Tinnitus in vascular conflict of the eighth cranial nerve: a surgical pathophysiological approach to ABR changes

Microvascular Compression of the Vestibulocochlear Nerve

“…If MVC of the cochlear nerve creates functional impairment of some fibers, the temporal coherence of firing will decrease, resulting in a decrease of the amplitude of peak II. This hypothesis is supported by clinical findings that show a peak II decrease in individuals with tinnitus ipsilateral to MVCs with recurrence of peak II when surgical decompression is successful [53]. This suggests that the tinnitus is causally related to dysfunctional signal transmission at the site of compression in the initial stage of compression.…”

“…The IPL I-III prolongation seems to be significantly related statistically to the degree of tinnitus after normalization for age [53]. Postoperatively, a shortening of the IPL I-III is not related to a clinical improvement in tinnitus but to an improvement in tinnitus frequencyspecific hearing loss [53].…”

“…In the first 2 years, no significant changes in ABR are noted in patients presenting with tinnitus and MVC [53]. Once peak II decreases are noted, IPL I-III prolongs [53].The fact that the IPL I-III prolongation is related to the duration of the tinnitus furthermore suggests that this is a dynamically progressive pathology [53] and that the effect of vascular contact with blood vessels creates changes over time, both electrophysiologically [53] and clinically [53].…”

“…Once peak II decreases are noted, IPL I-III prolongs [53].The fact that the IPL I-III prolongation is related to the duration of the tinnitus furthermore suggests that this is a dynamically progressive pathology [53] and that the effect of vascular contact with blood vessels creates changes over time, both electrophysiologically [53] and clinically [53]. The IPL I-III prolongation seems to be significantly related statistically to the degree of tinnitus after normalization for age [53]. Postoperatively, a shortening of the IPL I-III is not related to a clinical improvement in tinnitus but to an improvement in tinnitus frequencyspecific hearing loss [53].…”

“…It is known that the most common cause for tinnitus is auditory deprivation, inducing the development of an auditory phantom percept [78]. Therefore, it is likely that when the compression has resulted in a hearing loss this will result in tinnitus, specifically at the frequency of hearing loss [31,53,[79][80][81]. It has also been shown that the neural network in the brain that generates tinnitus changes with time [82], with a marked change before and after 4 years of tinnitus duration.…”