[Laterality of tinnitus: relationship to functional assymetries]

Tinnitus is a sensation of sound generated by the auditory system due to pathology, without any external acoustic or electrical stimulation. Clinical reports have indicated that tinnitus affects the left ear more frequently than the right one. Previous data suggest that the asymmetrical distribution of tinnitus is linked to handedness or other lateral signs, but no studies have heretofore examined lateral preferences in addressing this relationship. The literature concerning the laterality (localisation) of tinnitus is reviewed. The data confirm an asymmetrical distribution of tinnitus. Results of 7 studies (altogether 4634 patients) demonstrate that tinnitus occurs more often bilaterally (48.8%) than on the left side (28.0%) or the right (23.2%). There is no general predominance of the left ear. Handedness, eyedness, footedness, earedness and dichotic listening are examined in our own sample of 58 patients (23 men and 35 women) with acute, subacute or chronic tinnitus. A right sided preference was found for hand, foot, eye, ear preference and dichotic listening among 91%, 86%, 78%, 69% and 85% of the sample, respectively. Sixty per cent of the sample heard tinnitus only in the left ear, 21% only in the right ear and 19% in both ears. There is a higher correlation between localisation of tinnitus and dichotic listening than between other lateralities. Our investigation shows a significant relationship between localisation of tinnitus and laterality of dichotic listening, suggesting a possible link between tinnitus and hemisphere dominance. The result suggests a "functional" asymmetry of tinnitus.