Effects of botulinum toxin on electrophysiological monitoring the lateral spread response in the facial nerve microvascular decompression surgery

Abstract

Objective To investigate the effects of facial injecting botulinum toxin on electrophysiological monitoring indicator lateral spread response (LSR) in patients with hemifacial spasm in microvascular decompression surgery. Methods Ninety patients with facial spasm underwent microvascular decompression surgery in Guangdong No 2 Provincial People's Hospital from July 2013 to December 2014 were enrolled retrospectively. They were divided into either a botulinum toxin group (n=18) or a non-botulinum toxin group (n=72) according to whether they injected botulinum toxin or not. The effect of botulinum toxin on the changes of intraoperative LSR and the role of LSR changes in prognostic evaluation were observed. Results The mean LSR latency of the zygomatic branch in the botulinum toxin group was 11.4±2.1 ms, and in the non-botulinum toxin group was 9.3±1.4 ms. There was significant difference (P 0.05). The LSR amplitude of the zygomatic branch in botulinum toxin group was 116.1±61.1 μV, and in mandibular branch was 116.1±54.5 μV; the zygomatic branch was 125.9±52.1 μV, and the mandibular branch was 125.9±52.1 μV in the non-botulinum toxin group. There was no significant difference between the 2 groups. After implantation of shims, the LSR disappear rates of zygomatic branchs, and mandibular branch were 16/18and 17/18 respectively in the botulinum toxin group; the zygomatic branch disappear rate in the non-botulinum toxin group was 90% (65/72) and that in the mandibular branch was 96% (69/72). There was no significant difference between the 2 groups (P>0.05). The sensitivity of the disappearance of zygomatic branch LSR for prognostic judgment in the botulinum toxin group was 94% (15/16), and in the non-botulinum toxin group was 98% (64/65). There was significant difference (P<0.05). The mandibular branch LSR, and the sensitivities of both zygomatic branch and mandibular branch disappeared simultaneously for prognostic judgment in the botulinum toxin group were 94% (16/17) and 94% (15/16) respectively; and in the non-botulinum toxin group were 92% (64/69) and 96% (59/61) respectively. There was no significant difference between the 2 groups. Conclusions Botulinum toxin has influence on intraoperative LSR. It is expressed as the prolonged LSR latency of zygomatic branch. The way of monitoring with mandibular branch or in combination with zygomatic branch LSR may be better than simply monitoring zygomatic branch LSR. Key words: Microvascular decompression surgery; Nervous system physiological processes; Hemifacial spasm; Botulinum toxins; Lateral spread response