[Monitoring of the auditory stem evoked potentials in removal of tumors of the posterior cranial fossa].

The material of intraoperative monitoring of the acoustic stem evoked potentials (ASEP) in 9 patients with tumors of the stem and in 28 patients with the parastem localization was analyzed. It was shown that changes in the amplitude of ASEP rather than latency were the decisive factor in the assessment of the functional state of the brain stem. It was found that even the pronounced changes of the bioelectrical activity recorded during the excision of the tumor could be reversible after a change of the strategy of the operative intervention and/or after performing the necessary therapeutic measures. An important test of favorable prognosis of the postoperative course is considered to be the normalization of brain activity, ASEP included, at the final stages of the operation.