[Bone conduction auditory brainstem responses in normal hearing individuals].
BACKGROUND
bone conduction auditory brainstem responses (ABR) in normal hearing individuals.


OBJECTIVE
to evaluate the clinical applicability of bone conduction ABR, characterizing normality and determining an assessment protocol.


METHODS
participants of this study were 22 individuals with normal hearing (20dB NA), with ages between 20 and 30 years, 14 female and 8 male. All individuals were assessed using air and bone (vibrator positioned on the forehead and mastoid) conduction ABR. EP25 equipment, Interacoustic; 3A insertion phone; B-71 bone vibrator; click stimulus.


RESULTS
it was possible to evaluate the bone conduction ABR in all individuals. The results demonstrate that the electrophysiological threshold obtained when the vibrator was positioned on the forehead (32.69+/-5.63 and 32.5+/-7.07dB nHL) was higher than that obtained when the vibrator was positioned on the mastoid (25.00+/-7.33 and 30.00+/-5.34dB nHL) for both genders respectively. For this reason the vibrator was positioned on the mastoid. The electrophysiological threshold obtained by bone conduction was higher than that obtained by air conduction for both genders and also when all individuals were grouped together. Thus it is necessary to use a correction factor, according to the results, of 10dB nHL. The latency-intensity values of the V wave in the ipsilateral and contralateral recordings differed statistically according to gender, and should be considered separately. The value of 26.81+/-6.99dB nHL was adopted as being the normal threshold for bone conduction ABR.


CONCLUSIONS
it is possible to evaluate bone conduction ABR in the clinical environment. These results, when considered along with the air conduction ABR, increase the chances of a more precise diagnosis regarding the type of hearing loss.
de Freitas
Vanessa Sabino
VS
Faculdade de Odontologia de Bauru, Universidade de São Paulo. vanfreitas@gmail.com
de Alvarenga
Kátia Freitas
KF
Morettin
Marina
M
de Souza
Elidiane Fugiwara
EF
Filho
Orozimbo Alves Costa
OA
D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D001844:Bone Conduction / Q000502:physiology*; D002985:Clinical Protocols; D004594:Electrophysiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D005546:Forehead / Q000502:physiology; D034381:Hearing Loss / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008416:Mastoid / Q000502:physiology; D015233:Models, Statistical; D012737:Sex Factors; D014732:Vibration