Delayed facial palsy following laser stapedectomy: in vitro study of facial nerve temperature.

Delayed facial palsy following conventional stapes surgery is a rare event, but this complication appears to be more common when a laser is used. We have investigated the temperature in the facial canal during stapes surgery using a KTP laser or a microdrill in preserved human temporal bones. Thermocouples were placed in the facial canal and under the foot plate. The results show maximum rises in temperature of between 1.4 degrees C and 15.2 degrees C in the facial canal during laser surgery (mean 6.1 degrees C, SD 4.5 degrees C), but only between 0.45 degrees C and 2 degrees C during procedures in which a microdrill was used (mean 0.9 degrees C, SD 0.9 degrees C) (P = < 0.009). In addition, the facial nerve undergoes repeated heating and cooling cycles during the laser surgery. We conclude that heating of the facial nerve during laser surgery causes oedema, which in turn leads to compression of the nerve within its bony canal.