Hemifacial Spasm 

Updated: May 16, 2016
Author: Steven Gulevich, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE 

Overview

Background

First described by Gowers in 1884, hemifacial spasm represents a segmental myoclonus of muscles innervated by the facial nerve. The disorder presents in the fifth or sixth decade of life, almost always unilaterally, although bilateral involvement may occur rarely in severe cases. Hemifacial spasm generally begins with brief clonic movements of the orbicularis oculi and spreads over years to other facial muscles (corrugator, frontalis, orbicularis oris, platysma, zygomaticus).[1, 2]

Clonic movements progress to sustained tonic contractions of involved musculature. Chronic irritation of the facial nerve or nucleus, the near-universal cause of hemifacial spasm, may arise from numerous underlying conditions.

Facial musculature is subject to the same movement disorders as muscles of the limbs or trunk. Myoclonus, dystonia, and other movement disorders present with specific syndromes in the facial musculature. An understanding of the underlying mechanism leads to appropriate diagnostic evaluation and potential treatment.

The causes of hemifacial spasm include vascular compression, facial nerve compression by a mass, brainstem lesions such as stroke or multiple sclerosis plaques, and secondary causes such as trauma or Bell palsy.[3]

Although specific treatments are available for many craniofacial movement disorders, botulinum toxin (BTX) chemodenervation has proven useful in many of these disorders, supplanting surgery and medical therapy.

For patient education information, see the Procedures Center, as well as BOTOX® Injections.

Pathophysiology

Irritation of the facial nerve nucleus is believed to lead to hyperexcitability of the facial nerve nucleus, while irritation of the proximal nerve segment may cause ephaptic transmission within the facial nerve. Either mechanism explains the rhythmic involuntary myoclonic contractions observed in hemifacial spasm.[4]

Compressive lesions (eg, tumor, arteriovenous malformation, Paget disease) and noncompressive lesions (eg, stroke, multiple sclerosis plaque, basilar meningitis) may present as hemifacial spasm. Most instances of hemifacial spasm previously thought to be idiopathic were probably caused by aberrant blood vessels (eg, distal branches of the anterior inferior cerebellar artery or vertebral artery) compressing the facial nerve within the cerebellopontine angle.

Epidemiology

Hemifacial spasm affects all races equally. There is a slight female preponderance . Idiopathic hemifacial spasm typically begins in the fifth or sixth decade of life. Onset of hemifacial spasm in patients younger than 40 years is unusual and often heralds an underlying neurologic illness (eg, multiple sclerosis).

 

Presentation

History and Physical Examination

Involuntary facial movement is the only symptom of hemifacial spasm. Fatigue, anxiety, or reading may precipitate the movements. Spontaneous hemifacial spasm manifests with facial spasms that represent myoclonic jerks and are analogous to segmental myoclonus, which may affect other body regions. Postparalytic hemifacial spasm, following facial nerve trauma such as Bell palsy, manifests as facial synkinesis and contracture.

 

DDx

Diagnostic Considerations

Hemimasticatory spasm

Hemimasticatory spasm is analogous to hemifacial spasm and occurs with irritation to the motor trigeminal nerve. This rare condition is a segmental myoclonus and presents with unilateral involuntary contractions of the trigeminally innervated muscles of mastication (usually the masseter). Similar to hemifacial spasm, hemimasticatory spasm responds to treatment with medications and botulinum toxin. However, less evidence exists that exploratory surgery benefits patients with this condition.[5]

Myoclonic movements

Myoclonic movements affecting facial musculature also may arise from lesions at the brain or brainstem level. These are distinguished from hemifacial spasm by the distribution of abnormal movements (more generalized, possibly bilateral) and possibly by electrodiagnostic evaluation. Imaging studies may yield an underlying cause. Central myoclonus responds to anticonvulsant management.

Oromandibular dystonia

Oromandibular dystonia refers to dystonia affecting the lower facial musculature, predominantly the jaw, pharynx, and tongue. When oromandibular dystonia occurs in conjunction with blepharospasm, the disorder is termed Meige syndrome.

Jaw-opening forms of oromandibular dystonia indicate primary involvement of the digastric and lateral pterygoid. Jaw-closing oromandibular dystonia involves the masseter, temporalis, and medial pterygoid. Jaw deviation, indicating predominant involvement of the lateral pterygoid, is rare.

Botulinum toxin is the preferred treatment for oromandibular dystonia and is most effective in the jaw-closure type. Medications seldom yield acceptable results. When medications must be used, employ the same agents as for blepharospasm.[6] Because of the risk of aspiration, never inject botulinum toxin into the tongue.

Craniofacial tremor

Craniofacial tremor may occur in association with essential tremor, Parkinson disease, thyroid dysfunction, or electrolyte disturbance. It occurs rarely in isolation. Focal motor seizures must occasionally be distinguished from other facial movement disorders, particularly hemifacial spasm. Postictal weakness and greater involvement of the lower face are distinguishing features of focal motor seizures.

Facial chorea

Facial chorea occurs in the context of a systemic movement disorder (eg, Huntington disease, Sydenham chorea). Chorea is a random, flowing, nonpatterned set of movements. A related disorder, spontaneous orofacial dyskinesia of the elderly, is observed primarily in the edentulous. It usually responds to proper fitting of dentures.

Tics

Facial tics are brief, repetitive, coordinated, semipurposeful movements of grouped facial and neck muscles. Tics may occur physiologically or in association with diffuse encephalopathy. Some medications (ie, anticonvulsants, caffeine, methylphenidate, antiparkinsonian agents) are associated with producing tics. Single, repetitive, stereotyped movements (eg, repetitive grimacing, throat clearing, vocalizations) define a simple tic disorder.

Facial myokymia

Facial myokymia appears as vermicular twitching under the skin, often with a wavelike spread. This is distinguished from other abnormal facial movements by characteristic electromyogram discharges presenting as brief, repetitive bursts of motor unit potentials firing at 2-60 Hz interrupted by periods of silence of up to a few seconds. Facial myokymia may occur with any brainstem process. Severe cases may benefit from botulinum toxin. Most cases are idiopathic and resolve without treatment over several weeks.

 

Workup

Approach Considerations

Early cases of hemifacial spasm may be difficult to distinguish from facial myokymia, tics, or myoclonus originating in the cortex or brainstem. Neurophysiologic testing can be invaluable.

Spread and variable synkinesis on blink reflex testing and high-frequency discharges on electromyography (EMG) with appropriate clinical findings are diagnostic. Stimulation of one branch of the facial nerve may spread and elicit a response in a muscle supplied by a different branch. Synkinesis is not present in essential blepharospasm, dystonia, or seizures. Needle EMG shows irregular, brief, high-frequency bursts (150-400 Hz) of motor unit potentials, which correlate with clinically observed facial movements.

Imaging and Other Studies

Magnetic resonance imaging is the imaging study of choice, especially if an underlying compressive lesion is suspected. Cerebral angiography offers little diagnostic value in hemifacial spasm. Ectatic blood vessels rarely are identified, and it is difficult to correlate vessels with the facial nerve. Perform angiography and/or magnetic resonance angiography prior to a vascular decompression surgical procedure. Angiography is often performed before decompressive surgery to clarify the vascular anatomy, because it may identify an aneurysm or vascular anomaly.[7]

 

Treatment

Approach Considerations

In most patients with hemifacial spasm, the treatment of choice is injection of botulinum toxin under electromyographic (EMG) guidance. Chemodenervation safely and effectively treats most patients, especially those with sustained contractions. Relief of spasms occurs 3-5 days after injection and lasts approximately 6 months.

Medications used in the treatment of hemifacial spasm include carbamazepine and benzodiazepines for noncompressive lesions. Carbamazepine, benzodiazepines, and baclofen also may be used in patients who refuse botulinum toxin injections. Compressive lesions need to be treated surgically. Microvascular decompression surgery may be effective for those patients who do not respond to botulinum toxin. A study of 246 patients who underwent microvascular decompression surgery found no significant difference in outcomes and complications between patients who had botulinum toxin injections prior to their first surgery and those who did not.[8]

Botulinum Toxin Injection

The treatment of choice for hemifacial spasm is botulinum toxin injection of botulinum toxin under EMG guidance. Side effects of botulinum toxin injection (eg, facial asymmetry, ptosis, facial weakness) usually are transient. Most patients report a highly satisfactory response. Caution patients that although botulinum toxin ablates the muscular spasm, the sensation of spasm often persists.[9, 10]

Pharmacologic Therapy

Medications may be used in early hemifacial spasm (when spasms are mild and infrequent) or in patients who decline botulinum toxin injection. Use medications in patients with noncompressive lesions and early idiopathic hemifacial spasm. Response to medication varies but can be satisfactory in early or mild cases. The most helpful agents are carbamazepine and benzodiazepines (eg, clonazepam). Often, medication effects attenuate over time, necessitating more aggressive treatment.

Surgical Decompression

Treat compressive lesions surgically. Ectatic blood vessels cause hemifacial spasm by compressing the facial nerve as it exits the brainstem. Surgical decompression of these blood vessels can yield excellent results.[11, 12, 13, 14] A study evaluating the effect of microvascular decompression surgery on idiopathic hemifacial spasm with compression on different zones of facial nerve found that proper detection of offending vessels and complete decompression may increase cure rate.[15]

Patients with apparently idiopathic hemifacial spasm may benefit from posterior fossa exploration and microvascular decompression. Myectomy rarely is required.

 

Medication

Medication Summary

The goal of pharmacotherapy is reduction of abnormal muscle contractions. Botulinum toxin type A is the treatment of choice.[16, 17] Carbamazepine, benzodiazepines, and baclofen also may be used in patients who refuse BTX injections or who are not surgical candidates.

Neuromuscular Blockers, Botulinum Toxins

Class Summary

Botulinum toxin type A is the drug of choice.[16, 17] It causes presynaptic paralysis of the myoneural junction and reduces abnormal contractions. Therapeutic effects may last 3-6 months.

Botulinum toxin type B is useful in reducing excessive, abnormal contractions associated with blepharospasm[18] ; binds to receptor sites on the motor nerve terminals and after uptake inhibits release of acetylcholine, blocking transmission of impulses in neuromuscular tissue; 7-14 d after administering initial dose, assess patients for a satisfactory response; increase doses 2-fold over previously administered dose for patients who experience incomplete paralysis of the target muscle.

OnabotulinumtoxinA (BOTOX)

OnabotulinumtoxinA (BOTOX) is useful in reducing excessive, abnormal contractions associated with blepharospasm. It binds to receptor sites on the motor nerve terminals and, after uptake, inhibits the release of acetylcholine, blocking transmission of impulses in neuromuscular tissue. At 7-14 days after administration of the initial dose, assess patients for a satisfactory response. Increase the dose 2-fold over the previously administered dose in patients who experience incomplete paralysis of the target muscle.

RimabotulinumtoxinB (Myobloc)

When botulinum toxin injection is indicated and type A toxin is ineffective, injection with type B toxin (rimabotulinumtoxinB [Myobloc]) should be considered.

AbobotulinumtoxinA (Dysport)

AbobotulinumtoxinA (Dysport) binds to receptor sites on the motor nerve terminals and, after uptake, inhibits release of acetylcholine, blocking transmission of impulses in neuromuscular tissue. At 7-14 days after administration of the initial dose, assess the patient for a satisfactory response. Increase the dose 2-fold over the previously administered dose in patients who experience incomplete paralysis of the target muscle.

Benzodiazepines

Class Summary

Benzodiazepines may potentiate the effects of gamma-aminobutyric acid (GABA) and facilitate inhibitory GABA neurotransmission. It may act in the spinal cord to induce muscle relaxation. Treatment needs to be individualized for each patient.

Clonazepam (Klonopin)

Clonazepam (Klonopin) is useful in suppressing muscle contractions by facilitating inhibitory GABA neurotransmission and other inhibitory transmitters.

Skeletal Muscle Relaxants

Class Summary

Muscle relaxants may inhibit the transmission of monosynaptic and polysynaptic reflexes at the spinal cord level.

Baclofen (Lioresal, Gablofen)

Baclofen (Lioresal) may induce hyperpolarization of afferent terminals and inhibit both monosynaptic and polysynaptic reflexes at the spinal level.

Anticonvulsants

Class Summary

Anticonvulsants are used to manage severe muscle spasms and provide analgesia and mild sedation. Anticonvulsants are probably the best medications in terms of efficacy and long-term safety when botulinum toxin and surgery are not options.

Carbamazepine (Tegretol, Equetro, Epitol, Carbatrol)

Carbamazepine (Tegretol) is effective in the treatment of hemifacial spasm and complex partial seizures. It appears to act by reducing polysynaptic responses and blocking posttetanic potentiation. Once a response is attained, attempt to reduce the dose to the minimum effective level or discontinue the drug at least once every 3 months. In patients who cannot tolerate carbamazepine, consider oxcarbazepine (dosage not yet established).

Oxcarbazepine (Trileptal)

Oxcarbazepine (Trileptal) is effective in partial complex epilepsy. It shows promise in hemifacial spasm. Oxcarbazepine may be considered when first-line agents (eg, botulinum toxin, carbamazepine) have failed or are contraindicated.