Towards an objectification by classification of tinnitus.

OBJECTIVE

The objectives of this study are to identify the presence of tinnitus and classify its different forms, in terms of changes in noise.

METHODS

Late auditory evoked responses (LAERs) were recorded from Fz in response to 1000 Hz tone bursts of various intensities, in 13 tinnitus-free subjects and in 25 tinnitus sufferers (16 bilateral and 9 unilateral tinnitus sufferers). A classification of different forms of tinnitus, in terms of changes in noise, was also undertaken. N1-P2 component amplitudes and N1 and P2 latencies were measured.

RESULTS

Objective identification of the affected ear in unilateral tinnitus sufferers was found feasible on the basis of N1-P2 intensity-dependence and N1-P2 amplitude. The bilateral tinnitus group was found to differ from controls by greater intensity-dependence of the N1-P2 component and shorter N1 latency. These characteristics varied with tinnitus type: a classification on the basis of intensity-dependence and latencies proved feasible. The group of patients showing improved tinnitus in noise had greater intensity-dependence and longer N1 latency than did the group showing aggravated tinnitus in noise.

CONCLUSIONS

Data are discussed in light of the inhibitory role of frontal cortex on the sensory inputs and the modulatory function of central serotonergic system on the processing of auditory information.