Pretarsal blepharospasm: Clinical and electromyographic characteristics

Area of Science:

• Ophthalmology
• Neurology
• Clinical Electrophysiology

Background:

• Blepharospasm is a focal dystonia characterized by involuntary eyelid closure.
• Primary treatment failure to botulinum toxin suggests alternative underlying mechanisms.
• Selective involvement of the orbicularis oculi muscle's pretarsal portion can cause a distinct blepharospasm phenotype.

Purpose of the Study:

• To characterize the clinical and electromyographic features of blepharospasm originating from the pars pretarsalis of the orbicularis oculi muscle.
• To evaluate the efficacy of targeted botulinum toxin injections in patients with this specific type of blepharospasm.

Main Methods:

• Clinical assessment and simultaneous electromyography of eyelid muscles (levator palpebrae superioris, orbicularis oculi pars orbitaria and pretarsalis).
• Identification of patients with selective abnormal electromyographic activity in the pretarsal orbicularis oculi.
• Treatment with selective botulinum toxin injections into the pretarsal region.

Main Results:

• Twenty-four patients with electromyographically confirmed pretarsal blepharospasm were identified, all experiencing functional blindness.
• Three clinical-electromyographic patterns were observed: impaired eyelid opening, increased blinking, and spasms of eye closure with blinking issues.
• Botulinum toxin injections into the pretarsal muscle led to significant improvement, with 50% regaining near-normal vision, sustained by repeat treatments.

Conclusions:

• Pretarsal blepharospasm is a clinically identifiable and electromyographically confirmable condition.
• Early recognition and targeted botulinum toxin therapy yield excellent outcomes, improving vision and quality of life.