LAUSR

Abstract Aim The aim of the present study was to evaluate the effects of different doses of onabotulinum toxin A on the amplitude and latency values of the blink reflex and facial nerve in the pretarsal and preseptal portions of the orbicularis oculi muscle in patients with hemifacial spasm. Materials and methods Thirty patients with hemifacial spasm were assigned in two equal groups: Pretarsal Group: Five units of onabotulinum toxin A were injected into each of 2 points of the pretarsal portion; Preseptal Group: Five units of onabotulinum toxin A was injected into 4 points of the preseptal portion. We compared the electromyographic features of the patients before and 5 weeks after botulinum toxin (BTX) injection. Results In comparison of pre- and post-treatment measurements of blink reflex amplitude responses, the decreases in R1 (p = 0.003), R2 (p < 0.001), and R2C amplitudes (p = 0.031) were found to be significant in the BTX injected side in the pretarsal group. In the comparison of pre- and post-treatment measurements of facial nerve compound action potential amplitude changes, decreases in the amplitudes of the BTX injected (ipsilateral), and uninjected (contralateral) side in the pretarsal group were found to be significant (p < 0.001 for both groups). Decreases in the amplitudes of the BTX injected, and uninjected side in the preseptal group were found to be significant (p < 0.001, and p = 0.008, respectively). Conclusion According to our hypothesis, the smaller amount of BTX applied to the pretarsal portion was found to be more effective than higher amount of BTX injected into the preseptal portion of the orbicularis oculi muscle.