Exploration fonctionnelle du nerf cochléaire et de l’audition

Abstract

Since otoneurosurgical pathologies are being diagnosed increasingly early, the functional prognosis of surgery is gaining in importance. Hearing and cochlear nerve exploration can be carried out using three principal methods: pure-tone and speech audiometry, evoked otoacoustic emissions (EOAEs), and brainstem auditory evoked potentials (BAEPs). The aim of this paper is to present the current knowledge on auditory functional assessment. The medical and scientific literature from the Pubmed-Medline database was reviewed. Recently published related books were also included. RESULTS/DATA SYNTHESIS: Preoperative audiological evaluation makes it possible to assess pathology consequences on hearing. Depending on auditory status, conservative surgery, including intraoperative auditory monitoring, can be planned. From this perspective, prognostic factors for hearing preservation - such as the speech intelligibility score, the presence of transient EOAEs, and the presence of the BAEPs wave III - were identified. However, several surgical teams argue for a systematic conservative procedure, particularly when EOAEs are present, whatever the patient's preoperative hearing status. Postoperative audiological evaluation provides the opportunity for monitoring: in the short term, to detect complications early, through BAEPs recorded in the nonoperated ear; in the long term, to detect recurrence of the pathology. Moreover, the consequences of surgery on hearing can be assessed and long-term follow-up of auditory function can be carried out. Finally, the comparison of pre- and postoperative audiological status provides inductive feedback on surgery and electrophysiological monitoring, giving the otoneurosurgeon and neurophysiologist the opportunity to improve the entire procedure. Auditory functional assessment is essential for optimal care of tumor or functional pathologies involving the cochlear nerve and/or the cerebellopontine angle.