology 1987)
• In that study, 75% of patients enjoyed improvement in lower face spasms, an unexpected benefit after orbicular myectomy.

Surgical decompression — when advising patients on the alternative of surgical treatment of the facial nerve, consider the following:

• Improvement might be incomplete, with persistent symptoms still requiring botulinum injections.
• Neuropathy as a complication of the surgery can include hearing loss on the operative side and facial nerve weakness
• More significant but rare complications of manipulation of the vasculature include brainstem infarction or other effects of ischemia

Persistent compromise of visual function is the main concern; spasms can cause significant, if not complete, closure of the eye.

Social difficulties, particularly with the lower face, can cause chronic concerns with little relief from treatment.

Gordon described two cases of hemifacial spasm in 1947, one idiopathic and the other after facial nerve trauma with aberrant regeneration, and wrote "it would seem than when there is a true, uncontrollable spasm of one half of the face the term 'hemifacial spasm' is indicated" (Gordon, Arch Ophthalmol 1947).

Savino et al. described treatment of 15 hemifacial spasm patients with botulinum A toxin in 1985. All patients experienced relief, with relief lasting an average of 12.2 weeks (Savino, Arch Ophthalmol 1985).

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