J.J.S. Mulder

Current steering and current focusing in cochlear implants: comparison of monopolar, tripolar, and virtual channel electrode configurations.

Objectives: To compare the effects of Monopole (Mono), Tripole (Tri), and “Virtual channel” (Vchan) electrode configurations on spectral resolution and speech perception in a crossover design. Design: Nine experienced adults who received an Advanced Bionics CII/90K cochlear implant participated in a crossover design using three experimental strategies for 2 wk each. Three strategies were compared: (1) Mono; (2) Tri with current partly returning to adjacent electrodes and partly (25 or 75%) to the extracochlear reference; and (3) a monopolar “Vchan” strategy creating seven intermediate channels between two contacts. Each strategy was a variant of the standard “HiRes” processing strategy using 14 channels and 1105 pulses/sec/channel, and a pulse duration of 32 &mgr;sec/phase. Spectral resolution was measured using broadband noise with a sinusoidally rippled spectral envelope with peaks evenly spaced on a logarithmic frequency scale. Speech perception was measured for monosyllables in quiet and in steady-state and fluctuating noises. Subjective comments on music experience and preferences in everyday use were assessed through questionnaires. Results: Thresholds and most comfortable levels with Mono and Vchan were both significantly lower than levels with Tri. Spectral resolution was significantly higher with Tri than with Mono; spectral resolution with Vchan did not differ significantly from the other configurations. Moderate but significant correlations between word recognition and spectral resolution were found in speech in quiet and fluctuating noise. For speech in quiet, word recognition was best with Mono and worst with Vchan; Tri did not significantly differ from the other configurations. Pooled across the noise conditions, word recognition was best with Tri and worst with Vchan (Mono did not significantly differ from the other configurations). These differences were small and insufficient to result in a clear increase in performance across subjects if the result from the best configuration per subject was compared with the result from Mono. Across all subjects, music appreciation and satisfaction in everyday use did not clearly differ between configurations. Conclusions: (1) Although spectral resolution was improved with the tripolar configuration, differences in speech performance were too small in this limited group of subjects to justify clinical introduction. (2) Overall spectral resolution remained extremely poor compared with normal hearing; it remains to be seen whether further manipulations of the electrical field will be more effective.

Cochlear implantation and quality of life in postlingually deaf adults: long-term follow-up.

Objective To investigate long-term quality of life (QoL) in postlingually deaf adults after entering the cochlear implantation (CI) program. Study Design and Setting Follow-up study from 1998 onwards in tertiary university medical center. Long-term CI users, patients who have not received a CI, and relatively short-term CI users were re-evaluated six years after initial data collection in 1998 by using three questionnaires (NCIQ, HUI3, and SF36) and speech perception tests. Results and Conclusions In general, the beneficial effect of CI remained stable during long-term follow-up, though scores on the questionnaires decreased slightly. Outcomes before and after cochlear implantation were significantly different. The group without a CI demonstrated slightly decreasing trends in outcomes. Long-term speech perception performance improved in time. Significance This is the first study to investigate long-term follow-up of CI patients, in all aspects of QoL combined with speech perception performance, in comparison with postlingually deaf adults without CI.

Gamma knife radiosurgery for vestibular schwannomas: Results of hearing preservation in relation to the cochlear radiation dose

This study was designed to evaluate hearing preservation after gamma knife radiosurgery (GKRS) and to determine the relation between hearing preservation and cochlear radiation dose in patients with a sporadic vestibular schwannoma (VS).

Application of active middle ear implants in patients with severe mixed hearing loss.

Objective To determine the long-term benefit of the Vibrant Soundbridge (VSB) middle ear implant in patients with severe mixed hearing loss and to compare it with other hearing devices. Design A retrospective analysis. Setting University-affiliated medical center. Patients Six patients with severe mixed hearing loss and a mean sensorineural hearing loss component between 40 and 70 dB. Interventions Patients received a VSB with the floating mass transducer (FMT) coupled to the round window or to the oval window via a residual stapes structure. Main Outcome Measures Functional gain and speech recognition results. Results are compared with 2 control groups matched for mean sensorineural hearing loss: 1) patients with mixed hearing loss and a bone-anchored hearing device, and 2) patients with sensorineural hearing loss and traditional implantation of the VSB. Results There is large variance in functional gain between the patients suggesting high variability in the effectivity of the FMT coupling. The speech recognition results for the experimental group were not systematically better than in either control group. Conclusion There is large variability in results that might be ascribed to coupling effectivity. On the average, speech recognition results were not better or worse than those found in patients with similar hearing loss fitted with bone-anchored hearing devices.

Amplification options for patients with mixed hearing loss.

Objectives To compare amplification options for patients with mixed hearing loss. Devices tested include percutaneous and transcutaneous bone conductors (BCDs) and middle ear implants with their actuator directly coupled to the cochlea. Setting Tertiary academic medical center. Method and Participants Maximum output was studied with simulators. As simulators are lacking for the middle ear implants (the Vibrant Soundbridge [VSB] and the Cochlear’s Direct Acoustic Cochlear Stimulator [Codacs]), the maximum output had to be measured in patients (4 and 5 patients, respectively). Main Outcome Measure The maximum output averaged at 0.5, 1, and 2 kHz was the main outcome measure, which was expressed in dB HL, using appropriate transformation tables. Results The maximum output was the highest for the Codacs device and was above the patients’ uncomfortable loudness levels. The maximum output of the VSB varied between 65 and 85 dB HL, and that of percutaneous BCD varied between 68 and 80 dB HL depending on the type of device. The transcutaneous BCD, the Sophono device, had the lowest output. Conclusion Only with the Codacs device can the complete dynamic range be used. The maximum output of the VSB is lower and variable owing to the coupling to the cochlea. For patients with a sensorineural hearing loss component up to 50 dB HL, a percutaneous BCD forms a good treatment option that is completely independent of the middle ear status. The transcutaneous Sophono BCD is suitable for patients with a (sub-)normal sensorineural hearing loss component of 20 dB or less.

A needle guidance device compared to free hand technique in an ultrasound-guided interventional task using a phantom.

In this in vitro study, a needle guidance device and a ‘free hand’ technique for ultrasound guided needle insertion were compared in a simulated ultrasound‐guided interventional task using a porcine phantom. Residents inexperienced in using ultrasonography were asked to insert a needle, using an in‐plane techniques, and to make contact with metal rods at a depth of 2 and 4 cm in the phantom. The transducer made angles of 90°, 60° and 45° with the surface of the phantom. The times to perform the procedures were significantly shorter and the needle visualisation was significantly better when using the needle guidance device. The residents ranked their satisfaction with the needle‐guidance device significantly better than the ‘free‐hand’ technique. This device may be beneficial when performing ultrasound guided peripheral nerve blocks, especially by inexperienced operators.

Follow-up after gamma knife radiosurgery for vestibular schwannomas: volumetric and axial control rates

A prospective long‐term follow‐up study was conducted to evaluate the results of gamma knife radiosurgery (GKRS) for vestibular schwannoma (VS) patients. Both axial and volumetric measurements are used to determine tumor size during follow‐up.

Gamma Knife radiosurgery for vestibular schwannomas: evaluation of tumor control and its predictors in a large patient cohort in The Netherlands

OBJECT The authors of this study sought to assess tumor control and complication rates in a large cohort of patients who underwent Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) and to identify predictors of tumor control. METHODS The records of 420 patients treated with GKRS for VS with a median marginal dose of 11 Gy were retrospectively analyzed. Patients with neurofibromatosis Type 2 or who had undergone treatment for VS previously were excluded. The authors assessed tumor control and complication rates with chart review and used the Cox proportional hazards model to identify predictors of tumor control. Preservation of serviceable hearing, defined as Gardner-Robertson Class I-II, was evaluated in a subgroup of 71 patients with serviceable hearing at baseline and with available follow-up audiograms. RESULTS The median VS tumor volume was 1.4 cm(3), and the median length of follow-up was 5.1 years. Actuarial 5-and 10-year tumor control rates were 91.3% and 84.8%, respectively. Only tumor volume was a statistically significant predictor of tumor control rate. The tumor control rate decreased from 94.1% for tumors smaller than 0.5 cm(3) to 80.7% for tumors larger than 6 cm(3). Thirteen patients (3.1%) had new or increased permanent trigeminal nerve neuropathy, 4 (1.0%) had new or increased permanent facial weakness, and 5 (1.2%) exhibited new or increased hydrocephalus requiring a shunting procedure. Actuarial 3-year and 5-year hearing preservation rates were 65% and 42%, respectively. CONCLUSIONS The 5-year actuarial tumor control rate of 91.3% in this cohort of patients with VS compared slightly unfavorably with the rates reported in other large studies, but the complication and hearing preservation rates in this study were similar to those reported previously. Various factors may contribute to the observed differences in reported outcomes. These factors include variations in treatment indication and in the definition of treatment failure, as well as a lack of standardization of terminology and of evaluation of complications. Last, differences in dosimetric variables may also be an explanatory factor.

Predictors of future growth of sporadic vestibular schwannomas obtained by history and radiologic assessment of the tumor

Management of a sporadic vestibular schwannoma (VS) is still a subject of controversy, mainly due to distinct and unpredictable growth patterns. To embark on an appropriate therapy it is necessary to dispose of a reliable prediction about tumor progression. This study aims to design a risk profile with predictors for VS growth. A total of 234 VS patients who were managed conservatively were included. Data concerning (duration of) symptoms and localization of VS were analyzed with Cox proportional hazards regression models. Predictors for growth are unsteadiness/vertigo, no sudden onset of hearing loss and short duration of hearing loss. High-risk patients have (1) VS with an extrameatal localization, short duration of hearing loss and at least one of the two other predictors (unsteadiness/vertigo or no sudden sensorineural hearing loss) or (2) VS with an intrameatal localization and all three other predictors. Low-risk patients have (1) VS with an extrameatal component and no other predictor or (2) VS with an intrameatal localization and at most one other predictor. High-risk patients have a risk of growth of 36.9% in the first year and 64.6% in the second year. For patients with a low risk this is 2.5 and 12.7%, respectively. Simple data gathered at the moment of diagnosis may provide useful information since they may lead to a risk profile for growth.

Cochlear implantation in 3 patients with osteogenesis imperfecta: imaging, surgery and programming issues.

Osteogenesis imperfecta (OI) is a heterogeneous disease of the connective tissue caused by a defective gene that is responsible for the production of collagen type I, leading to defective bone matrix and connective tissue. Hearing loss affects 35–60% of the patients and will progress to deafness in 2–11% of OI patients for whom cochlear implantation may become the only remaining treatment option. Three patients with OI were retrieved from the Nijmegen Cochlear Implant Centre’s database. Most of the specific observations in ear surgery on patients with OI, such as brittle scutum, sclerotic thickening of the cochlea, hyperplastic mucosa in the middle ear and persistent bleeding, were encountered in these 3 patients. In case 3, with severe deformities on the CT scan, misplacement of the electrode array into the horizontal semicircular canal occurred. In all 3 cases, programming was hindered by nonauditory stimulation. Even after reimplantation, nonauditory sensations lead to case 3 becoming a nonuser. Averaged electrode voltages in case 3 were deviant in accordance with an abnormally conductive otic capsule. Spatial spread of neural excitation responses in cases 1 and 2 suggested intracochlear channel interaction for several electrodes, often in combination with facial nerve stimulation (FNS). In case 1, the estimated pitch of the electrodes that caused FNS varied consistently. Despite the electrophysiological changes, after 1-year follow-up, open set phoneme scores of 81% and 78% were reached in cases 1 and 2, respectively. When aware and prepared for the specific changes of the temporal bone in OI, cochlear implantation can be a safe and feasible procedure. Preoperative imaging is recommended to be fully informed on the morphology of the petrosal bone. In case of severe deformities on the CT scan, during counseling the possibility of misplacement should be mentioned. Rehabilitation is often hindered by FNS requiring frequent refitting.