The application of three-dimensional magnetic resonance imaging rendering of the inner ear in assessment for cochlear implantation

OBJECTIVE: To study the use of three-dimensional (3D) rendering of T2-weighted magnetic resonance imaging (MRI) images into 3D models of the inner ear in the preoperative assessment for cochlear implantation. STUDY DESIGN: A retrospective case review of cochlear implant candidates undergoing preoperative imaging studies to determine their suitability for surgical implantation. SETTING: A tertiary referral center for the northwest area of England with an established 10-year-old program in cochlear implantation. PATIENTS: Selected adult and pediatric patients referred for cochlear implant assessment from 1996 to 1998, who underwent computerized tomography (CT) and MRI studies. Intervention: Diagnostic imaging modality to assess the structure and patency of the inner ear. MAIN OUTCOME MEASURES: To see how detailed anatomic information provided by these 3D models influenced surgical decisions. RESULTS: Four case studies (with their 3D models) are presented to illustrate different points of interest. CONCLUSION: These 3D models provide the implanting surgeon with precise, detailed, and easily interpretable information about the cochlea, which help to guide surgical implantation, or in certain cases, to decide against attempting surgery in the presence of unfavorable anatomic factors.     

Computed tomography and/or magnetic resonance imaging before pediatric cochlear implantation? Developing an investigative strategy.

OBJECTIVE: To investigate and compare the usefulness of preoperative magnetic resonance (MR) imaging and high-resolution temporal bone computed tomography (HRCT) in pediatric cochlear implant candidates. STUDY DESIGN: Prospective. SETTING: Tertiary referral center. PATIENTS: A cohort of 92 pediatric patients with profound hearing. Inclusion criteria were MR, computed tomography, and cochlear implantation. INTERVENTION. DIAGNOSTIC: All patients had preoperative imaging of the petrous temporal bone (HRCT, T2-weighted fast spin echo, axial 3D Fast Imaging Employing Steady-state Acquisition [FIESTA] MR) and brain (Fast Fluid-attenuated Inversion-recovery [FLAIR] MR). MAIN OUTCOME MEASURE(S): Overall prevalence of inner ear dysplasias in this population and comparison of detection rates between HRCT, T2 Fast Spin Echo (FSE), and FIESTA MR sequences. RESULTS: Radiological abnormalities were observed in 32 and 59% of MR and HRCT temporal bone, respectively. Synchronous intracranial findings were noted in 40% on brain MR. Common vestibulocochlear nerve was observed in 3% ears and directed side of implantation. Consistent discrepancies noted on HRCT were inability to diagnose early obliterative labyrinthitis and presence of the cochlear nerve in the internal auditory canal. With respect to MR, enlarged vestibular aqueducts and narrow cochlear nerve canals were consistently under identified. CONCLUSION: Dual-modality imaging with HRCT and MR of petrous bone and MR brain in the precochlear implant pediatric population detects abnormalities related to deafness, which would not otherwise be found using either modality alone. There is overlap between the imaging modalities in the type of abnormalities detected, and we present a case for selective use of HRCT within a diagnostic algorithm, using the patient risk factors we have identified.     

Should a hearing aid in the contralateral ear be recommended for children with a unilateral cochlear implant?

OBJECTIVES: To predict bimodal benefit before cochlear implantation, we compared the performances of participants with bimodal fitting and with a cochlear implant alone on speech perception tests. METHODS: Twenty-two children with a cochlear implant in one ear and a hearing aid in the other (bimodal fitting) were included. Several aided and unaided average hearing thresholds and the aided word recognition score of the hearing aid ear were related to the bimodal benefit on a phoneme recognition test in quiet and in noise. Results with bimodal fitting were compared to results with the cochlear implant alone on a phoneme recognition test in quiet and in noise. RESULTS: No relationship was found between any of the hearing thresholds or the aided phoneme recognition score of the hearing aid ear and the bimodal benefit on the phoneme recognition tests. At the group level, the bimodal scores on the phoneme recognition tests in quiet and in noise were significantly better than the scores with the cochlear implant alone. CONCLUSIONS: Preoperatively available audiometric parameters are not reliable predictors of bimodal benefit in candidates for cochlear implantation. Children with unilateral implants benefit from bimodal fitting on speech tests. This improvement in performance warrants the recommendation of bimodal fitting even when bimodal benefit cannot be predicted.     

Indications for imaging the inner ear with CISS-MRI]

BACKGROUND: High-resolution CT images are often unable to visualize the extent of possible cochlear obliteration after meningitis or after temporal bone fracture. The exact estimation of this extent, however, is crucial for cochlear implant surgery planning. Thus MR imaging of intralabyrinthine pathology is becoming an increasingly significant imaging modality. METHODS: The clinical relevance of the CISS (constructive interference in steady state) MR sequence is explained using 5 selected cases of different inner ear pathology. RESULTS: Two of the examined patients had unsuspicious inner ear signals, whereas in 3 cases MRI rendered relevant information about partial or total cochlear obliteration. CONCLUSIONS: These clinical examples illustrate how the ideal fluid and tissue contrast of CISS-MRI make this new technique suitable as a primary tool for evaluating inner ear obliteration before cochlear implant surgery.     

Astragaloside IV inhibits apoptotic cell death in the guinea pig cochlea exposed to impulse noise

X-ray microtomography (micro-CT) is a new technique allowing for visualization of the internal structure of opaque specimens with a quasi-histological quality. Among multiple potential applications, the use of this technique in otology is very promising. Micro-CT appears to be ideally suited for in vitro visualization of the inner ear tissues as well as for evaluation of the electrode damage and/or surgical insertion trauma during implantation of the cochlear implant electrodes. This technique can greatly aid in design and development of new cochlear implant electrodes and is applicable for temporal bone studies. The main advantage of micro-CT is the practically artefact-free preparation of the samples and the possibility of evaluation of the interesting parameters along the whole insertion depth of the electrode. This paper presents the results of the first application of micro-CT for visualization of the inner ear structures in human temporal bones and for evaluation of the surgical positioning of the cochlear implant electrodes relative to the intracochlear soft tissues.     

High resolution micro-CT scanning as an innovative tool for evaluation of the surgical positioning of cochlear implant electrodes

X-ray microtomography (micro-CT) is a new technique allowing for visualization of the internal structure of opaque specimens with a quasi-histological quality. Among multiple potential applications, the use of this technique in otology is very promising. Micro-CT appears to be ideally suited for in vitro visualization of the inner ear tissues as well as for evaluation of the electrode damage and/or surgical insertion trauma during implantation of the cochlear implant electrodes. This technique can greatly aid in design and development of new cochlear implant electrodes and is applicable for temporal bone studies. The main advantage of micro-CT is the practically artefact-free preparation of the samples and the possibility of evaluation of the interesting parameters along the whole insertion depth of the electrode. This paper presents the results of the first application of micro-CT for visualization of the inner ear structures in human temporal bones and for evaluation of the surgical positioning of the cochlear implant electrodes relative to the intracochlear soft tissues.     

Topographic analysis of inner ear lesions in profoundly deafened patients with tympanogenic and meningogenic labyrinthitis using three-dimensional magnetic resonance imaging.

OBJECTIVE: High-resolution magnetic resonance imaging (MRI) provided clear images of three-dimensional (3D) reconstruction of the inner ear in candidates for cochlear implantation. In this study. semiquantitative analysis of the 3D MRI findings was performed to investigate topographic lesions of the inner ear caused by tympanogenic and meningogenic labyrinthitis. STUDY DESIGN: This was an observational study. SETTING: The study was performed in an academic, comprehensive, multispecialty group practice. PATIENTS: Postlingual deafened patients with cochlear implantation. The cause of deafness was tympanogenic or meningogenic labyrinthitis. INTERVENTION: High-resolution 3D MRI and postoperative speech recognition tests were used. RESULTS: Abnormal findings in the inner ear detected with MRI were found before surgery in 58.3% of the patients with meningogenic labyrinthitis, although the incidence was lower in patients with tympanogenic labyrinthitis. Abnormal MRI findings were frequently observed in the cochlear basal turn and semicircular canals more than in the middle and apical turn in cases with meningogenic etiology. Patients with tympanogenic labyrinthitis suffered less with a vestibular apparatus than did those patients with meningogenic labyrinthitis. Regarding the analysis of the inner ear lesions at the implanted side, the postoperative speech recognition ability did not correlate to the extent of abnormal MRI findings of the implanted ear. CONCLUSION: Improvement in 3D MRI technology provided an accurate preoperative picture of the inner ear apparatus. In cochlear implant patients with infectious labyrinthitis, the extent of the inner ear lesion detected with 3D MRI was different among etiologies of deafness.     

人工耳蜗植入术前的影像学检查

目的 :探讨CT和MRI检查对人工耳蜗植入术前评估的价值。方法 :对 2 6例感音性耳聋患者均采用颞骨轴位高分辨率CT螺旋扫描、MR水成像及内耳三维重建。结果 :1 8例先天性感音性耳聋患儿中检出Mondini畸形Ⅰ型 1例 (2耳 ) ,Ⅱ型 1例 (2耳 ) ,内耳纤维化 1例 (2耳 ) ;5例语后聋患者中检出慢性化脓性中耳炎 1例 (2耳 ) ,内耳骨化 1例 (2耳 )。结论 :对于人工耳蜗植入术的术前评估 ,CT检查具有重要价值 ,必不可少 ,MRI检查是必要的补充。对内耳的三维重建 ,MRI优于CT。     

Preoperative cochlear implant imaging: is magnetic resonance imaging enough?

OBJECTIVE: To investigate the accuracy of magnetic resonance imaging (MRI) as a preoperative imaging technique for cochlear implant candidates. STUDY DESIGN: Retrospective, blinded. SETTING: Tertiary medical center. PATIENTS: 31 cochlear implant candidates with various causes of hearing loss. INTERVENTION: Cochlear implant patients received preoperative high-resolution temporal bone computed tomography (CT), and high-resolution T2-weighted fast spin echo MRI (FSE-MRI). The images were read independently of each other and in a blinded manner by two neuroradiologists. The imaging results were also correlated with intraoperative findings. MAIN OUTCOME MEASURES: Lack of agreement between the findings for either imaging technique; also, lack of agreement between imaging findings and intraoperative findings. RESULTS: FSE-MRI is equal to CT imaging in the detection of abnormalities of cochlear patency. It is better than CT imaging in detecting cochlear dysplasia and large vestibular aqueducts, and in determining the presence of the cochlear nerve. CONCLUSION: FSE-MRI is accurate in predicting inner ear anomalies and obstruction of the cochlear lumen. It also adds information not gathered from CT imaging, such as the presence and size of the cochlear nerve.     

Image analysis of the inner ear with CT and MR imaging: pre-operative assessment for cochlear implant surgery]

Recent progress in magnetic resonance imaging (MRI) has made it possible to obtain detailed images of the inner ear by delineating the lymphatic fluid within the labyrinth. We analyzed CT scans and MR images in 70 ears manifesting profound deafness owing to inner ear lesions and compared their detective ability for inner ear lesions. The following results were obtained. 1) CT scan examination showed slight to extensive ossification of the labyrinth in six ears (9%), whereas MRI examination revealed low to absent signal intensity of the inner ear in nine ears (13%). Therefore, it was concluded that MRI is more sensitive in detecting abnormalities of the inner ear than CT scan. 2) MRI provided useful information as to whether the cochlear turn is filled with lymphatic fluid or obstructed. This point was one of the greatest advantages of MRI over CT scan. 3) Abnormal findings in either or both the CT scan and the MRI were detected in suppurative labyrinthitis occurring secondary to chronic otitis media, bacterial meningitis and in inner ear trauma. However, such abnormal findings were not detected in patients with idiopathic progressive sensorineural hearing loss, ototoxicity or sudden deafness. These findings should be taken into consideration in pre-operative assessment of cochlear implant candidates.     

Choosing which ear to implant in adult candidates with functional residual hearing

This study examined whether audiologists consider the potential benefits of contralateral hearing aid use following cochlear implantation when recommending which ear to implant in UK adult candidates with residual hearing. Thirty-four audiologists from providers of adult implantation services completed a decision-choice experiment. Clinicians were willing to consider recommending that the poorer ear be implanted, provided it had been aided continuously, suggesting that their decision making seeks to preserve access to residual hearing in the non-implanted ear where possible. Future approaches to determining candidacy should therefore consider that a sub-set of patients may obtain additional benefit from this residual hearing following implantation.     

Quantitative evaluation of new bone and fibrous tissue in the cochlea following cochlear implantation in the human

The formation of new bone and fibrous tissue in the human inner ear following cochlear implantation was evaluated by computer-assisted 3-D reconstruction. Seven temporal bones from patients who in life had undergone cochlear implantation were prepared for histological study with the implant in situ. The specimens were sectioned in the axial plane at a thickness of 20 microm. At least every tenth section was digitally reconstructed in three dimensions and volumes of new bone and fibrous tissue were calculated per millimeter length of the cochlea. New bone and fibrous tissue were found in all seven specimens, particularly at the cochleostomy site. In addition, new bone and fibrous tissue had extended to variable lengths along the track of the cochlear implant and in some cases extended beyond the distal end of the implanted electrode. This methodology provides a quantitative tool for evaluation of new bone and fibrous tissue in the inner ear following implantation. This should assist in correlating psychophysical and speech perception tests with intracochlear pathology, evaluating both electrode design and the techniques of preserving residual auditory function.     

Outcomes for cochlear implant users with significant residual hearing: implications for selection criteria in children

OBJECTIVES: To develop an evidence-based technique for providing recommendations to candidates for cochlear implantation with significant residual hearing and to assess the efficacy of the approach. DESIGN: Modified selection criteria were derived from an analysis of the postoperative performance for a large group of adult cochlear implant users. In particular, the distributions of results for implant users with significant preoperative open-set speech perception were reviewed. This suggested that the candidates had a good chance (>75%) of overall improvement if they obtained open-set sentence scores in quiet of up to 70% in the best-aided condition and scores of up to 40% in the ear to undergo implantation. PATIENTS: A group of 45 adult implantation candidates who fit the modified criteria and who underwent preimplantation and postimplantation assessment to compare actual results with those predicted from the distributions. RESULTS: The speech perception results showed that 36 subjects (80%) had improved open-set sentence scores with the cochlear implant compared with their best-aided preoperative performance (mean improvement, 20.5%). Forty-four (98%) had improved open-set sentence scores for the ear undergoing implantation (mean improvement, 65.3%). CONCLUSIONS: The general concept of using the distribution of speech perception results to make evidence-based recommendations for candidates for cochlear implants is supported by this study. The approach can be used across different subpopulations, including older children with significant residual auditory skills, and for different outcome measures. It is important that the data used to provide recommendations and modify selection criteria are from an unselected sample of implant users of adequate size. This study highlights the continuing need to evaluate speech perception performance carefully before and after cochlear implantation.     

Advantages of magnetic resonance imaging over computed tomography in preoperative evaluation of pediatric cochlear implant candidates.

OBJECTIVES: To compare magnetic resonance imaging (MRI) to high-resolution computed tomography (HRCT) in the preoperative evaluation of pediatric cochlear implant candidates. METHODS: The charts of pediatric cochlear implant candidates evaluated between July 1, 2000 and November 30, 2003 with an MRI scan of the inner ear were included in the study. Fifty-six patients were included. Associated HRCT scans were examined. Abnormalities of the cochlea, cochlear nerve, endolymphatic sac, endolymphatic duct, vestibule, and modiolus were noted. A pediatric neuroradiologist gave an opinion as to whether patients with anomalies seen with MRI but without associated HRCT would have been identified by HRCT. RESULTS: Of the 112 temporal bones imaged with MRI, the following abnormalities were encountered: 32% (36/112) had abnormalities of the cochlear turns, 30% (34/112) had abnormal signal in the modiolus, 23% (26/112) had abnormal vestibulae, 16% (18/112) had abnormal endolymphatic ducts, 15% (17/112) had abnormal endolymphatic sacs, 12% (13/112) had abnormalities of the cochlear nerves, 29% (17/56) had abnormalities of the brain. HRCT cannot directly evaluate the cochlear nerve. Available HRCT findings were combined with radiologic opinion and compared with MRI findings. The percentages of abnormalities identifiable by HRCT when compared with those seen with MRI are cochlea 42% (15/36), modiolus 35% (12/34), vestibulae 88% (23/26), endolymphatic duct 100% (18/18), and endolymphatic sac 6% (1/17). CONCLUSION: MRI is more sensitive and specific in diagnosing soft tissue abnormalities in the inner ear than HRCT in cochlear implant candidates (Fig. 4). Moreover, the abnormalities detected with MRI are more likely to influence the implantation process (e.g., asymmetric nerve aplasia, cochlear obstruction). (Figure is included in full-text article).     

Cochlear implantation in children with congenital inner ear malformations

OBJECTIVE/HYPOTHESIS: To assess the audiologic and surgical outcomes for pediatric cochlear implant patients with inner ear malformations. STUDY DESIGN: Retrospective review of 315 pediatric cochlear implant cases from 1994 to 2002. METHODS: Twenty-eight pediatric cochlear implant patients with known inner ear malformations determined on high-resolution computed tomography (HRCT) of the temporal bone were the subjects of review. Results of HRCT findings, intraoperative findings, postoperative complications, and objective measures of both closed- and open-set testing of speech perception were analyzed. RESULTS: Patients with the constellation of an incompletely partitioned (IP) cochlea, enlarged vestibular aqueduct (EVA), and a dilated vestibule (i.e., Mondini's malformation) as well as those with an isolated EVA or partial semicircular canal aplasia have relatively good levels of speech perception. Patients with total semicircular canal aplasia, isolated IP, cochlear hypoplasia, or common cavity demonstrated lower levels of performance. Poor performance may be related to associated developmental delays rather than labyrinthine anatomy alone. Complications of surgery were relatively limited. CONCLUSIONS: Cochlear implantation can be successfully performed in children with inner ear malformations. These children and their parents can expect significant auditory benefits from this intervention. The various types of inner ear malformations may have quite different prognoses for good auditory performance.     

Cochlear implantation in patients with substantial residual hearing

OBJECTIVES: Cochlear implantation is an effective means for providing auditory rehabilitation in adult patients with severe to profound sensorineural hearing loss. It has been hypothesized that patients with substantial, preoperative residual hearing would be excellent cochlear implant candidates because of surviving neural populations and a lack of auditory deprivation. The purpose of this study is to describe the outcomes of patients with substantial residual hearing who have undergone cochlear implantation. STUDY DESIGN: Retrospective chart review of patients with substantial preoperative residual hearing who underwent cochlear implantation. METHODS: Chart reviews were completed for patients with substantial residual hearing who underwent cochlear implantation (City University of New York Sentence Test [CUNY] > 60%, Hearing in Noise Test sentences presented in quiet [HINTQ] > 50%, or Consonant-Nucleus-Consonant [CNC] > 20% in the ear to be implanted). Preoperative and postoperative measures of audiologic performance as well as complications were assessed. RESULTS: All 12 patients who met inclusion criteria ultimately surpassed their preoperative aided performance level after implantation and gained significant benefit from their cochlear implant. At 6 months postimplantation, mean CUNY, HINTQ, and CNC scores were 93%, 78%, and 48% in the implant ear alone, respectively. However, progress was slower than expected for many patients, and at least one patient took 1 year to surpass his preoperative performance level. There were no complications from surgery in this selected group of patients. CONCLUSIONS: Patients with some degree of residual hearing do benefit from cochlear implantation. However, there may be an initial decline in performance as compared with preoperative levels. This decline is overcome in time in this patient population. These patients need to be counseled accordingly.     

Cochlear implants in systemic autoimmune vasculitis syndromes

The concept that autoimmunity may damage the inner ear was introduced by McCabe in 1979. Audiovestibular symptoms may occur in isolation or may be mediated by vasculitis in patients affected by systemic autoimmune disorders. Sensorineural hearing loss (SNHL) is typical in Cogan's syndrome but occurs less frequently in Be?het's syndrome and in systemic necrotizing vasculitides. Patients affected by immune-mediated profound SNHL represent ideal candidates for cochlear implantation as these patients become deaf after years of hearing. The disease itself and the medication taken may, however, influence the prognosis of cochlear implantation in these patients. We retrospectively evaluated the pre- and intraoperative findings as well as the postoperative course and performance of a group of five patients affected by a systemic vasculitis syndrome who received a cochlear implant. Implantation was successful in all patients, no complications occurred and excellent postoperative speech perception was achieved. We conclude that cochlear implantation in patients affected by immune-mediated inner ear disorders is effective although the long-term results remain to be evaluated.     

Optical coherence tomography imaging of the inner ear: a feasibility study with implications for cochlear implantation

Cochlear implantation is now being performed in ears with residual hearing. Those implant recipients who keep residual hearing may benefit from improved pitch resolution through both electrical and acoustic hearing. Preservation of cochlear function after implantation is a challenging task for the surgeon. Current topics of hearing preservation research include electrode design and surgical technique. To maintain hearing, surgeons strive to create a cochleostomy and place the electrode in a minimally traumatic fashion. In this study, we examine a novel catheter-based real-time imaging modality with 10- to 15-microm resolution, optical coherence tomography (OCT), on the inner ear. We demonstrate the capability of OCT to allow visualization of inner ear structures through bone in live mice. We additionally used OCT to image the inner ear in a human temporal bone. Optical coherence tomography was able to delineate soft tissue structures within the cochlea and may be useful as an adjunct to cochlear implantation. Other potential otologic applications of OCT are discussed.     

Preoperative Temporal Bone Computed Tomography Scan and Its Use in Evaluating the Pediatric Cochlear Implant Candidate

Preoperative computed tomography (CT) scan evaluation of the temporal bones in cochlear implant candidates plays a crucial role in determining candidacy and the side of implantation. The CT scans allow the surgeon to carefully review the anatomy of the inner ear and mastoid cavity in order to predict any potential difficulties or complications that may be encountered during the implant insertion. We retrospectively reviewed 50 preoperative CT scans of the temporal bone in children who have been successfully implanted. In these scans, we assessed the degree of mastoid pneumatization, cochlear anatomy and patency, size of the vestibular aqueduct, cochlear aqueduct, and internal auditory canal. We analyzed our findings and measurements and compared our results with the degree of difficulty noted in the insertion of the implant, the number of electrodes inserted in each case, and the overall complication rate. From this radiographic review, we have created a checklist for cochlear implant surgeons in order to highlight key features that need to be recognized in the temporal bone scan in preoperative evaluation of cochlear implant candidates.     

Cochlear implantation in children

Cochlear implantation has revolutionized the treatment and prognosis of children with severe to profound sensorineural hearing loss who receive limited benefits from hearing aids. Children who receive cochlear implantation at young age, in particular before 2 years of age, can be expected to reach their normal age-equivalent developmental milestones and have higher chance to integrate into the mainstream educational settings. With the positive outcomes after cochlear implantation and the improvements in technology and surgical techniques, candidacy for cochlear implantation in children has been expanding to include hearing-impaired children with significant residual hearing, severe inner ear malformations, multiple handicaps such as mental retardation or visual impairment, and auditory neuropathy. Furthermore, there is growing interest in offering bilateral cochlear implantation to give children the benefits of binaural hearing. As the candidacy criteria expand, cochlear implant programs including preoperative evaluation, surgery, and habilitation have become more complex. Therefore, candidates should be selected prudently by multidisciplinary approach and cochlear implantation in children is much better to be provided by experienced cochlear implant team consisting of experts in relevant fields for the best results.