Drill-induced Cochlear Injury During Otologic Surgery: Intracochlear Pressure Evidence of Acoustic Trauma

Delayed hearing loss after cochlear implantation: Re-evaluating the role of hair cell degeneration

Delayed loss of residual acoustic hearing after cochlear implantation is a common but poorly understood phenomenon due to the scarcity of relevant temporal bone tissues. Prior histopathological analysis of one case of post-implantation hearing loss suggested there were no interaural differences in hair cell or neural degeneration to explain the profound loss of low-frequency hearing on the implanted side (Quesnel et al., 2016) and attributed the threshold elevation to neo-ossification and fibrosis around the implant. Here we re-evaluated the histopathology in this case, applying immunostaining and improved microscopic techniques for differentiating surviving hair cells from supporting cells. The new analysis revealed dramatic interaural differences, with a > 80 % loss of inner hair cells in the cochlear apex on the implanted side, which can account for the post-implantation loss of residual hearing. Apical degeneration of the stria further contributed to threshold elevation on the implanted side. In contrast, spiral ganglion cell survival was reduced in the region of the electrode on the implanted side, but apical counts in the two ears were similar to that seen in age-matched unimplanted control ears. Almost none of the surviving auditory neurons retained peripheral axons throughout the basal half of the cochlea. Relevance to cochlear implant performance is discussed.

Risk of hearing loss in the opposite ear after tympanomastoidectomy

PURPOSE

The definitive treatment for chronic suppurative otitis media is surgery. Surgical technique and procedure varies according to individual case findings and pathology and may require mastoidectomies in which the canal wall is preserved or lowered to eradicate disease from mastoid air cells. Surgical treatment of chronic middle ear disease carries a risk of damage to the inner ear. The aim of this study was to investigate whether the noise produced by the tour system following chronic ear surgery causes sensorineural hearing loss, a condition for which not many studies have been published in the literature.

METHODS

The study consisted of a total of 49 patients with type I, type II and type III canal wall preservation and 62 patients with tympanoplasty with canal wall preservation and lowering. Bone and air thresholds were compared before and after middle ear surgery. Changes in bone and air thresholds were compared according to the type of tympanoplasty.

RESULTS

In the ICW-I, ICW-II and ICW-III tympanoplasties, and in the ICW and CWD tympanoplasties, the preoperative and postoperative values of the opposite ear hearing measurements were performed, and did not differ according to the type of surgery. There is no correlation drilling duration and hearing for the opposite ear.

CONCLUSION

The prevention of postoperative sensorineural hearing loss depends on multiple factors, and assessing the magnitude of hearing loss in relation to these factors is important in determining the success of the surgery.

Evaluation of inner ear damage by mastoid drilling with measurement of serum prestin (SLC26A5) levels

OBJECTIVE

The objective of this study is to demonstrate any inner ear injury caused by drilling in mastoid surgery with prestin, outer hair cell motor protein specific to the cochlea.

METHODS

The patients with chronic otitis media requiring mastoidectomy (n = 21) and myringoplasty (n = 21) were included. Serum prestin level obtained from blood samples was measured before surgery and on postoperative days 0, 3, and 7 using Human Prestin (SLC26A5) ELISA Kit. All patients underwent the Pure Tone Audiometry (PTA) test before surgery and on the postoperative 7th day. The drilling time was also recorded for all patients who underwent mastoidectomy.

RESULTS

In both mastoidectomy and myringoplasty groups, the postoperative serum prestin levels increased on days 0 and 7 (pday-0 = 0.002, pday-7 = 0.001 and pday-0 = 0.005, pday-7 = 0.001, respectively). There was no significant difference in the serum prestin levels between the two groups, postoperatively. The PTA thresholds at day 7 did not change in either group. A significant decline at 2000 Hz of bone conduction hearing threshold in both groups and a decline at 4000 Hz in the myringoplasty group were found. There was no correlation between the drilling time and the increase of prestin levels in the postoperative day 0, 3, and 7.

CONCLUSION

Our results showed that mastoid drilling is not related to a significant inner ear injury. Although the myringoplasty group was not exposed to drill trauma, there was a similar increase in serum prestin levels as the mastoidectomy group. Also, a significant decline at 2000 Hz of bone conduction hearing threshold in both groups and a decline at 4000 Hz in the myringoplasty group were found. These findings suggest that suction and ossicular manipulation trauma can lead to an increase in serum prestin levels and postoperative temporary or permanent SNHL at 2000 and 4000 Hz.

LEVEL OF EVIDENCE

Level-4.

Extracellular vesicles for developing targeted hearing loss therapy

Substantial efforts have been made for local administration of small molecules or biologics in treating hearing loss diseases caused by either trauma, genetic mutations, or drug ototoxicity. Recently, extracellular vesicles (EVs) naturally secreted from cells have drawn increasing attention on attenuating hearing impairment from both preclinical studies and clinical studies. Highly emerging field utilizing diverse bioengineering technologies for developing EVs as the bioderived therapeutic materials, along with artificial intelligence (AI)-based targeting toolkits, shed the light on the unique properties of EVs specific to inner ear delivery. This review will illuminate such exciting research field from fundamentals of hearing protective functions of EVs to biotechnology advancement and potential clinical translation of functionalized EVs. Specifically, the advancements in assessing targeting ligands using AI algorithms are systematically discussed. The overall translational potential of EVs is reviewed in the context of auditory sensing system for developing next generation gene therapy.

Noise-induced hearing loss in the contralateral ear during otologic and neurotologic surgeries

OBJECTIVE

Noise-induced hearing loss in the non-surgical ear during otologic/neurotologic surgery has not been well studied. The purpose of this study was to evaluate changes in hearing that may occur in the contralateral (i.e., non-surgical) ear after various otologic/neurotologic surgeries due to noise generated by drills. We hypothesized that otologic/neurotologic surgeries, longer in duration, would suggest longer drilling times and result in decreased hearing in the contralateral ear as evidenced by a change post-operative pure tone air conduction thresholds when compared to pre-operative thresholds.

METHODS

A retrospective chart review at a tertiary referral center. Adult patients (18-75 years old) who underwent otologic/neurotologic surgeries from May 1, 2016 through May 1, 2021 were considered for inclusion. Surgeries included vestibular schwannoma resection (translabyrinthine, middle cranial fossa, or retrosigmoid approaches), endolymphatic sac/shunt and labyrinthectomy for Meniere's disease, and tympanomastoid surgery for middle ear pathology (e.g., cholesteatoma). Patient characteristics obtained through record review included age, sex, surgical procedure, pre-operative and post-operative audiometric thresholds and word recognition scores (WRS) for the contralateral ear, and duration of surgery.

RESULTS

No significant differences were observed for change in audiometric thresholds in the contralateral ear for any surgery when considering individual frequencies. Additionally, no significant change in WRS was observed for any surgical approach.

CONCLUSIONS

The risk of hearing loss in the non-surgical ear during various otologic/neurotologic surgeries appears to be minimal when measured via routine clinical tests.

Measurement of vitreous humor pressure in vivo using an optic fiber pressure sensor

We conducted a study to assess the pressure difference between the aqueous and vitreous humors in rabbit eyes using a direct intraocular pressure (IOP) measurement method. A micro-optic-fiber pressure sensor was utilized for this purpose. Preliminary experiments with enucleated porcine eyes confirmed the sensor's accuracy in measuring both aqueous and vitreous humor pressure. The main study involved six healthy albino rabbits, where the sensor measured the pressure in the anterior chamber (aIOP) and posterior vitreous-cavity (pIOP). These measurements were compared to aIOP values obtained through rebound tonometry. Additionally, pre- and postoperative pressure comparisons were made after performing a vitrectomy. Results revealed a significant disparity between aqueous and vitreous humor pressures. Prior to vitrectomy, pIOP was 22.8 mmHg, over twice as high as aIOP (11.0 mmHg), but decreased to a similar level following the procedure. Comparison between the sensor measurements and rebound tonometry showed agreement in aIOP values. In conclusion, our study demonstrates that vitreous humor pressure is consistently higher than aqueous humor pressure, reaching the upper limit of normal IOP. Furthermore, vitrectomy effectively reduces pIOP, aligning it with aIOP. These findings contribute valuable insights into intraocular pressure dynamics and have implications for clinical interventions targeting ocular pressure regulation.

Effects of Varying Laser Parameters During Laser Stapedotomy on Intracochlear Pressures

OBJECTIVE

Sensorineural hearing loss is a known complication of stapes surgery. We previously showed that laser stapedotomy can result in intracochlear pressures that are comparable to high sound pressure levels. Optimizing laser settings to those that correspond with the lowest pressure changes may mitigate risk for postoperative hearing loss. Here we quantify the effects of various laser parameters on intracochlear pressures and test the hypothesis that intracochlear pressure changes are proportional to the laser energy delivered.

STUDY DESIGN

Basic and translational science.

SETTING

Cadaveric dissection and basic science laboratory.

METHODS

Cadaveric human heads underwent mastoidectomies. Intracochlear pressures were measured via fiber-optic pressure probes placed in scala vestibuli and tympani. Pulses of varied stimulus power and duration from a 980-nm diode laser were applied to the stapes footplate.

RESULTS

Sustained high-intensity pressures were observed in the cochlea during all laser applications. Observed pressure magnitudes increased monotonically with laser energy and rose linearly for lower stimulus durations and powers, but there was increased variability for laser applications of longer duration (200-300 ms) and/or higher power (8 W).

CONCLUSIONS

Results confirm that significant pressure changes occur during laser stapedotomy, which we hypothesize may cause injury. Overall energy delivered depends predictably on duration and power, but surgeons should use caution at the highest stimulus levels and longest pulse durations due to the increasing variability in intracochlear pressure under these stimulus conditions. While the risk to hearing from increased intracochlear pressures from laser stapedotomy remains unclear, these results affirm the need to optimize laser settings to avoid unintended injury.

Creation of an incus recess for a middle-ear microphone using a drill or laser ablation: a comparison of equivalent noise level and middle ear transfer function

PURPOSE

Studies have assessed the trauma and change in hearing function from the use of otological drills on the ossicular chain, but not the effects of partial laser ablation of the incus. A study of the effectiveness of a novel middle-ear microphone for a cochlear implant, which required an incus recess for the microphone balltip, provided an opportunity to compare methods and inform a feasibility study of the microphone with patients.

METHODS

We used laser Doppler vibrometry with an insert earphone and probe microphone in 23 ears from 14 fresh-frozen cadavers to measure the equivalent noise level at the tympanic membrane that would have led to the same stapes velocity as the creation of the incus recess.

RESULTS

Drilling on the incus with a diamond burr created peak noise levels equivalent to 125.1-155.0 dB SPL at the tympanic membrane, whilst using the laser generated equivalent noise levels barely above the baseline level. The change in middle ear transfer function following drilling showed greater variability at high frequencies, but the change was not statistically significant in the three frequency bands tested.

CONCLUSIONS

Whilst drilling resulted in substantially higher equivalent noise, we considered that the recess created by laser ablation was more likely to lead to movement of the microphone balltip, and therefore decrease performance or result in malfunction over time. For patients with greatly reduced residual hearing, the greater consistency from drilling the incus recess may outweigh the potential benefits of hearing preservation with laser ablation.

Surgical Approach for Rapid and Minimally Traumatic Recovery of Human Inner Ear Tissues From Deceased Organ Donors

OBJECTIVE

To develop a surgical approach for rapid and minimally traumatic recovery of inner ear tissue from human organ and tissue donors to provide fresh tissue for use in inner ear research.

STUDY DESIGN

Exploration of novel surgical methodology and evaluation of the steps necessary for obtaining specimens from donors during the procurement of organs for transplantation.

SETTING

Donor procurement locations across multiple local hospitals and tissue processing at the microsurgical temporal bone laboratory.

PATIENTS TISSUE SOURCE

Human organ and tissue donors.

INTERVENTIONS

Dissection and procurement of the inner ear tissue.

MAIN OUTCOME MEASURES

Development of rapid and minimally traumatic inner ear tissue recovery. Primarily, establishing an efficient process which includes collaboration with transplant network, implementing a consent protocol, developing and training an on-call recovery team, and designing a portable surgical kit suitable for use in a variety of settings.

RESULTS

The extraction procedure is described in three consecutive steps: the trans-canal exposure, the approach to the vestibule with extraction of the vestibular organs; and the approach to extract inner ear tissues from the cochlear duct.

CONCLUSIONS

Organ and tissue donors are a promising and underutilized resource of inner ear organs for purposes of research and future translational studies. Using our modified technique through the trans-canal/trans-otic approach, we were able to extract tissues of the vestibular and auditory end organs in a timely manner.

Measurement and Mitigation of Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion

HYPOTHESIS

High intracochlear pressure transients associated with cochlear implant placement are reduced with smaller, non-styleted arrays, and longer insertion durations.

BACKGROUND

With increasing focus on hearing preservation during cochlear implant surgery, atraumatic technique is of the utmost importance. Previous studies revealed that high intensity pressure transients can be generated during the insertion of implant electrodes. Resulting acoustic trauma may be one contributing factor to postoperative loss of residual hearing.

METHODS

Thirty ears in cadaveric specimens were surgically prepared with placement of intracochlear pressure sensors. Sequential implant insertions were made over 10, 30, or 60 seconds using seven randomly ordered electrode styles. Pressures were also measured during common post-insertion electrode manipulations and removal. Measurements were compared between electrode styles and characteristics using analysis of variance (ANOVA) and Pearson correlation.

RESULTS

Implant insertion and post-insertion manipulations produced high-intensity pressure transients with all electrodes tested, with some measurements exceeding 170 dB peak SPL. Average peak pressures were significantly lower for straight, non-stylet electrodes (p << 0.001). The likelihood of generating transients was lowest with the slowest insertions (p << 0.001).

CONCLUSIONS

Cochlear implant insertion can generate transients in intralabyrinthine pressure levels equivalent to high intensity, impulsive acoustic stimuli known to cause hearing loss. Although transients were observed in all conditions, exposure may be mitigated by using non-styleted electrodes and slow insertion speeds. Additional surgical manipulations can also produce similar high-pressure events. Results from this investigation suggest that use of non-styleted electrodes, slow but steady insertion speeds, and avoidance of post-insertional manipulations are important to reduce cochlear trauma.

Meta-analysis of hearing outcomes of chronic otitis media surgery in the only hearing ear

OBJECTIVE

To assess the hearing outcomes of surgery for patients with chronic otitis media (COM) with or without cholesteatoma in case of the only hearing ear (OHE).

METHODS

This meta-analysis included COM patients with hearing in only one ear. The PubMed, Scopus, and Cochrane databases were reviewed.

RESULTS

Thirteen studies were included, 252 excluded. The total number of operated ears was 229. The patients' ages ranged from 6 to 78 years. A change greater than 10 dB in hearing thresholds in the OHE was considered as a significant result. When both the COM with (cCOM) and without cholesteatoma (ncCOM) cases were considered, the air bone gap (ABG), air conduction (AC) and bone conduction (BC) thresholds were stable or improved in 91.06% (95% CI:81.94-97.19%), 87.91% (82.14-92.34%), and 94.99% (95% CI:90.20-97.97%) of patients, respectively. Stable or improved ABG, AC and BC thresholds were observed in 92.36% (95% CI:81.67-97.86%), 87.36% (95% CI:71.46-96.23%), and 94.85% (95% CI:81.36-99.49%) of those with ncCOM, respectively. For patients with cCOM, the results were 85.96% (95% CI:81.36-99.49%), 85.20% (95% CI:76.04-91.87%), and 97.01% (95% CI:89.62-99.63%), respectively. There were no significant differences in these thresholds between either category.

CONCLUSION

Hearing deterioration in AC and BC thresholds can be expected in about 13-15% and 5-3%, respectively, of patients, with ncCOM or cCOM. Our results should not be construed as a guide for determining surgery eligibility in patients with COM in the OHE.

Development and Validation of a Prognostic Model to Predict Hearing Recovery for Patients With Chronic Otitis Media

OBJECTIVE

To explore the factors affecting postoperative hearing recovery in chronic otitis media (COM) patients, establish a clinical prediction model for hearing recovery, and verify the accuracy of the model.

METHODS

Data of patients with COM who were admitted to our hospital between January 1, 2012 and September 30, 2020 were retrospectively analyzed. We collected data on relevant clinicopathological characteristics of patients. The patients were randomly divided into the development cohort and validation cohorts. A postoperative air-bone gap (ABG) ≤20 dB was defined as successful hearing recovery. Univariate and multivariable logistic regression analyses were used to investigate the association of several prognostic factors with hearing recovery. These factors were then used to establish a nomogram. The model was subjected to bootstrap internal validation and performance evaluation in terms of discrimination, calibration, and clinical validity.

RESULTS

This study included 2146 patients with COM: the development cohort comprised 1610 patients (mean [standard deviation; SD] age, 44.1 [14.7] years; 733 men [45.5%]) and the validation cohort included 536 patients (mean [SD] age, 42.9 [14.4] years; 234 men [43.7%]). Multivariable logistic regression analysis showed that age, duration of onset, styles of surgery (tympanoplasty, canal wall up-CWU, or canal wall down-CWD), ossicular prosthesis, granulation or calcified blocks around the ossicular chain, ossicular chain integrity, duration of drilling, eustachian tube dysfunction, mixed hearing loss, semicircular canal fistula, and second surgery were associated with hearing recovery. A nomogram based on these variables was constructed. The area under the curve was 0.797 (95% confidence interval [CI], 0.778-0.812) in the development cohort and 0.798 (95% CI, 0.7605-0.8355) in the validation cohort.

CONCLUSIONS

This study demonstrated the various clinical factors correlated with hearing recovery in patients with COM. The nomogram developed with these data could provide personalized risk estimates of hearing recovery to enhance preoperative counseling and help to set realistic expectations in patients.

Hearing changes after temporomandibular joint arthroscopy: a prospective study

Temporomandibular Joint (TMJ) arthroscopy is considered an effective and safe minimally invasive surgical approach. While the long-term outcomes of arthroscopy tend to be positive and free of secondary effects, patients occasionally complain about their hearing following the treatment. The aim of this prospective study was to investigate possible hearing changes associated with TMJ arthroscopy. Pure-tone audiograms were performed in patients two weeks before TMJ arthroscopy and repeated six weeks after intervention. A total of 15 patients (mean age of 41.73±16.36) were enrolled; 25 TMJ arthroscopies were performed (five unilateral and ten bilateral). Statistically significant differences were found between preoperative and postoperative audiograms in the frequencies 256Hz (P=0.011) and 8kHz (P=0.058, borderline). For the frequency 256Hz the difference was favourable, but not superior to 5dB. For the frequency 8kHz, in three patients the TMJ arthroscopy resulted in a decrease of 10dB. However, no clinical hearing changes or complaints were observed in the involved patients. No differences in audiograms between level 1 or 2 arthroscopy were observed. The study reinforces the safety of the TMJ arthroscopy level 1 and 2 with the reported protocol. The authors recommend larger studies to validate the results, specially for frequency 8kHz.

Middle Ear Actuator Performance Determined From Intracochlear Pressure Measurements in a Single Cochlear Scala

HYPOTHESIS

Intracochlear pressure measurements in one cochlear scala are sufficient as reference to determine the output of an active middle ear implant (AMEI) in terms of "equivalent sound pressure level" (eqSPL).

BACKGROUND

The performance of AMEIs is commonly calculated from stapes velocities or intracochlear pressure differences (PDiff). However, there are scenarios where measuring stapes velocities or PDiff may not be feasible, for example when access to the stapes or one of the scalae is impractical.

METHODS

We reanalyzed data from a previous study of our group that investigated the performance of an AMEI coupled to the incus in 10 human temporal bones. We calculated eqSPL based on stapes velocities according to the ASTM standard F2504-05 and based on intracochlear pressures in scala vestibuli, scala tympani, and PDiff.

RESULTS

The AMEI produced eqSPL of ∼100 to 120 dB at 1 Vrms. No significant differences were found between using intracochlear pressures in scala vestibuli, scala tympani, or PDiff as a reference. The actuator performance calculated from stapes displacements predicted slightly higher eqSPLs at frequencies above 1000 Hz, but these differences were not statistically significant.

CONCLUSION

Our findings show that pressure measurements in one scala can be sufficient to evaluate the performance of an AMEI coupled to the incus. The method may be extended to other stimulation modalities of the middle ear or cochlea when access to the stapes or one of the scalae is not possible.

Risks of Intracochlear Pressures From Laser Stapedotomy

HYPOTHESIS

Surgical manipulations during laser stapedotomy can produce intracochlear pressure changes comparable to pressures created by high-intensity acoustic stimuli.

BACKGROUND

New-onset sensorineural hearing loss is a known risk of stapes surgery and may result from pressure changes from laser use or other surgical manipulations. Here, we test the hypothesis that high sound pressure levels are generated in the cochlea during laser stapedotomy.

METHODS

Human cadaveric heads underwent mastoidectomy. Fiber-optic sensors were placed in scala tympani and vestibuli to measure intracochlear pressures during key steps in stapedotomy surgery, including cutting stapedius tendon, lasering of stapedial crurae, crural downfracture, and lasering of the footplate.

RESULTS

Key steps in laser stapedotomy produced high-intensity pressures in the cochlea. Pressure transients were comparable to intracochlear pressures measured in response to high intensity impulsive acoustic stimuli.

CONCLUSION

Our results demonstrate that surgical manipulations during laser stapedotomy can create significant pressure changes within the cochlea, suggesting laser application should be minimized and alternatives to mechanical downfracture should be investigated. Results from this investigation suggest that intracochlear pressure transients from stapedotomy may be of sufficient magnitude to cause damage to the sensory epithelium and affirm the importance of limiting surgical traumatic exposures.

Characterizing Insertion Pressure Profiles During Cochlear Implantation: Simultaneous Fluoroscopy and Intracochlear Pressure Measurements

BACKGROUND

Combined electrical-acoustical stimulation (EAS) has gained popularity as patients with residual hearing are increasingly undergoing cochlear implantation. Preservation of residual hearing correlates with hearing outcomes, but loss of hearing occurs in a subset of these patients. Several mechanisms have been proposed as causing this hearing loss; we have previously described high amplitude pressure transients, equivalent to high-level noise exposures, in the inner ear during electrode insertion. The source of these transients has not been identified.

METHODS

Cadaveric human heads were prepared with an extended facial recess. Fiber-optic pressure sensors were inserted into the scala vestibuli and scala tympani to measure intracochlear pressures. Two cochlear implant (CI) electrode styles (straight and perimodiolar) were inserted during time-synced intracochlear pressures and video fluoroscopy measurements.

RESULTS

CI electrode insertions produced pressure transients in the cochlea up to 160 to 170 dB pSPL equivalent for both styles, consistent with previous results. However, the position of the electrode within the cochlea when transients were generated differed (particularly contact with the medial or lateral walls).

CONCLUSIONS

These results begin to elucidate the insertion pressure profiles of CI electrodes, which can be used to improve CI electrode designs and facilitate "silent-insertions" to improve chances of hearing preservation.

Lateral Semicircular Canal Pressures During Cochlear Implant Electrode Insertion: a Possible Mechanism for Postoperative Vestibular Loss

HYPOTHESIS

Insertion of cochlear implant electrodes generates transient pressure spikes within the vestibular labyrinth equivalent to high-intensity acoustic stimuli.

BACKGROUND

Though cochlear implant (CI) surgery is regarded as having low risk of impacting the vestibular system, several studies have documented changes in vestibular function after implantation. The mechanism of these changes is not understood. We have previously established that large, potentially damaging pressure transients can be generated in the cochlea during electrode insertion, but whether pressure transients occur within the vestibular labyrinth has yet to be determined. Here, we quantify the exposure of the vestibular system to potentially damaging pressure transients during CI surgery.

METHODS

Five human cadaveric heads were prepared with an extended facial recess and implanted sequentially with eight different CI electrode styles via a round window approach. Fiber-optic sensors measured intralabyrinthine pressures in scala vestibuli, scala tympani, and the lateral semicircular canal during insertions.

RESULTS

Electrode insertion produced a range of high-intensity pressure spikes simultaneously in the cochlea and lateral semicircular canal with all electrodes tested. Pressure transients recorded were found to be significantly higher in the vestibular labyrinth than the cochlea and occurred at peak levels known to cause acoustic trauma.

CONCLUSION

Insertion of CI electrodes can produce transients in intralabyrinthine fluid pressure levels equivalent to high-intensity, impulsive acoustic stimuli. Results from this investigation affirm the importance of atraumatic surgical techniques and suggest that in addition to the cochlea, the vestibular system is potentially exposed to damaging fluid pressure waves during cochlear implantation.

Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion: Effect of Micro-mechanical Control on Limiting Pressure Trauma

HYPOTHESIS

Use of micro-mechanical control during cochlear implant (CI) electrode insertion will result in reduced number and magnitude of pressure transients when compared with standard insertion by hand.

INTRODUCTION

With increasing focus on hearing preservation during CI surgery, atraumatic electrode insertion is of the utmost importance. It has been established that large intracochlear pressure spikes can be generated during the insertion of implant electrodes. Here, we examine the effect of using a micro-mechanical insertion control tool on pressure trauma exposures during implantation.

METHODS

Human cadaveric heads were surgically prepared with an extended facial recess. Electrodes from three manufacturers were placed both by using a micro-mechanical control tool and by hand. Insertions were performed at three different rates: 0.2 mm/s, 1.2 mm/s, and 2 mm/s (n = 20 each). Fiber-optic sensors measured pressures in scala vestibuli and tympani.

RESULTS

Electrode insertion produced pressure transients up to 174 dB SPL. ANOVA revealed that pressures were significantly lower when using the micro-mechanical control device compared with insertion by hand (p << 0.001). No difference was noted across electrode type or speed. Chi-square analysis showed a significantly lower proportion of insertions contained pressure spikes when the control system was used (p << 0.001).

CONCLUSION

Results confirm previous data that suggest CI electrode insertion can cause pressure transients with intensities similar to those elicited by high-level sounds. Results suggest that the use of a micro-mechanical insertion control system may mitigate trauma from pressure events, both by reducing the amplitude and the number of pressure spikes resulting from CI electrode insertion.

Inappropriate Use of the "Rosowski Criteria" and "Modified Rosowski Criteria" for Assessing the Normal Function of Human Temporal Bones

Important research by Rosowski et al. [Twenty-Seventh Meeting of the Association for Research in Otolaryngology, 2004, p. 275] has led to a standard practice by the American Society for Testing Materials [West Conshohocken: ASTM International; 2014] to assess normal function of temporal bones used in the development of novel middle ear actuators and sensors. Rosowki et al. [Audiol Neurotol. 2007; 12(4): 265-76] have since suggested that the original criteria are too restrictive and have proposed modified criteria. We show that both the original and modified criteria are inappropriate for assessing individual temporal bones. Moreover, we suggest that both the original and modified Rosowski criteria should be applied with caution when assessing whether mean data from a study are within physiological norms because the multiple comparisons resulting from verification at each frequency will lead to very liberal rejection. The standard practice, however, has led to the collection of more extensive and consistent data. We suggest that it is now opportune to use these data to further modify the Rosowski criteria.

Post-operative Sensorineural Hearing Loss After Middle Ear Surgery

Chronic suppurative otitis media is managed by tympanomastoid surgery often requires mastoid drilling. Sometimes patients develop sensorineural hearing loss after middle ear surgery. Objective of the study was to compare pre and post operative bone conduction thresholds after middle ear surgeries. The study was conducted on 90 patients who had undergone middle ear surgeries, 30 patients of tympanoplasty (group I), modified intact canal wall mastoidectomy and tympanoplasty type-I (group II) and modified radical mastoidectomy (group III) each ware included. Demographic and clinical data were reviewed. Duration of surgery, ossicular and middle ear status and drilling time noted. Pre operative and post operative (after 3-4 months) bone conduction thresholds were compared statistically. A value of p < 0.05 was considered statistical significant. The average pre-operative hearing loss of study group was 43.78 ± 14.22 dB. Though postoperatively mean air conduction threshold improved to 36.07 ± 13.05 dB, six patients presented with deterioration of hearing. Mastoidectomy has been performed in all six. Post-operative worsening of bone conduction was seen in three patients (13.75-21.5 dB), one patient of group II and two patients of group III developed postoperative worsening of bone conduction thresholds. Significant hearing losses may occur after tympanomastoid surgery in few patients. While we are evaluating the results besides reporting average results such individual patient should be identified.