الفهرس 
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Abstract
The need for objective measures to evaluate hearing sensitivity has grown dramatically with newborn hearing screening programs around the world these measures are of special significance in neonates, children and uncooperative subjects, who couldn’t give accurate results by conventional pure tone audiometry.
There were as several Studies had demonstrated the accuracy of ASSR confidently estimating behavioral hearing threshold in children. ASSR has several advantages such as it use a wide range of stimulus levels up to 120 dBHL and multiple frequency recordings.
Chirp stimulus has been developed by Elberling and collegues , it was intended to compensate time delay related to the cochlear travelling wave, and so larger amplitude. It has been applied in various fields of evoked response audiometry including ABR and ASSR.
In this study we examine whether the newly developed NB-CE chirp ASSR had advantages over conventional PTA in normal hearing and hearing impaired children. The study was carried out at audiology unit, Menofia University Hospital, from Oct 2015 till Feb 2017 after obtaining ethics committee approval. One hundered subjects aged 6-12 years of both sex with normal middle ear function were included in the study, exclusion criteria included any neurological, mental abnormality and any other ENT complaints. Subjects were classified into four groups according to PTA thresholds (conventional PTA) as group I includes 20 children (40ears) diagnosed as normal hearing sensitivity. group II: included 24 children (48 ears) diagnosed as mild to moderate SNHL. group III included 28 children (56 ears) diagnosed as moderate to.
moderately severe SNHL. group IV: included 28 children (56 ears) diagnosed as severe to profound SNHL.
The selected patients were subjected to the following:
Full general and audiological history.
Otological examination.
Basic audiological evaluation.
Auditory Brainstem Response (ABR) using tone burst stimuli and narrow band NB-Chirp stimuli.
Auditory Steady State Response using NB-Chirp stimuli
Results obtained from this study could be summarized as follow: -
1) The use of a chirp-ABR testing ensures higher sensitivity and accuracy than that of auditory stead-state evoked response (ASSR) for measuring frequency-specific thresholds in young children.
2) Chirp ABR is faster than tone burst ABR.
3) ABRs to chirps CE-chirp evoked larger responses than Tb-ABR stimulus in normal hearing &hearing impaired children at all presentation levels.
4) Regarding pure tone threshold prediction values of Tb-ABR stimuli, best prediction was at 4000 Hz in normal hearing and hearing impaired children respectively, while poorest prediction was at 500 Hz in all groups.
5) The examiner needs to do chirp ASSR in addition to chirp ABR as a test battery to obtain frequency specific threshold estimation in children with various degrees of hearing loss.