ABSTRACT
Introduction:
Hemifacial spasm (HFS) is characterized by the involuntary tonic-clonic movement of the muscles of the hemiface. It is usually treated with botulinum toxin (BTX). The classically described unilateral application of BTX results in an asymmetry similar to facial paralysis. The aim of this study was to standardize the treatment of HFS by applying BTX bilaterally to prevent the occurrence of iatrogenic facial asymmetry.
Methods:
The outcomes of 66 applications in 15 patients were analyzed according to the protocol of the facial paralysis service, to which pretarsal sites were added on the HFS side. On reassessment 15 days later, a complementary dose was administered to patients who exhibited some residual degree of spasm or asymmetry with the aim of determining the dose required to achieve satisfactory spasm control without causing facial asymmetry.
Results:
The total mean dose was 20.2 U at the contralateral side and 28.4 U at the spasm side (a total dose of 48.6 U per application). There was a significant difference between the doses applied to the zygomaticus, orbicularis oris, and orbicular oculi muscles on each hemiface.
Conclusions:
The proposed bilateral BTX application technique was effective in controlling HFS and prevented iatrogenic asymmetry. In general, application should be performed at a ratio of 1:1.5 U in the orbicularis oculi (lateral portion) and 1:2 U in the orbicularis oris. In the remaining muscles, the same dose should be administered on both sides and an additional dose can be applied 15 days later if some degree of spasm is present. The pretarsal region of the orbicularis oculi muscle is the only area for which BTX application on the healthy side is unnecessary.
Keywords:
Botulinum toxin type A; Facial paralysis; Facial asymmetry/therapy; Hemifacial spasm
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