[Evoked oto-acoustic emissions in patients with retinitis pigmentosa]

Evoked otoacoustic emissions (EOE) offer a unique opportunity to measure objectively the function of outer hair cells in human beings. In this paper the Authors report a study carried out employing EOE evaluation on cochlear function in subjects with retinitis pigmentosa. Nine patients with retinitis pigmentosa with normal hearing in both ears upon traditional audiometric evaluation were studied. The frequency spectrum of the EOE was taken into consideration, evaluated in frequency bands of 50 Hz, in order to ascertain the presence or absence of the emissions and, when present, their amplitude. These data were compared statistically, using the Student's T Test, to those obtained in a homogeneous control group of normal subjects. In subjects with retinitis pigmentosa, average EOE intensity values were statistically lower than those found in normal subjects. In fact, the Student's T Test evaluation revealed significant differences in EOE intensity in 64 of the 127 frequency bands examined. Moreover, the distribution of the EOE in patients with retinitis pigmentosa proved to be more discontinuous than that observed in the normal subjects. These data appear to indicate authentic alterations in the cochlear mechanics in patients with retinitis pigmentosa. Such alterations may well be related to outer hair cell lesions. It seems likely that the auditory system is involved in retinitis pigmentosa degenerative processes more frequently than traditional audiometric tests have been able to show.