P. Ashley Wackym

Multicenter U.S. bilateral MED-EL cochlear implantation study: Speech perception over the first year of use

Objective: Binaural hearing has been shown to support better speech perception in normal-hearing listeners than can be achieved with monaural stimulus presentation, particularly under noisy listening conditions. The purpose of this study was to evaluate whether bilateral electrical stimulation could confer similar benefits for cochlear implant listeners. Design: A total of 26 postlingually deafened adult patients with short duration of deafness were implanted at five centers and followed up for 1 yr. Subjects received MED-EL COMBI 40+ devices bilaterally; in all but one case, implantation was performed in a single-stage surgery. Speech perception testing included CNC words in quiet and CUNY sentences in noise. Target speech was presented at the midline (0 degrees), and masking noise, when present, was presented at one of three simulated source locations along the azimuth (−90, 0, and +90 degrees). Results: Benefits of bilateral electrical stimulation were observed under conditions in which the speech and masker were spatially coincident and conditions in which they were spatially separated. Both the “head shadow” and “summation” effects were evident from the outset. Benefits consistent with “binaural squelch” were not reliably observed until 1 yr after implantation. Conclusions: These results support a growing consensus that bilateral implantation provides functional benefits beyond those of unilateral implantation. Longitudinal data suggest that some aspects of binaural processing continue to develop up to 1 yr after implantation. The squelch effect, often reported as absent or rare in previous studies of bilateral cochlear implantation, was present for most subjects at the 1 yr measurement interval.

More challenging speech-perception tasks demonstrate binaural benefit in bilateral cochlear implant users.

Objective: Preliminary studies show that bilateral cochlear implantation improves speech-recognition ability in many subjects; however, the magnitude of this improvement has been variable. The objective of our research was to explore means to better differentiate the binaural benefit that many patients who receive bilateral cochlear implants (CIs) describe. Hypothesis: Binaural improvements in speech-perception performance will be consistently evident across patients when they are tested in more challenging listening situations. Design: This was a prospective clinical study. Speech-perception performance was compared between the unilateral and bilateral cochlear implant conditions. Because the purpose was to investigate testing parameters that would demonstrate binaural benefit, word- and sentence-recognition tests were administered under several stimulation conditions: with and without noise and at three presentation levels. In addition, all subjects completed the Abbreviated Profile of Hearing Aid Benefit as a measure of subjective benefit. Subjects were adult cochlear implant recipients. Three device manufacturers were represented (Advanced Bionics Corporation, Cochlear Americas, and the Med-El Corporation); three patients received simultaneous implantation, and the other four patients received sequential CIs. The setting was a comprehensive cochlear implant program/tertiary referral center. The main outcomes measures were speech-recognition scores in percent correct, mean score difference for unilateral versus bilateral conditions, and subjective benefit scores. Results: The most significant improvements in binaural cochlear implant use were found when subjects were tested with sentence material presented at 60 dB SPL with a +8 dB signal-to-noise ratio. Six of seven subjects showed significant binaural improvement, with a mean improvement score of 12.43% (SD = 5.32). All subjects preferred the binaural listening condition. Measured improvements in quality of life were seen. Conclusions: Preliminary study findings suggest that significant cochlear implant binaural benefit in speech perception may be observed when testing in more difficult listening situations (i.e., lower presentation levels and in noise). According to the outcome of our study, testing the binaural benefit of CIs requires consideration of suitable test materials and stimulation parameters.

Complication rate of transtemporal hydroxyapatite cement cranioplasties: A case series review of 76 cranioplasties

Objective: The objective of this study was to evaluate the complication rate of transtemporal cranioplasties using hydroxyapatite cement (HAC) for repair. Study Design: We conducted a retrospective case review of patients receiving HAC cranioplasties in the Acoustic Neuroma and Skull Base Surgery Program between July 1998 and December 2002. Setting: This study was conducted at a tertiary referral center. Patients: A total of 76 HAC cranioplasties were performed in 72 patients undergoing lateral skull base surgery. Patients undergoing anterior skull base surgery or those in which HAC was used for other reconstructive purposes were excluded from the study. Interventions: We studied transtemporal approaches for otologic procedures requiring cranioplasty. Main Outcome Measures: Main outcomes measures consisted of complications requiring medical or surgical intervention. Results: Of the 76 HAC cranioplasties, two cranioplasty grafts became infected, requiring explantation. The first case involved a wound infection that extended into and involved the HAC graft; the second involved seeding of the HAC graft after meningitis after a percutaneous, endoscopic gastrostomy tube placement performed several days after the primary skull base surgery. This gives our series a wound infection incidence rate of 1.3% and an overall complication incidence rate of 2.63%. Conclusions: This retrospective review provides the largest series to date evaluating the incidence of infection in HAC cranioplasties. Despite having a much larger series, our complication rate is the lowest published rate of HAC cranioplasty explantation, and the incidence of superficial wound infections reported here is consistent with the published data for neurosurgical and neurotologic procedures.

Effect of Magnetic Resonance Imaging on Internal Magnet Strength in Med-El Combi 40 Cochlear Implants

Objective: Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med‐El Combi 40+ cochlear implant internal magnets after MRI studies.

MicroRNA-21 overexpression contributes to vestibular schwannoma cell proliferation and survival.

Hypothesis: Elevated levels of hsa-microRNA-21 (miR-21) in vestibular schwannomas (VSs) may contribute to tumor growth by downregulating the tumor suppressor phosphatase and tensin homolog (PTEN) and consequent hyperactivation of protein kinase B (AKT), a key signaling protein in the cellular pathways that lead to tumor growth. Background: Vestibular schwannomas are benign tumors that arise from the vestibular nerve. Left untreated, VSs can result in hearing loss, tinnitus, vestibular dysfunction, trigeminal nerve dysfunction, and can even become life threatening. Despite efforts to characterize the VS transcriptome, the molecular pathways that lead to tumorigenesis are not completely understood. MicroRNAs are small RNA molecules that regulate gene expression posttranscriptionally by blocking the production of specific target proteins. Methods: We examined miR-21 expression in VSs. To determine the functional significance of miR-21 expression in VS cells, we transfected primary human VS cultures with anti-miR-21 or control, scrambled oligonucleotides. Results: We found consistent overexpression of miR-21 when compared with normal vestibular nerve tissue. Furthermore, elevated levels of miR-21 correlated with decreased levels of PTEN, a known molecular target of miR-21. Anti-miR-21 decreased VS cell proliferation in response to platelet-derived growth factor stimulation and increased apoptosis, suggesting that increased miR-21 levels contributes to VS growth. Conclusion: Because PTEN regulates signaling through the growth-promoting phosphoinositide 3-kinase/AKT pathway, our findings suggest that miR-21 may be a suitable molecular target for therapies aimed specifically at reducing VS growth.

Fungal biofilm formation on cochlear implant hardware after antibiotic-induced fungal overgrowth within the middle ear.

Cochlear implantation in patients with chronic suppurative otitis media is managed with perioperative antibiotics; however, fungal overgrowth can occur. We present a child who received oral cefdinir and topical ofloxacin (Floxin). After 6 weeks, a fungal (Candida) biofilm was demonstrated on the implant surface. In this clinical setting, an antimicrobial strategy using an oral antifungal to prevent fungal overgrowth is a possibility.

Gamma Knife Surgery of Vestibular Schwannomas: Volumetric Dosimetry Correlations to Hearing Loss Suggest Stria Vascularis Devascularization as the Mechanism of Early Hearing Loss

Objective: Determine which variables are correlated with early hearing changes after gamma knife surgery of vestibular schwannomas (VSs). Study Design: Prospective clinical study of hearing outcomes, radiation dosimetry, conformity, and tumor size of all sporadic unilateral VS patients treated between June 2000 and July 2009. Setting: Tertiary referral center. Patients: Fifty-nine VS patients with at least 6 months of follow-up data were studied. Interventions: Audiometry and imaging were performed to determine auditory thresholds, speech discrimination, and tumor size. Radiation doses to 5 volumes were measured. Main Outcome Measures: Pretreatment and posttreatment comparisons were performed with regard to change in tumor size; radiation dose to specific volumes including the internal auditory canal, cochlea, basal turn of the cochlea, and modiolus; and conformity of the treatment. Results: The mean follow-up was 63.76 months (standard deviation, ±29.02 mo; range, 9-109 mo). The median follow-up was 65.5 months. A statistically significant association between maximum radiation dose to the cochlea volume and 3-frequency pure-tone average in patients starting with 50 dB or lesser PTA3 was demonstrated using linear regression analysis. Conclusion: Longitudinal changes in hearing occur over time, with the largest changes seen in the first 12 months after treatment. With our study outcomes as basis, limiting the dose of radiation to the cochlea to no more than 4 Gy would likely reduce vascular injury to the stria vascularis and improve hearing outcomes. Shielding the cochlea during the treatment planning process would be one mechanism to accomplish this goal.

Quantitative Analysis of Electrically Evoked Auditory Brainstem Responses in Implanted Children With Auditory Neuropathy/dyssynchrony

Objective: Cochlear implantation is a common treatment approach for children with auditory neuropathy/dyssynchrony (AN/AD) who do not benefit from hearing aids. The auditory brainstem response (ABR) is a measure of neural synchrony along the auditory pathway up through the brainstem. By definition, acoustically evoked ABR is absent in AN/AD, however, ABR can be elicited by electrical stimulation through the cochlear implant (electrically evoked ABR [EABR]). Reports of EABR with AN/AD to date have been primarily descriptive in nature. The objective of this study was to quantify EABR wave V measures in implanted children with and without AN/AD. Study Design: Retrospective analysis of EABR waveforms from March 2000 through February 2005. Setting: Comprehensive Cochlear Implant Program/Tertiary Referral Center. Patients: Pediatric cochlear implant users of two etiologic groups: congenital AN/AD (n = 5) and other congenital profound sensorineural hearing loss (n = 27). Intervention: Diagnostic. Main Outcome Measures: Intraoperative EABR wave V threshold, suprathreshold amplitude, and latency measures were compared between groups. Results: The EABR threshold and suprathreshold amplitude measures across the population were variable regardless of etiology. With some exceptions, a trend was observed for the AN/AD group that included average or below-average thresholds and below-average suprathreshold response amplitudes. Conclusion: Cochlear implantation can provide synchronous neural responses to auditory stimulation in AN/AD, as previously known. The quantification of EABR measures in this study indicates that subjects with AN/AD have sufficient neural sensitivity to electrical stimulation, however, they may experience less robust neural responses at suprathreshold levels. Given the heterogeneity of potential causes of AN/AD, however, caution needs to be applied when grouping this population for analyses.

Longitudinal Cognitive and Neurobehavioral Functional Outcomes Before and After Repairing Otic Capsule Dehiscence

Objective: Patients with peripheral vestibular dysfunction because of gravitational receptor asymmetries display signs of cognitive dysfunction and are assumed to have neurobehavioral sequelae. This was tested with pre- and postoperatively quantitative measurements in three cohort groups with superior semicircular canal dehiscence syndrome (SSCDS) symptoms with: 1) superior canal dehiscence (SCD) repaired via a middle cranial fossa craniotomy and canal plugging only; 2) otic capsule defects not visualized with imaging (no-iOCD) repaired with round window reinforcement (RWR) only; or 3) both SCD plugging and subsequent development of no-iOCD followed by RWR. Study Design: Prospective patient series. Setting: Tertiary referral center. Patients: There were 13 adult and 4 pediatric patients with SSCDS who had completion of neuropsychology test batteries pre- and every 3 months postoperatively. Eight patients had no-iOCD and RWR exclusively, 5 had SCD and plugging exclusively, and 4 had both SCD plugging and then development of no-iOCD with RWR. These cohorts included SSCDS with 2 different dehiscence locations. Interventions: Completion of a neuropsychology test battery preoperatively and at 3, 6, 9, and 12 months postoperatively that included: Beck Depression Inventory-II (BDI); Wide Range Intelligence Test (WRIT FSIQ) including average verbal (crystallized intelligence) and visual (fluid intelligence); Wide Range Assessment of Memory and Learning (WRAML), including the four domains of verbal memory, visual memory, attention/concentration, and working memory; and Delis–Kaplan Executive Function System (D-KEFS). The Dizziness Handicap Inventory (DHI) and the Headache Impact Test (HIT-6) were also completed to assess the impact of their disease on activities pre- and postoperatively. Main Outcome Measures: Quantitative and statistical analysis of their cognitive and neurobehavioral function. Results: The pattern of differences between the SCD group and the no-iOCD group from WRAML verbal, visual, and attention test performance indicate different postoperative clinical trajectories. For the WRAML, there was a statistically significant improvement for visual memory and verbal memory for the no-iOCD only and both (SCD and subsequent no-iOCD) groups, but no mean improvement for the SCD only group. By contrast, the no-iOCD group had significantly lower scores on the WRAML attention test preoperatively, but they recovered postoperatively to match the other groups. The preoperative findings and postoperative outcomes did not differ significantly among patient groups on the WRAML working memory test, D-KEFS motor scores, D-KEFS number and letter scores, or Wide Range Intelligence Test scores. There was a significant decrease in the BDI for all groups. The IQ scores were unchanged. There was a statistically significant improvement in the DHI and HIT-6 scores postoperatively in all groups. Conclusions: There was a marked overall improvement in cognitive and neurobehavioral function postoperatively. Variability may result from duration of underlying disease before intervention. The initial decrement or delay in performance improvement measured in several patients may represent brain reorganization. Greater longitudinal data and greater subject numbers are necessary to better understand and optimize cognitive recovery.

Distortion of Magnetic Resonance Images Used in Gamma Knife Radiosurgery Treatment Planning: Implications for Acoustic Neuroma Outcomes

Objective: To quantify the image distortion of our series of acoustic neuromas treated with gamma knife radiosurgery. Study Design: Retrospective chart and digital radiographic file review with quantitative assessment of gamma knife treatment plans. Setting: Tertiary referral center. Patients: Patients undergoing gamma knife radiosurgery for the treatment of acoustic neuromas. Intervention: Gamma knife radiosurgery. Main Outcome Measures: Gamma knife treatment plans containing magnetic resonance images were reviewed at each axial, sagittal, and coronal slice. The length of the greatest displacement of the treatment plan was measured and the volume of the treatment plan that fell outside of the internal auditory canal calculated. Known clinical measurements of audiometric, vestibular, facial, and trigeminal nerve functions were then compared with current measurements of tumor size. Results: Twenty-two of the 23 patients had measurable image shifts on the axial images. The range of the image shift was 0 to 5.8 mm, with a mean shift of 1.92 ± 1.29 mm (± standard deviation). Tumor volumes of the treatment plan that fell outside of the internal auditory canal ranged from 0 to 414 mm3, with a mean of 90.5 mm3. The mean percentage that fell outside of the internal auditory canal was 16.7% of total tumor volume (range, 2.4-77.6%). We could not draw any consistent correlations between degree of image shift and continued tumor growth or objective examination values. Conclusion: We have demonstrated a small but potentially significant shift in the treatment plan of gamma knife radiosurgery when based on magnetic resonance images. Although the image shift does not seem to affect the growth of the acoustic neuromas or auditory or facial nerve function, longer term follow-up is required to fully appreciate the true impact of this image shift.