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Blepharospasm
Primary
or idiopathic Blepharospasm consists of repeated forceful spasm of eye closure
usually accompanied by an increased periodic blink rate and photophobia
(sensitivity to light). Discomfort or soreness of the eyes and eyelids is often described.
It affects adults exclusively with a mean age at presentation of 51
years. The onset is usually
insidious.
Variability
is characteristic particularly in the early stages.
Idiopathic Blepharospasm generally worsens during the course of the day
and is acutely exacerbated by bright light, social stress and excessive movement
in the environment (e.g. in crowds). It
may improve with concentration, talking, singing or humming and sometimes with
digital pressure on the temple. It
usually progressively worsens over a few years then stabilises with
fluctuations. Very rarely it
resolves spontaneously but most sufferers will have to stop driving, working and
even recreational use of the eyes such as reading or watching television.
Secondary social isolation and reactive depression are therefore quite
common.
In
about 50% of patients spasms of the eye closure are accompanied by contraction
of lower facial muscles. Other
cranial muscle groups such as temporalis, masseter and the pterygoids may also
be involved, as may the neck muscles. The
condition is then clearly a movement disorder and is classified as cranial
Dystonia. In most cases there is
electrophysiological evidence of hyperexcitability of the blink reflex recovery
cycle, which may be due to abnormal extrapyramidal inputs.
The cause is obscure. About
30% of patients have a family history of either blepharospasm which is often triggered
by acute external eye or lid disease. Hormonal
factors are important and women are affected twice as often as men with the
onset frequently at the time of the menopause.
In a
variant, pre-tarsal blepharospasm, the eyelids appear to be passively closed
until the patient or observer attempts to open them when spasm in the pre-tarsal
orbicularis oculi is seen. This may
be an isolated phenomenon or occur in Parkinson’s disease or progressive
supranuclear palsy providing further circumstantial evidence for an
extrapyramidal origin for the condition. The
differential diagnosis includes (for example in Tourette’s syndrome),
Hemifacial spasm, facial myokymia, orbicularis oculi myotionia and secondary
blepharospasm due to ocular surface disorders.
Most
cases of idiopathic blepharospasm can be diagnosed clinically and do not require
investigation such as neuro-imaging. In
cases where there is diagnostic difficulty, blink reflex studies may be helpful.
The patient and relative require an explanation of the problem as an
organic movement disorder probably due to chemical imbalance in the movement
control centres. They should be
reassured that the condition will remain localised and that even cranial
Dystonia will not spread to become generalised.
It should be emphasised that the condition cannot be cured but that the
aim of treatment is to minimise the disability and enable the sufferer to
continue to lead as normal a life as possible.
The
first line treatment is injections of Botulinum toxin A into the orbicularis
oculi muscle to reduce the intensity and often the frequency of forceful eye
closure. Side effects such as
partial Ptosis or temporary double vision are relatively rare and resolve
spontaneously. About two thirds of
patients benefit from this treatment, about one third of them to the extent that
injections have to be repeated at 2 to 3 month intervals indefinitely.
Systemic
drug treatment is rarely beneficial. Claims
have been made for anticholinergics and clonazepam; they are worth trying if
there is poor or incomplete response to botulinum toxin.
Symptomatic treatment with ocular lubricants is sometimes helpful.
In cases that are totally refractory an attempt may be made to either
denervate the orbicularis oculi muscle permanently by facial nerve avulsion or
to remove the muscle (orbicularis oculi myectomy).
Both are difficult operations that need to be done by specialists in the
field; each has side effects and drawbacks.
Brow suspension may be helpful in pre-tarsal variant.
Written by John
Elston,
Taken from Eye News,
courtesy of The Dystonia Society,
London
.
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