Loudness Balance Test with Ipsilateral and Contralateral Test Tone in Unilateral Tinnitus Patients

Chon, Kyong Myong

Abstract

BACKGROUND: Quantification of the loudness of tinnitus is important for evaluating tinnitus treatments and for assessing the validity of compensational claims, as well as for the fact that it is fundamental to many other types of tinnitus research. A common method for measuring the level of tinnitus is loudness matching test, i.e., adjusting the dB level of an external tone to match the loudness of tinnitus. Hence the objective comparision can be made between the tinnitus and the test tone. Traditionally the test measures ipsilateral side of the tinnitus. However due to recruitment, the result yields a misleadingly low sensation level.
OBJECTIVES
The purpose of this study was to evaluate the differences of results between ipsilateral and contralateral test tone in loudness balance test. MAERIALS AND METHODS: Applying the loudness matching method, tinnitus levels were measured ipsilaterally and contralaterally for 55 patients with unilateral tinnitus. The subjects were divided into two subgroups according to hearing levels. The one subgroup (n=16) had normal hearing ranges while the other subgroup (n=39) experienced difficulties in hearing. To correct the effects of recruitment when there was sensorineural hearing loss in the ear to which the test sound was applied, the effective loudness level representation was adopted. Estimates of effective loudness levels were obtained using a normogram.
RESULTS
The result is as follows: in the hearing-difficulty group, tinnitus levels measured ipsilaterally were correlated with those from the contralateral side. The correlation coefficient was 0.647. In the normal hearing group, tinnitus levels measured ipsilaterally did not correlate with those from the contralateral side. The correlation coefficient was 0.037.
CONCLUSIONS
The results revealed that there is a difference between ipsilateral and contralateral methods in the loudness balance test of unilateral tinnitus due to compound effects of the recruitment, the hearing loss of tinnitus ear, and the neural interaction of central nervous system. It is therefore suggested that ipsilateral test tone is more accurate than contralateral tone for the evaluation of loudness balance.