Towards an objectification by classification of tinnitus

Objective: The objectives of this study are to identify the presence of tin nitus and classify its different forms, in terms of changes in noise. Metho ds: Late auditory evoked responses (LAERs) were recorded from Fz in respons e to 1000 Hz tone bursts of various intensities, in 13 tinnitus-free subjec ts and in 25 tinnitus sufferers (16 bilateral and 9 unilateral tinnitus suf ferers). A classification of different forms of tinnitus, in terms of chang es 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 w as found to differ from controls by greater intensity-dependence of the N1- P2 component and shorter N1 latency. These characteristics varied with tinn itus type: a classification on the basis of intensity-dependence and latenc ies proved feasible. The group of patients showing improved tinnitus in noi se had greater intensity-dependence and longer N1 latency than did the grou p showing aggravated tinnitus in noise. Conclusions: Data are discussed in light of the inhibitory role of frontal cortex on the sensory inputs and th e modulatory function of central serotonergic system on the processing of a uditory information. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.