@article{giardina_brown_adunka_buchman_hutson_pillsbury_fitzpatrick_2019, title={Intracochlear Electrocochleography: Response Patterns During Cochlear Implantation and Hearing Preservation}, volume={40}, ISSN={["1538-4667"]}, DOI={10.1097/AUD.0000000000000659}, abstractNote={Objectives: Electrocochleography (ECochG) obtained through a cochlear implant (CI) is increasingly being tested as an intraoperative monitor during implantation with the goal of reducing surgical trauma. Reducing trauma should aid in preserving residual hearing and improve speech perception overall. The purpose of this study was to characterize intracochlear ECochG responses throughout insertion in a range of array types and, when applicable, relate these measures to hearing preservation. The ECochG signal in cochlear implant subjects is complex, consisting of hair cell and neural generators with differing distributions depending on the etiology and history of hearing loss. Consequently, a focus was to observe and characterize response changes as an electrode advances. Design: In 36 human subjects, responses to 90 dB nHL tone bursts were recorded both at the round window (RW) and then through the apical contact of the CI as the array advanced into the cochlea. The specific setup used a sterile clip in the surgical field, attached to the ground of the implant with a software-controlled short to the apical contact. The end of the clip was then connected to standard audiometric recording equipment. The stimuli were 500 Hz tone bursts at 90 dB nHL. Audiometry for cases with intended hearing preservation (12/36 subjects) was correlated with intraoperative recordings. Results: Successful intracochlear recordings were obtained in 28 subjects. For the eight unsuccessful cases, the clip introduced excessive line noise, which saturated the amplifier. Among the successful subjects, the initial intracochlear response was a median 5.8 dB larger than the response at the RW. Throughout insertion, modiolar arrays showed median response drops after stylet removal while in lateral wall arrays the maximal median response magnitude was typically at the deepest insertion depth. Four main patterns of response magnitude were seen: increases > 5 dB (12/28), steady responses within 5 dB (4/28), drops > 5 dB (from the initial response) at shallow insertion depths (< 15 mm deep, 7/28), or drops > 5 dB occurring at deeper depths (5/28). Hearing preservation, defined as < 80 dB threshold at 250 Hz, was successful in 9/12 subjects. In these subjects, an intracochlear loss of response magnitude afforded a prediction model with poor sensitivity and specificity, which improved when phase, latency, and proportion of neural components was considered. The change in hearing thresholds across cases was significantly correlated with various measures of the absolute magnitudes of response, including RW response, starting response, maximal response, and final responses (p’s < 0.05, minimum of 0.0001 for the maximal response, r’s > 0.57, maximum of 0.80 for the maximal response). Conclusions: Monitoring the cochlea with intracochlear ECochG during cochlear implantation is feasible, and patterns of response vary by device type. Changes in magnitude alone did not account for hearing preservation rates, but considerations of phase, latency, and neural contribution can help to interpret the changes seen and improve sensitivity and specificity. The correlation between the absolute magnitude obtained either before or during insertion of the ECochG and the hearing threshold changes suggest that cochlear health, which varies by subject, plays an important role.}, number={4}, journal={EAR AND HEARING}, author={Giardina, Christopher K. and Brown, Kevin D. and Adunka, Oliver F. and Buchman, Craig A. and Hutson, Kendall A. and Pillsbury, Harold C. and Fitzpatrick, Douglas C.}, year={2019}, pages={833–848} }
 @article{giardina_khan_pulver_adunka_buchman_brown_pillsbury_fitzpatrick_2018, title={Response Changes During Insertion of a Cochlear Implant Using Extracochlear Electrocochleography}, volume={39}, ISSN={["1538-4667"]}, DOI={10.1097/AUD.0000000000000571}, abstractNote={Objectives: Electrocochleography is increasingly being utilized as an intraoperative monitor of cochlear function during cochlear implantation (CI). Intracochlear recordings from the advancing electrode can be obtained through the device by on-board capabilities. However, such recordings may not be ideal as a monitor because the recording electrode moves in relation to the neural and hair cell generators producing the responses. The purposes of this study were to compare two extracochlear recording locations in terms of signal strength and feasibility as intraoperative monitoring sites and to characterize changes in cochlear physiology during CI insertion. Design: In 83 human subjects, responses to 90 dB nHL tone bursts were recorded both at the round window (RW) and then at an extracochlear position—either adjacent to the stapes or on the promontory just superior to the RW. Recording from the fixed, extracochlear position continued during insertion of the CI in 63 cases. Results: Before CI insertion, responses to low-frequency tones at the RW were roughly 6 dB larger than when recording at either extracochlear site, but the two extracochlear sites did not differ from one another. During CI insertion, response losses from the promontory or adjacent to the stapes stayed within 5 dB in ≈61% (38/63) of cases, presumably indicating atraumatic insertions. Among responses which dropped more than 5 dB at any time during CI insertion, 12 subjects showed no response recovery, while in 13, the drop was followed by partial or complete response recovery by the end of CI insertion. In cases with recovery, the drop in response occurred relatively early (<15 mm insertion) compared to those where there was no recovery. Changes in response phase during the insertion occurred in some cases; these may indicate a change in the distributions of generators contributing to the response. Conclusions: Monitoring the electrocochleography during CI insertion from an extracochlear site reveals insertions that are potentially atraumatic, show interaction with cochlear structures followed by response recovery, or show interactions such that response losses persist to the end of recording.}, number={6}, journal={EAR AND HEARING}, author={Giardina, Christopher K. and Khan, Tatyana E. and Pulver, Stephen H. and Adunka, Oliver F. and Buchman, Craig A. and Brown, Kevin D. and Pillsbury, Harold C. and Fitzpatrick, Douglas C.}, year={2018}, pages={1146–1156} }
 @article{ovsianikov_chichkov_adunka_pillsbury_doraiswamy_narayan_2007, title={Rapid prototyping of ossicular replacement prostheses}, volume={253}, ISSN={0169-4332}, url={http://dx.doi.org/10.1016/j.apsusc.2007.01.062}, DOI={10.1016/j.apsusc.2007.01.062}, abstractNote={Materials used in ossicular replacement prostheses must demonstrate appropriate biological compatibility, acoustic transmission, stability, and stiffness properties. Prostheses prepared using Teflon®, titanium, Ceravital and other conventional materials have demonstrated several problems, including migration, perforation of the tympanic membrane, difficulty in shaping the prostheses, and reactivity with the surrounding tissues. We have used two-photon polymerization for rapid prototyping of Ormocer® middle-ear bone replacement prostheses. Ormocer® surfaces fabricated using two-photon polymerization exhibited acceptable cell viability and cell growth profiles. The Ormocer® prosthesis was able to be inserted and removed from the site of use in the frozen human head without fracture. Our results demonstrate that two-photon polymerization is able to create ossicular replacement prostheses and other medical devices with a larger range of sizes, shapes and materials than other microfabrication techniques.}, number={15}, journal={Applied Surface Science}, publisher={Elsevier BV}, author={Ovsianikov, A. and Chichkov, B. and Adunka, O. and Pillsbury, H. and Doraiswamy, A. and Narayan, R.J.}, year={2007}, month={May}, pages={6603–6607} }