Imaging for cochlear implantation: Structuring a clinically relevant report

Cochlear Implantation: Systematic Approach to Preoperative Radiologic Evaluation

Sensorineural hearing loss results from abnormalities that affect the hair cells of the membranous labyrinth, inner ear malformations, and conditions affecting the auditory pathway from the cochlear nerve to the processing centers of the brain. Cochlear implantation is increasingly being performed for hearing rehabilitation owing to expanding indications and a growing number of children and adults with sensorineural hearing loss. An adequate understanding of the temporal bone anatomy and diseases that affect the inner ear is paramount for alerting the operating surgeon about variants and imaging findings that can influence the surgical technique, affect the choice of cochlear implant and electrode type, and help avoid inadvertent complications. In this article, imaging protocols for sensorineural hearing loss and the normal inner ear anatomy are reviewed, with a brief description of cochlear implant devices and surgical techniques. In addition, congenital inner ear malformations and acquired causes of sensorineural hearing loss are discussed, with a focus on imaging findings that may affect surgical planning and outcomes. The anatomic factors and variations that are associated with surgical challenges and may predispose patients to periprocedural complications also are highlighted. ^© RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

The feasibility of cochlear implantation in early infancy

OBJECTIVES

To determine the key image anatomical parameters that are relevant to cochlear implantation (CI) using temporal bone high-resolution computed tomography (HRCT) scans and to identify age group differences in order to provide image anatomical support for early CI.

METHODS

The data of 346 temporal bone HRCTs of 173 children from 5 months to 18 years of age were retrospectively selected and reviewed. Parameters of the human temporal bone that are relevant to CI key surgical steps include mastoid thickness (MT), the facial recess width (FRW), and an angle representing the round window visibility. All measurements are performed on axial images.

RESULTS

There was no significant difference in the above morphological values by gender (p > 0,05). Two-sided FRW was not significantly different (p > 0,05), but MT and angle A were significantly different (p < 0,001). FRW and angle were independent of age (p > 0,05). However, MT had been found to exhibit postnatal development. The linear function of MT were calculated as y = 2463 × group(s) + 20,574 (p < 0,001).

CONCLUSIONS

Based on preoperative imaging analysis at different ages, middle ear development was stable at 5 months of age, allowing early CI in infancy with severe to severe hearing loss at this age. These data must be considered exploratory and more extensive clinical studies are needed.

Transtympanic Visualization of Cochlear Implant Placement With Optical Coherence Tomography: A Pilot Study

OBJECTIVE

This study aimed to evaluate the ability of transtympanic middle ear optical coherence tomography (ME-OCT) to assess placement of cochlear implants (CIs) in situ.

PATIENT

A 72-year-old man with bilateral progressive heredodegenerative sensorineural hearing loss due to work-related noise exposure received a CI with a slim modiolar electrode for his right ear 3 months before his scheduled checkup.

INTERVENTION

A custom-built swept source ME-OCT system (λo = 1550 nm, ∆λ = 40 nm) designed for transtympanic middle ear imaging was used to capture a series of two- and three-dimensional images of the patient's CI in situ. Separately, transtympanic OCT two-dimensional video imaging and three-dimensional imaging were used to visualize insertion and removal of a CI with a slim modiolar electrode in a human cadaveric temporal bone through a posterior tympanotomy.

MAIN OUTCOME MEASURE

Images and video were analyzed qualitatively to determine the visibility of implant features under ME-OCT imaging and quantitatively to determine insertion depth of the CI.

RESULTS

After implantation, the CI electrode could be readily visualized in the round window niche under transtympanic ME-OCT in both the patient and the temporal bone. In both cases, characteristic design features of the slim modiolar electrode allowed us to quantify the insertion depth from our images.

CONCLUSIONS

ME-OCT could potentially be used in a clinic as a noninvasive, nonionizing means to confirm implant placement. This study shows that features of the CI electrode visible under ME-OCT can be used to quantify insertion depth in the postoperative ear.

Temporal bone computed tomography checklist-TeSLANO: introduction of a standardized preoperative imaging evaluation for middle ear surgery

PURPOSE

Aim of the study was to evaluate if the introduction of the imaging checklist TeSLANO would improve the identification of crucial anatomical findings from temporal bone computed tomography (TBCT) scans among a cohort of Otolaryngology residents.

STUDY DESIGN

Single-blinded prospective cohort study.

SETTING

Tertiary care university hospital and referral center for otology and skull base surgery.

METHODS

The cohort was composed by eight Otorhinolaryngology residents (four junior and four senior) that were individually asked to identify all relevant anatomic findings from preoperative TBCT scans. Supervising surgeon showed to each resident four TBCT scans before and four after the introduction of a systematic checklist evaluation system based on the TeSLANO acronym. Statistical analysis was performed using McNemar's test and results were considered significant with a P value < 0.05.

RESULTS

Introduction of the checklist improved global identification of critical anatomical structures from 48.75 to 89.17% (P < 0.05). The postimplementation identification percentage improved for both the senior and junior groups (P < 0.05).

CONCLUSIONS

The imaging checklist TeSLANO allows a systematic approach to review TBCT scans and significantly improves identification of critical anatomical structures in Otorhinolaryngology residents.

Utility and value of pre-operative CT and MRI for cochlear implantation in the elderly

PURPOSE

To determine the utility and value of pre-operative imaging among the elderly population ≥70 y.o. with bilateral progressive sensorineural hearing loss undergoing cochlear implantation.

MATERIALS AND METHODS

A retrospective, cross-sectional review was performed at a tertiary referral center between 2010 and 2018 including patients ≥70 y.o. with bilateral presbycusis who underwent preoperative imaging and cochlear implantation. Primary outcome was whether pre-operative imaging changed the surgeon's surgical plan such as side of implant or abort procedure entirely. Patient characteristics including age, sex, side of implant, imaging modality, whether imaging changed surgical plan, and surgical complications were reviewed. One-way analysis of variance with post-hoc tests using the Bonferroni and Fisher's exact test were used to examine differences between groups. Secondary outcome was cost of preoperative imaging.

RESULTS

One hundred thirty-three patients (mean age 79.38 [5.51 SD]) who underwent a total of 142 surgical cases and 147 total scans. There were 92, 27, and 14 patients who underwent CT, MRI, or both, respectfully (n=133). Of the 142 implants that were placed, preoperative imaging did not reveal a contraindication to placing implant on one side over another. Total cost of imaging was $29,694. Estimated cost if 20% of cochlear implant eligible patients ≥70 y.o. underwent imaging is $7,763,490.

CONCLUSION

Decreasing unnecessary preoperative imaging can potentially decrease cost in cochlear implantation. In this sample, preoperative imaging did not affect the surgeon's choice of which side to operate on. However, imaging may provide an anatomic roadmap and contribute to either surgical confidence or caution. With the increasing amount of cochlear implant eligible elderly adults, preoperative imaging needs to be more clearly defined in this unique population.

Radiological and surgical aspects of round window visibility during cochlear implantation: a retrospective analysis

Purpose

The round window approach has become the most preferred option for cochlear implant (CI) insertion, however, sometimes it may not be possible due to the (in)visibility of the round window membrane (RWM). We addressed the prevalence, consequences and indicators of difficult detection of the RWM in cochlear implant surgery.

Methods

This study retrospectively analysed the operative reports and preoperative high resolution axial-computed tomography (CT) scans of a consecutive cohort of patients who underwent a CI insertion. The main outcomes were surgical outcomes of the RW approach, and assessment of radiological markers.

Results

The operative reports showed that RWM insertion was feasible in 151 out of 153 patients. In 18% of the patients the RWM was difficult to visualize. All these patients had at least one intraoperative event. The chorda tympani nerve (CTN) or posterior canal wall was affected in 8% of the 153 patients and the fallopian canal in 6%. These patients had a facial-chorda tympani nerve distance on the CT scan that was considerably smaller than normal patients (1.5 mm vs 2.3 mm). In addition, a prediction line towards the anterolateral side of the RWM was found to be more prevalent in these patients’ CT scans (sensitivity 81%, specificity 63%).

Conclusion

The RW approach is feasible in almost all patients undergoing CI surgery. Difficult visualisation of the RWM seems to lead to at least one intraoperative event. Radiological measures showed that these patients had a smaller facial recess and a more anteriorly placed facial nerve, which can be used to better plan a safe insertion approach.

Cone-beam CT versus Multidetector CT in Postoperative Cochlear Implant Imaging: Evaluation of Image Quality and Radiation Dose

BACKGROUND AND PURPOSE

Cone-beam CT is being increasingly used in head and neck imaging. We compared cone-beam CT with multidetector CT to assess postoperative implant placement and delineate finer anatomic structures, image quality, and radiation dose used.

MATERIALS AND METHODS

This retrospective multicenter study included 51 patients with cochlear implants and postoperative imaging via temporal bone cone-beam CT (n = 32 ears) or multidetector CT (n = 19 ears) between 2012 and 2017. We evaluated the visualization quality of single electrode contacts, the scalar position of the electrodes, cochlear walls, mastoid facial canal, metallic artifacts (using a 4-level visual score), and the ability to measure the insertion angle of the electrodes. The signal-to-noise ratio and radiation dose were also evaluated.

RESULTS

Cone-beam CT was more sensitive for visualizing the scalar position of the electrodes (P = .046), cochlear outer wall (P = .001), single electrode contacts (P < .001), and osseous spiral lamina (P = .004) and had fewer metallic artifacts (P < .001). However, there were no significant differences between both methods in visualization of the modiolus (P = .37), cochlear inner wall (P > .99), and mastoid facial canal wall (P = .07) and the ability to measure the insertion angle of the electrodes (P > .99). The conebeam CT group had significantly lower dose-length product (P < .001), but multidetector CT showed a higher signal-to-noise ratio in both bone and air (P = .22 and P = .001).

CONCLUSIONS

Cone-beam CT in patients with cochlear implants provides images with higher spatial resolution and fewer metallic artifacts than multidetector CT at a relatively lower radiation dose.

The Feasibility of Magnetic Resonance Imaging Without General Anesthesia Using the "Bundle and Scan" Technique for Infants With Sensorineural Hearing Loss

OBJECTIVE

The purpose of this study is to determine the feasibility of magnetic resonance imaging (MRI) without general anesthesia (GA) for infants being evaluated for sensorineural hearing loss (SNHL) using the bundle and scan technique.

STUDY DESIGN

Retrospective study.

SETTING

Pediatric tertiary care hospital.

PATIENTS

All infants who underwent MRI using the bundle and scan technique as part of the diagnostic workup for unilateral or bilateral SNHL between June 2016 to April 2019 were included.

MAIN OUTCOME MEASURE

The primary outcome was the proportion of clinically useful images produced.

RESULTS

We reviewed 21 bundle and scan MRI examinations in infants being evaluated for SNHL. Patients had a median age of 10 (range: 6-25) weeks at the time of MRI. Motion artifact was noted in 38% (8/21) of cases. Eighty-six percent (18/21) of the magnetic resonance images produced using the bundle and scan technique were of diagnostic quality and/or sufficient for surgical planning for cochlear implantation. Repeat imaging with GA was required for three cases (14%) as the initial images were not clinically useful. All patients requiring GA had unilateral SNHL. All patients with bilateral SNHL successfully underwent MRI without GA using the bundle and scan technique.

CONCLUSION

The results of our study demonstrate that it is feasible to perform MRI using the bundle and scan technique in the majority of young infants being evaluated for SNHL. This has the potential to help determine cochlear implant candidacy earlier, reduce exposure to GA, and reduce healthcare costs.

The role of preoperative imaging for auditory implants in children

&lt;b&gt;Introduction:&lt;/b&gt; Preoperative imaging, besides audiological evaluation, plays a major role in evaluation of candidacy for auditory implants, and in particular cochlear implants. It is essential to assess whether the basic criteria necessary for implantation are met. Diagnostic imaging is crucial not only in determining candidacy, but also determining the feasibility of cochlear implantation as it allow to anticipate surgical difficulties which could preclude or complicate the implantation of the device. The aim of the study is to present the protocol for the evaluation of preoperative imaging studies with particular focus on the factors potentially affecting clinical decisions in children qualified for cochlear implantation. &lt;br&gt;&lt;b&gt;Material and method:&lt;/b&gt; Preoperative imaging studies of 111 children performed prior to cochlear implantation were analyzed: high-resolution computed tomography (HRCT) of temporal bones and MRI. The assessment was made according to the presented protocol. &lt;br&gt;&lt;b&gt;Results:&lt;/b&gt; Pathologies and anomalies identified during the assessment of preoperative imaging studies significantly altered clinical decisions in 30% of patients. In the study group, in 17% of patients inner ear malformations were identified. 2.7% of children were disqualified from a cochlear implantation due to severe congenital inner ear malformations. 9% of the patients have had bacterial meningitis. In 50% of them difficulties related to complete or progressive cochlear ossification occurred. In 4.5% of patients less common surgical approaches other than mastoidectomy with a posterior tympanotomy were applied. &lt;br&gt;&lt;b&gt;Discussion:&lt;/b&gt; Preoperative imaging allow for the identification of significant pathologies and anomalies affecting qualification decisions and further treatment. HRCT and MRI are complementary to each other for preoperative imaging. The two modalities in combination allow accurate and optimal evaluation of the anatomical structures prior to implantation. Inner ear malformations and cochlear ossification following meningitis are relatively frequently encountered in children qualified for a cochlear implant.

Predictors of round window membrane visibility in pediatric cochlear implant surgery using temporal bone HRCT: A retrospective study

OBJECTIVE

To predict round window membrane (RWM) visibility and electrode insertion sites using high-resolution computed tomography (HRCT) in pediatric cochlear implant surgery.

MATERIALS AND METHODS

Sixty-two ears of 36 infants less than 1 year old were included in our study. Intraoperative RWM visibility was classified into three types corresponding to three different surgical approaches. Radiologic parameters were measured on preoperative axial temporal HRCT images and correlated with RWM visibility and surgical approaches.

RESULTS

A significant correlation was found between the degree of RWM visibility and the following two parameters: 1) a line (l_w) was drawn from the posterior margin of the RWM to the intersection point of the posterior wall of the external auditory canal (EAC) and mastoid cortex. Another line (l_f) was drawn between the posterior margin of the RWM and the lateral margin of the FN. The angle between l_w and l_f was measured as angle A, P < 0.01, R² = -0.809; 2) a line (l_m) was drawn from the anterior to posterior margin of the RWM, and the angle between l_m and l_f was measured as angle B, P < 0.01, R² = -0.850. A nonsignificant correlation was found between the degree of RWM visibility and the facial recess width, p > 0.05, R² = -0.00015.

CONCLUSION

RWM visibility showed a high correlation with the two angular measurements (angle A and angle B) and was associated with electrode insertion sites. In children less than one year old, surgeons can depend on those two parameters in predicting the RWM visibility.

CT-scan contouring technique allows for direct and reliable measurements of the cochlear duct length: implication in cochlear implantation with straight electrode-arrays

OBJECTIVES

The advent of hybrid electro-acoustic implants requires precise positioning of the electrode-array (EA) within the cochlea. The cochlea size, that is, the length of the cochlear scala tympani, is often indirectly estimated from distance A by Escudé's method. This technique has been confirmed by anatomical studies, in a bunch of cadaveric specimens, but it is not yet widely established in the field of computed tomography (CT). We compared cochlear duct length obtained by Escudé's method to those directly acquired on CT images.

MATERIALS AND METHODS

The lengths of cochlear scala tympani were directly measured on CT scans by contouring the external cochlear wall (contouring technique-CoT). In fifteen patients implanted with a straight EA, the length of the EA and the measured length of the cochlea by the CoT were compared, to check the reliability of the CoT. Then, in 200 CT-scans, the length of the cochlear duct was measured by the CoT then compared to Escudé's method.

RESULTS

In the 200 CT-scans which served for cochlear length measurements, a significant variability between the cochleae were observed, as expected. At 360°, the correlation between the measurements of the length of the cochlear scala tympani between the two techniques differed, with a difference of 0.2 ± 0.7 mm at 360° (extreme: 2 mm; p < 0.001) and 2.2 ± 1.2 mm at 540° (extreme: 5.6 mm; p < 0.001).

CONCLUSION

The CoT can predict with accuracy the length of EA-insertion depth, more precisely than estimation methods such as Escudé's.

Efficacy of a selective imaging paradigm prior to pediatric cochlear implantation

OBJECTIVES/HYPOTHESIS

There is no consensus on the necessary preoperative imaging in children being evaluated for cochlear implantation (CI). Dual-imaging protocols that implement both magnetic resonance imaging (MRI) and high resolution computed tomography (HRCT) create diagnostic redundancy in the face of potentially unnecessary radiation and anaesthetic exposure. The objectives of the current study were to examine the efficacy of an MRI-predominant with selective HRCT imaging protocol.

STUDY DESIGN

Retrospective review.

METHODS

The protocol was implemented over a 4-year period, during which HRCT was obtained in addition to MRI only if specific risk factors on clinical assessment were identified or if imaging findings in need of further evaluation were detected on initial MRI evaluation. Retrospective review of operative reports and prospective review of imaging were performed; anesthetic exposure and costing information were also obtained.

RESULTS

Of the 240 patients who underwent assessment, seven (2.9%) had combined HRCT and MRI performed concurrently based on initial clinical assessment, 15 (6.3%) underwent HRCT based on imaging anomalies found on MRI, and MRI alone was ordered for the remaining 218 (90.1%). All patients were implanted without complication. Overall, radiation exposure, general anesthesia (GA), and healthcare costs were reduced.

CONCLUSIONS

MRI alone can be used in the vast majority of cases for preoperative evaluation of pediatric CI candidates resulting in a significant reduction in healthcare costs, radiation, and GA exposure in children. The additional need for HRCT occurs in a small proportion and can be predicted up front on clinical assessment or on initial MRI.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2627-2633, 2019.

Surgeon Oriented Preoperative Radiologic Evaluation in Cochlear Implantation - Our experience with a Proposed Checklist

Introduction  Preoperative temporal bone imaging studies have been routinely performed prior to cochlear implantation. Radiologists need to report these examinations with special focus on the surgeon's expectations. Objectives  To provide a basic structured format, in the form of a checklist, for reporting preoperative computed tomography (CT) and to its clinical impact on operative findings. Methods  The preoperative temporal bone CT scans of 47 patients were analyzed and reported according to the proposed checklist. Intraoperative assessment of mastoidectomy, posterior tympanotomy and round window access was done by the surgeon in a blinded fashion and were correlated with the radiological findings to assess its significance. Results  The proposed radiological checklist was reliable in assessing operative difficulty during cochlear implantation. Contracted mastoid and lower tegmen position were associated with a greater difficulty of the cortical mastoidectomy. Presence of an air cell around the facial nerve (FN) was predictive of easier facial recess access exposure. Facial nerve location and posterior external auditory canal (EAC) wall inclination were predictive of difficult round window (RW) accessibility. Conclusion  Certain parameters on the preoperative temporal bone CT scan may be useful in predicting potential difficulties encountered during the key steps involved in cochlear implant surgery.

Bony cochlear nerve canal and internal auditory canal measures predict cochlear nerve status

Objectives:

The bony cochlear nerve canal is the space between the fundus of the internal auditory canal and the base of the cochlear modiolus that carries cochlear nerve fibres. This study aimed to determine the distribution of bony labyrinth anomalies and cochlear nerve anomalies in patients with bony cochlear nerve canal and internal auditory canal atresia and stenosis, and then to compare the diameter of the bony cochlear nerve canal and internal auditory canal with cochlear nerve status.

Methods:

The study included 38 sensorineural hearing loss patients (59 ears) in whom the bony cochlear nerve canal diameter at the mid-modiolus was 1.5 mm or less. Atretic and stenotic bony cochlear nerve canals were examined separately, and internal auditory canals with a mid-point diameter of less than 2 mm were considered stenotic. Temporal bone computed tomography and magnetic resonance imaging scans were reviewed to determine cochlear nerve status.

Results:

Cochlear hypoplasia was noted in 44 out of 59 ears (75 per cent) with a bony cochlear nerve canal diameter at the mid-modiolus of 1.5 mm or less. Approximately 33 per cent of ears with bony cochlear nerve canal stenosis also had a stenotic internal auditory canal and 84 per cent had a hypoplastic or aplastic cochlear nerve. All patients with bony cochlear nerve canal atresia had cochlear nerve deficiency. The cochlear nerve was hypoplastic or aplastic when the diameter of the bony cochlear nerve canal was less than 1.5 mm and the diameter of the internal auditory canal was less than 2 mm.

Conclusion:

The cochlear nerve may be aplastic or hypoplastic even if temporal bone computed tomography findings indicate a normal cochlea. If possible, patients scheduled to receive a cochlear implant should undergo both computed tomography and magnetic resonance imaging of the temporal bone. The bony cochlear nerve canal and internal auditory canal are complementary structures, and both should be assessed to determine cochlear nerve status.

Taste Disturbance Due to Cochlear Implant Stimulation

OBJECTIVE

To characterize stimulation of taste fibers in the facial nerve following cochlear implantation.

PATIENT

A 34-year old presented with reversible dysgeusia following activation of a cochlear implant.

INTERVENTION

Reprogramming targeted to specific offending electrodes reduced symptom intensity. Computed tomography demonstrated dehiscence of the bone separating the labyrinthine segment of the facial nerve and the basal turn of the cochlea in proximity to the electrode array.

RESULTS

Dysgeusia was attributed to stimulation of taste fibers in the facial nerve by electrodes 13 to 16 of the cochlear implant array located in the superior-most portion of the basal turn.

CONCLUSIONS

Dysgeusia following cochlear implant activation has not previously been reported. This likely results from stimulation of taste fibers through dehiscence of the bone separating the labyrinthine segment of the Fallopian canal and the basal turn of the cochlea. While in some cases of apparent dehiscence there may be thin bone present, recognition of this potential anatomic feature may influence the choice of which ear and which electrode design to implant.

Cochlear implantation in a subject with a narrow facial recess: Importance of preoperative radiological findings

OBJECTIVE

This case report aims to emphasize the importance of preoperative computed tomography to evaluate the anatomy of the facial recess (FR) in order to prevent complications during cochlear implantation (CI) and to discuss alternative surgical approaches for the management of a narrow FR. Failure to notice this anomaly may result in facial nerve (FN) injury or inability to complete CI.

CASE PRESENTATION

A 50-year-old female with bilateral sensorineural hearing loss presented for CI. High-resolution CT (HRCT) demonstrated a narrow FR; specifically the space between the vertical segment of the FN and external auditory canal (EAC) was narrow. A section of the EAC was removed to obtain adequate exposure and was repaired with a cartilage graft following CI.

CONCLUSION

CI surgery may be difficult in patients with a narrow FR. Such surgical difficulty could be avoided if cochlear implant surgeons have adequate preoperative radiological imaging to evaluate the anatomy of the temporal bone. HRCT is the only modality that can detect this abnormality preoperatively. If the surgeon identifies this abnormality on preoperative HRCT, an alternative surgical technique could be used.

Semicircular Canal Fibrosis as a Biomarker for Lateral Semicircular Canal Function Loss

Background and purpose

Radiological abnormalities at the level of the semicircular canals are frequently observed without known correlation to a pathologic condition or function. They include narrowing or sclerosis on computed tomography (CT) and narrowing or signal loss on T2-weighted magnetic resonance imaging (MRI). Our hypothesis was that these radiological abnormalities at the level of the semicircular canals reflect an aspecific but advanced stage of vestibular decay.

Materials and methods

Retrospective study in 35 consecutive patients with bilateral profound deafness eligible for cochlear implantation. Electronystagmography, CT, and MRI were performed as part of evaluation for cochlear implant candidacy.

Results

In our population, 31.4% had a bilateral lateral semicircular canal function loss, while 11.4% had a unilateral lateral semicircular canal function loss. CT-scan abnormalities did not correlate to lateral semicircular canal function loss at a statistically significant level. However, abnormalities observed on MRI correlated significantly with ipsilateral lateral semicircular canal function loss. This statistically significant difference was present not only if abnormalities were observed in at least one of the semicircular canals but also if we studied the posterior, superior, and lateral semicircular canals separately.

Conclusion

Semicircular canal abnormalities on T2-weighted MRI (including narrowing and/or signal loss in one or more semicircular canals) are correlated to lateral semicircular canal function loss.

Three-dimensional models of cochlear implants: A review of their development and how they could support management and maintenance of cochlear implant performance

Three-dimensional (3D) computational modeling of the auditory periphery forms an integral part of modern-day research in cochlear implants (CIs). These models consist of a volume conduction description of implanted stimulation electrodes and the current distribution around these, coupled with auditory nerve fiber models. Cochlear neural activation patterns can then be predicted for a given input stimulus. The objective of this article is to present the context of 3D modeling within the field of CIs, the different models, and approaches to models that have been developed over the years, as well as the applications and potential applications of these models. The process of development of 3D models is discussed, and the article places specific emphasis on the complementary roles of generic models and user-specific models, as the latter is important for translation of these models into clinical application.

Utility of preoperative computed tomography and magnetic resonance imaging in adult and pediatric cochlear implant candidates

OBJECTIVES/HYPOTHESIS

Determine the utility of preoperative imaging in adult and pediatric cochlear implant candidates.

STUDY DESIGN

Retrospective chart review.

METHODS

Medical records of 101 consecutive adult and 20 consecutive pediatric patients who underwent 137 cochlear implantation (CI) procedures at a single institution were reviewed.

RESULTS

Computed tomography (CT) was obtained preoperatively in 110 (90.9%) patients, preoperative magnetic resonance imaging (MRI) was obtained in 102 (84.3%) patients, and both were obtained in 94 (77.7%) patients. MRI revealed one acoustic neuroma and two meningiomas, which affected surgical planning for three (2.2%) procedures. MRI identified enlarged vestibular aqueduct (EVA) in 2.0% of adult patients. CT demonstrated middle ear disease in four (3.3%) patients. CT was useful in indicating round window and cochlear patency in three (2.2%) patients with cochlear otosclerosis. Twenty pediatric patients underwent 27 CI procedures. Preoperative CT in the pediatric cohort demonstrated five (25%) dysplastic cochleae, three (15%) dysplastic vestibules and/or semicircular canals, and three (15%) EVAs. In one patient, CT demonstrated a duplicated right internal auditory canal (IAC) and hypoplastic left IAC; MRI confirmed hypoplastic cochlear nerves.

CONCLUSIONS

Preoperative MRI can demonstrate retrocochlear pathology, cochlear patency, and EVA in adults being evaluated for cochlear implantation. CT may provide additional information in patients with chronic otitis media or otosclerosis. However, in postlingually deafened adults without conductive or asymmetrical hearing loss, imaging is unlikely to affect surgical decision making. Both CT and MRI can identify anomalies in pediatric patients. MRI does not offer substantial benefit over CT for routine evaluation of pediatric inner ear and temporal bone anatomy.

LEVEL OF EVIDENCE

4 Laryngoscope, 126:1440-1445, 2016.