sirvan najafi

Tinnitus is one of the most difficult challenges in audiology and otology. Previous studies have been shown that tinnitus may interfere with the function of central auditory system (CAS). Involvement of CAS abilities including speech perception and auditory processing has led to serious problems in people with tinnitus. Due to the lack of enough information about the impact of tinnitus on CAS and its function, and given that there is no standardized protocol for assessment and management of tinnitus, this study aimed to review the studies on the effect of tinnitus on the CAS function.

Sixteen eligible articles were reviewed. Temporal and spectral resolution, frequency differentiation and speech perception deficits were reported in patients with tinnitus, especially in background noise. This was reported even in tinnitus patients with normal hearing.

Assessment of central auditory pro cessing and speech perception in noise seems to be useful for proper management of tinnitus in clinical practice.

Approximately 20% of general population is struggling with tinnitus. Recent theories on tinnitus are mainly based on impairments in the central auditory system that can lead to tinnitus. Recent studies have shown that tinnitus is not simply a result of the involvement of one brain region or pathway; but it can be caused by simultaneous involvement of multiple brain regions. Due to lack of information about the tinnitus etiology, site, and pathophysiology, there is still no any specific and common method for its management. In recent years, neuromodulation techniques such as transcranial direct current stimulation (tDCS) has been proposed for management of tinnitus. In this study, we aimed to review the role of tDCS in tinnitus management.

Based on the inclusion criteria, 7 eligible articles were selected for review. Most of them showed the beneficial effects of tDCS on tinnitus management.

The tDCS can be an effective technique for management of tinnitus. One of the main challenges for using tDCS in tinnitus patients is the differnce in stimulation parameters; therefore, more studies are recommended for obtaining its ideal parameters.

Based on neurophysiological measurements, auditory and non-auditory pathways are involved in tinnitus. People who experience tinnitus may suffer from several problems such as attention disorder. The auditory evoked potential P300 is an endogenous response and depends on cognitive processes like attention. The purpose of this study was to compare the auditory P300 characteristics (amplitude and latency) in adults with and without tinnitus.

Participants were 20 adults with idiopathic bilateral tinnitus with mean duration of 8.4 ± 4.73 months, and 20 healthy adults. The P300 was recorded using oddball paradigm consisted of two standard (1000 Hz) and target stimuli (2000 Hz). To reduce eye blink during recording, all participants was instructed to look at and fixate on a dot sign located in front of them. The tinnitus handicap inventory (THI) was completed and pitch matching (PM) and loudness matching (LM) were measured in tinnitus group.

P300 amplitude was lower at both Fz and Cz electrode placements in tinnitus patients compared to the normal group, but it was not statistically significant (p = 0.57). Tinnitus patients had delayed latency at Fz and Cz, but this difference was not significant either psychometric and psychoacoustic assessment had no statistically significant correlation with P300 amplitude and latency.

It seems that P300 characteristics are not different between adults with and without idiopathic bilateral tinnitus, may be due to using low sample size.

Auditory P300 is an event-related potential. Cognitive factors like attention are involved in the generation of P300. It seems that normative variation of P300 is necessary for clinical purposes. Thus, the current study was designed to establish preliminary normative variation of P300 amplitude and latency at Fz and Cz sites in adults.
This cross-sectional study was performed on 20 right-handed volunteers aged 18 to 33 years. P300 was recorded monaurally with two channels at Fz and Cz placements. Two tone bursts of 1000Hz and 2000Hz were used as frequent and target stimuli, respectively.
The mean values of P300 amplitude and latency at Cz were 7.43±2.61 µv and 325.19±21.34 ms in the right ear and 7.38±2.73µv and 320.29±21.56 ms in the left ear, respectively. At Fz, the mean values of P300 amplitude and latency were 5.34±1.74 µv and 330.09±25.58 ms in the right ear and 5.67±2.30 µv and 329.52±29.25 ms in the left ear, respectively. The differences between the ears at Cz and Fz were not statistically significant (p˃0.05).The mean value of amplitude of P300 was significantly greater at Cz than Fz (p=0.001) although the difference in latency was not statistically significant between Cz and Fz (p˃0.05).
Amplitude of P300 was greater at Cz than Fz although latency was not different. Based on these findings, amplitude and latency values can be probably used for clinical purposes to assess auditory disorders.