A quantitative assessment of the brain stem auditory evoked response during intraoperative monitoring.

The brain stem auditory evoked response (BAER) was monitored intraoperatively in 11 patients with tumors of the posterior fossa. A technique for the objective quantitative assessment of the BAER based on the variance of the phase angle between small group averages is described. The resulting component synchrony measure corroborated standard peak latency and amplitude changes of the BAER during operative manipulation. A discussion of the replication and use of the objective measure is presented.