The Methodology and Electro-physiological Classification of Pre-operative Trans-tympanic Electrically-Evoked Auditory Brainstem Response (TT-EABR)
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Pre-operative Transtympanic EABR (TT-EABR) is an effective clinical procedure which can decrease the likelihood of placing a cochlear implant in a non-stimulable ear, and may provide the clinician with a valuable tool for selection of the most appropriate ear for implantation . It has been shown that the presence of normal TT-EABR may indicate a significantly better outcome after cochlear implant surgery than for ears which had abnormal or absent TT-EABR .
Pre-operative TT-EABR Methodology
The authors have used the technique previously described by Gibson and Sanli .
The whole procedure takes about 20 min on each side and can be performed as a day care procedure. The myringotomy heals in 2 weeks time in most patients.
Kumar–Dutt Classification of Reporting Responses of TT-EABR
Description of the Wave Form Types A, B, C and D according to the Kumar-Dutt electrophysiological classification for TT-EABR
Robust Wave V Morphology; repeatable peak III and V with peak V latency within 5 ms
Good Wave V Morphology; repeatable peak V (and not III), with latency within 5 ms
Fair/acceptable Wave V Morphology; peak V present with delayed latency (beyond 5 ms)
Poor or Absent Wave V
In today’s era of advanced radiology and hence advanced diagnosis of anatomical anomalies of the cochleo-vestibular system, it is important to identify the patients in whom a cochlear implantation would help in improving the hearing abilities. The above proposed classification system provides an objective method for establishing the stimulability of the cochlear nerve in such patients.
Polterauer et al.  have described a similar procedure for establishing cochlear implant candidacy in individual where the acoustic auditory brain stem response audiometry did not show reproducible recording even at very high acoustic levels. They compared the Transtympanic EABR with the intra-operative EABR measurements that were stimulated using the implanted CI electrode array and found similar wave forms.
Several researchers including Kileny et al.  have described the use of TTEABR in special cases of congenital temporal bone malformation to establish the functional status of the auditory pathway before implantation. However, no system has been described to classify the responses obtained. Kumar–Dutt classification aims to fill this gap in our knowledge of TTEABR and hence improve the reportability of responses obtained.
- 1.Kileny PR, Zwolan TA (2004) Pre-perioperative, transtympanic electrically evoked auditory brainstem response in children. Int J Audiol 43(Suppl 1):S16–S21Google Scholar