[Steady state multi-frequency auditory evoked potentials as a technique to determine hearing threshold]. / Potenciales evocados auditivos de estado estable a multifrecuencia como técnica de determinación de umbrales auditivos.

OBJECTIVE: Since the set up of Steady-State Auditory Evoked Potentials as a routine technique, it has became necessary the establishment of clinic capabilities and limitations. In this study, we have compared SSEP to behavioural thresholds, considering the last one as "gold standard" technique. MATERIALS AND METHODS: We have recorded SSEP to multiple frequencies and behavioural thresholds in 84 ears. The obtained data were statistically processed to obtain correlations and others indicators. RESULTS: SSEP thresholds are slightly higher than behavioural, whose average difference was calculated as 23 dB. It is worth to note that this difference diminishes at high frequencies and hearing loss cases. CONCLUSIONS: SSEP to multiple frequencies technique is capable to determine auditory thresholds accurately, being closer to the behavioural value at high frequencies and high threshold values. It is necessary the establishment of exploration protocols to assure the highest accuracy of the system. In this work, a diagnostic algorithm has been proposed to reach better results by using SSEP.

[Auditory neuropathies in infants]. / Neuropatía auditiva en lactantes.

Auditory neuropathy is a sensorineural disorder characterized by absent or abnormal auditory evoked potentials, and normal cochlear outer hair cell function. It is believed that a variety of processes are involved in its pathophysiology and their influence on hearing can differ. We describe the diagnostic sequence and management of two new cases of auditory neuropathy in infants. The first case was a girl with no risk factors for hearing loss. Her absence of response to sounds was compared with her twin's reactions. Otoacoustic emissions were present but no auditory evoked potential response was detected. Her evolution was characteristic of deep sensorineural hearing loss without a hearing aid. At present she is awaiting a cochlear implant. The second case was a boy who underwent hearing loss screening for hyperbilirubinemia. Examinations were repeated three months later because the mother suspected hearing loss. Objective tests showed a pattern of auditory neuropathy. The boy's evolution was different: in spite of the presence of destructured auditory evoked potentials; it was evident that the boy conserved some hearing and had thresholds suggestive of moderate hearing loss.