Narrow Internal Auditory Canal Research Articles

Internal auditory canal volume in normal and malformed inner ears

PurposeA narrow bony internal auditory canal (IAC) may be associated with a hypoplastic cochlear nerve and poorer hearing performances after cochlear implantation. However, definitions for a narrow IAC vary widely and commonly, qualitative grading or two-dimensional measures are used to characterize a narrow IAC. We aimed to refine the definition of a narrow IAC by determining IAC volume in both control patients and patients with inner ear malformations (IEMs).MethodsIn this multicentric study, we included high-resolution CT (HRCT) scans of 128 temporal bones (85 with IEMs: cochlear aplasia, n = 11; common cavity, n = 2; cochlear hypoplasia type, n = 19; incomplete partition type I/III, n = 8/8; Mondini malformation, n = 16; enlarged vestibular aqueduct syndrome, n = 19; 45 controls). The IAC diameter was measured in the axial plane and the IAC volume was measured by semi-automatic segmentation and three-dimensional reconstruction.ResultsIn controls, the mean IAC diameter was 5.5 mm (SD 1.1 mm) and the mean IAC volume was 175.3 mm3 (SD 52.6 mm3). Statistically significant differences in IAC volumes were found in cochlear aplasia (68.3 mm3, p < 0.0001), IPI (107.4 mm3, p = 0.04), and IPIII (277.5 mm3, p = 0.0004 mm3). Inter-rater reliability was higher in IAC volume than in IAC diameter (intraclass correlation coefficient 0.92 vs. 0.77).ConclusionsVolumetric measurement of IAC in cases of IEMs reduces measurement variability and may add to classifying IEMs. Since a hypoplastic IAC can be associated with a hypoplastic cochlear nerve and sensorineural hearing loss, radiologic assessment of the IAC is crucial in patients with severe sensorineural hearing loss undergoing cochlear implantation.

“A COMPARATIVE STUDY OF MRI AND HRCT OF SENSORINEURAL HEARING LOSS”

Background: In 2012, the World Health Organization (WHO) estimated that 360 million people, that is 5.3% of the world's population had hearing loss. In India, 63 million people (6.3%) have a signicant hearing loss. High-resolution computed tomography (HRCT) of the temporal bone and magnetic resonance imaging (MRI) of the inner ear have been used in this group of patients with some advantages and disadvantages of each modality. To Aim: compare both imaging modality in the evaluation of sensorineural hearing loss and to create a systemic approach for cochlear implant candidacy. This observational study was conducted in the Department of Radiodiagnosis Materials and methods: comprising of 80 ears of 40 patients who having congenital moderate to profound SNHL and were potential candidate for cochlear implant surgery. All patients underwent combined HRCT of temporal bone and MRI inner ear including brain. Results: The mean age of the patients was 3.30 ± 1.49 years with male predominance (57.5%). HRCT found abnormality in 19 ears while MRI picked up abnormality in 22 ears. The number of ears with cochlear (10), vestibular (8) and semi-circular canal (8) abnormalities were similar by both imaging modalities. However, MR additionally detected abnormalities of endolymphatic duct system (12) as compared to vestibular aqueduct (10) on HRCT. Narrow internal auditory canal was found in 5 ears detected by both imaging modalities and all were associated with abnormal cochlear nerve. However, 2 additional cochlear nerve abnormalities associated with normal IAC. We found MRI slightly superior in detection of cause Conclusion: of SNHL. MRI better depicts the uid-lled structures of the inner ear and cochlear nerve, retro-cochlear and cerebral pathology that leads to determination and feasibility of candidacy for cochlear implantation. HRCT is mandatory to rule out any bony anatomical variation and facial nerve course to determine side of implant and minimize intraoperative complication. Therefore, we advocate use of both MRI and HRCT in cochlear implant candidates.

De novo sensorineural hearing loss sequelae of narrow, duplicated internal auditory canal: Case series and literature review.

IntroductionA narrow duplicated internal auditory canal (IAC) is an extremely rare anomaly, likely associated with congenital sensorineural hearing loss due to aplasia/hypoplasia of the vestibulocochlear nerve or the cochlear branch alone. We aimed to review our experience with IAC duplication, describe its clinical characteristics, and present a literature review.Case presentationOur Otology database was searched for children who showed duplication of the IAC. Clinical characteristics of two children with bilateral duplication of the IAC are described. Data regarding clinical history, auditory assessment, magnetic resonance imaging (MRI), and computed tomography (CT) were collected and analyzed. The separated, accessory bony canals were demonstrated on high-resolution CT scans, and the nerves were demonstrated on MRI.DiscussionTo date, a few cases of narrow duplicate IAC have been reported in the literature, Approximately 20% of patients with congenital SNHL are found to show inner-ear bony abnormalities on CT, but much uncertainty still exists about the mechanism underlying IAC stenosis.5 Imaging findings of the temporal bone in our case series demonstrated asymmetrical narrowing of both IACs, there is no clear evidence in the literature supporting the predominance of one side over the other. In our series, facial nerve function was intact bilaterally. As for our cases, both patients were enrolled in a single-sided deafness evaluation for a trial of options such as BAHA, CROS, cochlear implants, and other non-implantable hearing aids. Furthermore, addressing the important factors will optimize the outcomes including surgery at early age to optimize neural plasticity, with intense long-term therapy.ConclusionCongenital duplication of the IAC likely convoying sensorineural hearing loss due to aplasia/hypoplasia of the vestibulocochlear nerve. Early diagnosis and intervention are essential to optimize patient outcomes.

Persistent endochondral cartilage in a child with profound sensorineural hearing loss: A roadblock for cochlear implantation

A unique case of persistent endochondral cartilage in temporal bone in a child with profound hearing loss is being reported This has never been reported earlier. High-resolution computed tomography of the temporal bone suggested bilateral narrow internal auditory canal and absent semicircular canals with small vestibule but a normal cochlea. The mastoid cavity showed few lucent areas among the air cells. Magnetic resonance imaging showed similar findings along with bilateral thin auditory nerves. During the surgical procedure, the mastoid air cells on the right side were filled with cartilaginous tissue separating it from the posterior fossa. With absolutely no landmarks and a contracted antrum, further procedure was abandoned. Although there are a few contraindications for cochlear implantation, this unique case report highlights one of the rarest conditions which can provide a surgical challenge to the surgeon.

Value of Routine Magnetic Resonance Imaging for the Preoperative Assessment of Cochlear Implant Candidates.

BackgroundThe selection of an appropriate imaging technique for assessment before cochlear implantation is critical for precise diagnosis and management. While magnetic resonance imaging (MRI) is used for the diagnosis of several conditions, such as labyrinthitis ossificans, cochlear nerve deficiency, and neoplasms, high-resolution computed tomography (HRCT) provides excellent details of the temporal bone. However, it remains unclear whether routine MRI provides any additional benefits over HRCT.ObjectivesTo assess the added value of MRI as a screening tool for temporal bone abnormalities in cochlear implant candidates through comparisons of its findings with those of HRCT.Materials and methodIt is a retrospective analysis of preoperative HRCT and MR images in a tertiary referral center. A total of 308 patients who underwent MRI and HRCT examinations before cochlear implantation between 2013 and 2015 were included. Preoperative HRCT and MR images were screened for temporal bone abnormalities by a senior neurotologist and a neuroradiologist.ResultsHRCT detected inner ear deformities in 51 of the 308 (16.6%) subjects, whereas MRI revealed abnormalities in only 18 (5.8%) of subjects. HRCT detected the same inner abnormalities in 16 of the 18 (88.9%) subjects diagnosed by MRI, whereas it showed normal results for the remaining two subjects. MRI detected cochlear nerve aplasia/hypoplasia in 13 subjects, 11 of whom had associated inner ear deformities that were detected by HRCT. The MR images of nine subjects showed cochlear fibrosis, which was confirmed by HRCT in all nine subjects.ConclusionIn this study, MRI did not exhibit significant additional benefits over HRCT, and its routine use for the preoperative assessment of CI candidates was not justified. However, MRI is warranted for subjects at an increased risk of cochlear nerve aplasia due to an inner ear deformity or a narrow internal auditory canal. The establishment of criteria that facilitate the performance of MRI only when absolutely needed will reduce healthcare costs, prevent unnecessary exposure to the risks associated with general anesthesia, and shorten delays before cochlear implantation.

Comparison of the prevalence and features of inner ear malformations in congenital unilateral and bilateral hearing loss

ObjectivesThe aim of the study was to clarify differences in the prevalence and features of bony malformations in inner ear between congenital unilateral sensorineural hearing loss (USNHL) and congenital bilateral sensorineural hearing loss (BSNHL). MethodsWe conducted a retrospective study of 378 consecutive infants referred from routine newborn hearing screening in the past 18 years. Clinical background, audiological data, and temporal bone computed tomography (CT) findings were analyzed. The prevalence of malformations between USNHL and BSNHL groups were compared using the Chi-square test. ResultsThe proportion of family history of hearing loss was significantly higher in infants with BSNHL than in those with USNHL (26/107 [24.3%] vs. 4/105 [3.7%]; p = 0.0001). Temporal bone CT scanning revealed significantly a higher prevalence of inner ear malformations in infants with USNHL than in those with BSNHL (93/109 [85.3%] vs. 4/107 [3.7%]; p < 0.0001). The most frequent anomaly in USNHL was cochlear nerve canal stenosis (69.7%), followed by cochlear malformations (20.2%), and narrow internal auditory canal (17.4%). Four infants with BSNHL accompanied by inner ear anomaly had complications such as Down's syndrome, developmental delay, or epilepsy. ConclusionsThe prevalence of bony malformations in inner ear and/or IAC was markedly higher in infants with congenital USNHL than in infants with BSNHL. Temporal bone CT scanning may help to clarify the etiology of congenital hearing loss, especially in USNHL.

Clinical Value of Measurement of Internal Auditory Canal in Pediatric Cochlear Implantation.

The aims of this study were to clarify the clinical value of the bony cochlear nerve canal (BCNC) and internal auditory canal (IAC) in children with bilateral sensorineural hearing loss (b-SNHL) and to reveal the correlation between these parameters and outcomes after cochlear implantation (CI). Ninety-four ears with b-SNHL that received CI and 100 ears with normal hearing were enrolled. Parameters of IAC and pre- and post-CI categories of auditory performance scores were analyzed. The width of the BCNC and the width, height, and length of the IAC were shorter in the b-SNHL group. BCNC and IAC width were associated with b-SNHL. The calculated cutoff values for BCNC and IAC width were 2.055 mm in the BCNC and 4.245 mm in the IAC, setting the sensitivity to 90%. Patients with narrow BCNCs and IACs had significantly worse post-CI auditory performance. BCNC and IAC widths were narrower in children with b-SNHL than in normal-hearing children. Narrow BCNC and IAC width had a negative impact on post-CI outcomes. The proposed cutoff values for BCNC and IAC width were meaningful when predicting the auditory outcome after CI, especially considering both.

Extremely common radiographic finding of cochlear nerve deficiency among infants with prelingual single-sided deafness and its clinical implications

ObjectivesTo clarify the common radiographic findings of audiologically documented prelingual single-sided deafness (SSD) and identify the prevalence of cochlear nerve deficiency (CND) in SSD infants referred from the newborn hearing screening program. MethodsBetween March 2012 and March 2017, the records of all infants referred to our otology clinic after undergoing newborn hearing screening program were retrospectively reviewed. Twenty-four consecutive well infants without risk factors who had a confirmed diagnosis of prelingual SSD under the age of 1 year and who underwent internal auditory canal (IAC) magnetic resonance imaging (MRI) were included. The sizes of cochlear nerve (CN), IAC, and cochlear nerve canal (CNC) were measured on MRI. The presence of CND was visually determined by comparing the CN size to the ipsilateral facial nerve (FN) in the affected side via an oblique sagittal view of IAC MRI and defined when CN was absent or smaller than FN. ResultsCND was seen in all 24 deaf ears (100%) on MRI. There was one with incomplete partition type I, and another with combined cochleovestibular nerve absence. Twenty-four subjects demonstrated either an absent (20/24, 83.3%) or small (4/24, 16.7%) CN. When the absent and small CN groups were compared, the former group had a higher prevalence of narrow CNC and narrow IAC. Of the 20 infants without identifiable CN on the affected side, 17 (85%) had narrow IAC and 17 (85%) had narrow CNC. In the 20 ears with absent CN, only one had both normal-sized IAC and CNC. ConclusionThe contribution of CND to prelingual SSD in Korean infants reached 100%, according to IAC MRI alone.

Favorable Long-Term Functional Outcomes and Safety of Auditory Brainstem Implants in Nontumor Patients.

Auditory brainstem implants (ABIs) were designed to restore hearing in deaf patients with auditory tumors or those unable to receive cochlear implants. Although ABIs may help some patients, their long-term outcomes have been rarely studied. To assess the long-term benefits and safety of ABIs in nontumor patients with sensorineural hearing loss (SNHL). We retrospectively reviewed the histories of 15 deaf patients (8 females, 7 males; mean age, 15.5 yr; range, 1-56 yr) who received ABIs for treatment of SNHL at our hospital from July 2008 to November 2015. These included 11 children with narrow internal auditory canals and 4 deaf adults with severe cochlear ossification. In each patient, a 12-channel ABI electrode was placed in the cochlear nucleus complex via a retrosigmoid approach. Auditory performance was evaluated using the Categories of Auditory Performance (CAP) index and sound detection and word identification tests. One year after ABI placement, 13 of 15 patients showed adequate or significantly improved auditory function based on the CAP scores at the last follow-up. Generally, adult patients tended to show better CAP scores (3.50) than pediatric patients (2.15), but the difference was not significant (P = .058). Postoperative complications included electrode migration, cerebrospinal fluid leakage, nonauditory stimulation, and minor seizures without severe sequelae or mortality. ABIs show favorable functional outcomes and long-term safety in nontumor deaf patients with limited treatment options. Collectively, our data indicate that ABIs represent an important treatment option for SNHL.

Limitation of High Pitch Sound Perception in Nontumor Patients with Auditory Brainstem Implantation

Background and Objectives Auditory brainstem implantation (ABI) is another option for hearing rehabilitation in non-neurofibromatosis type 2 patients who cannot undergo cochlear implantation (CI). However, the average performance of ABI is worse than that of CI. We analyzed the psycho-electrical parameters of each electrode and psycho-acoustic response to different frequency sounds in nontumor patients with ABI. Subjects and Method Sixteen patients with ABI from July 2008 to May 2013 were included in the study. They were followed up for 4 to 56 months. Among them, 12 were prelingual deaf with a narrow internal auditory canal or cochlear ossification. The remaining four were postlingual deaf adults with severely ossified cochleae. We analyzed the electrical parameters [impedance, threshold level (T level), and dynamic range] of each of the 12 electrodes. We also evaluated the sound field pure-tone threshold, Ling 6 sound detection-identification test (Ling 6 test), and pitch ranking data of these patients. Results The impedance, T level, and dynamic range did not significantly differ among electrodes. However, the pure-tone threshold to sound field stimulation was elevated in the high tone area, where more variables were found than in the low frequency area. Patients could not identify /S/ and /Sh/ sounds in the Ling 6 test. The mean T level and the dynamic range of the three highest pitch-perceiving electrodes in each patient was higher and narrower, respectively, than those of the three lowest pitch-perceiving electrodes. Conclusion The nontumor patients with ABI have difficulty perceiving high pitch sound. More sophisticated penetrating type electrodes and, if possible, bimodal stimulation with CI, could be considered. Key words: Auditory brainstem implantation ㆍ Cochlear ossification ㆍ Narrow internal auditory canal ㆍ nontumor ㆍ Outcomes.

Duplicated internal auditory canal with inner ear malformation: Case report and literature review

Internal auditory canal anomalies are rare. Narrow internal auditory canal is believed to occur as a result of aplasia or hypoplasia of the vestibulocochlear nerve. Narrow duplication of the internal auditory canal is considered to be very rare. Narrow duplication of the internal auditory canal with inner ear malformation has been reported in only 3 cases. We present 2 cases of narrow duplication of the internal auditory canal with inner ear malformation. The first case had inner ear malformation on only one side and the second case had inner ear malformation on both sides. The embryogenesis may be different between internal auditory canal and inner ear.

Is There a Relationship Between Bell's Palsy and Internal Auditory Canal?

In the present study, we evaluated the diameter of internal acoustic canal in patients with Bells palsy to investigate the role of anatomical differences of the temporal bone in etiology of Bell's palsy. Sixty-four patients who were diagnosed as Bells Palsy and temporal bone computed tomography imagings of them were included into the study group (Group 1). The control group (Group 2) was consisted of 35 healthy subjects without Bell's Palsy. All patients had temporal bone computed tomography imaging. The internal auditory canal inlet, mid-canal, outlet and canal lengths were measured at the most distinctive cross-section of the seventh and eighth cranial nerves bifurcation. In the study group, Bells palsy was on the right side in 26 patients (40.6%) and on the left side in 38 patients (59.4%). Initial House-Brackmann (HB) score was HB-2 in 29 patients (45.3%), HB-3 in 18 patients (28.1%), HB-4 in 13 patients (20.3%) and HB-5 in 4 patients (6.2%). At 6-month evaluation, HB-score of the patients were HB-1 in 37 patients (57.8%), HB-2 in 25 patients (39.1%) and HB-3 in 2 patients (3.1%). Internal auditory canal (IAC) measurements of the groups showed that there were no significant differences between the measurements of right-mid canal, right canal length; and left canal outlet and left canal length of the study and control groups. Right inlet and outlet; and left inlet and mid-canal values of the study group (Bell's palsy) were significantly lower than those of the control group. In Bell's palsy group, left inlet, outlet and canal length values were significantly higher than those of the right ones. Correlation analysis showed that there were no significant correlation between paralysis side; initial HB stage; and IAC measurement results. In patients with higher initial HB score, their 6-month later HB-score was also higher. In patients with higher 6-month HB score; R canal inlet, R mid-canal, L-canal inlet, and L-mid canal values were lower. Lower IAC inlet and mid-canal values were detected in patients with Bell's palsy. Therefore narrow IAC inlet and mid-canal values may be one of the risk factors for Bell's palsy.

The Cochlear Nerve Canal and Internal Auditory Canal in Children with Normal Cochlea but Cochlear Nerve Deficiency

There is an increasing frequency of requests for cochlear implantation (CI) in deaf children and more detailed image information is necessary for selecting appropriate candidates. Cochlear nerve deficiency (CND) is a contraindication to CI. Magnetic resonance imaging (MRI) has been used to evaluate the integrity of the cochlear nerve. The abnormalities of the cochlear nerve canal (CNC) and internal auditory canal (IAC) have been reported to be associated with CND. To correlate CNC manifestation, size, and IAC diameter on high-resolution CT (HRCT) with CND diagnosed by MRI in children. HRCT images from 35 sensorineurally deaf children who had normal cochlea but bilateral or unilateral CND diagnosed by MRI were studied retrospectively. The CNC and IAC manifestation and size were assessed and correlated with CND. CND was diagnosed by MRI in 54/70 ears (77.1%). Thirty-two ears had an absent cochlear nerve (59.3%), while 22 ears had a small cochlear nerve (40.7%). The CNC diameter was <1.5 mm in 36 ears (66.7%). The CNC diameter ranged between 1.5 and 2.0 mm in seven ears (13.0%) and was >2.0 mm in 11 ears (20.4%). The IAC diameter was <3.0 mm in 25 ears (46.3%) and >3.0 mm in 29 ears (53.7%). The hypoplastic CNC might be more highly indicative of CND than that of a narrow IAC.

High prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss

ObjectiveRadiological and genetic examination has recently advanced for diagnosis of congenital hearing loss. The aim of this study was to elucidate the prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss (USNHL) for better management of hearing loss and genetic and lifestyle counseling. MethodsWe conducted a retrospective study of charts and temporal bone computed tomography (CT) findings of 69 consecutive patients 0–15 years old with USNHL. In two cases, genetic examination was conducted. ResultsOf these patients, 66.7% had inner-ear and/or internal auditory canal malformations. The prevalence of malformations in infants (age <1 year) was 84.6%, which was significantly higher than that in children 1–15 years old (55.8%; p<0.01). Almost half of the patients (32; 46.4%) had cochlear nerve canal stenosis; 13 of them had cochlear nerve canal stenosis alone, and in 19 it accompanied other malformations. Internal auditory canal malformations were observed in 22 subjects (31.8%), 14 (20.3%) had cochlear malformations, and 5 (7.2%) had vestibular/semicircular canal malformations. These anomalies were seen only in the affected ear, except in two of five patients with vestibular and/or semicircular canal malformations. Two patients (2.9%) had bilateral enlarged vestibular aqueducts. Mutations were found in SLC26A4 in one of the two patients with bilateral large vestibular aqueducts. The prevalence of a narrow internal auditory canal was significantly higher in subjects with cochlear nerve canal stenosis (50.0%) than in subjects with normal cochlear nerve canals (11.1%; p<0.01). There were no correlations between the type and number of malformations and hearing level. ConclusionsThe prevalence of inner-ear and/or internal auditory canal malformations detected by high-resolution temporal bone CT in children with USNHL was very high. Radiological and genetic examination provided important information to consider the pathogenesis and management of hearing loss. Temporal bone CT should be recommended to children with USNHL early in life. SLC26A4 mutation also should be examined in cases with bilateral enlarged vestibular aqueduct.

Inner ear anomalies seen on CT images in people with Down syndrome

Although dysplasia of inner ear structures in Down syndrome has been reported in several histopathological studies, the imaging findings have not been widely studied. To evaluate the prevalence and clinical significance of inner ear anomalies detected on CT images in patients with Down syndrome. The temporal bone CT images of patients with Down syndrome were assessed for inner ear anomalies; clinical notes and audiograms were reviewed for hearing loss. Logistic regression models were employed to identify which CT findings were associated with sensorineural hearing loss (SNHL). Inner ear anomalies were observed in 74.5% (38/51) of patients. Malformed bone islands of lateral semicircular canal (LSCC), narrow internal auditory canals (IACs), cochlear nerve canal stenoses, semicircular canal dehiscence (SCCD), and enlarged vestibular aqueducts were detected in 52.5% (53/101), 24.5% (25/102), 21.4% (21/98), 8.8% (9/102) and 2% (2/101) of patients' ears, respectively. IAC stenosis had the highest odds ratio (OR = 5.37, 95% CI: 1.0-28.9, P = 0.05) for SNHL. Inner ear anomalies occurred in 74.5% of our population, with malformed (<3mm) bone island of LSCC being the most common (52.5%) anomaly. Narrow IAC was seen in 24.5% of patients with Down syndrome and in 57.1% of ears with SNHL. High-resolution CT is a valuable for assessing the cause of hearing loss in people with Down syndrome.

MAP optimization as a predictor of cochlear implant outcomes in children with narrow internal auditory canal

ObjectivesThe purposes of this study were to investigate the auditory performance and MAP characteristics of implanted children with narrow internal auditory canal (IAC), and to examine the clinical usefulness of MAP optimization as a predictor of their cochlear implant (CI) outcomes by analyzing their auditory performance and habilitation methods in relation to MAP optimization. MethodsEight children with narrow IAC who had used a CI over 3 years were included. We retrospectively examined their auditory performance and MAPs. Auditory performance was measured by the Categories of Auditory Performance (CAP) and monosyllabic word tests before and after implantation. The relationship between auditory performance and MAP parameters was explored, and their habilitation methods were analyzed. ResultsMean CAP scores improved from .25 preoperatively to 3.5 3 years postoperatively. Mean scores for monosyllabic word tests improved from 0% preoperatively to 27.8% 3 years postoperatively. The children used MAPs with a wider pulse width than the default setting. Four children using optimal MAPs achieved open-set speech perception, so were trained in the oral approach. The other four using suboptimal MAPs because of non-auditory stimulation achieved no open-set speech perception, so were trained in the total communication approach. ConclusionsMAP optimization had a predictable value in determining the postoperative performance of children with narrow IAC who received a CI. The most suitable habilitation method can be determined early after implantation by identifying the presence of MAP optimization.

Cochlear Implant Outcomes of Cases with Temporal Bone Malformations

Objective: 1) To reveal the relationship between cochlear implant (CI) outcomes and the types of temporal bone malformation.2) To establish a high-resolution CT (HRCT)–based classification of temporal bone malformations for predicting CI outcomes. Method: We retrospectively evaluated 23 deaf children with cochleovestibular and/or internal auditory canal (IAC) malformations who underwent cochlear implantation from 2004 to 2010 at our hospital. Their temporal bone malformations were assessed by HRCT and their CI outcomes were evaluated by speech discrimination scores and category of auditory performance scores. Results: We classified cochleovestibular and IAC malformations into 3 groups by 1) presence of a bony modiolus in the cochlea and 2) patency of cochlear nerve canal (CNC) and IAC. Eleven cases with a bony modiolus and patent CNC/IAC (Group 1) showed excellent CI outcomes and could communicate without visual language, while all of 6 cases with atresia of CNC or narrow IAC (Group 3) needed lipreading or sign language for understanding common phrases, even if their cochleae were well developed. The remaining 6 cases with a cystic cochlea and patent CNC/IAC (Group 2) showed varying CI outcomes depending on maturity of the cochlea. Conclusion: Our classification based on presence of a bony modiolus in the cochlea and patency of CNC/IAC covered the all types of temporal bone malformations including cochleovestibular and CNC/IAC abnormalities and was useful to predict CI outcomes of children with temporal bone malformations.

Surgical complications of pediatric auditory brain stem implantation in patients with narrow internal auditory canal following retrosigmoid approach

Surgical complications of pediatric auditory brain stem implantation in patients with narrow internal auditory canal following retrosigmoid approach

Early surgical results of auditory brainstem implantation in nontumor patients

An auditory brainstem implant (ABI) that stimulates the cochlear nucleus in the brainstem was initially designed for patients with neurofibromatosis type-2. Recently, promising surgical outcomes after ABI have been reported in nontumor patients with sensorineural hearing loss including those with cochlear nerve aplasia or ossified cochlea. We herein describe the surgical results and auditory outcomes of ABI in nontumor patients. Retrospective case series at a tertiary hospital. Eleven deaf patients who received ABI from 2008 to 2010 were included in this study. The first group included eight patients with narrow internal auditory canals (IACs) and the second group consisted of three postlingually deaf adults with cochlear ossification. Pulsar CI100 ABI (Med-El Co., Innsbruck, Austria) was implanted via the suboccipital approach. All eight patients with narrow IACs clearly demonstrated behavioral responses following initial stimulation using an ABI. The category of auditory performance (CAP) scores were progressively improved to reach auditory performances of CAP 4 in three patients, CAP 3 in two patients, CAP 2 in two patients, and CAP 1 in one patient. The three patients with ossified cochlea also reported auditory sensations when the ABI was activated. Two of them showed an auditory performance of CAP 4 or 5, but the third patient could not use the device due to nonauditory stimulation. Based on our experience, ideal nontumor candidates for ABI include congenitally deaf children who experienced failure after cochlear implantation owing to cochlear nerve deficiency and postlingually deaf adults with severe cochlear ossification.

The cochleovestibular nerve identified during auditory brainstem implantation in patients with narrow internal auditory canals: Can preoperative evaluation predict cochleovestibular nerve deficiency?

To analyze the value of preoperative diagnostic tools in predicting the status of the cochleovestibular nerve (CVN) in patients with narrow internal auditory canals (IAC). Retrospective case series at a tertiary hospital. Eight profoundly deaf patients with narrow IACs who received auditory brainstem implantation were included in this study. The results of preoperative imaging, electrophysiologic, and auditory tests were correlated with the CVN status identified during auditory brainstem implantation. Temporal bone computed tomography (CT) findings, including the patency of the bony cochlear nerve canal and the diameter of the IAC, were limited in accurately reflecting the status of the CVN. Magnetic resonance imaging (MRI) and preoperative auditory responses to either pure tone or environmental sounds were more accurate markers for detecting the presence of a CVN than CT; however, there were limitations in cases with a very thin CVN or combined severe mental retardation. Absence of promontory or intracochlear electrically evoked auditory brainstem responses were not always indicative of an absent CVN. Visualization on MRI and detection of auditory responses suggested the presence of a CVN in patients with narrow IACs; however, the possibility of the presence of a CVN should be considered even when there is no clear evidence of a CVN on preoperative evaluations. Therefore, physicians should be prudent when determining candidacy for cochlear implantation or auditory brainstem implantation in patients with narrow IACs.