[Electric response audiometry (brain stem potentials and late potential N1) in patients with acoustic neurinoma or space-occupying lesion in the region of the brain stem].

In patients with acoustic neuronoma or space-occupying lesion in the region of the brainstem we recorded preoperatively the brainstem potentials as well as the late potential N1. With one exception all patients investigated showed changes in the brainstem potential pattern. When stimulating monaurally there exists a clear side difference, that means the changes in the potential pattern are more distinct on the side of the tumour than on the opposite side and then only if an obstructive hydrocephalus exists. Moreover we could demonstrate in patients with tumours in the region of the brainstem that the brainstem potential IV is no longer suitable for measuring the hearing threshold. On the other hand in these patients an exact determination of the hearing threshold is possible with the late potential N1. Altogether the findings show, that the recording of the brainstem potentials when stimulating monaurally is an important additional diagnostic tool to recognize impairment of the acoustic pathways within the brainstem and probably affords the possibility of perceiving pathological pressure within the brain.