Benign essential blepharospasm (BEB) is a rare neurological disorder in which affected individuals experience involuntary muscle spasms and contractions of the muscles around the eyes. These spasms come and go (intermittent). Symptoms may begin as eye twitching, blinking and/or irritation. Eventually, BEB causes involuntary closure of the eyes. The exact cause of BEB is unknown. The disorder is one of a group of disorders collectively known as dystonia.
Dystonia is a group of movement disorders that vary in their symptoms, causes, progression, and treatments. This group of neurological conditions is generally characterized by involuntary muscle contractions that force the body into abnormal, sometimes painful, movements and positions (postures).
In the early stages, benign essential blepharospasm is characterized by frequent or forced blinking and eye irritation that often occurs as a result of specific stimuli including bright lights, fatigue, emotional tension, and environmental factors such as wind or air pollution. BEB virtually always affects both eyes (bilateral).
The frequency of muscle spasms and contractions may increase causing involuntary narrowing of the opening between the eyelids or closure of the eyelids. It may become progressively harder for affected individuals to keep their eyes open. In severe cases, the spasms may intensify to the point where the eyelids are closed several hours at a time. Although an individual’s vision remains unaffected, prolonged closure of the eyelids may cause a person to become functionally blind.
BEB may occur in association with dystonia of the lower part of the face, mouth or jaw. In these cases, BEB may be associated with jaw clenching, grimacing or tongue protrusion. This is called Meige syndrome or cranial dystonia. BEB may also be associated with abnormally dry eyes.
In most cases, spasms and contractions occur during the daytime and disappear while the individual is sleeping, only to recur the next day. Symptoms of BEB may be temporarily alleviated by a variety of activities including singing, laughing, yawning, and chewing.
Other activities may worsen symptoms. Such activities include reading, walking, watching television, exposure to bright lights, and driving. Stress may also worsen symptoms.
The cause of benign essential blepharospasm is unknown. Researchers speculate that the cause of BEB may be multifactorial (e.g., caused by the interaction of certain genetic and environmental factors).
Malfunctioning of a region of the brain known as the basal ganglia may play a role in the development of BEB. The basal ganglia are structures composed of nerve cells located deep in the brain. The basal ganglia are involved in the regulation of motor and learning functions. The exact problem(s) associated with the basal ganglia in individuals with BEB is unknown.
In some cases, BEB runs in families. In these rare instances, it is more obvious that BEB may be inherited. More study is required to determine the exact role genetics plays in the development of BEB.
In some cases, affected individuals may have a history of local eye disease such as eye trauma. However, no proven relationship between local eye disease and the development of BEB has been established. In most cases, BEB develops spontaneously with no known precipitating factor.
BEB may occur secondary to other disorders such as tardive dyskinesia or generalized dystonia, Wilson disease, and various parkinsonian syndromes. BEB may also occur secondary to the use of certain drugs, specifically the drugs used to treat Parkinson’s disease.
Benign essential blepharospasm affects women more often than men. The average age of onset is 56.
It is estimated that approximately 2,000 new cases of BEB are diagnosed each year in the United States. The prevalence of BEB in the general population is approximately 5 per 100,000 individuals.
No laboratory tests exist to make a definitive diagnosis of benign essential blepharospasm. A diagnosis is made based upon a thorough clinical evaluation, a detailed patient history and identification of characteristic symptoms.
Treatment of BEB consists of oral drug therapy, focal injections of botulinum toxin (four different brands are available in the USA) or surgery to remove eyelid muscle, used alone or in conjunction with the botulinum toxin injections.
Approximately one-third of affected individuals are treated with oral medications (drug therapy) specifically anticholinergic drugs and with dopamine depleters such as tetrabenazine. The results of these drug treatments are usually moderate or unsatisfactory and often temporary. Additional drugs that have been used to treat BEB include clonazepam, trihexyphenidyl, diazepam, and baclofen.
Botulinum toxin has been approved by the Food and Drug Administration (FDA) as a treatment for blepharospasm and has become the primary form of treatment. The technique of injecting small amounts of botulinum toxin into the orbicularis oculi weakens these muscles for approximately three months, after which time the procedure must be repeated. Botulinum toxin injections have been helpful for many individuals with blepharospasm, but some people do not respond well. Botox, distributed by Allergan, and Xeomin, distributed by Merz Pharmaceuticals, are type A botulinum toxin products that are FDA approved for the treatment of blepharospasm.
Two surgical approaches are in use in cases in which drug therapy does not work. In a procedure called a protractor myectomy, the eyelid muscles themselves are removed either partially or completely.
In the past a procedure known as a neurectomy was performed to treat individuals with BEB. However, the complication rate is much higher than with a myectomy and this procedure is rarely used anymore. In a neurectomy, sections are taken off the branches of the facial nerve leading to the orbicularis oculi. Paralysis of the entire upper face may result, but the nerve branches tend to regenerate after a period of months or years.
Dysport, a type A botulinum toxin product, and Myobloc, a type B botulinum toxin product, have been used to treat blepharospasm but are not yet FDA approved for this indication.
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