Hemifacial Spasm

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Article initiated by:

Elysa McClintic, MD, MS, Christopher Komanski MD

All contributors:

Nagham Al-Zubidi, MD, Elysa McClintic, MD, MS, Gangadhara Sundar, MD, Anne Barmettler, MD, Michael T Yen, MD, Cat Nguyen Burkat, MD FACS

Assigned editor:

Gangadhara Sundar, MD, Sonali Singh MD

Review:

Assigned status Up to Date

 by Gangadhara Sundar, MD on November 6, 2024.

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Contributing Editors:	add

Hemifacial Spasm

ICD-10

[1]51.3

ICD-9

351.8

Disease Entity

• Clonic Hemifacial Spasm ICD-10 Code G51.3
• (ICD 9 Code 351.8 Other facial nerve disorders)

Disease

Hemifacial spasm(HFS) is a movement disorder that is characterized by involuntary tonic - clonic contractions of the mimetic muscles on one side of the face. Bilateral cases are uncommon. The affected muscles are those of facial expression which are innervated by cranial nerve VII - the Facial nerve, a predominantly motor nerve. It often initially affects the orbicularis oculi muscle and may spread to include other muscles of facial expression. Clinical presentation and severity may fluctuate based on stress levels, position of the head and neck but often of unknown ethology. Chronic hemifacial spasm is often associated with synkinesis, or involuntary movements occurring with voluntary facial movements. It should be differentiated from Blepharomyokymia and Blepharospasms ( both benign essential blepharospasm (BEB) and secondary blepharospasm which is typically bilateral and mainly periorbital , although the midface may also be involved (Meige syndrome).

Epidemiology

• Rare disease (8-15 out of 100,000 people in the US)
• More common in women than men (~2x more common in women)
• Most common in middle-aged and older people (typical age of onset 50-60 years old)

Etiology

There are a number of known causes of hemifacial spasm which may be classified as primary or secondary. Primary hemifacial spasm is defined as compression of the facial nerve at its exit from the brainstem as first described by Campbell and Keedy in 1947 . Although not always identified, the most common mechanism is thought to be compression secondary to a dolichoectatic artery as described by Jannetta in 1975 . The most commonly implicated artery is the anterior inferior cerebellar artery (AICA) . Secondary hemifacial spasm is not uncommon and causes include atherosclerosis, arteriovenous malformations, aneurysms, tumors of the parotid gland and cerebellopontine angle, peripheral facial nerve trauma, brainstem lesions including stroke and demyelinating conditions such as multiple sclerosis, and Bell’s Palsy. There is also a rare, genetically linked hemifacial spasm .

Risk Factors

• Facial trauma
• Cranial nerve seven injury
• Bell’s Palsy
• Atherosclerosis
• Family History

Pathophysiology

The pathophysiology of primary hemifacial spasm is not well understood and likely varies by etiology. Essentially, compressive forces are felt to incite inappropriate activation of the facial nerve - either in whole or some of its fibres . Similarly, a diseased nerve is susceptible to ephaptic excitation as a result of demyelination. This occurs when the electrical activity of one nerve or group of nerves induces activation of a nearby nerve resulting in involuntary muscle activation and subsequent movement. This differs from benign essential blepharospasm which is presumed to involve the basal ganglia and is more commonly bilateral.

Primary prevention

While primary hemifacial spasms is not preventible, a more complete facial nerve recovery following lower motor neurone facial nerve injury or inflammatory facial palsy (Bell's palsy) with optimal managment may reduce the incidence of secondary HFS.

Diagnosis

History

Patients present with the complaint of involuntary twitches or spasms of segmental or whole of one side of the face - from the frontal region to the neck. They describe an intermittent twitch or flutter of the eyelid followed by sustained and involuntary eyelid closure. These spasms may also include muscles of the lower face and even the neck (platysma) on the same side of the eyelid spasms. Often, the spasm is more noticeable in stressful situations and may be relieved with pressure to certain points on the face. Patients are often self-conscious about the spasm and how they are received in public. They may also experience sleep disturbances or insomnia secondary to the spasm.

Physical examination

Spasm of the orbicularis oculi can be seen in addition to spasm of the other facial muscles on one side of the face. Involuntary eyelid closure is often accompanied by elevation of the brow. Subtle facial muscle weakness may also be elicited. Decreased hearing may also be noted.

Signs and Symptoms

Hemifacial spasm presents in a typical and atypical form. In the typical form which is unilateral, the patient first develops an involuntary tonic and clonic movement of the upper and/or lower eyelids. This then gradually spread down the face involving other muscles including the platysma. The atypical form presents with involuntary tonic and clonic movements of the orbicularis oris and then spreads up the face to the eye. Pulsatile tinnitus may also be present if the tensor tympani is involved. Hemifacial spasm may be posture related and may be present during sleep, which differentiates it from benign essential blepharospasm (BEB). Although functional blindness is rare due to the unilateral nature of the disease, spasms can be debilitating and interfere with daily functioning.

Diagnostic procedures

Hemifacial spasm is essentially a clinical diagnosis based on presentation and findings and the absence of a known primary cause. Although not regularly performed, an electromyogram (EMG) may be used to confirm diagnosis. Neuroimaging in the form of computed-tomography imaging (CT) - where an MRI is not readily available or ideally magnetic resonance imaging (MRI) of the cerebellopontine angle and along the course of the facial nerve from the brain stem to its exit from the skull base is recommended to rule out a compressive space occupying lesion . MRI is is non-invasive, and sensitive in detecting vascular abnormalities (such as a dolichoectatic vessel) and potential tumors of the cerebellopontine angle. Depending on the resolution of the MRI, a high proportion of patients with HFS will demonstrate a vascular compromise, sometimes by multiple vessels or a single vessel at multiple points. It is typically visualised in the hyper T2 sequences, although a vast majority of normal individuals may also have asymptomatic neurovascular conflict.

Differential diagnosis

• Facial Tics (Tourette syndrome)
• Blepharomyokymia
• Blepharospasm
• Tardive Dyskinesia
• Seizure

Management

Medication

Various medications have been used to treat hemifacial spasm. These are anticonvulsants and include carbamazepine, clonazepam, phenytoin, gabapentin, and baclofen. However, efficacy is limited and side effects are significant .

Botulinum Toxin

Injection with botulinum toxin comprises this first line treatment for most patients. The efficacy approaches that of microvascular decompression with a much more favorable side effect profile. The injections typically take up to one week to become effective and last for about 3-4 months. Though effective, results may be variable and must be repeated long term. The frequency and targeted muscles of injections may however be variable between patients and visits. Frequent injections may however result in resistance and should thus be avoided. Side effects include ptosis, dry eye, diplopia, and lagophthalmos . Commercially available neuromodulators including Botox(R), Dysport (R), Xeomin(R) and others.

Microvascular decompression

Surgery can be performed in primary HFS to distract the aberrant artery away from the seventh cranial nerve by placing a sponge between the vessel and nerve. This has been shown to be highly effective in experienced hands. However, the risk profile includes intracerebral hemorrhage, facial paralysis, deafness, and death. Thus, the benefits and risks must be appropriately weighed for each patient. It is used more often in refractory cases and the young .

Prognosis

• 80-85% of Patients improve with botulinum toxin.
• 90% of patients improve with microvascular decompression.
• Patients with Hemifacial spasm often need long term reassurance and occasional urgent consultations when the spasms become exaggerated affecting their social or general quality of life.