SJ Lim, et al / Ganglion Impar Block With Botulinum Toxin Type A 69 ical studies rather than animal experiments, which provides a basis for the sustained effect and the decrease in VAS as compared with cases in which the patient underwent blockage of the ganglion impar using conventional types of local anesthetics. Accordingly, as shown in animal ex- periments in which formalin was used [8], the mechanism of BoNT-A is not referred to as direct destruction of nerve fibers, rather based on blockage of pain-controlling neurotransmitters. A reversible, transient analgesic effect is considered one of the advantages in the current case, and. in agreement with an experimental animal reports by Kim et al. [18] in which BoNT-A caused no marked histo- pathologic changes as compared with cases in which blockage was done using alcohol or phenol, and the effects were persistently present for ＞ 1 month. 　　In the current case, the use of BoNT-A for blockage of the ganglion impar was safer than neurolysis based on the previous types of chemical or high-frequency ablation. The effects were superior to cases in which local anes- thetics were solely used, and the analgesic period was prolonged. Based on these advantages, BoNT-A is pro- posed as a new method for blocking the sympathetic nerv- ous system. Aside from these advantages, there are also disadvantageous in that BoNT-A can pose a safety issue. BoNT-A is rather expensive and requires serial use. In as- sociation with this, in adults weighing 70 kg in which the LD50 of BoNT-A amounts to 3,000 U, the common clinical dose is at most 25-100 U and it can therefore be consid- ered very safe. 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