A dystonia is a movement disorder that causes the muscles to contract and spasm involuntarily. Blepharospasm is a focal cranial dystonia characterized by increased blinking and involuntary closing of the eyes.
The first record of blepharospasm and lower facial spasm was found in the 16th century in a painting titled De Gaper. At that time, and for several ensuing centuries, patients with such spasms were regarded as being mentally unstable and often were institutionalized in insane asylums. Little progress was made in the diagnosis or treatment of blepharospasm until the early 20th century, when Henry Meige (pronounced "mehzh"), a French neurologist, described a patient with eyelid and midface spasms, spasm facial median, a disorder now known as Meige syndrome.  At about the same time, the first medical treatments became available, including alcohol injections into the facial nerve, facial nerve avulsion, neurotomy, and neurectomy. The adverse effects of these treatments, including loss of facial expression and movements, functional and cosmetic deformities of ptosis, and eyelid malposition, were often as bad as the disease.
Modern physicians realize that blepharospasm is a neuropathologic disorder, rather than psychopathologic, as was once believed. The cause of blepharospasm is multifactorial. Although it is likely that a central control center for coordination and regulation of blink activity exists, somewhere in the basal ganglia, midbrain, and/or brain stem, it is unlikely that a single defect in this elusive control center is the primary cause of this disease. [2, 3, 4, 5, 6, 7, 8, 9]
Today, most view blepharospasm as a defect in circuit activity, rather than a defect at a specific locus. Fayers et al have found a decrease in corneal sensitivity in patients with blepharospasm, implying an impairment in cortical processing of sensory input, with a resultant loss of blink reflex inhibition. 
If the central control center fails to regulate blinking in blepharospasm, it is believed to be only one component of an overloaded, defective circuit. This circuit forms a blepharospasm vicious cycle, which has a sensory limb, a central control center located in the midbrain, and a motor limb. The sensory limb responds to multifactorial stimuli, including light, corneal or eyelid irritation, pain, emotion, stress, or various other trigeminal stimulants. These stimuli are transmitted to the central control center, which may be genetically predisposed or weakened by injury or age. This abnormal central control center fails to regulate the positive feedback circuit. The motor pathway is composed of the facial nucleus, facial nerve, and orbicularis oculi, corrugator, and procerus muscles. Other facial muscles also may be involved.
It is estimated that there are at least 50,000 cases of blepharospasm in the United States, with up to 2000 new cases diagnosed annually. The prevalence of blepharospasm in the general population is approximately 5 in 100,000.
At one end of the clinical spectrum, essential blepharospasm is manifested by simple increased blink rate and intermittent eyelid spasms, while at the other end of the spectrum, blepharospasm is a disabling condition with ocular pain and functional blindness. Patients may report that they are disabled to the point where they have stopped watching television, reading, driving, and/or walking. Patients may develop anxiety, avoid social contact, become depressed, become occupationally disabled, and become suicidal. [11, 12, 13]
A female preponderance of 1.8:1 exists.
The mean age of onset of blepharospasm is 56 years, and two thirds of patients are age 60 years or older. 
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