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Original Articles

Hearing preservation using combined monitoring of extra-tympanic electrocochleography and auditory brainstem responses during acoustic neuroma surgery

, , , &
Pages 178-184 | Received 17 Jan 2007, Published online: 07 Jul 2009
 

Abstract

The aim of this study was to evaluate the efficacy of an intraoperative monitoring hearing preservation strategy that includes simultaneous recordings of an auditory brainstem response (ABR) and non-invasive electrocochleography (ECochG). The combined ABR and tympanic membrane (TM) ECochG testing was performed in 74 patients undergoing acoustic neuroma (AN) surgery. In addition, EMG recordings were conducted to monitor the facial nerve function. Hearing was preserved in 19 of the 30 patients with residual hearing prior to surgery (63%), and facial nerve function was maintained in 89% of the patients. In most cases, the presence of both auditory brainstem and TM-ECochG responses at the end of surgery was associated with preservation of postoperative functional hearing; however, eight patients had a TM-ECochG response with a complete loss of the ABR, pointing to deafferentation of the auditory nerve. Tumour size and preoperative hearing thresholds significantly affected the postoperative hearing. The TM-ECochG response yielded large reproducible responses, which, in some patients, was the only way to monitor the auditory function. This auditory monitoring approach offers a valuable auditory tool that helps to improve the hearing preservation during AN surgery.

Abbreviations
ECochG=

Electrocochleography

AN=

Acoustic neuroma

TM=

Tympanic membrane

ABR=

Auditory brainstem response

CAP=

Compound action potential

GR=

Gardner and Robertson

HB=

House and Brackmann

PTA=

Pure tone average

DSS=

Discrimination speech

Abbreviations
ECochG=

Electrocochleography

AN=

Acoustic neuroma

TM=

Tympanic membrane

ABR=

Auditory brainstem response

CAP=

Compound action potential

GR=

Gardner and Robertson

HB=

House and Brackmann

PTA=

Pure tone average

DSS=

Discrimination speech

Sumario

El objetivo de este estudio fue evaluar la eficiencia de la estrategia de monitoreo para preservar la audición que incluye los registros simultáneos de potenciales evocados auditivos de tallo cerebral (ABR) y de electrococleografía no invasiva (ECochG). Se realizaron ABR y ECochG sobre la membrana timpánica (TM) a 74 pacientes que se sometieron a cirugía de neuroma acústico. Además, se realizó EMG para monitorear la función del nervio facial. Se preservó la audición en 19 de los 30 pacientes (63%) con audición residual preoperatoria y la función del nervio facial se conservó en 89% de los pacientes. En la mayoría de los casos la presencia de respuestas en los ABR y en TM-ECochG al final de la cirugía se asoció con preservación postoperatoria de la audición; sin embargo, ocho pacientes tuvieron una respuesta TMECochG con pe′rdida completa de los ABR lo que apunta a una desaferentación del nervio auditivo. El tamaño del tumor y los umbrales auditivos preoperatorios afectaron significativamente la audición postoperatoria. Las respuestas TM-ECochG fueron amplias y reproducibles, y en algunos pacientes fue la única forma de monitorear la función auditiva. El monitoreo auditivo propuesto representa una herramienta valiosa que ayuda a mejorar la preservación auditiva durante la cirugía del nervio auditivo.

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