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== Epidemiology and Demographics == | == Epidemiology and Demographics == | ||
The mean annual incidence is 0.10% and the prevalence of blepharospasm in the general population is approximately 5 in 100,000. On the one hand, it is a simple increased blinking rate and occasional eyelid spasms, and on the other hand, it results in functional blindness and eye pain. Females are more commonly affected by blepharospasm than males. The peak incidence is in the 50 to 59-year-old age group. People living in developed areas are at greater risk of developing blepharospasm compared to those living in less populated areas, similarly white-collar workers have higher chance of having blepharospasm. | |||
== Risk Factors == | |||
Mental health problems, dry eye conditions, sleep disturbances, white-collar jobs, Parkinsonism, high urbanization and rosacea are potential risk factors for benign essential blepharospasm. | |||
==Diagnosis== | ==Diagnosis== | ||
Revision as of 19:26, 27 July 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Eyelid twitch
Overview
A blepharospasm ('eye twitching') is any abnormal tic or twitch of the eyelid (from blepharo, eyelid, and spasm, an uncontrolled muscle contraction). However, it is normally distinguished from less serious disorders and refers to Benign Essential Blepharospasm, a focal dystonia (a neurological movement disorder involving involuntary and sustained muscle contractions) of the muscles around the eyes. The cause is often undetermined, but fatigue or a an irritant are possible contributing factors. Symptoms usually last for a few days then disappear without treatment, but in some cases the twitching is chronic and persistent. Occasionally, the symptoms are severe enough to result in effective blindness.
Historical Perspective
Blepharospasm was first found in a painting called De Gaper in the 16th century. Later, at the turn of the 20th century, Henry Meige, a French neurologist, described a patient with eyelid and midface spasm, a condition today known as Meige Syndrome. C. D. Marsden suggested that blepharospasm should be regarded as a focal form of dystonia along with other disorders such as oromandibular dystonia, cervical dystonia, and writer's cramp. Marsden also identified a variety of clinical characteristics, including female preference, peak age at onset between the 5th and 7th decade, a propensity to extend to neighboring areas of the body, and potential correlation with tremor in the head or upper limbs.
Classification
Primary Blepharospasm
It is also referred to as benign essential blepharospasm. Mostly sporadic, however, autosomal dominant patterns of inheritance have been observed in a few families. Coffee consumption could possibly be protective.
Secondary Blepharospasm
This is less frequent than idiopathic blepharospasm but can occur from focal lesions in multiple brain areas, including thalamus, basal ganglia, lower brain stem, cerebellum, midbrain, and cortex. Blepharospasm can also occur in patients with PD or tardive dyskinesia. In addition, conditions associated with lid weakness, such as facial palsy and myasthenia, may also give rise to blepharospasm. Reflex blepharospasm, a type of secondary blepharospasm triggered by dry eyes, blepharitis, intraocular inflammation, meningeal irritation, and light sensitivity.
Pathophysiology
There are many pathways that trigger the essential blepharospasm, but the precise cause is unclear. However, several studies suggest that the facilitation of the blink reflex is a result of a failure in inhibitory processes. There is an increased excitability of the blink and corneal reflex and deficiency in the cycle of recovery of the R2 portion of the blink reflex.The interneurons that mediate the R2 response of the blink reflex in the basal ganglia are hyperexcited and thus dysfunctional in blepharospasm.
Another study divided patients into 3 subclasses on the basis of EMG pattern of the Orbicularis Oris and levator palpebrae muscles. The first group had patients with blepharospasm alone, could have abnormal R2 recovery index. The second group included patients with blepharospasm with spontaneous levator palpebrae inhibition. The last group had patients with involuntary levator palpebrae inhibition but no blepharospasm, had a normal R2 recovery index. This suggested that cranial dystonias are not homogenous pathophysiologically.
Transcranial Magnetic Stimulation (TMS) has shown that the excitability of primary motor cortex activity is impaired in blepharospasm, as shown by decreased short-term intracortical inhibition in the hand muscles and shortened duration of cortical silent period in the cranial muscles of these patients. Patients with blepharospasm exhibit an increased somatosensory temporal discrimination threshold (STDT) and is more sensitive than blink reflex recovery for identifying underlying pathophysiology.
Causes
In most cases, blepharospasm seems to develop spontaneously. Many blepharospasm patients have a previous history of dry eyes and/or light sensitivity. Blepharospasm can also come from abnormal functioning of the brain's basal ganglia. Concomitance with dry eye, as well as other dystonias such as Meige's syndrome, has been observed. Some drugs can induce blepharospasm, such as Dimercaprol, those used to treat Parkinson's disease, as well as sensitivity to hormone treatments, including estrogen replacement therapy for women going through menopause. Blepharospasms can be caused by concussions in some rare cases, when a blow to the back of the head damages the basal ganglia.
Differentiating blepharospasm from other Diseases
Blepharospasm must be differentiated from apraxia of eyelid opening, myasthenia gravis causing ptosis due to weakness of the levator palpebrae or Muller muscles and Hemifacial spasm.
Epidemiology and Demographics
The mean annual incidence is 0.10% and the prevalence of blepharospasm in the general population is approximately 5 in 100,000. On the one hand, it is a simple increased blinking rate and occasional eyelid spasms, and on the other hand, it results in functional blindness and eye pain. Females are more commonly affected by blepharospasm than males. The peak incidence is in the 50 to 59-year-old age group. People living in developed areas are at greater risk of developing blepharospasm compared to those living in less populated areas, similarly white-collar workers have higher chance of having blepharospasm.
Risk Factors
Mental health problems, dry eye conditions, sleep disturbances, white-collar jobs, Parkinsonism, high urbanization and rosacea are potential risk factors for benign essential blepharospasm.
Diagnosis
History and Symptoms
- Uncontrollable tics or twitches of the eye muscles and surrounding facial area
- Excessive blinking of the eyes, or forced closure of durations longer than the typical blink reflex
- Dryness of the eyes
- Sensitivity to the sun and bright light
Treatment
Medical Therapy
- Drug therapy for blepharospasm has proved generally unpredictable and short-termed. Finding an effective regimen for any patient usually requires trial and error over time. In some cases a dietary supplement of magnesium chloride has been found effective.
- Botulin toxin injections have been used to induce localized partial paralysis.
Non-Pharmacotherapy
- Dark glasses are often worn because of sunlight sensitivity, as well as to hide the eyes from others.
- Stress management and support groups can help sufferers deal with the disease and prevent social isolation.
- Using tweezers to remove excess eyelashes from the outer corner of the eyelid may sometimes resolve this condition.
Surgery
Patients that do not respond well to medication or botulinum toxin injection are candidates for surgical therapy. The most effective surgical treatment has been protractor myectomy, the removal of muscles responsible for eyelid closure.
References
External Links
- Blepharospasm Resource Guide from the National Eye Institute (NEI).