Blepharospasm

Benign essential blepharospasm is a focal dystonia causing involuntary, bilateral, synchronous contraction of orbicularis oculi, procerus and corrugator.

• Onset usually between 40 and 70 years, women more than men (about 2 to 3:1).
• Prevalence about 5 per 100,000. Sporadic in most; rare familial forms.
• Pathophysiology: dysfunction of basal ganglia and thalamocortical sensorimotor integration, with abnormal blink reflex excitability. Photophobia and dry eye act as sensory triggers.
• Functional blindness results from eyelid closure despite normal eyes, with impaired driving, reading and mobility.

• Increased blink rate progressing to sustained spasms of eye closure lasting seconds to minutes.
• Triggers: bright light, wind, stress, driving, reading, crowds. Relief with talking, singing, humming, pulling the lid or touching the brow (sensory tricks).
• Spasms vanish in sleep.
• Spread to lower face and jaw (Meige syndrome: blepharospasm with oromandibular dystonia) in about 15 to 20 percent.
• Associated dry eye, photophobia, ocular surface discomfort in most.
• Examination of the globe is normal apart from surface disease.

• Clinical, from observation of the blink pattern and sensory tricks.
• Exclude secondary causes: hemifacial spasm (unilateral, persists in sleep, asynchronous lower lid onset), apraxia of lid opening, myokymia, tic, reflex blepharospasm from ocular surface disease, tardive dyskinesia from dopamine antagonists.
• Review drugs: neuroleptics, metoclopramide, levodopa, antidepressants.
• MRI brain if atypical features, young onset, unilateral signs, or other neurological findings.
• Tear film and ocular surface assessment (Schirmer, fluorescein staining) because treating surface disease reduces triggers.

• First line: botulinum toxin A injections into pretarsal and preseptal orbicularis, orbital orbicularis and corrugator.
  • OnabotulinumtoxinA 1.25 to 2.5 units per site, 4 to 6 sites per eye (total usually 10 to 15 units per eye), every 3 to 4 months. Effect begins at 3 to 7 days and lasts 8 to 12 weeks.
  • Adverse effects: ptosis, lagophthalmos, dry eye, diplopia, ectropion. Avoid injecting medial lower lid (diplopia, epiphora).
  • Efficacy about 90 percent of patients. Resistance from neutralising antibodies is uncommon; switch to another toxin serotype.
• Lubricants, treat blepharitis and dry eye; tinted lenses (FL-41 tint) for photophobia.
• Oral drugs have modest benefit: clonazepam 0.5 to 2 mg at night, trihexyphenidyl 2 to 20 mg daily in divided doses, tetrabenazine 12.5 to 75 mg daily.
• Surgery for toxin failure: upper lid protractor myectomy (orbicularis, procerus, corrugator), with improvement in 75 to 90 percent. Complications include dry eye, brow ptosis and lagophthalmos.
• Eyelid crutches for ptosis type apraxia, supportive counselling and patient support groups.