The Effect of Electrode Position on Behavioral and Electrophysiologic Measurements in Perimodiolar Cochlear Implants.

BACKGROUND: The shape and position of cochlear implant electrodes could potentially influence speech perception, as this determines the proximity of implant electrodes to the spiral ganglion. However, the literature to date reveals no consistent association between speech perception and either the proximity of electrode to the medial cochlear wall or the depth of insertion. These relationships were explored in a group of implant recipients receiving the same precurved electrode. METHODS: This was a retrospective study of adults who underwent cochlear implantation with Cochlear Ltd.'s Slim Perimodiolar electrode at the Royal Victorian Eye and Ear Hospital between 2015 and 2018 (n = 52). Postoperative images were obtained using cone beam computed tomography (CBCT) and analyzed by multi-planar reconstruction to identify the position of the electrode contacts within the cochlea, including estimates of the proximity of the electrodes to the medial cochlear wall or modiolus and the angular depth of insertion. Consonant-vowel-consonant (CVC) monosyllabic phonemes were determined preoperatively, and at 3 and 12 months postoperatively. Electrically evoked compound action potential (ECAP) thresholds and impedance were measured from the implant array immediately after implantation. The relationships between electrode position and speech perception, electrode impedance, and ECAP threshold were an analyzed by Pearson correlation. RESULTS: Age had a negative impact on speech perception at 3 months but not 12 months. None of the electrode-wide measures of proximity between electrode contacts and the modiolus, nor measures of proximity to the medial cochlear wall, nor the angular depth of insertion of the most apical electrode correlated with speech perception. However, there was a moderate correlation between speech perception and the position of the most basal electrode contacts; poorer speech perception was associated with a greater distance to the modiolus. ECAP thresholds were inversely related to the distance between electrode contacts and the modiolus, but there was no clear association between this distance and impedance. CONCLUSIONS: Speech perception was significantly affected by the proximity of the most basal electrodes to the modiolus, suggesting that positioning of these electrodes may be important for optimizing speech perception. ECAP thresholds might provide an indication of this proximity, allowing for its optimization during surgery.

Four-point impedance as a biomarker for bleeding during cochlear implantation.

Cochlear implantation has successfully restored the perception of hearing for nearly 200 thousand profoundly deaf adults and children. More recently, implant candidature has expanded to include those with considerable natural hearing which, when preserved, provides an improved hearing experience in noisy environments. But more than half of these patients lose this natural hearing soon after implantation. To reduce this burden, biosensing technologies are emerging that provide feedback on the quality of surgery. Here we report clinical findings on a new intra-operative measurement of electrical impedance (4-point impedance) which, when elevated, is associated with high rates of post-operative hearing loss and vestibular dysfunction. In vivo and in vitro data presented suggest that elevated 4-point impedance is likely due to the presence of blood within the cochlea rather than its geometry. Four-point impedance is a new marker for the detection of cochlear injury causing bleeding, that may be incorporated into intraoperative monitoring protocols during CI surgery.

Case Report: Massive epistaxis from juvenile angiofibroma in an adolescent with severe haemophilia A.

Epistaxis may be profuse in individuals with normal bleeding parameters, but in an individual with haemophilia, it may be life-threatening. It is even more dangerous when epistaxis is caused by an undetected concomitant juvenile angiofibroma, and only one such case has been reported in the English literature. We report another case, of an 18-year-old Filipino adolescent with severe haemophilia A who was referred for repeated massive epistaxis. The epistaxis had been attributed to his haemophilia and managed with nasal packing, multiple blood transfusions and Factor VIII administration. After two years of unsuccessful management, nasal endoscopy was performed for the first time, revealing an intranasal mass. Imaging showed a right intranasal vascular tumour supplied mainly by the right sphenopalatine artery. He subsequently underwent preoperative embolization and endoscopic excision of the tumour with Factor VIII transfused pre-, intra-, and post-operatively, and recombinant Factor VII added post-operatively. Final histopathology was consistent with juvenile angiofibroma. There has been no nasal obstruction or recurrence of epistaxis seven years since the surgery. Clinicians should be more meticulous in assessing epistaxis in any patient with a bleeding disorder and investigate more subtle symptoms such as nasal obstruction. Verification of the source by direct visualization and ancillary diagnostic techniques (such as imaging) when indicated should be the standard of care for all patients presenting with epistaxis, whether or not a concomitant bleeding disorder exists. A high index of suspicion for juvenile angiofibroma should be maintained in adolescent males with epistaxis and nasal obstruction.