Blinking Parameters Do Not Normalize After Botulinum Toxin Therapy in Blepharospasm and Hemifacial Spasm Patients

Area of Science:

• Ophthalmology
• Neurology
• Biomedical Engineering

Background:

• Blinking parameter changes after botulinum toxin (BoNT) injections for blepharospasm (BSP) and hemifacial spasm (HFS) are not well understood.
• Investigating these objective changes is crucial for understanding treatment efficacy and patient outcomes.

Purpose of the Study:

• To objectively assess the impact of botulinum toxin (BoNT) injections on blinking parameters in patients with BSP and HFS.
• To compare post-treatment blinking metrics with those of healthy individuals.

Main Methods:

• Thirty-seven BSP and HFS patients were evaluated before and 30 days after onabotulinumtoxinA injections.
• A high-speed camera and microlight-emitting diodes were used to record blinking frequency, amplitude, and eyelid closure velocity.
• Data were compared between pre- and post-treatment states and with 12 age-matched controls.

Main Results:

• BoNT injections significantly reduced blinking amplitude, frequency, and velocity in BSP and HFS patients compared to baseline.
• Post-treatment, blinking amplitude and velocity remained significantly lower in BSP and affected HFS sides compared to controls.
• Even before treatment, BSP and HFS patients exhibited significantly lower eyelid closure velocity than controls.

Conclusions:

• While blinking frequency approached normal levels, amplitude and velocity did not normalize after BoNT treatment in BSP and HFS patients.
• Blinking parameters, particularly velocity, remain altered post-treatment, indicating incomplete normalization.
• Reduced eyelid closure velocity is an intrinsic characteristic of BSP and HFS, present even before BoNT intervention.