Mechanically evoked tinnitus after cochlear implantation with preservation of residual hearing

Abstract

In the recent past, inclusion criteria for cochlear implant surgery expanded to patients with ever more residual acoustic hearing in the low frequencies. By applying the meticulous hearing preservation surgical strategy and specifically designed atraumatic electrode arrays, residual hearing can be preserved to a meaningful extent in a large majority of patients. In this paper, we describe two female patients suffering from mechanically evoked tinnitus after hearing preservation cochlear implantation surgery with MEDEL flex electrodes. The occurrence of audible perceptions through mechanical stimulation in the region of the external ear is believed to be due to the direct transmission of movements via the electrode array to the basilar membrane of the inner ear. In both cases, the mechanically evoked tinnitus led to revision surgery with immobilization of the array in the mastoid cavity. Despite eliminating the tinnitus, the revision surgery led to a loss of residual hearing in one patient, whereas the relatively poor residual hearing in the other revision case remained unchanged. The presence of mechanically evoked tinnitus seems to be associated with increased fragility of inner ear structures and hearing function, possibly due to direct mechanical contact of the electrode array with the basilar membrane. Consequently, the electrode array needs to be carefully immobilized in the mastoid cavity at a distance from soft tissue to prevent mechanical damage of inner ear structures, particularly in female patients with fine muscular tissue.

Keywords:

• Cochlear implant
• Hearing preservation
• Mechanical tinnitus
• Complication
• Electrode array extrusion
• Electrode array fixation
• Electrode array malposition prevention
• Revision surgery

Additional information

Funding

None.

Notes on contributors

Lenka Vankatova

Lenka Vankatova - after graduating from the First Faculty of Medicine, Charles University in Prague in 2012. Lenka Vankatova has completed her Otorhinolarygology - Head and Neck Surgery residency (2019) and Phoniatrics fellowship (2022) in the Service of ORL and HNS in Geneva University Hospitals.

Julien Wen Hsieh

Julien Wen Hsieh received his MD degree in 2012 from the University Of Geneva in Switzerland where he worked on human olfaction following nasal surgery and the control of genome expression in yeast cells. In 2013, he carried out an Ear, Nose and Throat (ENT) residency at Luxembourg Hospital Center in Luxembourg. He won the “Junior Scientific Excellence Prize” for the development of a Smell and Taste clinic in Luxembourg to treat chemosensory disorders and promote research in this field. In 2014, he joined the Rockefeller University Hospital in New York (USA) as an instructor in clinical investigation (clinical scholar) at the Vosshall's Laboratory of Neurogenetics and behavior. There, he worked with Andreas Keller and Leslie Vosshall and invented SMELL-RS, a universal smell test that may help diagnose patients with olfactory dysfunction. In 2017, he returned to Geneva to continue his ENT residency at the Geneva University Hospitals (Switzerland) and trained with Basile Landis, an expert in clinical olfaction. In 2019, he was promoted young physician-scientist by the University of Geneva - Faculty of medicine with 50% protected time to conduct research at the bench and patient's bedside. In Pascal Senn's Inner Ear and Olfaction Laboratory, he carried out research on olfactory neuroregeneration to find a cure for patients with post-traumatic smell loss. He received several international awards such as the “European Chemoreception Research Organization Young Investigator Award” in 2018 and the “Clinical olfactory working group - German ENT society Award” in 2019.

Dimitrios Daskalou

Dimitrios Daskalou received his medical degree from the Aristotle University of Thessaloniki School of Medicine, Greece, in 2018, where he also attended a master's program in Medical Research Methodology. He is currently an ENT medical resident in Geneva university hospitals with a primary focus on otology and especially on medical and surgical management of hearing loss.

Pascal Senn

Pascal Senn, MD has graduated from the University of Bern in 1997 and is currently professor and chairman of the Service of ORL, HNS at the University hospitals of Geneva, Switzerland with a clinical focus on ear surgery and cochlear implantation.