Incidence, Time Course, and Implications of Electrode Abnormalities in Pediatric Cochlear Implant Recipients.

OBJECTIVES: To identify the incidence of specific abnormal impedance patterns or electrode faults, and determine their implication and significance, in a pediatric population of cochlear implant recipients. DESIGN: Nine hundred fifty-six cochlear implant devices (621 recipients) were included in this retrospective study. Devices were included if the implantation surgery was performed at our tertiary care hospital, and the recipient was 21 years of age or younger at the time the device was implanted. Device models incapable of producing impedance measures by telemetry were excluded from the study. Individual devices with abnormal impedance measures indicating an open circuit (OC), short circuit (SC), or partial short circuit (partial SC) were included in the study, unless these abnormalities occurred only in the OR and not postoperatively. Device and patient characteristics were examined to determine their relationship to increased incidence of electrode faults or atypical patterns. RESULTS: The incidence of software-identified electrode faults in our exclusively pediatric population was similar to that reported in the literature containing mixed-age cohorts. Nine percent of devices experienced at least one OC or one pair of SCs. Although higher incidence of these faults was seen in some specific device models, the long-term average of these faults was equivalent across manufacturers. No factors examined in this study increased the likelihood of experiencing a software-identified electrode fault. Within the study period under examination (October 1997 to March 2018), partial SCs (presenting as zig-zag or low-flat impedance patterns) were only observed in Cochlear devices. While the incidence of these partial SC abnormalities (non-software-identified faults) was 6% across all models of Cochlear devices, the CI24RCS experienced the highest incidence of partial SCs. The incidence of this pattern was lower in models manufactured after CI24RCS. CONCLUSIONS: This study provides incidence of various cochlear implant electrode impedance abnormalities across a large cohort of pediatric recipients. The incidence of all electrode abnormalities was relatively low, particularly partial SCs, which are less well recognized and not currently identified by clinician-accessible software. Incidence of software-identified electrode faults (i.e., SCs and OCs) in our pediatric-only study is similar to the incidence reported in other mixed-population and adult-only studies. These common electrode faults generally are not associated with device failure, and clinicians should feel comfortable reassuring families that an individual electrode fault does not imply an impending device failure. Conversely, those atypical impedance patterns not currently flagged by the programming software as abnormal, but visible to the clinician's eye (i.e., partial SCs in zig-zag or low-flat patterns), have a higher likelihood of device damage and failure. Performance in patients with electrode arrays exhibiting these atypical patterns should be closely monitored for any functional decrement, and proactively managed to maintain performance whenever possible.

Audiologic phenotype and progression in GJB2 (Connexin 26) hearing loss.

OBJECTIVES: To document the audiologic phenotype of children with biallelic GJB2 (connexin 26) mutations, and to correlate it with the genotype. DESIGN: Prospective, observational study. SETTING: Tertiary care children's hospital. PATIENTS: Infants and children with sensorineural hearing loss (SNHL). INTERVENTION: Sequencing of the GJB2 (connexin 26) gene. MAIN OUTCOME MEASURES: Degree and progression of SNHL. RESULTS: From December 1, 1998, through November 30, 2006, 126 children with biallelic GJB2 mutations were identified. Of the 30 different mutations identified, 13 (43%) were truncating and 17 (57%) were nontruncating; 62 patients had 2 truncating, 30 had 1 truncating and 1 nontruncating, and 17 had 2 nontruncating mutations. Eighty-four patients (67%) initially had measurable hearing in the mild to severe range in at least 1 of 4 frequencies (500, 1000, 2000, or 4000 Hz). Of these 84 patients with residual hearing, 47 (56%) had some degree of progressive hearing loss. Patients with 2 truncating mutations had significantly worse hearing compared with all other groups. Patients who had 1 or 2 copies of either an M34T or a V37I allele had the mildest hearing loss. CONCLUSIONS: Hearing loss owing to GJB2 mutations ranges from mild to profound and is usually congenital. More than 50% of patients will experience some hearing loss progression, generally gradually but occasionally precipitously. Hearing loss severity may be influenced by genetic factors, such as the degree of preserved protein function in nontruncating mutations, whereas hearing loss progression may be dependent on factors other than the connexin 26 protein. Genetic counseling for patients with GJB2 mutations should include the variable audiologic phenotype and the possibility of progression.

Factors associated with sensorineural hearing loss among survivors of extracorporeal membrane oxygenation therapy.

OBJECTIVES: To endeavor to explain why some graduates of extracorporeal membrane oxygenation (ECMO) therapy develop sensorineural hearing loss (SNHL) whereas others do not, to study the variability seen in the degree of SNHL, to attempt to explain why some graduates with SNHL experience progressive worsening whereas others do not, and to describe the time course of the onset of SNHL on the basis of identified risk factors. DESIGN: A retrospective chart review with proportional-hazards regression analysis to identify specific risk factors for SNHL from a list of patient and treatment variables. SETTING: Children's Hospital Boston, a pediatric tertiary-care facility and ECMO center. PATIENTS: Neonatal ECMO graduates born in 1986-1994 who survived to discharge and underwent audiologic evaluations (n = 111) and a random sample of ECMO graduates who survived to discharge and did not undergo audiologic evaluations (n = 30). OUTCOME MEASURES: Audiologic data, including the presence or absence of SNHL, the severity of SNHL at the most recent evaluation, the stability or progressive worsening of hearing (with the first evaluation compared with the most recent evaluation), and the occurrence of delayed-onset SNHL. RESULTS: Twenty-nine (26%) of 111 ECMO graduates who underwent audiologic testing had SNHL at the last evaluation. Of these 29 subjects with SNHL, 21 (72%) had progressive SNHL, of whom 14 (48%) had delayed-onset SNHL. The age of identification of SNHL ranged from 4 months to 8 years 11 months. Factors identified with proportional-hazards regression analyses as being associated significantly with the time to onset of SNHL were a primary diagnosis of congenital diaphragmatic hernia (hazard ratio: 2.60), length of ECMO therapy (hazard ratio: 7.18), and number of days children received aminoglycoside antibiotics (hazard ratio: 5.56). Kaplan-Meier "time-to-event" curves were constructed to illustrate the time course of onset of SNHL, as affected by each of the variables identified as significant risk factors. CONCLUSIONS: These findings illustrate the need for early, routine, audiologic evaluations throughout childhood for all ECMO graduates. Children at even greater risk for developing SNHL because of a history of congenital diaphragmatic hernia, prolonged ECMO therapy, and/or a lengthy course of aminoglycoside antibiotic therapy should be monitored even more closely throughout childhood, depending on the child's individual risk indicators, as suggested here. On the basis of these risk indicators, efforts can be made to minimize the risk of hearing loss while a child is being treated with ECMO. In addition, these risk indicators can assist with counseling families of ECMO graduates regarding the child's specific risk of developing SNHL and how it can be managed should it occur.

Congenital absence of the incus bilaterally without other otologic anomalies: a new case report.

We describe only the third reported case of congenital, bilaterally absent includes that were not accompanied by another otologic abnormality. This condition was detected in a 3-year-old boy who was being evaluated for a hearing impairment and speech and language delay. The patient was treated with partial ossicular replacement prostheses, which resulted in an improvement in his hearing.