[Intraoperative ABR Monitoring in Neurosurgery]

Monitoring of the intraoperative auditory brainstem response (ABR) is a less invasive, easy, and useful method for hearing preservation in patient undergoing cerebellopontine angle surgery such as microvascular decompression (MVD) and excision of an acoustic neurinoma. The ABR is tolerant of both inhalation and intravenous anesthesia. However, ABR recordings are highly susceptible to electrical noise from surgical devices. Therefore, for ABR recordings to be reliable, noise must be minimized and appropriate evaluation of waveform changes is critical. Electrode setting with low contact impedance and bilateral derivation effectively address these issues. Prolongation of the wave V latency alerts to surgical stress on the cochlear nerve due to nerve stretching from cerebellar retraction. According to Sekiya, the surgeon performing MVD or acoustic neurinoma excision should be warned as soon as latency prolongation exceeds 1.5 msec or characteristics of ABR must be understood. even less than 0.5 msec, respectively. However, hearing was preserved in some patients with false-positive results with respect to intraoperative wave V diminution. To use it as a useful intraoperative modality, the Characteristics of ABR must be understood.