[Effect of contralateral stimulation on otoacoustic evoked emissions in acute deafness]

23 patients with unilateral hearing loss and presence of TEOAE on both ears were examined with regard to the association between contralateral acoustic stimulation and evoked otoacoustic emissions. Contralateral white noise of 40 dB HL, 50 dB HL and 60 dB HL decreases the amplitude of TEOAE both at the ear with and without hearing loss. In comparison with a group of subjects with normal hearing, the decrease in the amplitude of TEOAE was less in the group of patients with hearing loss. Two paradoxical cases were found with an increase in the TEOAE amplitude in the ear with hearing loss during contralateral stimulation. It is assumed that impairment of the efferent synapses on the outer hair cells or of the decussated efferent nerve fibres at the floor of the fourth ventricle contributes to the pathogenesis of hearing loss. Impairment of the efferent system at brainstem level can explain the lower decrease in the amplitude both in the diseased ear and the normal ear. The behaviour of the normal ear during stimulation of the diseased ear can also be caused by disturbance of the afferent system.