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BERA – Brainstem Auditory Evoked Responses
Dr. K. K. Desarda
Professor and Head, Otolaryngology.

Dr. A. N. Sangekar
Audiologist and Speech Pathologist,
KEM Hospital, Pune 411 011, Maharashtra, India.

BERA (BSER OR BAEP) has proved to be a useful tool in diagnosing hearing impairments in children which could be conductive or sensorineural in nature. Thanks to early detection, rehabilitative procedures could be started early which will help speech and language development.

We have studied 150 cases below five years of age, and our observations are recorded with case history profiles like high risks, referral for adaptions, congenital malformations and delayed speech. We feel BERA is the only tool which can present an accurate picture of hearing sensitivity.

Introduction
Hearing problems are common among the children which could be conductive or sensorineural in nature. Early diagnosis of hearing impairment is important as the rehabilitative procedure can be started early which will help speech and language development.

Various audiological test procedures are used to assess the hearing sensitivity of children. Some of the common ones are: Behavioral Observation. All the above techniques are useful in estimating hearing sensitivity but have their own limitations. The major difficulties involved in the use of these techniques are: BERA, (BSER or BAEP) has proved to be a useful objective tool in diagnosing hearing impairments in children. The use of Auditory Brainstem Response (ABR) (1) audiometry as an audiological tool focused on two principal areas: To achieve this objective, the paradigm employed is to collect appropriate ABR data for a case, analyze it and compare the data with relevant norms and draw inferences.

Material and Methods
In this study, an attempt is made to study the findings of BERA in children below the age of five years. These children reported to us or were referred to us for the following reasons:
Test Procedure
All patients were administered the test procedures with prior appointment. An ENT check up was done to rule out the possibility of wax, ear infection, middle ear problems etc. The parents were instructed to wash the scalp of the child thoroughly as a requirement of the test. Prior to the test, each child was examined by the pediatrician and the dosage for sedation was prescribed. Drugs used for sedation were Trichloryl and Phenergan in combination.

Test was carried out in pre–cooled, quiet (not treated) room. The instrument used was Nicolet EP Four Compact which is a fully computerized machine with the facility of artifact rejection. The skin was cleaned with spirit and OMEN abrasive skin preparatory paste. The silver electrode were placed as follows: Cz–vertex, A–1 LF mastoid, A–2 values was not more than 1ohms. Electrode electrolyte gel was used and electrodes were fixed. Acoustically shielded THD 32 ear phones were placed on the ear and head bands were adjusted. The clicks of 11.4/sec duration were used as stimulus. The filter settings used were a 50Hz–300Hz. The polarity used was alternate and the analysis time was 10m/sec. About 4,000 responses were averaged. First, stimulus was given at 105 dBnHL level (i.e. maximum intensity level available). If peak V was detected at a particular level, intensity was increased by 5dB. The existence of peak V was considered as sound stimulus heard and perceived by the auditory mechanism. The threshold for each ear was confirmed. The guidelines used for the confirmation of peak V were as follows: Since the measurement of hearing sensitivity in children under five years of age was the only aim of this study, the latency values and interpeak intervals even though measured, are not considered. Each child's hearing sensitivity was assessed, and they were sub–grouped in the following categories.

Normal hearing sensitivity. Hg. thresholds up to 25dB level and below.
Mild hearing impairment. Hg. thresholds between 30dB to 45dB.
Moderate hearing impairment Hg. thresholds between 50dB to 65dB.
Severe hearing impairment. Thresholds between 70dB to 85dB.
Profound hearing impairment. Thresholds above 90dB.

Observation
We have studies BERA findings of 150 children (below the age of five yrs) for this study.
Given below is the age–wise distribution of these children:
AGE No.
0–1 52
1–2 52
2–4 24
4–5 22

The case history profile of these cases is as follows:
High risk clinics. 82 cases
Referred for adoption. 31 cases
Patients with ear anamolies (congenital). 3 cases
Patients brought by atresia. 34 cases
Patients with complaint of delayed speech or inability to respond to sound.

The BERA findings of 15 cases studied:
Normal hearing sensitivity. 53
Mild hearing impairment. 12
Moderate hearing impairment. 21
Severe hearing impairment. 30
Profound hearing impairment. 34
Total 150

Out of 53 patients with normal hearing sensitivity, 33 were sent for adaption, 26 patients were found to be mentally subnormal and 5 patients had multiple anomalies. Out of 12 patients with mild hearing impairment nine patients had history of ear discharge and out of 21 patients with moderate hearing loss 10 had history of ear discharge either in one ear or in both ears and three patients had congenital anomalies of the ear and four had a history of high risk factors. Out of 30 patients with severe hearing impairment 22 had high risk factors contributing to their history and of 34 patients of profound hearing loss, 23 had high risk factors contributing to their history.

Out of 82 high risk cases, 22 had severe hearing loss, 23 had profound hearing loss, four had moderate hearing loss, 33 had normal hearing sensitivity. All the above cases were sent for further rehabilitative procedures as per their requirement.

Conclusion
BERA is a very useful in early detection of hearing loss and planning rehabilitative procedures. In case of multiple handicaps, BERA is the only test which can give accurate picture of hearing sensitivity. In cases of high risk babies, BERA should be carried out as a routine procedure to detect hearing loss. BERA test helps us to conclude regarding the cause of delay in speech and language development. BERA is the only tool which can confirm the normal sensitivity of hearing whenever required.

References Contributed by Dr. K. K. Desarda