Towards an objectification by classification of tinnitus

Objectives: 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.