Object: Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery.
Methods: Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone-elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed.
Results: A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade.
Conclusions: Preservation of function was significantly better for patients who received extended recuperation treatment.
Keywords: AEDNAP = auditory evoked dorsal cochlear nucleus action potential; AN = acoustic neuroma; APR = amplitude preservation ratio; AUC = area under the curve; BAEP = brainstem auditory-evoked potential; FREMAP = facial nerve root exit zone–elicited compound muscle action potential; GR = Gardner-Robertson; HB = House-Brackmann; M-max = maximum peak-to-peak amplitude; ROC = receiver operating characteristic; acoustic neuroma surgery; continuous direct brainstem auditory evoked potential monitoring; oncology.