Hemifacial spasm (HFS) is a rare

neuromuscular disease A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and w ...

characterized by irregular, involuntary

muscle contractions Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as w ...

(

spasm A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a muscle c ...

s) on one side (hemi-) of the face (-facial). The facial muscles are controlled by the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...

(seventh cranial nerve), which originates at the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...

and exits the skull below the ear where it separates into five main branches. This disease takes two forms: typical and atypical. In typical form, the twitching usually starts in the lower

eyelid An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyel ...

orbicularis oculi muscle The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short ...

. As time progresses, it spreads to the whole lid, then to the

orbicularis oris In human anatomy, the orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth. It is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance ...

muscle around the lips, and

buccinator muscle The buccinator () is a thin quadrilateral muscle occupying the interval between the maxilla and the mandible at the side of the face. It forms the anterior part of the cheek or the lateral wall of the oral cavity.Illustrated Anatomy of the Head ...

in the

cheekbone In the human skull, the zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is s ...

area. The reverse process of twitching occurs in atypical hemifacial spasm; twitching starts in

muscle around the lips, and

in the

area in the lower face, then progresses up to the

in the eyelid as time progresses. The most common form is the typical form, and atypical form is only seen in about 2–3% of patients with hemifacial spasm. The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons. This disorder occurs in both men and women, although it affects

middle-aged In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...

elderly Old age refers to ages nearing or surpassing the life expectancy of human beings, and is thus the end of the human life cycle. Terms and euphemisms for people at this age include old people, the elderly (worldwide usage), OAPs (British usage ...

women more frequently. Hemifacial spasm is much more common in some

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

n populations. It may be caused by a facial

nerve injury Nerve injury is an injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injuries. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve f ...

, a

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

, or it may have no apparent cause. Individuals with

on both sides of the face are very rare.

Signs & Symptoms

The first sign of hemifacial spasm is typically muscle movement in the patient's eyelid and around the eye. It can vary in intensity. The intermittent twitching of the eyelid, which can result in forced closure of the eye which gradually spreads to the muscles of the lower part of the face (Typical form- See Image). In atypical form the spasms start in the cheekbone area and spreads to the eyelid. Ultimately, all the muscles on that side are affected, nearly all the time. This sometimes causes the mouth to be pulled to the side. Experts have linked hemifacial spasm to facial nerve injury,

Bell's palsy Bell's palsy is a type of facial paralysis that results in a temporary inability to control the facial muscles on the affected side of the face. In most cases, the weakness is temporary and significantly improves over weeks. Symptoms can vary fr ...

and

s. Although the most frequent cause is a blood vessel pressing on the

at the spot where it leaves the patient's brain stem, sometimes there is no known cause. When the affected individual is younger than 40, doctors suspect an underlying cause such as

multiple sclerosis Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This d ...

Causes

Three theories exist to explain the facial nerve dysfunction found in hemifacial spasm. The first proposed theory is ephaptic transmission, which is electrical activity crossing from one demyelinated neuron to another resulting in a false

synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...

. The second theory involves abnormal activity of

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

s at the

root end zone secondary to compressive damage/

demyelination A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This damage impairs the conduction of signals in the affected nerves. In turn, the reduction in conduction ability causes deficiency i ...

. The third theory or "Kindling theory" involves increased excitability of the

nucleus due to feedback from a damaged facial nerve. It is generally accepted as compression of the

by vessels of the posterior circulation. In detail compression of the

seventh cranial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...

by a dolichoectatic (a distorted, dilated, and elongated)

vertebral artery The vertebral arteries are major arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry o ...

is accepted to be the general cause of hemifacial spasm. Less than 1% of cases are caused by tumor. Hemifacial spasm is much more common in some Asian populations. Several families with hemifacial spasm have been reported, suggesting a genetic

etiology Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...

or predisposition in some cases. There appears to be an

autosomal dominant In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

pattern of inheritance in these families with low

penetrance Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...

, and except for a younger age at onset, the clinical features overlap with the

idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...

cases. Evaluation of

single-nucleotide polymorphism In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently lar ...

s in genes related to vascular change causing compression of blood vessels did not show an association with hemifacial spasm. Clarifying the role of genetic susceptibility in hemifacial spasm may help to better understand the

pathogenesis Pathogenesis is the process by which a disease or disorder develops. It can include factors which contribute not only to the onset of the disease or disorder, but also to its progression and maintenance. The word comes from Greek πάθος ''pat ...

of this disease.

Diagnosis

There are several tests done to diagnose hemifacial spasm. Diagnosing a case of hemifacial spasm begins with a complete neurological exam, including an

Electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyog ...

(EMG – a test that measures and records electrical activity generated in muscle at rest and in response to muscle contraction),

Magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

(MRI – a test that uses magnetic waves to make pictures of structures inside the head), Computed tomography (CT scan – a type of x-ray that uses a computer to make pictures of structures inside the head), and

Angiography Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is performe ...

(an x-ray exam of the blood vessels when they are filled with a contrast material). Studies have shown that the most effective method of hemifacial spasm screening is MRI. In one study only 25% of the CT scans showed the abnormality in hemifacial spasm patients, whilst more than half of the MRI imaging demonstrated a vascular anomaly. MRI imaging should be the initial screening procedure in the assessment of patients with hemifacial spasm.

Prevention

There is no known way to prevent hemifacial spasm.

Treatments

Mild cases of hemifacial spasm may be managed with sedation or

carbamazepine Carbamazepine (CBZ), sold under the trade name Tegretol among others, is an anticonvulsant medication used primarily in the treatment of epilepsy and neuropathic pain. It is used as an adjunctive treatment in schizophrenia along with other medi ...

(an anticonvulsant drug). Microsurgical decompression and botulinum toxin injections are the current main treatments used for hemifacial spasm.

Microvascular Decompression

Microvascular decompression Microvascular decompression (MVD), also known as the Jannetta procedure, is a neurosurgical procedure used to treat trigeminal neuralgia (along with other cranial nerve neuralgias) a pain syndrome characterized by severe episodes of intense facial p ...

appears to be the most popular surgical treatment at present. Microvascular decompression relieves pressure on the facial nerve, which is the cause of most hemifacial spasm cases. Excellent to good results are reported in 80% or more cases with a 10% recurrence rate. In the present series approximately 10% had previously failed surgery. Serious complications can follow microsurgical decompressive operations, even when performed by experienced surgeons. These include cerebellar haematoma or swelling,

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

infarction (blood vessel of the brain stem blocked),

cerebral infarction A cerebral infarction is the pathologic process that results in an area of necrotic tissue in the brain (cerebral infarct). It is caused by disrupted blood supply ( ischemia) and restricted oxygen supply ( hypoxia), most commonly due to thromboemb ...

(ischemic stroke resulting from a disturbance in the blood vessels supplying blood to the brain),

subdural haematoma A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surround ...

and intracerebral infarction (blockage of blood flow to the brain). Death or permanent disability (hearing loss) can occur in 2% of patients of hemifacial spasm.

Botulinum Toxin

Observational data from studies (the updated review in 2020 did not find any randomized controlled trials) indicates that

botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...

is safe and effective in the treatment of hemifacial spasm with success rates between 76 - 100%. The injections are administered as an outpatient or office procedure. Whilst side effects occur, these are never permanent. Repeated injections over the years remain highly effective. Whilst the toxin is expensive, the cost of even prolonged courses of injections compares favourably with the cost of surgery. Patients with HFS should be offered a number of treatment options. Very mild cases or those who are reluctant to have surgery or

Botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...

injections can be offered medical treatment, sometimes as a temporary measure. In young and fit patients microsurgical decompression and

Botulinum Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...

injections should be discussed as alternative procedures. In the majority of cases, and especially in the elderly and the unfit,

injection is the treatment of first choice. Imaging procedures should be done in all unusual cases of hemifacial spasm and when surgery is contemplated. Patients with hemifacial spasm were shown to have decreased sweating after botulinum toxin injections. This was first observed in 1993 by Khalaf Bushara and David Park. This was the first demonstration of nonmuscular use of BTX-A. Bushara further showed the efficacy of botulinum toxin in treating hyperhidrosis (excessive sweating). BTX-A was later approved for the treatment of excessive underarm sweating. This is technically known as severe primary axillary hyperhidrosis – excessive underarm sweating with an unknown cause which cannot be managed by topical agents (see focal hyperhidrosis).

Epidemiology

The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons. Hemifacial spasm is more prevalent among females over 40 years of age. The estimated prevalence for women is 14.5 per 100,000 and 7.4 per 100,000 in men. Prevalence for hemifacial spasm increase with age, reaching 39.7 per 100,000 for those aged 70 years and older. One study divided 214 hemifacial patients based on the cause of the disease: The patients who had a

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a c ...

in the

at the end of the

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

as the primary hemifacial spasm and patients who had peripheral facial palsy or nerve lesion due to

tumors A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

trauma Trauma most often refers to: * Major trauma, in physical medicine, severe physical injury caused by an external source * Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic i ...

, or infection as secondary hemifacial spasm. The study found that 77% of hemifacial spasm is due to primary hemifacial spasm and 23% is due to secondary hemifacial spasm. The study also found both sets of patients to share similar age at onset, male to female ratios, and similar affected side. Another study with 2050 patients presented with hemifacial spasm between 1986 and 2009, only 9 cases were caused by a

cerebellopontine angle syndrome The cerebellopontine angle syndrome is a distinct neurological syndrome of deficits that can arise due to the closeness of the cerebellopontine angle to specific cranial nerves.Rolak LA. ''Neurology Secrets'', 4th Ed. Chapter 10, "Cerebellar Dis ...

, an incidence of 0.44%.

History

The earliest descriptions about hemifacial spasm is by Shultze in 1875 and Gowers in 1899. The

of hemifacial spasm and location of the abnormality have been debated for more than a century. Surgical treatment for hemifacial spasm in the early 20th century included neurolysis (destruction of nerve tissue), stretching the

(seventh cranial nerve), and high-pressure irrigation of the nerve with lactate ringer's solution. The medical regimens of that time involved injection of the nerve with

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

electrical stimulation Functional electrical stimulation (FES) is a technique that uses low-energy electrical pulses to artificially generate body movements in individuals who have been paralyzed due to injury to the central nervous system. More specifically, FES can ...

, application of toxic compounds (

nitrate of silver Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar caustic' ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant ...

s) as well as medications such as

Dilantin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence seizures. The intr ...

or other

anticonvulsants Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of b ...

. Additional advances in understanding the

and improving treatments for hemifacial spasm did not occur until the mid-seventies. In 1977, 47 cases of hemifacial spasm underwent

microvascular decompression Microvascular decompression (MVD), also known as the Jannetta procedure, is a neurosurgical procedure used to treat trigeminal neuralgia (along with other cranial nerve neuralgias) a pain syndrome characterized by severe episodes of intense facial p ...

of the facial nerve using the

operating microscope An operating microscope or surgical microscope is an optical microscope specifically designed to be used in a surgical setting, typically to perform microsurgery. Design features of an operating microscope are: magnification typically in the ran ...

. The results illustrated nerve-vessel conflicts (or

cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of the ...

) to be located at the root exit zone of the

in all cases. The root exit zone is where the central

glial Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form mye ...

al insulation of the nerve ends and the

peripheral nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

axonal myelination begins, this is known as The Obersteiner-Redlich zone.

Biopsies A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

of the root exit zone demonstrated degeneration of

axons An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, th ...

, denuded axis cylinder and interrupted

myelin Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...

. The results of the experiment strengthened the theory that

vascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

compression of the facial nerve was the primary cause of hemifacial spasm, and proposed a specific region of the facial nerve where the effects of longstanding compression results in

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

dysfunction.

Signs & Symptoms

Causes

Diagnosis

Prevention

Treatments

Microvascular Decompression

Botulinum Toxin

Epidemiology

History

References

Further reading