The range of ailments falling under the umbrella-term of "abnormal involuntary movement disorders" is diverse and includes conditions as different from each other as Parkinson's disease, restless legs syndrome and blepharospasm. Cases of blepharospasm, like those of other movement disorders, often go unrecognized or are blamed on other causes.

The term "blepharospasm" is the sum of its parts. "Blepharon" is Greek for eyelid and "spasm" means excessive muscular contractions. In blepharospasm the eyes blink excessively. The blinking can be too frequent, too sustained, or both. The distinction between normal blinking and excessive blinking is not exact. A practical method for sorting out cases relies on the answers to two questions:

• Does the blinking cause distress?
• Does the blinking interfere with usual activities?

Blepharospasm can occur alone or in combination with other involuntary movements. When paired with involuntary movements of the lower face -- like puckering of the lips or grimacing expressions -- the problem is collectively known as Meige syndrome, named for Dr. Henri Meige who described the condition in 1904. Blepharospasm and Meige syndrome are forms of dystonia, a sub-grouping within the overall range of involuntary movement disorders. Another example of dystonia is torticollis, in which there is sustained involuntary twisting or cocking of the neck.

Blepharospasm, like any other condition, can be mild, moderate or severe. It is not necessarily disabling, but if the blinking is so frequent or sustained that it interferes with vision, then it can impact activities like driving. Blepharospasm does not appear to be an insurmountable barrier for people whose job is to appear in public, as a well-known television personality with blepharospasm seems to be doing just fine.

How common is this condition? Not very. Researchers at Mayo Clinic tracked cases of blepharospasm in Olmsted County, Minnesota, between 1976 and 1995. They calculated just 1.2 new cases per year per population of 100,000, although this might be an underestimate of the true incidence because it doesn't include undiagnosed cases. The diagnosed patients were equally divided between the sexes and half of the people had Meige syndrome, meaning that the blepharospasm was accompanied by dystonia of the lower face. One in four cases resolved on their own.

The diagnosis of blepharospasm is based mainly on its appearance. This condition is sometimes misidentified as a reaction to (or "secondary" to) an irritation of the eyes, and is treated with eyedrops. However, in true cases of blepharospasm (designated as "primary" or "essential" blepharospasm) the excessive blinking is not driven by irritation of the eyes. Instead, the eyelids are just following orders from overactive brain-circuits, though in fairness, those brain-circuits might be misinterpreting non-irritated eyes as being irritated. Eyedrops are not helpful for primary blepharospasm.

Another condition which is similar in appearance is hemifacial spasm in which there is excessive blinking of just one eye, often accompanied by excessive twitching of the lower face on the same side. But hemifacial spasm is not a form of primary blepharospasm. In hemifacial spasm the affected muscles are driven by an overactive nerve rather than an overactive brain-circuit. That's why just one side of the face is affected. There is another, unaffected nerve controlling the opposite side of the face.

Although the source of excessive blinking in blepharospasm is undoubtedly the brain, the disorder does not show up on usual, brain-oriented tests like computed tomographic (CT) scans, magnetic resonance imaging (MRI) scans or electroencephalograms (EEGs).

How about treatment? There is no curative treatment available. Existing treatments can relieve symptoms, but don't affect the course of the underlying disorder which usually continues long-term. Thus, the state of a person's blepharospasm in five or ten years will be the same whether or not symptom-relieving treatment is used in the meantime.

That said, many patients benefit from symptom-relieving treatment which nowadays usually takes the form of periodic injections of botulinum toxin (e.g. brand name Botox) beneath the skin, overlying the affected muscles. This weakens or relaxes the muscles involved in the excessive blinking to an extent that relieves the symptom without interfering with normal eye closure. Typical treatment cycles are no more often than every three months. Prior to the development of botulinum treatment for blepharospasm it was often treated with orally administered medications, though usually with a lower success rate.

As an example of clinical experience in treating blepharospasm, we can look at the results obtained by neurologists at the Sao Paulo School of Medicine in Brazil. Over the ten-year span from 1993 to 2003 they administered a total of 379 botulinum toxin treatments to 30 patients with blepharospasm. Sixty-six percent of the patients had previously tried oral medications for their condition and just 15% considered them satisfactory. (Of course, patients who were totally satisfied with oral medications were unlikely to seek treatment with botulinum toxin, so this figure probably underestimates the success rate with oral medication.)

So how did they do? Ninety-three percent of the patients showed significant improvement after their first injections with botulinum toxin and there was no loss of effectiveness when the first and last treatments were compared. Adverse effects -- "mostly minor" -- developed at least once in 53% of the patients. Six patients (20%) discontinued the treatment.

(C) 2006 by Gary Cordingley