[Wave-length changes of the early auditory evoked potentials in acoustic neuroma].

In 37 patients with a surgically proven unilateral acoustic neuroma early auditory evoked potentials (EAEP) were studied. The waves showed alterations, which allowed classification of the patients into groups with special potential characteristics. In Group A, waves I to V were normal; Group B showed a normal wave I whereas waves II to V were altered. In Group C wave I was altered, too, whereas Group D showed only a delayed wave V. In Group E it was not possible to detect waves at all. Classification into Groups A to E facilitates differentiation between a cochlear and retrocochlear lesion. The waves of the contralateral side allow an assessment of the size of the tumour. Large neuromas compress the brain stem and produce a deterioration of the midbrain answer by herniation of the midbrain in the tentorium gap.