Quantitative changes in botulinum toxin a treatment over time in patients with essential blepharospasm and idiopathic hemifacial spasm

PURPOSE: To evaluate the quantitative changes in botulinum toxin A (BTA) treatment required over time to achieve relief for 3 to 4 months in patients with essential blepharospasm (EBS) and idiopathic hemifacial spasm (IHFS). DESIGN: Interventional case series. METHODS: In this retrospective longitudinal study in an institutional ophthalmologic outpatient clinic, data were retrieved from patient files and a comparison between patients with EBS and IHFS was performed. The patient population consisted of 27 patients, 17 with EBS and 10 with IHFS, who were treated for the first time with BTA injections and were followed up for 4 to 6 consecutive years. All patients initially received 12 or more courses of treatment with a lower dose (≤20 U) and were then switched to a higher dose (>20 U). The main outcome measures were the shift in the dose-response relationship between the lower and higher doses and were analyzed with respect to four variables: average number of treatments, dosage, duration of therapy, and interval of symptomatic relief. RESULTS: In the EBS group the mean dose for each patient changed from 16.0 ± 1.4 U (lower dose) to 24.2 ± 1.4 U (higher dose). The shift occurred after a mean of 8.8 ± 2.9 treatments per patient given for a mean of 33.5 ± 13.3 months. The mean interval of relief was longer with the lower dose than with the higher dose (4.0 ± 1.4 months vs 3.2 ± 1.0 months, respectively). In the IHFS group, the mean dose / patient changed from 16.8 ± 1.2 U to 25.0 ± 1.8 U, and the switch occurred after a mean of 6.5 ± 2.3 treatments given over a mean period of 23.8 ± 6.6 months. The mean duration of treatment with the lower dose was shorter than with the higher dose. The interval of relief was similar for both dose ranges (3.8 ± 10 months and 4.1 ± 1.3 months, respectively). The IHFS group switched to the higher dose earlier, by both number and duration of treatments, than the EBS group. Only minor and transient side effects of treatment were observed in both groups. CONCLUSIONS: Botulinum toxin A is an effective and safe treatment for EBS and IHFS. The dose in our study was increased over time by 50% to achieve 3 to 4 months of symptomatic relief with minimal complications.