[An analysis of the level and bilateralness of disorders of the brain stem auditory evoked potential in tumors of the posterior cranial fossa with different locations].

The method of stem auditory evoked potential was used in the examination of 39 patients with tumors of the posterior cranial fossa of various localization. The time indices of the response were analysed: the peak latency of components I, III, and V and interpeak I-III, III-V, and I-V intervals. The most coarse disorders were revealed in patients with tumors of the cerebellopontile angle (100% of cases), which were clearly lateralized. Changes of stem auditory evoked potential in patients with cerebellar tumors were encountered somewhat less frequently (in up to 90%) and the response was asymmetric in most cases. As compared to the first group, however, a high percentage of disorders of component V to stimulation of the intact side was noted. Among patients with median localization of the tumor (vermis cerebelli, floor of fourth ventricle) changes were found in 62% of cases (component V). No authentic differences to stimulation of different sides were revealed. The authors discuss problems on the levels of occurrence of disorders of stem auditory evoked potential in patients with lesions of posterior cranial fossa structures.