Blepharospasm: That Blinkety-Blink Movement Disorder
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