Delayed facial nerve paresis after using the KTP laser in the treatment of cholesteatoma despite inter-operative facial nerve monitoring

To describe an unforeseen complication that occurred in three patients following the use of the KTP laser. We present a case series including three consecutive patients (two boys and one girl, mean age 11.7 years) who underwent tympanomastoidectomy using a KTP laser and standard intra-operative facial nerve monitoring, and in whom a post-operative facial nerve injury was identified. Intra-operatively, the facial nerve was not encountered or exposed, and the KTP laser was not used directly on the nerve. The facial nerve monitor did not alarm. The three patients began experiencing a paresis from POD #7-9, with House-Brackmann facial nerve score of II-III at maximum severity. This resolved fully between 4 and 7 weeks after the onset of the paralysis. The KTP laser during cholesteatoma surgery has been shown to decrease residual disease but may however also cause a temporary, delayed, mild facial nerve paresis. We discuss the mechanisms for injury and the role of intra-operative facial nerve monitoring in the context of this uncommon and unforeseen complication.