Objective: To investigate the effectiveness of BoNT treatment in patients with essential blepharospasm and determine the most common reasons for discontinuation of the
treatment.

Background: Essential blepharospasm is a focal dystonia characterized by involuntary, excessive contractions of the eyelid muscles. The first-line treatment is BoNT injections.

Method: We studied the patients who have received BoNT injection in the Pauls Stradiņš Clinical University Hospital at least once between the years 2018-2020. The
following data was collected from our local registry and phone call interviews: gender, age of onset, the total number of injections, the date of the first BoNT injection, response to BoNT, side effects, reasons for treatment discontinuation. The registry contains 74 patients data of which 56 were interviewed over the phone and included in the study.

Results: Out of all 56 included patients 77% (n=43) were female. Mean age was 67.8+/-11 years, the youngest patient was 41, the oldest – 90 years old. The mean age at the onset of blepharospasm was 57.7+/-11.7 (23-80) years. The mean time from the disease onset till BoNT treatment was 5.5 years, the longest time till treatment – 49 years. The patient group received a total of 478 treatments, and a mean treatment number was 8.5+/-7.3. Only 7% (n=4) of patients estimated injections as ineffective. 50%(n=28) of patients experienced side effects, 21% (n=12) after every injection. The most common side effect was transient ptosis (Table1). [Table1]. 
Overall, 57% (n=32) patients discontinued or postponed therapy. The most common reason was the COVID-19 pandemic with 31% (n=10) of discontinuation cases (Figure1). The second most common reason was side effects – 28% (n=9). Four patients noted multiple reasons. Two patients who discontinued treatment because of the COVID-19 pandemic have since resumed it. 
[Figure1]. 
Half of the treatment discontinuation cases – 50% (n=16) occurred in the year 2020.

Conclusion: The most common reason for discontinuation of treatment with BoNT was the Covid-19 pandemic, and only a minority of those patients have resumed the treatment. As the pandemic still continues, we have to provide a safe injection environment for patients. Another common reason for discontinuation of the treatment is the side effects. The possibility of the side effects should be explained and emphasized.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-main-reasons-for-essential-blepharospasm-botulinum-neurotoxin-bont-treatment-discontinuation-in-latvian-population/