الفهرس 
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Abstract
Sensorineural hearing loss occurs when the part of the ear that transforms sound to electrical information (the cochlea) and sends the information to the brain (auditory nerve) is damaged .It can be genetic or caused by the natural aging process, diseases or exposure to noise and certain kinds of chemicals. Auditory Neuropathy is a form of sensorineural hearing loss where the auditory nerve is damaged or malfunctions.
The auditory brain stem response (ABR) is an onset sensitive neural response that is useful in assessing the integrity of the auditory system through the level of the brain stem. Clinically, the ABR is used to indirectly estimate auditory threshold in adults and infants and to detect peripheral and central nervous system pathology . Often transient stimuli, such as clicks are used to obtain ABRs because their rapid onset and broad-frequency characteristics support higher neural synchrony and larger waveform amplitude . TheABR is limited by the cochlea’s travellingwave. It takes time for a stimulus to travelfrom the high to low frequency regionsof the cochlea.
The CE-Chirp is a new broadbandstimulus designed to counteract thetemporal dispersion of the travellingwave inherent in the cochlea bypresenting lower frequency energy beforehigher frequency energy ,resulting in an increased Wave V amplitude . CE-Chirp Octave Bands arenow available for frequency specificthreshold estimation. Designed along thesame principle as the broadband CEChirp, CE-Chirp octave band stimulielicit optimal waveforms forfrequency specific evaluation.
The aim of this study is to compare betweenABR thresholds to click, CE chirp, 500Hz NB chirp, 1kHz NB chirp, 2kHz NB chirp and 4kHz NB chirp stimuli in comparison to overall behavioral hearing thresholds and comparison between ABR thresholds to chirp and click stimuli in SNHL patients .
All subjects were subjected tofull history taking,otological examination, pure tone audiometry, SpeechReceptionThershold, tympanometry,acoustic reflex threshold andCE-Chirp&click evoked ABR.
The result of this study there was no significant difference between ABR thresholds to CEchirp and behavioral hearing thresholds in control (as mean difference is2dBnHL higher with CE chirp )and cases (mean difference is 1.4dBnHL higher with CE chirp). However,ABR thresholds to click were significantly higher than PTA thresholds at 2kHz &4kHz in control( mean difference is 5dBnHL) and case( mean difference is 5.7dBnHL) groups. Also ,in both groups ABR thresholds to click were significant higher than ABR thresholds to CEchirp. It was found that ABR thresholds to 500Hz NB CE chirp were significantly higher than PTA thresholds at 500 Hz in both groups with mean difference in group 1 (2.3 dBnHL) and in group 2 (4.4dBnHL), ABR thresholds to 1kHz NB CE chirp were insignificantly higher than PTA thresholds at 1k Hz in group 1 (mean difference 0.2 dBnHL)but significantly higher than PTA thresholds at 1kHz in group 2 with mean difference 2.8 dBnHL, ABR thresholds to 2kHz NB CE chirp were insignificantly higher than PTA thresholds at 2k Hz in group 1 (mean difference1.7 dBnHL ) but significantly higher than PTA thresholds at 2kHz in group 2 with mean difference 3.8 dBnHL and ABR thresholds to 4kHz NB CE chirp were insignificantly higher than PTA thresholds at 4k Hz in both groups with mean difference in group 1 (2.00 dBnHL) and in group 2 (4.4dB nHL).CE-chirp and NB CE chirphearing threshold s fell within 5dB nHL of the subjective behavioral hearing thresholds.
Also wave v latency at threshold with click is lower than that with CE chirp in both groups.Wave v amplitudes at threshold with CE chirp are larger than those with click in both groups.Wave V amplitude increased and latency decreased as stimulus frequency increased.
So we conclude that CE chirp is more accurate than click in determining the hearing threshold andthe use of CE-Chirp Octave Band stimuli provides robust and fastfrequency-specific threshold estimationin both NH subjects and those with SNHL for a more thorough evaluation.