The normal adult blinks at a rate of 10 to 20 times per minute. This tends to be reduced when reading or using the computer. An increase in lid closure frequency and tone is known as blepharospasm. This is a focal dystonia appearing in adults with recurrent spasms of eye closure; the orbicularis oculi muscle contracts forcibly and involuntarily. This lasts for periods varying from seconds to minutes and often repeatedly. The spectrum of disease ranges from an increased blink rate with occasional spasms to a severe, disabling and painful condition. Occasionally, it can be so intense it results in severe visual impairment.
Blepharospasm is a subtype of focal dystonia. Most cases are idiopathic and termed benign essential blepharospasm or primary blepharospasm. In the case of blepharospasm, the involuntary closure of the eyelids is due to spasms of the orbicularis oculi muscle. This is as opposed to a failure of contraction of the levator palpebrae muscle, which is the case in apraxia of eyelid opening, which occurs in Parkinsonian conditions. The aetiology of blepharospasm is not understood. It has been thought to be caused by pathology within the basal ganglia, although this has not been proven. It appears that multiple cortical and subcortical structures may be involved.The circuit involved in blinking involves a sensory limb, a central control area in the midbrain and a motor limb. It is thought that there is a defect in this neuronal circuit activity. The precise mechanism is not known but it is likely that there is more than one defective locus resulting in neurotransmission overload and blepharospasm.
There are cases of secondary blepharospasm due to identifiable organic disease. Ocular causes include:
- Eye trauma (mechanical, chemical or thermal) - particularly to the cornea - will cause acute blepharospasm.
- Conjunctivitis, iritis, keratitis.
- Dry eye.
- Other chronic lid disease or ocular surface disease.
- Less commonly, glaucoma or uveitis.
It may also occur in systemic conditions:
- Multiple sclerosis (uncommon manifestation).
- Focal brain injury or tumour
- Infections (viral encephalitis, Reye's syndrome, subacute sclerosing panencephalitis, Jakob-Creutzfeldt disease, AIDS, tuberculosis, tetanus).
- Atypical Parkinson's disease/multiple system atrophy/progressive supranuclear palsy.
- Adverse drug reactions - eg, olanzapine, levodopa.
- Tardive dyskinesia.
- Tourette's syndrome.
- Cerebral palsy.
There is evidence of some genetic component, although there is only around 5% chance of it being inherited. In one study of relatives of 56 affected individuals, it was found 27% had a first-degree relative affected by blepharospasm or other dystonia.Autosomal dominant transmission was assumed.
Prevalence estimates vary widely and range from 16 to 133 per million. Essential blepharospasm affects women more commonly than men.It is more common with advancing age and typically develops in the sixth decade.
- Spasms of eye closure usually occur in bright light or when reading or watching television. Driving, fatigue and stress can also bring the spasms on.
- Concentration on a task may improve or abate the spasms or reduce their frequency. Talking, whistling, touching the face, walking and relaxation have also been found to improve the problem. (Most people blink more frequently during conversation than at rest, whereas in those with blepharospasm this is reversed.)
- There may be associated eye irritation, mid-facial or lower facial spasm, brow spasm and eyelid tic.
- Nocturnal symptoms are unusual.
- In essential blepharospasm, symptoms are always eventually bilateral, although they may begin unilaterally.
- Hemifacial spasm. "Babinski's other sign": It is sometimes tricky to distinguish blepharospasm from hemifacial spasm. In the latter, the frontalis muscle contracts at the same time as orbicularis oculi, producing a net effect of the eye being tightly squeezed shut with a raised eyebrow. This cannot be reproduced voluntarily.
- Apraxia of eyelid opening.
- Myasthenia gravis.
- It may be linked with an oromandibular dystonia characterised by recurrent spasms of face, oropharynx and larynx. This causes spasms of lip and jaw movement, chin jutting and problems with speaking and swallowing. Patients may develop oromandibular dystonia after blepharospasm and vice versa. Where blepharospasm is associated with involuntary movements of the lower facial and/or jaw muscles this is often called Meige (or Meige's) syndrome. As Meige himself was neither the first person to describe this nor a sufferer, it has been pointed out there is no reason for the syndrome to bear his name.
- Brueghel's syndrome is characterised by blepharospasm associated with severe mandibular and cervical muscle involvement. Likewise it has been pointed out that definitions vary and are imprecise.
- Cognitive dysfunction has been reported in these patients but has not been widely studied and therefore little is known of this at present.
- Untreated, the condition can cause severe psychological distress and is associated with significant psychiatric comorbidity.
Reflex blepharospasm to a secondary cause must be ruled out but, otherwise, isolated blepharospasm does not usually require investigating. Any associated neurological problem should prompt a neurology review.
The Blepharospasm Disability Index is a scale used to assess the functional impairment in these patients. It is a self-rating response scale. It correlates well with the Jankovic Rating Scale, an objective measure of severity and frequency of involuntary lid movements.Both may be used in a specialist setting to assess treatment outcomes and are also useful research tools.
- Blepharospasm can be a reflex reaction to an underlying disease (most commonly, ocular surface disease) and this needs to be ruled out/managed initially.
- Wearing dark glasses can reduce bright light triggers and prevent embarrassment due to the stares of onlookers.
- Voluntary manoeuvres, such as pulling the eyelid, pinching the neck, talking, yawning, humming and singing, help some individuals.
- Patients with severe blepharospasm must not drive. Those with mild or well-controlled blepharospasm may drive subject to a consultant's approval.
- Blepharospasm does not respond well to antispasmodics or benzodiazepines.
- A number of drugs have been tried with varying success with different types of blepharospasm but, overall, their efficacy is limited. Tetrabenazine has been shown to be of moderate benefit in some patients.
Botulinum toxin injections
The preferred treatment is injection of botulinum toxin type A into the orbicularis oculi muscle. A Cochrane systematic review found the treatment to be highly effective, helping up to 90% of patients compared with placebo.Botulinum toxin interferes with the acetylcholine release from nerve terminals, so resulting in temporary spasm of the injected muscle. Predetermined doses are injected in four spots along the upper and lower lids resulting in a temporary relief in most patients.
Dose is dependent on preparation used and the product leaflet should be consulted. Subsequent treatment is determined by the patient's response (there may be a need for a slight increase or decrease in units given). Most patients need re-treatment every three months or so and progressively larger doses may be needed over a long period of time.
Side-effects include lagophthalmos, ectropion or entropion. Epiphora, dry eye and occasionally associated keratitis have also been noted. Accidental migration of the toxin into the orbit can result in a ptosis ± diplopia. All these effects (as well as the beneficial ones) wear off over three to four months.
Where vision is severely impaired by prolonged, severe eye closure, unresponsive to pharmacological techniques, protractor myomectomy may be used (removal of some muscles of eye closure). It can significantly improve visual disability in those in whom botulinum toxin injection is ineffective, and for those who have associated apraxia of eyelid opening (a condition not improved by injections).
Deep brain stimulation
Deep brain stimulation (DBS) has been used for other forms of dystonia. It is occasionally used for refractory blepharospasm, in particular when it is a part of Meige syndrome.
Most cases of primary blepharospasm cannot be cured although symptomatic relief is good with botulinum toxin injections. The long-term safety and efficacy of this drug appears to be excellent.[18, 19]
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