Vascular compression of the cochlear nerve and tinnitus : a pathophysiological investigation

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. 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. 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. Preoperatively, there is a marginal significant difference between the ipsi- and contralateral IPL III-V, which disappears postoperatively.