Objective: Chronic microvascular compressions of the eighth nerve induce a slowing down of signal transmission in the auditory nerve, electrophysiologically characterized by IPL I-III prolongation.
Methods: The authors hypothesize this is compensated by an active slowing down of signal transmission of the contralateral input at the level of the brainstem, characterized by contralateral IPL III-V prolongation.
Results: Differences between ipsilateral and contralateral IPL I-III and IPL III-V are analyzed before and after microvascular decompression. ABR diagnostic criteria for microvascular compression are ipsilateral IPL I-III prolongation or ipsilateral peak II decrease + ipsilateral IPL I-III prolongation. With IPL I-III as diagnostic criterion, unlike preoperatively the difference between the ipsi- and contralateral IPL I-III is significant postoperatively. When using the stricter diagnostic criterion of IPL I-III + peak II, there is a preoperative significant difference between ipsi- and contralateral IPL I-III, but postoperatively the difference between the ipsi- and contralateral IPL I-III is not significant.
Conclusions: Preoperatively, there is a marginal significant difference between the ipsi- and contralateral IPL III-V, which disappears postoperatively.