Noise-induced tinnitus: auditory evoked potential in symptomatic and asymptomatic patients

Abstract

OBJECTIVES:We evaluated the central auditory pathways in workers with noise-induced tinnitus with normal hearing thresholds, compared the auditory brainstem response results in groups with and without tinnitus and correlated the tinnitus location to the auditory brainstem response findings in individuals with a history of occupational noise exposure.METHOD:Sixty individuals participated in the study and the following procedures were performed: anamnesis, immittance measures, pure-tone air conduction thresholds at all frequencies between 0.25–8 kHz and auditory brainstem response.RESULTS:The mean auditory brainstem response latencies were lower in the Control group than in the Tinnitus group, but no significant differences between the groups were observed. Qualitative analysis showed more alterations in the lower brainstem in the Tinnitus group. The strongest relationship between tinnitus location and auditory brainstem response alterations was detected in individuals with bilateral tinnitus and bilateral auditory brainstem response alterations compared with patients with unilateral alterations.CONCLUSION:Our findings suggest the occurrence of a possible dysfunction in the central auditory nervous system (brainstem) in individuals with noise-induced tinnitus and a normal hearing threshold.

Middle Latency Auditory Evoked Potential (MLAEP) in Workers with and without Tinnitus who are Exposed to Occupational Noise

“…The MLAEP was used to obtain the Na and Pa wave amplitudes and latencies both contralaterally (C3/A2, C4/A1) and ipsilaterally (C3/A1) [ 19 , 20 ]. It is noteworthy that 23.3% of subjects in the control group and 53.3% of subjects in the study group showed BAEP abnormalities [ 5 ].…”

“…Tinnitus is the perception of sound without an external acoustic stimulus [ 1 ]. The mechanisms underlying tinnitus are still not fully understood and, although this symptom is often associated with hearing loss, many individuals may experience it in the presence of normal hearing [ 2 – 5 ]. Tinnitus may result from a pathological state of the auditory system, which triggers a series of events increasing neuronal activity at different levels of the central auditory pathway [ 5 ].…”

“…The mechanisms underlying tinnitus are still not fully understood and, although this symptom is often associated with hearing loss, many individuals may experience it in the presence of normal hearing [ 2 – 5 ]. Tinnitus may result from a pathological state of the auditory system, which triggers a series of events increasing neuronal activity at different levels of the central auditory pathway [ 5 ]. Other systems also take part in the generation and maintenance of this symptom, particularly the limbic and autonomic nervous systems (“neurophysiological concept of tinnitus generation”) [ 5 , 6 ].…”

“…Tinnitus may result from a pathological state of the auditory system, which triggers a series of events increasing neuronal activity at different levels of the central auditory pathway [ 5 ]. Other systems also take part in the generation and maintenance of this symptom, particularly the limbic and autonomic nervous systems (“neurophysiological concept of tinnitus generation”) [ 5 , 6 ]. Some authors have proposed that tinnitus originates in the cochlea; however, the maintenance of this abnormal activity is perpetuated by the central auditory pathways [ 6 , 7 ].…”

“…An important aspect to consider regarding tinnitus is that it may also be caused by various diseases that affect different structures along the auditory pathway. Therefore, studies should control for these variables by evaluating a population that is homogeneous in terms of possible causes of tinnitus, e.g., individuals exposed to occupational noise [ 5 , 13 ].…”