Abstract
Objectives
To compare hearing outcomes in patients with far advanced otosclerosis (FAO) undergoing cochlear implantation to an age-matched group of controls, to describe the effects of cochlear ossification on hearing, and to review the adverse effects of implantation in patients with FAO.
Hypothesis
Hearing performance in patients with FAO after cochlear implantation is comparable to similarly treated postlingually deafened adults without FAO. Ossification or retrofenestral otosclerosis does not predict poor hearing outcomes. Modiolar-hugging technology reduces postoperative facial nerve stimulation.
Study Design
Retrospective chart review.
Setting
Academic neurotologic tertiary referral center.
Patients
Thirty patients with FAO, who metaudiological criteria for cochlear implantation, were compared to 30 age-matched controls, postlingually deafened by non-otosclerotic causes.
Main Outcome Measures
Audiometric pre- and postoperative speech reception threshold, word, and sentence scores were analyzed. The presence of retrofenestral findings on computed tomography or intraoperative cochlear ossification were noted.
Results
In the FAO group, radiographic abnormalities were noted in 26.4% of patients. Intraoperative ossification requiring drillout was seen in 29.4% of patients. None developed postoperative facial nerve stimulation. There was no difference between the FAO and control groups in the mean short-term and long-term postoperative speech reception threshold, word, and sentence scores ( P = .77). The presence of radiographic abnormalities did not predict hearing outcome. Intraoperative cochlear ossification was not associated with worse short-term word and sentence scores ( P = .58 and 0.79, respectively), and for the long-term hearing outcome ( P = .24).
Conclusions
In patients with FAO, effective and safe hearing rehabilitation can be accomplished with cochlear implantation.
1
Introduction
Otosclerosis is a disease that affects the endochondral bone of the otic capsule. An otosclerotic lesion is characterized by disordered resorption and deposition of bone. Histologically, it consists of areas of bone resorption, new bone formation, vascular proliferation, and a connective tissue stroma. Otosclerosis occurs at sites of predilection within the otic capsule. The most common site is the fissula ante fenestram located anterior to oval window . “Clinical” otosclerosis occurs when a lesion involves the stapes or stapediovestibular joint, resulting in conductive hearing loss. The metabolic condition may eventually progress, resulting in sensorineural hearing loss (SNHL) or “cochlear” otosclerosis. House and Sheehy first described far advanced otosclerosis (FAO) in 1961 as clinical otosclerosis with air conduction thresholds over 85 dB and immeasurable bone conduction thresholds due to the limits of audiometers at the time . In 1992, Iurato et al described very far advanced otosclerosis (VFAO) as patients with otosclerosis with undetectable air and bone conduction levels with standard clinical audiometers, resulting in a blank audiogram . It has been estimated that 1.6% of patients with otosclerosis will eventually develop profound SNHL .
Stapedectomy or stapedotomy with hearing aid amplification has been proposed as a first-line treatment for patients with FAO, as it has been shown to be effective in 60% to 80% of patients with FAO and in 42.3% of patients with VFAO . Lippy et al showed that within 1 month of stapedectomy, word recognition score (WRS) improvements of 16.5% were observed for all patients . Furthermore, improvements were shown to continue past the immediate postoperative period. After 2 years, WRS continued to improve by an additional 12% in 71% of patients. This was thought to be consistent with acclimatization or recovery from auditory deprivation after hearing restoration.
Although stapes surgery provides a good initial treatment option for hearing restoration in patients with otosclerosis, several studies have demonstrated that cochlear implantation may be more effective for aural rehabilitation in patients with FAO and VFAO . Cochlear implantation, regardless of the etiology of SNHL, has shown an improvement of WRS in the immediate postoperative period, which continued to improve in long-term follow-up . It is well established that patients with FAO and VFAO undergoing cochlear implantation demonstrate significant improvement in the short term; however, the extent of hearing restoration in the long term has not been reported, and the likelihood for the need for drillout of basilar turn ossification has not been quantified. In addition, an elevated incidence of facial nerve stimulation after cochlear implantation has been reported in patients with otosclerosis .
The objective of this study is to evaluate the short- and long-term hearing outcomes of cochlear implantation in patients with FAO. In order to analyze the outcome, we compared a group of patients with FAO to a randomly selected group of adult controls, postlingually deafened by other etiologies. We hypothesized that there is no difference in long-term hearing outcome between the study groups. In addition, we analyzed the incidence of adverse effects, in particular, the incidence of facial nerve stimulation, and whether preoperative radiographic findings on high-resolution computed tomography (CT) of the temporal bone predicted postoperative hearing outcomes or complications.
2
Materials and methods
2.1
Subjects
After departmental and institutional review board approval, the cochlear implant database at University Hospitals, Case Medical Center was reviewed (IRB 09-10-05). Only patients who had undergone standard evaluation for cochlear implant candidacy were included in this database. Standard evaluation includes comprehensive audiologic testing, counseling, and preoperative CT or magnetic resonance imaging.
This study is a retrospective chart review of patients from this database. Patients with the diagnosis of obliterative, nonobliterative, and cochlear otosclerosis ( ICD-9 387.0, 387.1, and 387.2, respectively) that underwent cochlear implantation between January 2003 and March 2011 were included in this study. The diagnosis of FAO was made clinically on the basis of a history of slowly progressive unilateral or bilateral hearing impairment, normal otoscopic examination, previous stapedectomy, and an audiogram demonstrating mixed or profound SNHL according to Sheehy’s audiometric description .
Thirty-two consecutive patients with FAO (36 ears) that underwent cochlear implantation were identified in the database. Two patients were excluded due to inadequate clinical or audiometric data. The remaining 30 patients (34 years) in the FAO group were compared to an age-matched control group of 30 patients (32 ears) of postlingually deafened adults obtained from the same cochlear implant database. This cohort of patients was randomly selected from a patient database that was recorded during a previous analysis from the same department . Patients were implanted for etiologies other than otosclerosis during the same period of time.
2.2
Surgical technique
All surgeries were performed under general anesthesia. Facial nerve monitoring was used in all cases. A mastoidectomy with facial recess approach was performed. The internal receiver stimulator was placed in a subperiosteal pocket and the electrode array was introduced atraumatically through a cochleostomy into the scala tympani. If applicable, the ground electrode was placed in a pocket underneath the temporalis muscle. When ossification was encountered, a drill-out was performed until luminal patency was observed. All patients had a full insertion of the electrode array.
When sequential implantation was performed on the contralateral ear, the same technique was employed; however, bipolar cautery was used instead of monopolar cautery. Neural response telemetry was completed in all patients at the conclusion of the operation and a plain skull radiograph was obtained in the immediate recovery period to confirm appropriate positioning of the implant.
2.3
Outcome assessment
Several parameters were surveyed in this study. Demographic data, including age at implantation (to the nearest year) and sex, were recorded. Clinical parameters obtained included duration of hearing deprivation and prior history of stapes surgery. Radiographic and surgical findings were recorded with emphasis on the presence of signs of retrofenestral otosclerosis, cochlear ossification, and number of electrodes inserted. Audiologic data were compiled for each patient. The preoperative and postoperative pure tone average in decibels at 0.5, 1, 2, and 4 kHz and speech reception thresholds (SRT) in decibels, when available, were recorded for the best-aided conditions. When no response was measured at the maximal limits of the audiometer (anacusis), the threshold was set at 120 decibels. In addition, pre and postoperative open-set words score and sentence measures were obtained in all patients. Results were reported as short-term (ST) when obtained at or less than 12 months after implantation and long-term (LT) when obtained more than 12 months after implantation. The words scores were recorded according to the NU-6 chip (Northwestern University words score chip). All sentence scores were determined by hearing in noise testing. All immediate or long-term surgical complications after implantation were documented.
2.4
Data analysis
Data from the chart review were collected and analyzed by a statistician. Individual values were entered into an Excel file (Excel software; Microsoft, Seattle, WA) and imported into a statistical program (R project for statistical computing, version 2.12.0) for analysis. Data missing in the postoperative audiometric analysis were considered missing completely at random and were computed using the multiple imputation technique. Analysis of normality using the Shapiro-Wilk multivariate normality test revealed that both groups did not have a normal distribution ( P < .0001 for both groups). The nonparametric Permutation Hotelling’s T 2 test was used for the multivariate comparison of means between both groups. When a difference is found, univariate analysis using the 2-sided Wilcoxon rank sum test was used. Criterion for statistical significance was set at P = .05, 2-tailed.
2
Materials and methods
2.1
Subjects
After departmental and institutional review board approval, the cochlear implant database at University Hospitals, Case Medical Center was reviewed (IRB 09-10-05). Only patients who had undergone standard evaluation for cochlear implant candidacy were included in this database. Standard evaluation includes comprehensive audiologic testing, counseling, and preoperative CT or magnetic resonance imaging.
This study is a retrospective chart review of patients from this database. Patients with the diagnosis of obliterative, nonobliterative, and cochlear otosclerosis ( ICD-9 387.0, 387.1, and 387.2, respectively) that underwent cochlear implantation between January 2003 and March 2011 were included in this study. The diagnosis of FAO was made clinically on the basis of a history of slowly progressive unilateral or bilateral hearing impairment, normal otoscopic examination, previous stapedectomy, and an audiogram demonstrating mixed or profound SNHL according to Sheehy’s audiometric description .
Thirty-two consecutive patients with FAO (36 ears) that underwent cochlear implantation were identified in the database. Two patients were excluded due to inadequate clinical or audiometric data. The remaining 30 patients (34 years) in the FAO group were compared to an age-matched control group of 30 patients (32 ears) of postlingually deafened adults obtained from the same cochlear implant database. This cohort of patients was randomly selected from a patient database that was recorded during a previous analysis from the same department . Patients were implanted for etiologies other than otosclerosis during the same period of time.
2.2
Surgical technique
All surgeries were performed under general anesthesia. Facial nerve monitoring was used in all cases. A mastoidectomy with facial recess approach was performed. The internal receiver stimulator was placed in a subperiosteal pocket and the electrode array was introduced atraumatically through a cochleostomy into the scala tympani. If applicable, the ground electrode was placed in a pocket underneath the temporalis muscle. When ossification was encountered, a drill-out was performed until luminal patency was observed. All patients had a full insertion of the electrode array.
When sequential implantation was performed on the contralateral ear, the same technique was employed; however, bipolar cautery was used instead of monopolar cautery. Neural response telemetry was completed in all patients at the conclusion of the operation and a plain skull radiograph was obtained in the immediate recovery period to confirm appropriate positioning of the implant.
2.3
Outcome assessment
Several parameters were surveyed in this study. Demographic data, including age at implantation (to the nearest year) and sex, were recorded. Clinical parameters obtained included duration of hearing deprivation and prior history of stapes surgery. Radiographic and surgical findings were recorded with emphasis on the presence of signs of retrofenestral otosclerosis, cochlear ossification, and number of electrodes inserted. Audiologic data were compiled for each patient. The preoperative and postoperative pure tone average in decibels at 0.5, 1, 2, and 4 kHz and speech reception thresholds (SRT) in decibels, when available, were recorded for the best-aided conditions. When no response was measured at the maximal limits of the audiometer (anacusis), the threshold was set at 120 decibels. In addition, pre and postoperative open-set words score and sentence measures were obtained in all patients. Results were reported as short-term (ST) when obtained at or less than 12 months after implantation and long-term (LT) when obtained more than 12 months after implantation. The words scores were recorded according to the NU-6 chip (Northwestern University words score chip). All sentence scores were determined by hearing in noise testing. All immediate or long-term surgical complications after implantation were documented.
2.4
Data analysis
Data from the chart review were collected and analyzed by a statistician. Individual values were entered into an Excel file (Excel software; Microsoft, Seattle, WA) and imported into a statistical program (R project for statistical computing, version 2.12.0) for analysis. Data missing in the postoperative audiometric analysis were considered missing completely at random and were computed using the multiple imputation technique. Analysis of normality using the Shapiro-Wilk multivariate normality test revealed that both groups did not have a normal distribution ( P < .0001 for both groups). The nonparametric Permutation Hotelling’s T 2 test was used for the multivariate comparison of means between both groups. When a difference is found, univariate analysis using the 2-sided Wilcoxon rank sum test was used. Criterion for statistical significance was set at P = .05, 2-tailed.
3
Results
Thirty patients with 34 implanted ears were identified in the FAO group. For patients with bilateral implantation, the surgeries occurred independently and each ear was analyzed separately ( Tables 1 and 2 ). Thirty control patients with 32 implanted ears were selected at random from the database for comparison ( Tables 1 and 2 ). The mean age of the FAO group was 72 ± 5 years, compared to 70 ± 4 years in the control group. There was no statistical difference between both groups ( P = .63). In the FAO group, 47% were men and 53% were women. In the control group, 50% were men and 50% were women. A previous stapedectomy had been performed on 42.8% of the patients in the FAO group. All of these patients reported dissatisfaction with the results of their stapedectomy and desired cochlear implantation. Two patients (13.3% of the patients who failed stapedectomy) reported full hearing loss following stapedectomy. Patients in the control group underwent cochlear implantation for suspected AIED (n = 13), adult-onset slowly progressive bilateral hearing loss of unknown cause (n = 11), hearing loss from childhood illness (n = 7), and chronic ear disease with presumed labyrinthitis (n = 1).
| N | Age at CI | Sex | Previous stapedectomy | MRI/CT abnormalities | Cochlear ossification/fibrosis | Type of CI | Insertion |
|---|---|---|---|---|---|---|---|
| 1 | 78 | F | Y | N | N | L/NF | F |
| 2 | 78 | F | Y | N | N | R/C24 | F |
| 3 | 62 | M | N | N | N | L/NF | F |
| 4 | 78 | M | N | N | N | R/HiRes | F |
| 5 | 61 | F | N | N | Y | L/N5 | F |
| 6 | 63 | M | Y | N | Y | L/N5 | F |
| 7 | 79 | F | Y | N | N | L/NF | F |
| 8 | 73 | M | Y | N | Y | L/C24 | F |
| 9 | 60 | F | N | N | N | R/NF | F |
| 10 a | 40 | F | N | N | N | R/C24 | F |
| 11 a | 39 | F | N | Y | N | L/C24 | F |
| 12 | 79 | M | Y | Y | N | R/NF | F |
| 13 | 85 | M | N | N | N | R/N5 | F |
| 14 | 75 | F | N | N | N | R/NF | F |
| 15 | 72 | F | Y | Y | N | L/N5 | F |
| 16 | 48 | F | N | N | N | R/C24 | F |
| 17 | 79 | F | Y | N | N | R/NF | F |
| 18 | 86 | F | N | N | Y | R/C24 | F |
| 19 | 68 | M | Y | Y | Y | R/NF | F |
| 20 a | 52 | F | N | N | N | R/NF | F |
| 21 a | 52 | F | N | N | N | L/C24 | F |
| 22 | 63 | F | N | N | Y | L/C24 | F |
| 23 | 70 | M | N | N | N | L/NF | F |
| 24 a | 48 | M | N | Y | N | L/C24 | F |
| 25 a | 49 | M | N | Y | N | R/N5 | F |
| 26 | 72 | M | N | N | N | R/C24 | F |
| 27 | 69 | M | Y | N | Y | R/NF | F |
| 28 | 69 | M | N | Y | Y | R/N5 | F |
| 29 a | 63 | F | Y | Y | Y | L/N5 | F |
| 30 a | 62 | F | Y | Y | Y | R/NF | F |
| 31 | 41 | F | N | N | N | R/C24 | F |
| 32 | 85 | F | Y | N | N | R/N5 | F |
| 33 | 68 | M | Y | N | N | L/HiRes | F |
| 34 | 86 | M | Y | N | N | R/N5 | F |
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