- Clonic Hemifacial Spasm ICD-10 Code G51.3
- (ICD 9 Code 351.8 Other facial nerve disorders)
Hemifacial spasm is a movement disorder that is characterized involuntarily tonic and clonic contractions of the mimetic muscles on one side of the face. (Bilateral cases may be seen but are extremely rare.) The affected muscles are innervated by cranial nerve seven. It often initially affects the orbicularis oculi muscle and may spread to include other muscles of facial expression. Hemifacial spasm is often coupled with synkinesis, or involuntary movements occurring with voluntary facial movements.
Figure 1. The facial nerve originates in the brainstem and exits the skull beneath the ear where it has five main branches that control the muscles of facial expression.
- 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)
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 . The most common mechanism is thought to be compression secondary to a dolichoectatic artery as described by Jannetta in 1975 . The implicated artery is the anterior inferior cerebellar artery . Secondary hemifacial spasm is less common 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 .
- Facial trauma
- Cranial nerve seven injury
- Bell’s Palsy
- Family History
The pathophysiology is not well understood and likely varies by etiology. Essentially, compressive forces are felt to incite inappropriate activation of the facial nerve. 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.
Patients present with the complaint of inability to keep their eyelid open on the affected side. 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 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.
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, the patient first develops an involuntary tonic and clonic movement of the lower eyelid. This then gradually spread down the face and remains unilateral. 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 present during sleep which differentiates it from benign essential blepharospasm (BEB). It is also unilateral (though rarely bilateral cases have been reported) versus BEB which is a bilateral process. Although functional blindness is rare due to the unilateral nature of the disease, spasms can be debilitating and interfere with daily functioning.
There are a number of tests available to diagnose hemifacial spasm. These include electromyogram (EMG), computed-tomography imaging (CT), magnetic resonance imaging (MRI), and angiography. MRI is felt to be the optimal test as it is non-invasive, sensitive in detecting vascular abnormalities and potential tumors of the cerebellopontine angle.
- Facial Tics (Tourette syndrome)
- Tardive Dyskinesia
Figure 2. (left) During MVD, a craniectomy is made in the skull behind your ear. Figure 3. (right) Hemifacial spasm is most often caused by an artery compressing the facial nerve.
Figure 4. A sponge is inserted between the artery and the nerve to relieve the pressure and stop the facial muscle spasms.
A number of medicines have been used to treat hemifacial spasm. These are anticonvulsants and include carbamazepine, clonazepam, phenytoin, gabapentin, and baclofen. However, efficacy of this approach is felt to be limited .
Injection with botulinum toxin comprises this first line treatment for many patients. The efficacy approaches that of microvascular decompression with a much more favorable side effect profile. The injections typically take up to one week days to become effective and last for about 3-4 months. Though effective, this treatment must be repeated long term. Side effects include ptosis, dry eye, diplopia, and lagophthalmos .
Surgery can be performed 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. 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 .
- 80-85% of Patients improve with botulinum toxin
- 90% of patients improve with microvascular decompression.
- American Academy of Ophthalmology. Hemifacial spasm Practicing Ophthalmologists Learning System, 2017 - 2019 San Francisco: American Academy of Ophthalmology, 2017.
- Auger, R. G., & Whisnant, J. P. (1990). Hemifacial spasm in Rochester and Olmsted County, Minnesota, 1960 to 1984. Archives of Neurology, 47(11), 1233–1234. doi:10.1001/archneur.1990.00530110095023
- CAMPBELL, E., & KEEDY, C. (1947). Hemifacial spasm; a note on the etiology in two cases. Journal of Neurosurgery, 4(4), 342–347.
- Ruby, J. R., & Jannetta, P. J. (1975). Hemifacial spasm: ultrastructural changes in the facial nerve induced by neurovascular compression. Surgical Neurology, 4(4), 369–370.
- Payner, T. D., & Tew, J. M. J. (1996). Recurrence of hemifacial spasm after microvascular decompression. Neurosurgery, 38(4), 681–686.
- Micheli, F., Scorticati, M. C., Gatto, E., Cersosimo, G., & Adi, J. (1994). Familial hemifacial spasm. Movement Disorders : Official Journal of the Movement Disorder Society, 9(3), 330–332. doi:10.1002/mds.870090310
- Kenney, C., & Jankovic, J. (2008). Botulinum toxin in the treatment of blepharospasm and hemifacial spasm. Journal of Neural Transmission. doi:10.1007/s00702-007-0768-7
- Ababneh, O. H., Cetinkaya, A., & Kulwin, D. R. (2014). Long-term efficacy and safety of botulinum toxin A injections to treat blepharospasm and hemifacial spasm. Clinical & Experimental Ophthalmology, 42(3), 254–261. doi:10.1111/ceo.12165
- American Academy of Ophthalmology, Basic and Clinical Science Course. Section 5: Neuro-ophthalmology Chapter 11. Pages 273-274.