[Ghost curves and early auditory evoked potentials. Role of temporary deafness].

Phantom ear responses, contralateral to the transducer (head-phone), can be observed during recording of early evoked auditory potentials, as in conventional audiometry, and can ease the problem of temporary deafness. Their appearance obeys laws common to audiometric tests, stimulus transfer to the opposite ear being through bone of cranium with attenuation inversely proportional to bony surface at level of transducer. However, the analogy between conventional and objective audiometry stops there. Normally, the electrophysiologic V wave response is not present or absent alone, as would be a voluntary response of the patient, but varies by its latency and amplitude as a function of intensity and nature of stimulus. These supplementary criteria should make identification simple, allow an abnormal response to be recognized and indications for treatment of the temporary deafness to be better defined. This is illustrated by the present study of 50 cases of unilateral kophosis, using a TDM 39 transducer employed most commonly in both objective and conventional audiometry.