Jonathan C. Kopelovich

Risk factors for loss of ipsilateral residual hearing after hybrid cochlear implantation.

Objective Residual low-frequency acoustic hearing benefits cochlear implantees in difficult listening situations such as understanding speech in noise and music appreciation. Most subjects retain functional residual hearing in the operated ear. A small number of patients, however, will lose significant ipsilateral residual hearing after short-electrode cochlear implantation. The objectives of this retrospective series are to determine whether predisposition to hearing loss after implantation exists in a subset of patients and to assess the functional impact of this hearing loss on clinical measures of combined electric and acoustic hearing. Study Design Retrospective case series. Setting Multicenter clinical trial; tertiary care facility. Patients Hearing preservation cochlear implant recipients. Main Outcome Measure Frequency-averaged ipsilateral hearing loss at 1 year after activation. Results Eighty-five patients from the Hybrid S8 FDA trial had serial postoperative audiometric measurements. Twenty-two of these patients, implanted at the home institution, provided additional medical data. Univariate analysis (Pearson’s, Spearman’s, Student’s t test) showed that the severity of hearing loss at 1 year after activation was significantly correlated with age, male gender, and noise-induced hearing loss as the etiology of hearing impairment. A multivariate regression model corroborated these variables. No other medical factors were predictive. Clinical measures of speech perception (Consonant-Nucleus-Consonant and Hearing in Noise Test) worsened with hearing loss in ipsilateral but not bilateral listening conditions. Conclusion Age, male gender, and a history of noise-induced hearing loss correlate with the severity of hearing loss at 1 year after activation. Even the most severely affected patients benefit from bilateral electric and acoustic inputs.

Pneumocephalus with BiPAP use after transsphenoidal surgery

While the benefits of continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) for patients with obstructive sleep apnea are well described, reports in the literature of complications from its use are rare. A patient who received postoperative BiPAP after undergoing transsphenoidal craniopharyngioma resection developed severe pneumocephalus and unplanned intensive care unit admission. Although the pneumocephalus resolved with conservative management over two weeks, we propose caution in the use of CPAP postoperatively in patients undergoing procedures of the head and neck.

Subtotal petrosectomy and mastoid obliteration in adult and pediatric cochlear implant recipients.

Objective To investigate the effect of subtotal petrosectomy and mastoid obliteration (SPMO) on the overall success of adult and pediatric cochlear implant (CI) recipients. Study Design Retrospective case series. Setting Tertiary care referral center. Patients Thirty-nine ears in 36 patients (23 adults and 13 children) received both surgeries between 1990 and 2012. Intervention CI candidates underwent SPMO to permit implantation and minimize the risks of infectious complications in the recipient ear. SPMO was performed before (69.3%), at the time of (25.6%), and after CI (5.13%). Mastoids were obliterated with fat (30.8%), muscle (66.7%), and bone pate (2.56%). Main Outcome Measure Feasibility, complications, and success of SPMO and CI were assessed with standard statistical analysis and Fisher’s exact test with 2-sided p values. Results Ear disease was definitively managed, and CI was successfully placed in all but one case. Complications including abscess (n = 3), subcutaneous emphysema (n = 1), ear canal granulation formation (n = 1), and electrode extrusion (n = 1) occurred in 15.4% of patients. Predisposing syndromes were present in children more often than adults (43.8% versus 13.0%, p = 0.0598). Adults more often than children had previous mastoid surgery for middle ear disease (30.4% versus 0.0%, p = 0.0288). CIs were placed under local anesthetic and sedation (n= 3) and after radiation treatment for nasopharyngeal cancer (n = 2) in adult ears. Conclusion SPMO is an effective and safe procedure for definitivelymanaging middle ear disease and implanting adultand pediatric CI candidates.

Hearing Loss After Activation of Hearing Preservation Cochlear Implants Might Be Related to Afferent Cochlear Innervation Injury.

Objective Characterize hearing loss (HL) after hearing preservation cochlear implantation and determine the association between high charge electrical stimulation (ES) and late loss of acoustic hearing. Methods A retrospective cohort analysis of all hearing preservation implantees at our center (n = 42) assayed HL as a function of maximum charge. We analyzed serial audiometry from 85 patients enrolled in the multicenter Hybrid S8 trial to detail the hearing loss greater than 1 month after implantation. Cochleotypic explant cultures were used to assess susceptibility to high levels of ES. Results Early HL after implantation tends to be mild and averages 12.2 dB. After activation of the Hybrid S8 device, 17 (20%) of 85 patients experienced acceleration of HL. Compared with the majority of patients who did not lose significant hearing after activation, these patients experienced more severe HL at 1 year. Five patients implanted at our center experienced acceleration of HL after high charge exposure. In patients implanted at our center, high charge was associated with late HL (Pearson 0.366, p = 0.016). In rat cochleotypic explants, high voltage ES damaged afferent nerve fibers, reflected by blebbing and a 50% reduction in the number of fibers innervating the organ of Corti. In contrast, hair cells displayed only minor differences in cell number and morphology. Conclusions Based on clinical and in vitro data, we theorize that the combination of acoustic amplification and ES in the setting of intact hair cells and neural architecture may contribute, in part, to cochlear toxicity, perhaps by damaging the afferent innervation.

Mouse cochleostomy: A minimally invasive dorsal approach for modeling cochlear implantation

The murine model has been used extensively to model and study human deafness. Technical difficulty in the surgical approach due to the small size of the tympanic bulla and a robust stapedial artery has limited its application for studies of cochlear implantation and electrical stimulation. We describe a minimally traumatic, stapedial artery–sparing approach to the round window that may be used to access the mouse cochlea for acute or chronic studies of implantation and stimulation.

Frequency and electrode discrimination in children with cochlear implants.

The objective of this study was to develop reliable pediatric psychophysical methodologies in order to address the limits of frequency and electrode discrimination in children with cochlear implants. Discrimination was measured with a two-alternative, adaptive, forced choice design using a video game graphical user interface. Implanted children were compared to normal-hearing children in the same age ranges. Twenty-nine implanted children and 68 children with normal-hearing performed frequency discrimination studies at varying frequencies. Electrode discrimination was assessed in thirty-four implanted children at varying electrode locations and stimulation intensities. Older children had better frequency discrimination than younger children, both for implanted and hearing subjects. Implanted children had worse frequency discrimination overall and exhibited learning effects at older ages than hearing children. Frequency discrimination Weber fractions were smallest in low frequencies. Electrode discrimination improved with stimulus intensity level for older but not younger children at all electrode locations. These results support the premise that developmental changes in signal processing contribute to discrimination of simple acoustic stimuli. For implanted children, auditory discrimination improved at lower frequencies and with electrodes at higher intensity. These findings imply that spatial separation may not be the key determinant in creating discriminable electrical stimuli for this population.

The hybrid lid crease approach to address lateral frontal sinus disease with orbital extension.

Objective: This study aimed to describe the hybrid lid crease approach in conjunction with functional endoscopic sinus surgery (FESS) for lateral frontal sinus disease with orbital extension. Study Design: Retrospective case review. Methods: Patients undergoing hybrid lid crease approach with FESS for frontal sinus disease were reviewed retrospectively. Surgical indications consisted of inverting papilloma with extension into the frontal sinus (n = 1) and frontal sinus mucocele (n = 2). Inclusion criteria included presence of disease in the lateral frontal sinus with extension into the orbital space and erosion of the superior orbital rim. Preoperative and postoperative parameters included complete ophthalmologic exam, endoscopic exam, and computed tomography scan. Results: We were able to access the frontal sinus and orbit in all 3 cases and address sinus pathology of the lateral frontal sinus and orbit using the lid crease approach with FESS. All patients had improvement in ophthalmologic symptoms and interval disease resolution and were satisfied with their postoperative lid crease incision. Conclusion: The lid crease approach offers direct access to the frontal sinus with minimal dissection through a well-hidden incision. In our case series of lateral frontal sinus pathology with orbital extension, the hybrid lid crease approach with FESS allowed complete eradication of disease without recurrence.

Acoustic Hearing After Murine Cochlear Implantation: Effects of Trauma and Implant Type.

Objectives: To model the contribution of implant material and insertion trauma on loss of acoustic hearing after cochlear implantation in an appropriate animal model. Methods: Sixty-five C57Bl/6J mice underwent unilateral implantation with implant grade materials: 2 implant grade silicones and a third uncoated platinum wire. A sham surgery group was included as a control. Serial auditory brainstem response (ABR) thresholds and distortion product otoacoustic emissions (DPOAEs) were used to discern effects on hearing over 22 weeks. Histologic measurements of damage to the organ of Corti and spiral ganglion were correlated with degree of hearing loss and material type. Results: Organ of Corti damage correlated with rate of hearing loss soon after implantation (0-2 weeks) but not subsequently (2-22 weeks). Organ of Corti damage did not depend on implant type and was present even in sham surgery subjects when hearing was severely damaged. Spiral ganglia appeared unaffected. There was no evidence of an inflammatory or toxic effect of the materials beyond the site of implant insertion. Conclusions: Hearing loss and cochlear damage appear to be related to insertion trauma, with minimal effect on delayed hearing loss caused by different materials. In the C57Bl/6J mouse model, the sensory epithelium appears to be the location of damage after cochlear implantation.

Intracochlear Electrical Stimulation Suppresses Apoptotic Signaling in Rat Spiral Ganglion Neurons after Deafening in Vivo

Objective To establish the intracellular consequences of electrical stimulation to spiral ganglion neurons after deafferentation. Here we use a rat model to determine the effect of both low and high pulse rate acute electrical stimulation on activation of the proapoptotic transcription factor Jun in deafferented spiral ganglion neurons in vivo. Study Design Experimental animal study. Setting Hearing research laboratories of the University of Iowa Departments of Biology and Otolaryngology. Methods A single electrode was implanted through the round window of kanamycin-deafened rats at either postnatal day 32 (P32, n = 24) or P60 (n = 22) for 4 hours of stimulation (monopolar, biphasic pulses, amplitude twice electrically evoked auditory brainstem response [eABR] threshold) at either 100 or 5000 Hz. Jun phosphorylation was assayed by immunofluorescence to quantitatively assess the effect of electrical stimulation on proapoptotic signaling. Results Jun phosphorylation was reliably suppressed by 100 Hz stimuli in deafened cochleae of P32 but not P60 rats. This effect was not significant in the basal cochlear turns. Stimulation frequency may be consequential: 100 Hz was significantly more effective than was 5 kHz stimulation in suppressing phospho-Jun. Conclusions Suppression of Jun phosphorylation occurs in deafferented spiral ganglion neurons after only 4 hours of electrical stimulation. This finding is consistent with the hypothesis that electrical stimulation can decrease spiral ganglion neuron death after deafferentation.

Electrical Stimulation Reduces Apoptotic Signaling in SGNs

Objective: To establish the intracellular consequences of electrical stimulation (ES) to spiral ganglion neurons (SGNs) after deafferentation. SGNs die as a result of loss of hair cells, their sole afferent input. Some histologic animal studies of chronic ES after deafening show that ES alone may improve SGN survival. Here we use a rat model to determine the effect of both low and high pulse rate ES on activation of the pro-apoptotic transcription factor Jun in deafferented SGNs in vivo. Methods: A single electrode was implanted through the round window of kanamycin-deafened rats at either postnatal day 32 (P32) or P60 for 4 hours of ES (monopolar, biphasic pulses, amplitude twice eABR threshold) at either 100 or 5000 Hz. Jun phosphorylation, a proapoptotic signaling event known to occur in apoptotic SGNs after deafening, was assayed by immunofluorescence to quantitatively assess the effect of ES on proapoptotic signaling. Results: Jun phosphorylation was reliably suppressed by 100 Hz ES in deafened cochleae of P32 rats (P = .045) but this effect was less robust when 5000 Hz ES was used. This effect was most significant in the cochlear turn just apical to the stimulating electrode and was not significant in P60 rats. Conclusion: Suppression of phospho-Jun occurs in deafferented SGNs after only 4 hours of ES, consistent with the hypothesis that ES provides trophic support to SGNs after deafferentation. Stimulation frequency may be consequential: 100 Hz ES was significantly more effective than 5000 Hz ES in suppressing phospho-Jun.