Spectral Resolution and Speech Perception in Cochlear Implanted School-Aged Children.

OBJECTIVE: Cochlear implantation of prelingually deaf infants provides auditory input sufficient to develop spoken language; however, outcomes remain variable. Inability to participate in speech perception testing limits testing device efficacy in young listeners. In postlingually implanted adults (aCI), speech perception correlates with spectral resolution an ability that relies independently on frequency resolution (FR) and spectral modulation sensitivity (SMS). The correlation of spectral resolution to speech perception is unknown in prelingually implanted children (cCI). In this study, FR and SMS were measured using a spectral ripple discrimination (SRD) task and were correlated with vowel and consonant identification. It was hypothesized that prelingually deaf cCI would show immature SMS relative to postlingually deaf aCI and that FR would correlate with speech identification. STUDY DESIGN: Cross-sectional study. SETTING: In-person, booth testing. METHODS: SRD was used to determine the highest spectral ripple density perceived at various modulation depths. FR and SMS were derived from spectral modulation transfer functions. Vowel and consonant identification was measured; SRD performance and speech identification were analyzed for correlation. RESULTS: Fifteen prelingually implanted cCI and 13 postlingually implanted aCI were included. FR and SMS were similar between cCI and aCI. Better FR was associated with better speech identification for most measures. CONCLUSION: Prelingually implanted cCI demonstrated adult-like FR and SMS; additionally, FR correlated with speech identification. FR may be a measure of CI efficacy in young listeners.

A comparison of endolymphatic shunt surgery and intratympanic gentamicin for meniere's disease.

OBJECTIVE: To report audiovestibular outcomes following endolymphatic shunt surgery (ELS) and intratympanic gentamicin injections (ITG) in patients with Meniere's disease (MD). STUDY DESIGN: Retrospective matched cohort study METHODS: Patients with MD refractory to medical management between 2004 and 2017 were reviewed: 44 patients underwent ELS and had outcomes available, while 27 patients underwent ITG and had outcomes available. Mean follow-up durations for the ELS and ITG groups were 39.1 and 43.3 months, respectively. Twenty-six patients from the ELS group and 24 patients from the ITG group were then included in a pretreatment hearing- and age-matched analysis. Main outcome measures were successful control of vertigo, pure-tone average (PTA; 0.5, 1, 2 and 4 kHz), word recognition score (WRS), and treatment complications. RESULTS: A matched analysis showed vertigo control rates of 73.1% in the ELS group and 66.8% in the ITG group, which were not significantly different (P = .760). The change in PTA following treatment was statistically similar between the ELS group (6.2 dB) and ITG group (4.6 dB) (P = .521), while the change in WRS for the ELS group (+3.9 %) was significantly more favorable than the ITG group (-13.6 %) (P = .046). Chronic post-treatment unsteadiness was reported in 25.0% of the ITG group and was not encountered in the ELS group (P = .009). CONCLUSION: ELS provided successful vertigo control at least as well as ITG with a lower incidence of audiovestibular complications. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:2455-2460, 2020.

The development of biophysical models of the electrically stimulated auditory nerve: Single-node and cable models.

In the last few decades, biophysical models have emerged as a prominent tool in the study and improvement of cochlear implants, a neural prosthetic that restores a degree of sound perception to the profoundly deaf. Owing to the spatial phenomena associated with extracellular stimulation, these models have evolved to a relatively high degree of morphological and physiological detail: single-node models in the tradition of Hodgkin-Huxley are paired with cable descriptions of the auditory nerve fiber. No singular model has emerged as a frontrunner to the field; rather, parameter sets deriving from the channel kinetics and morphologies of numerous organisms (mammalian and otherwise) are combined and tuned to foster strong agreement with response properties observed in vivo, such as refractoriness, summation, and strength-duration relationships. Recently, biophysical models of the electrically stimulated auditory nerve have begun to incorporate adaptation and stochastic mechanisms, in order to better realize the goal of predicting realistic neural responses to a wide array of stimuli.

Patterns of Long-term Hearing Loss in Hearing Preservation Cochlear Implant Surgery.

OBJECTIVE: To describe patterns of hearing loss in patients with low-frequency residual hearing after cochlear implantation. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: Cochlear implant candidates with immediate postoperative residual low-frequency hearing. INTERVENTIONS: Hybrid or traditional cochlear implant. MAIN OUTCOME MEASURE: Audiograms to measure postoperative hearing. RESULTS: Of the 166 patients reviewed, 17 ears met the inclusion criteria. The age ranged from 3 years 2 months to 86 years. Etiology was unknown (n = 6), presbycusis (n = 5), genetic (n = 4), acoustic trauma (n = 1), and measles virus (n = 1). The Nucleus Hybrid S8 and S12 (n = 7) was the most common electrode array, and then Nucleus 422 (n = 6), Nucleus Contour Advance (n = 2), Med-El Flex 28 (n = 2), and Advanced Bionics Mid Scala (n = 1). Cochleostomy was performed in nine, and round window approach in nine patients. Average follow-up was 28 months (2-68 mo). Postoperative loss was mixed in eight and purely sensorineural in eight. The most common patterns of hearing loss were gradual decline (n = 7), and then fluctuating hearing (n = 6), stable (n = 3), and sudden loss (n = 1). One patient only had one postoperative audiogram. CONCLUSION: Some long-term hearing preservation was achieved in 94% of patients with immediate postoperative hearing preservation. Patients developed both mixed and sensorineural loss postoperatively. A majority of patients with mixed hearing loss had a supra-preoperative bone curve. Gradual decline and fluctuating hearing loss were the most common patterns of hearing loss; few patients had stable hearing and one had a sudden loss.

An experimental vestibular neural prosthesis: design and preliminary results with rhesus monkeys stimulated with modulated pulses.

A vestibular neural prosthesis was designed on the basis of a cochlear implant for treatment of Meniere's disease and other vestibular disorders. Computer control software was developed to generate patterned pulse stimuli for exploring optimal parameters to activate the vestibular nerve. Two rhesus monkeys were implanted with the prototype vestibular prosthesis and they were behaviorally evaluated post implantation surgery. Horizontal and vertical eye movement responses to patterned electrical pulse stimulations were collected on both monkeys. Pulse amplitude modulated (PAM) and pulse rate modulated (PRM) trains were applied to the lateral canal of each implanted animal. Robust slow-phase nystagmus responses following the PAM or PRM modulation pattern were observed in both implanted monkeys in the direction consistent with the activation of the implanted canal. Both PAM and PRM pulse trains can elicit a significant amount of in-phase modulated eye velocity changes and they could potentially be used for efficiently coding head rotational signals in future vestibular neural prostheses.

Middle cranial fossa facial nerve decompression before two years of age.

We present a case report of a 17-month old patient who underwent serial bilateral total facial nerve decompression procedures for complete bilateral facial paralysis in the setting of craniometaphyseal dysplasia via combined middle cranial fossa and transmastoid approaches. The surgical decision-making process and procedures were reviewed. The patient recovered without complications from the staged surgical procedures, and developed partial return of function of both facial nerves postoperatively, with symmetric House-Brackmann grades of II-III. Despite its technical difficulty in the setting of this particular disorder, facial nerve decompression may be appropriate in the setting of acute facial palsy in craniometaphyseal dysplasia, with the potential for return of function. Given the extremely rare nature of the disease process, variable surgical experience and the clinical condition of the patient remain our best guides for management.

Implantation of the semicircular canals with preservation of hearing and rotational sensitivity: a vestibular neurostimulator suitable for clinical research.

HYPOTHESIS: It is possible to implant a stimulating electrode array in the semicircular canals without damaging rotational sensitivity or hearing. The electrodes will evoke robust and precisely controlled eye movements. BACKGROUND: A number of groups are attempting to develop a neural prosthesis to ameliorate abnormal vestibular function. Animal studies demonstrate that electrodes near the canal ampullae can produce electrically evoked eye movements. The target condition of these studies is typically bilateral vestibular hypofunction. Such a device could potentially be more widely useful clinically and would have a simpler roadmap to regulatory approval if it produced minimal or no damage to the native vestibular and auditory systems. METHODS: An electrode array was designed for insertion into the bony semicircular canal adjacent to the membranous canal. It was designed to be sufficiently narrow so as to not compress the membranous canal. The arrays were manufactured by Cochlear, Ltd., and linked to a Nucleus Freedom receiver/stimulator. Seven behaviorally trained rhesus macaques had arrays placed in 2 semicircular canals using a transmastoid approach and "soft surgical" procedures borrowed from Hybrid cochlear implant surgery. Postoperative vestibulo-ocular reflex was measured in a rotary chair. Click-evoked auditory brainstem responses were also measured in the 7 animals using the contralateral ear as a control. RESULTS: All animals had minimal postoperative vestibular signs and were eating within hours of surgery. Of 6 animals tested, all had normal postoperative sinusoidal gain. Of 7 animals, 6 had symmetric postoperative velocity step responses toward and away from the implanted ear. The 1 animal with significantly asymmetric velocity step responses also had a significant sensorineural hearing loss. One control animal that underwent canal plugging had substantial loss of the velocity step response toward the canal-plugged ear. In 5 animals, intraoperative electrically evoked vestibular compound action potential recordings facilitated electrode placement. Postoperatively, electrically evoked eye movements were obtained from electrodes associated with an electrically evoked vestibular compound action potential wave form. Hearing was largely preserved in 6 animals and lost in 1 animal. CONCLUSION: It is possible to implant the vestibular system with prosthetic stimulating electrodes without loss of rotational sensitivity or hearing. Because electrically evoked eye movements can be reliably obtained with the assistance of intraoperative electrophysiology, it is appropriate to consider treatment of a variety of vestibular disorders using prosthetic electrical stimulation. Based on these findings, and others, a feasibility study for the treatment of human subjects with disabling Ménière's disease has begun.

Auditory outcomes following implantation and electrical stimulation of the semicircular canals.

We measured auditory brainstem responses (ABRs) in eight Rhesus monkeys after implantation of electrodes in the semicircular canals of one ear, using a multi-channel vestibular prosthesis based on cochlear implant technology. In five animals, click-evoked ABR thresholds in the implanted ear were within 10 dB of thresholds in the non-implanted control ear. Threshold differences in the remaining three animals varied from 18 to 69 dB, indicating mild to severe hearing losses. Click- and tone-evoked ABRs measured in a subset of animals before and after implantation revealed a comparable pattern of threshold changes. Thresholds obtained five months or more after implantation--a period in which the prosthesis regularly delivered electrical stimulation to achieve functional activation of the vestibular system--improved in three animals with no or mild initial hearing loss and increased in a fourth with a moderate hearing loss. These results suggest that, although there is a risk of hearing loss with unilateral vestibular implantation to treat balance disorders, the surgery can be performed in a manner that preserves hearing over an extended period of functional stimulation.

Characterization of the electrically evoked compound action potential of the vestibular nerve.

OBJECTIVE: We recorded intraoperative and postoperative electrically evoked compound action potentials (ECAPs) in rhesus monkeys implanted with a vestibular neurostimulator. The objectives were to correlate the generation of slow-phase nystagmus or eye twitches induced by electrical stimulation of the implanted semicircular canal with the presence or absence of the vestibular ECAP responses and to assess the effectiveness of ECAP monitoring during surgery to guide surgical insertion of electrode arrays into the canals. DESIGN: Four rhesus monkeys (a total of 7 canals) were implanted with a vestibular neurostimulator modified from the Nucleus Freedom cochlear implant. ECAP recordings were obtained during surgery or at various intervals after surgery using the Neural Response Telemetry feature of the clinical Custom Sound EP software. Eye movements during electrical stimulation of individual canals were recorded with a scleral search coil system in the same animals. RESULTS: Measurable vestibular ECAPs were observed intraoperatively or postoperatively in 3 implanted animals. Robust and sustained ECAPs were obtained in 3 monkeys at the test intervals of 0, 7, or greater than 100 days after implantation surgery. In all 3 animals, stimulation with electrical pulse trains produced measurable eye movements in a direction consistent with the vestibulo-ocular reflex from the implanted semicircular canal. In contrast, electrically evoked eye movements could not be measured in 3 of the 7 implanted canals, none of which produced distinct vestibular ECAPs. In 2 animals, ECAP waveforms were systematically monitored during surgery, and the procedure proved crucial to the success of vestibular implantation. CONCLUSION: Vestibular ECAPs exhibit similar morphology and growth characteristics to cochlear ECAPs from human cochlear implant patients. The ECAP measure is well correlated with the functional activation of eye movements by electrical stimulation after implantation surgery. The intraoperative ECAP recording technique is an efficient tool to guide the placement of electrode array into the semicircular canals.

Gorham-stout syndrome of the petrous apex causing chronic cerebrospinal fluid leak.

OBJECTIVE: To describe the clinical course, diagnostic features, and treatment of a case of Gorham-Stout syndrome involving the petrous apex and causing chronic cerebrospinal fluid (CSF) leak. STUDY DESIGN: Clinical capsule report. SETTING: Academic pediatric hospital. PATIENT: A 12-year-old boy presented with a destructive lesion of the right petrous apex and a 1-month history of headache, nausea, and vomiting. INTERVENTIONS: Computed tomographic and magnetic resonance imaging revealed a nonenhancing lytic lesion of the right petrous apex and mandibular condyle. The lesions were bright on T2-weighted imaging with high signal intensity extending into the surrounding soft tissues. Leptomeningeal enhancement and an opening pressure of 0 cm of water on lumbar puncture suggested chronic CSF hypotension. Initial surgical exploration revealed diffuse infiltration of CSF into the soft tissue lateral to the temporal bone. Subsequent middle ear and mastoid obliteration was performed to definitely repair the CSF leak. RESULTS: The clinical presentation, physical, laboratory, radiologic, and operative findings are consistent with a diagnosis of Gorham-Stout syndrome. In this case, lymphangiomatosis led to massive osteolysis of the petrous apex with CSF fistula into the surrounding soft tissues and middle ear with chronic intracranial hypotension. CONCLUSION: This is the second report of chronic CSF leak resulting from lymphangiomatosis of the cranial base (Gorham-Stout syndrome).

Small acoustic neuromas: surgical outcomes versus observation or radiation.

OBJECTIVE: Evaluate factors affecting outcomes of small acoustic neuroma (AN) removal via a middle cranial fossa (MCF) approach, and compare results to published data on observation and radiation therapy. STUDY DESIGN: Retrospective chart review. SETTING: Academic tertiary referral center. METHODS: 162 consecutive patients (ages 19-70) with unilateral AN (0.2-2.5 cm in largest dimension) removed through a MCF approach were reviewed focusing on preservation of hearing, facial nerve function and complications. One hundred thirteen patients had pre-operative word recognition scores (WRS)>70%. RESULTS: Both tumor size and pre-operative WRS were related to post-operative WRS (p<0.01). Overall, at least some hearing was preserved in 94 (60%) of the 156 patients who had hearing before surgery. If the WRS was also >70% (N=113), 56 (50%) maintained WRS>70%. Importantly, WRS for 12 others improved to >70% after surgery. When the patients were stratified by tumor size, the patients with small tumors (2-10 mm) faired better than the overall group. At least some hearing was preserved in 65 (72%) of the 90 patients. If the WRS was also >70% (N=66), 39 (59%) maintained WRS>70%. WRS for eight others improved to >70% after surgery. When the tumor was 1.1-1.4 cm (N=34), the chance of preserving some hearing decreased to 42% (14/33). If the WRS was also >70% (N=23), 9 (39%) maintained WRS>70%. WRS for three others improved to >70% after surgery. When the tumor reached 1.5-2.5 cm (N=35), the hearing preservation rate was 43%. If the WRS was also >70% (N=24), only eight (33%) maintained WRS of 70%, and one other improved to >70%. The addition of intra-operative whole eighth nerve near field monitoring improved results during small tumor (70% WRS in 76% (22/29) of those with >70% pre-operative WRS. Good facial nerve function (HB I-II) was achieved in 97% (86% HB I). When tumor size was

How cochlear implants encode speech.

PURPOSE OF REVIEW: This review summarizes the history of cochlear implant signal processing and provides the rationale underlying current approaches. Present strategies are explained and recent research findings are summarized. It is suggested how these results may drive future advancements in signal processing. RECENT FINDINGS: Substantial advances have been made in our understanding of the spectral and temporal cues necessary for cochlear implant recipients to perceive music, speech in noise, and interaural timing. It is clear that higher levels of both spectral and temporal resolution, as well as better loudness and pitch coding are necessary for higher levels of performance. These factors are highly interrelated, however, and are beneficial for differing aspects of hearing. Signal processing algorithms incorporating these findings are under active development and some are currently undergoing clinical investigation. SUMMARY: Current implant devices, and those soon to be available, have substantial untapped potential to improve the auditory experience of their recipients. It is likely that in the near future, recent findings on pitch and loudness perception, as well as techniques to better emulate the normal functions of the cochlea will result in much higher levels of prosthetic hearing fidelity than are possible today. As the performance of these remarkable devices continues to improve, the population of hearing-impaired individuals who can benefit from implantation is likely to increase significantly.

Three-dimensional localization of cochlear implant electrodes using epipolar stereophotogrammetry.

Three-dimensional (3-D) localization of individual cochlear implant electrodes within the inner ear is of importance for modeling the electrical field of the cochlea, designing the electrode array, and programming the associated speech processor. A 3-D reconstruction method of cochlear implant electrodes is proposed to localize individual electrodes from two X-ray views in combination with the spiral computed tomography technique. By adapting epipolar geometry to the configuration of an X-ray imaging system, we estimate individual electrode locations in the least square sense without using a patient attachment required by an existing stereophotogrammetry technique. Furthermore, our method does not require any knowledge of the intrinsic and extrinsic parameters of the imaging system. The performance of our method is studied in numerical simulation and with patient data and is found to be sufficiently accurate for clinical use. The maximum root mean-square errors measured are 0.0445 and 0.214 mm for numerical simulation and patient data, respectively.

Neuroepithelial cysts of the middle ear.

Neuroepithelial cysts are lesions of the central nervous system that have previously been reported in cerebral parenchyma, in the spinal cord, and within the ventricles in association with the choroid plexus. We describe 2 cases of neuroepithelial cysts of the middle ear. One was diagnosed after surgery for a retraction pocket and chronic otitis media complicated by an intraoperative cerebrospinal fluid (CSF) leak. The other produced bilateral spontaneous CSF otorrhea and mimicked the presentation of arachnoid granulations. Both cases were verified with immunohistochemical stains. Neuroepithelial cysts, although rare, should be considered in the differential diagnosis of spontaneous CSF otorrhea or an epitympanic mass.