الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Tinnitus is the experience in which the individual hears a sound without a corresponding sound stimulus.(215) The pathogenesis and site of origin have yet to be clearly established. It is often a feature of primary ear disease usually associated with hearing loss, but it may also occur in patients with normal hearing.(14) In recent demonstration normal hearing thresholds do not necessarily indicate absence of cochlear damage. Normal hearing thresholds can also be accompanied by impaired function of efferent fibers that project from the brainstem to the cochlea.(211)
This work was designed to study the auditory brainstem response in tinnitus patients with normal hearing. They were divided in two groups. The first was the study group consisted of adult patients with bilateral tinnitus and bilateral normal hearing and the second was the control group.
Comparison between study and control groups as regard pure tone audiometry revealed no significant difference across the frequency range 250-8000 Hz including 3000 and 6000 Hz.
ABR was recorded using rarefaction click stimuli presented ipsilaterally at 80 dBnHL. Results showed that ABR wave I amplitude was significantly reduced in the study group when compared to control group. Also the ratio V/I was significantly higher in the study group compared to control group suggesting degeneration of a subset of AN fibers and cochlear synaptopathy.
The absolute latency of wave I was significantly increased in the study group compared to control group. IPL I-V was significantly decreased in the study group compared to control group suggesting loss of neural fibers and decrease in neural synchrony of the AN.
Differences in ABR in normal hearing tinnitus patients compared to normal hearing control reflect defects in the integrity of the brainstem of those patients. Therefore ABR testing should be considered as one of tinnitus evaluation tests.