Authors (including presenting author) :
Lai KKH(1), Tsang AWT(1), Kuk AKT (1), Wang ST(1), Ko CKL (1), Chan E(1), Ko STC(1)
Affiliation :
(1) Department of Ophthalmology, Tung Wah Eastern Hospital
Introduction :
Botulinum neurotoxins are bacterial exotoxins produced by several bacteria of the genus Clostridia and they interfere with the exocytotic release of vesicular neurotransmitters in both motor and sensory neurons. The limited diffusion of Botulinum neurotoxin from the site of injection as well as its reversibility gives this toxin a good therapeutic potential.
Both BEB and HFS are facial dystonias that can impair daily activities and affect psychosocial life. Any delay in treatment may lead to serious complications, such as functional blindness and poor quality of life. Botulinum neurotoxin is a popular and well-established treatment for both movement disorders.
Development of tolerance is an adaptive response of the body to prolonged exposure to the drug, it is commonly reported in antiepileptic drugs. Tolerance occurs when the body becomes accustomed to the medication so that a higher dosage is needed to give a similar therapeutic effect. The poor responsiveness to Botulinum neurotoxin among different muscle disorders have been reported and one of the explanations would be the immunological response with the development of antibodies. Jankovic and Schwartz et al reported that the level of antibodies was correlated with the complete failure of response to Botulinum neurotoxin injections. However, Siatkowski et al reported that the presence of antibodies failed to correlate with the patient’s clinical response among patients with BEB, HFS, and Spasmodic torticollis.
Objectives :
Our Botox clinic has been serving those with BEB and HFS for over 20 years at Tung Wah Eastern Hospital in Hong Kong. In this study, we aim to report the long-term complications and report any tolerance to Botox in patients with BEB and HFS from our experience.
Methodology :
A retrospective review of clinical documents and procedure records of consecutive BEB and HFS patients receiving onabotulinumtoxin A(Botox) treatment in our BOTOX clinic over the past 20 years.
Result & Outcome :
The information of 105 patients diagnosed with HFS(74) and BEB(31) were reviewed, and all patients were Asian. The average age of disease onset was 61(range,31-83) and 59(range,37-80) years old for HFS and BEB respectively. The average follow-up interval was 84(range,12-240) months and the average number of Botox injections per patient received was 19(range,1-61)sessions. The Botox dose per session ipsilaterally increased significantly in both BEB(16.5vs 21.6 units, p< 0.05) and HFS(22.6 vs 26.9 units, p< 0.05) patients after an average of 18 injection sessions. The Botox dose increased substantially without reaching a plateau, meanwhile, the onset time, effective duration and subjective spasm alleviation scale to assess the subjective treatment outcome were similar over time(18injections)in both BEB and HFS patients. At least one local complication was reported among 26% and 41% of patients with BEB and HFS respectively and ptosis (32%) was the most frequent complication. All local complications resolved gradually within 6 weeks without systemic or life-threatening event.
Conclusion:
The Botox dose increased significantly over time without compromising the treatment outcome in both BEB and HFS patients. We suggest to emphasize the potential tolerance phenomenon in the long term Botox usage to either BEB/HFS patients during pre-injection consultation.
