Tinnitus: Development of a neurophysiologic correlate

Abstract

Although tinnitus severely afflicts 7.2 million Americans, the pathophysiology of this problem remains obscure because there presently exists no good animal model in which to study the phenomenon. We have examined changes in activity in the guinea pig auditory pathway using an autoradiographic method of functional brain mapping after short-term and long-term cochlear ablations which can, in humans, initiate the occurrence of tinnitus. With this method we have observed a reduction in activity in various nuclei in the auditory pathway between 4 hrs and 10 days after unilateral cochlear ablation. In contrast to these findings we have found a return of activity in these same nuclei if they are observed from 12 to 48 days following the lesion. These preliminary data suggest that this return of activity in the absence of sensory input may be a valid experimental analogue for tinnitus in humans. Such evidence for auditory plasticity may represent a significant first step toward understanding this common and profound otologic symptom.

Tinnitus and Patterns of Hearing Loss

“…The strong link between the presence of tinnitus and damaged hearing supports the hypothesis that both may have a common cause probably in the auditory periphery. However, the perception of tinnitus is reported to persist even after cochlear ablation or auditory nerve section (Sasaki et al 1981). This suggests that tinnitus is a central phenomenon, and plastic changes in central auditory structures are currently thought to generate and maintain the perception of tinnitus (Dehmel et al 2012; Kaltenbach et al 2005).…”

Both Central and Peripheral Auditory Systems Are Involved in Salicylate-Induced Tinnitus in Rats: A Behavioral Study

“…Rats were anesthetized (as described above). Subsequently, auditory nerves were bilaterally ablated, based on the methods described in previous studies [23] , [24] . The surgical procedure was applied under aseptic conditions and was carried out visually for ∼1 h at 5× to 10× magnification of a dissecting microscope (Zhenjiang Xin Tian Medical Devices Company, Limited, Nanjing, China).…”

“…Ablating a possible “tinnitus generator” along the auditory pathway is an important approach to investigating its role in tinnitus generation. Some previous researches have found that in guinea pigs central neuronal activities whose increase levels are correlated to tinnitus reduced immediately after ablation of ispilateral auditory nerve and would not increase before a latency period of at least 3 days [23] , [24] , indicating that auditory nerve ablation could not produce tinnitus within 3 days after ablation.…”

The Pathophysiologic Mechanism of Tinnitus

“…Interestingly, vascular decompression has favorable effects in patients with acute tinnitus, while many patients with chronic tinnitus did not benefit from surgical decompression. In addition, tinnitus has been sustained in those patients where their auditory nerve had been surgically dissected due to acoustic neuroma [23]. Based on these observations, tinnitus by compression of auditory nerve might trigger plastic reorganization of the central auditory pathway [13].…”