Zonas mortas na cóclea em freqüências altas: implicações no processo de adaptação de prótese auditivas

Abstract

Em perdas auditivas de grau moderado a severo nas freqüências altas, a lesão coclear pode estar relacionada a "zonas mortas", regiões onde as células ciliadas internas e/ou neurônios adjacentes não são funcionais. OBJETIVO: Avaliar o reconhecimento de fala em pacientes com e sem zonas mortas na cóclea em freqüências altas. MATERIAL e MÉTODO: Estudo clínico e experimental de 30 indivíduos adultos, distribuídos em dois grupos: grupo 1 - 15 indivíduos sem zonas mortas, e grupo 2 - 15 com zonas mortas na cóclea. Os pacientes foram submetidos à pesquisa do índice de reconhecimento de fala, limiar de reconhecimento de sentenças, sem e com ruído competitivo. Os testes de fala foram realizados sem prótese, com próteses auditivas amplificando a faixa de freqüências de 100 a 8000 Hz (programa 1) e com amplificação restrita, 100 a 2560 Hz (programa 2). RESULTADOS: O grupo 1 apresentou melhor desempenho utilizando as próteses auditivas no programa 1. Já o grupo 2 obteve melhor desempenho com o programa 2. CONCLUSÕES: Pacientes sem zonas mortas na cóclea obtêm maior benefício com a amplificação em freqüências altas. Na presença de zonas mortas em freqüências altas, o melhor desempenho é obtido com a amplificação restrita nestas freqüências.

Study of the long-term effects of frequency compression by behavioral verbal tests in adults

“…These patients usually have normal or almost normal hearing sensitivity in low and medium frequencies and were elected as candidates with restrictions for the use of amplification due to technological limitations (1) and to poor speech perception in noisy environments, once high-frequency amplification is not enough to provide good audibility of speech sounds and cannot be reused because of organic limitations (2) . In view of this, some researchers recommend the prescription of little or none amplification in high frequencies during adaptation of hearing aids for patients with steeply sloping hearing loss (3,4) . Conversely, it is known that information input at high frequencies can significantly improve speech perception, especially in noisy environments (5)(6)(7) .…”

Diagnosing Cochlear “Dead” Regions and Its Importance in the Auditory Rehabilitation Process

“…In the studies carried out by Baer, Moore and Kluk (2002)11, Vestergaard (2003) 12 , Gordo (2004) 13 and Almeida and Buzo (2005) 14 , cochlear dead zones diagnosis was carried out through the TEN test, and the authors did not find difficulties to perform the test, and the results found were reliable and matched the theoretical assumptions related to the presence of cochlear dead zones. In the studies carried out by Baer, Moore and Kluk (2002) 11 , Vestergaard (2003) 12 and Gordo (2004) 13 , there are references as to speech recognition, which is the main goal of the individual eligible to the use of hearing aids, and showed the importance of diagnosing dead zones in the cochlea: sound amplification is avoided in this region, and speech recognition improves.…”

“…Gordo (2004) 14 applied the TEN (HL) test in thirty adult individuals with bilateral descending sensorineural hearing loss. He used a two channel audiometer to control pure tone and noise separately, connected to a CD player.…”

Compressão de freqüências e suas implicações no reconhecimento de fala

“…The amplification of sounds in the frequency range that corresponds to the dead regions does not result in benefit and may even impair speech intelligibility. Therefore, some authors recommend caution in high frequencies amplification when hearing threshold is above 55 dB HL (3,4).…”