Advances in monitoring of seventh and eighth cranial nerve function duringposterior fossa surgery

Objective: This study aimed to illustrate some recent advances in intraoper ative monitoring of the seventh and eighth cranial nerves (i.e., direct rec ording of cochlear nerve action potentials [CNAPs] and facial nerve action potentials [FNAPs]). Study Design: Reports of representative cases and average postoperative res ults obtained in subjects submitted to cerebellopontine angle surgical proc edures are examined. Results obtained in patients with direct recording tec hniques are compared with those obtained with the classical monitoring tech niques (auditory brain stem response [ABR], electrocochleography [ECoG], fa cial electromyography [EMGI]). Setting: The study was conducted at an Ear Nose and Throat Department, Univ ersity of Verona, Verona, Italy. Intervention: Intraoperative monitoring during cerebellopontine angle surge ry was performed. Results: Patients monitored with direct audiomonitoring techniques presente d better postoperative auditory functions compared to patients monitored wi th ABR. The FNAP and EMG groups showed FN outcome that did not differ signi ficantly. Conclusions: Intraoperative monitoring of cranial nerves furnishes a valid tool for identification of neural structures, prevention of damage, underst anding of the pathophysiology of damage, and prediction of postoperative fu nction. The fundamental prerequisite for obtaining optimal benefits from mo nitoring is the use of techniques of direct and continuous electrophysiolog ic recording with instantaneous feedback to the surgeon, such as CNAPs and FNAPs.