Novel microscope-based visual display and nasopharyngeal registration for auditory brainstem implantation: a feasibility study in an ex vivo model.

PURPOSE: An auditory brainstem implant (ABI) represents an alternative for patients with profound hearing loss who are constrained from receiving a cochlear implant. The positioning of the ABI electrode influences the patient's auditory capacity and, therefore, quality of life and is challenging even with available intraoperative electrophysiological monitoring. This work aims to provide and assess the feasibility of visual-spatial assistance for ABI positioning. METHODS: The pose of the forceps instrument that grasps the electrode was electromagnetically navigated and interactively projected in the eyepieces of a surgical microscope with respect to a target point. Intraoperative navigation was established with an experimental technique for automated nasopharyngeal patient registration. Two ABI procedures were completed in a human specimen head. RESULTS: An intraoperative usability study demonstrated lower localization error when using the proposed visual display versus standard cross-sectional views. The postoperative evaluations of the preclinical study showed that the center of the electrode was misplaced to the planned position by 1.58 mm and 3.16 mm for the left and the right ear procedure, respectively. CONCLUSION: The results indicate the potential to enhance intraoperative feedback during ABI positioning with the presented system. Further improvements consider estimating the pose of the electrode itself to allow for better orientation during placement.

Improved outcomes in auditory brainstem implantation with the use of near-field electrical compound action potentials.

OBJECTIVE: To compare the outcomes (auditory threshold and open-set speech perception at 48-month follow-up) of a new near-field monitoring procedure, electrical compound action potential, on positioning the auditory brainstem implant electrode array on the surface of the cochlear nuclei versus the traditional far-field electrical auditory brainstem response. STUDY DESIGN: Retrospective study. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Among the 202 patients with auditory brainstem implants fitted and monitored with electrical auditory brainstem response during implant fitting, 9 also underwent electrical compound action potential recording. These subjects were matched retrospectively with a control group of 9 patients in whom only the electrical auditory brainstem response was recorded. Electrical compound action potentials were obtained using a cotton-wick recording electrode located near the surface of the cochlear nuclei and on several cranial nerves. RESULTS: Significantly lower potential thresholds were observed with the recording electrode located on the cochlear nuclei surface compared with the electrical auditory brainstem response (104.4 ± 32.5 vs 158.9 ± 24.2, P = .0030). Electrical brainstem response and compound action potentials identified effects on the neighboring cranial nerves on 3.2 ± 2.4 and 7.8 ± 3.2 electrodes, respectively (P = .0034). Open-set speech perception outcomes at 48-month follow-up had improved significantly in the near- versus far-field recording groups (78.9% versus 56.7%; P = .0051). CONCLUSIONS: Electrical compound action potentials during auditory brainstem implantation significantly improved the definition of the potential threshold and the number of auditory and extra-auditory waves generated. It led to the best coupling between the electrode array and cochlear nuclei, significantly improving the overall open-set speech perception.

Bidirectional telemetry controller for neuroprosthetic devices.

We present versatile multifunctional programmable controller with bidirectional data telemetry, implemented using existing commercial microchips and standard Bluetooth protocol, which adds convenience, reliability, and ease-of-use to neuroprosthetic devices. Controller, weighing 190 g, is placed on animal's back and provides bidirectional sustained telemetry rate of 500 kb/s , allowing real-time control of stimulation parameters and viewing of acquired data. In continuously-active state, controller consumes approximately 420 mW and operates without recharge for 8 h . It features independent 16-channel current-controlled stimulation, allowing current steering; customizable stimulus current waveforms; recording of stimulus voltage waveforms and evoked neuronal responses with stimulus artifact blanking circuitry. Flexibility, scalability, cost-efficiency, and a user-friendly computer interface of this device allow use in animal testing for variety of neuroprosthetic applications. Initial testing of the controller has been done in a feline model of brainstem auditory prosthesis. In this model, the electrical stimulation is applied to the array of microelectrodes implanted in the ventral cochlear nucleus, while the evoked neuronal activity was recorded with the electrode implanted in the contralateral inferior colliculus. Stimulus voltage waveforms to monitor the access impedance of the electrodes were acquired at the rate of 312 kilosamples/s. Evoked neuronal activity in the inferior colliculus was recorded after the blanking (transient silencing) of the recording amplifier during the stimulus pulse, allowing the detection of neuronal responses within 100 mus after the end of the stimulus pulse applied in the cochlear nucleus.

Implante auditivo de tronco cerebral en niños / Auditory brainstem implant in children

Objetivo: Mostrar los resultados obtenidos mediante el uso del Implante Auditivo de Tronco Cerebral (IATC) en niños con imposibilidad de recibir un implante coclear (IC), con hipoacusia no asociada a Neurofibromatosis tipo II (NFII). Tipo de estudio: Presentación de casos. Material y método: Se muestran los resultados obtenidos en los dos primeros casos en América en niños (3 y 10 años, respectivamente) a los que se les colocó un I A TC por agenesia de nervio y cóclea. Resultados: Se logró niveles de 30db a 40 db en las audiometrías posteriores a la activación en frecuencias de 250-6.000 Hz, lograron detectar el test de Ling en su totalidad, con buena y rápida respuesta al nombre en una situación estructurada y sin pistas visuales dentro del primer mes de activación. Conclusiones: De acuerdo con nuestra reciente experiencia los casos de niños con agenesia de cóclea y/o nervio, pueden ser considerados para la colocación de un IATC porque la anatomía de los núcleos auditivos está intacta.

Aim: To discuss the results obtained with auditory brainstem implant (ABI) in children non-eligible for cochlear implant, presenting with non-NFII related hypoacusia. A case report study. Materials and Method: Two cases are presented, both of children (aged 3 and 10 years old, respectively), who underwent ABI because of nerve and cochlear agenesis Results: Post-implant audiometric levels were 30 to 40 dB for frequencies between 25 and 6000 Hz. Both patients were able to fully detect the Ling sound test with good and fast answers in a structured non-visual cues-situation within the first post-activation month. Conclusions: In our experience, children with nerve and/or cochlear agenesis could be considered for ABS implantation, because the auditory nuclei's anatomy is intact.