Anatomic variability of oval window as pertaining to stapes surgery.

PURPOSE: The purpose of the study is to study the details of dimensions and shape of oval window in different age groups, sides and genders and their clinical implications. The oval window is a key structure while performing surgeries in relation to stapes. An intricate knowledge of the shape and size of the oval window is important for the reconstruction and fitting of cartilage compatible with the native shape of the oval window. METHODS: Sixty normal wet cadaveric temporal bones of known age; gender and side were micro-dissected. The maximum height and width of the oval window was measured. The shape of the oval window was noticed. RESULTS: The mean value for maximum height and width of the oval window was 1.31 ± 0.28 mm and 2.67 ± 0.42 mm, respectively. The height and width of the oval window ranged between 1 mm and 1.5 mm and 2 mm and 3 mm in majority of the cases. he oval window was found to be oval shaped in 53.3% cases, other shapes such as kidney, D shape, rectangular or trapezoidal were also observed. CONCLUSIONS: The refined morphometric information of the oval window will help in preoperative assessment and surgical planning of various oval window-related surgical procedures. The knowledge may also help in designing and selecting proper cartilage shoe for the best outcome. Narrow oval window may cause procedural complications and surgeon discomfort in various stapes surgeries.

Applied anatomy of round window and adjacent structures of tympanum related to cochlear implantation / Anatomia aplicada da janela redonda e estruturas adjacentes relacionadas ao implante coclear

Abstract Introduction: Various aspects of the round window anatomy and anatomy of posterior tympanum have relevant implications for designing cochlear implant electrodes and visualizing the round window through facial recess. Preoperative information about possible anatomical variations of the round window and its relationships to the adjacent neurovascular structures can help reduce complications in cochlear implant surgery. Objective: The present study was undertaken to assess the common variations in round window anatomy and the relationships to structures of the tympanum that may be relevant for cochlear implant surgery. Methods: Thirty-five normal wet human cadaveric temporal bones were studied by dissection for anatomy of round window and its relation to facial nerve, carotid canal, jugular fossa and other structures of posterior tympanum. The dissected bones were photographed by a digital camera of 18 megapixels, which were then imported to a computer to determine various parameters using ScopyDoc 8.0.0.22 version software, after proper calibration and at 1× magnification. Results: When the round window niche is placed posteriorly and inferiorly, the distance between round window and vertical facial nerve decreases, whereas that with horizontal facial nerve increases. In such cases, the distance between oval window and round window also increases. Maximum height of the round window in our study ranged from 0.51-1.27 mm (mean of 0.69 ± 0.25 mm). Maximum width of round window ranged from 0.51 to 2.04 mm (mean of 1.16 ± 0.47 mm). Average minimum distance between round window and carotid canal was 3.71 ± 0.88 mm (range of 2.79-5.34 mm) and that between round window and jugular fossa was 2.47 ± 0.9 mm (range of 1.24-4.3 mm). Conclusion: The distances from the round window to the oval window and facial nerve are important parameters in identifying a difficult round window niche. Modification of the electrode may be a better option than drilling off the round window margins for insertion of cochlear implant electrodes.

Resumo Introdução: Vários aspectos da anatomia da janela redonda e da anatomia da caixa timpânica posterior são relevantes, devido a suas implicações no desenho dos eletrodos para o implante coclear e na visibilidade da janela redonda através do recesso facial. Informações prévias sobre possíveis variações anatômicas da janela redonda e suas relações com as estruturas neurovasculares adjacentes podem ajudar a reduzir as complicações dessa cirurgia. Objetivo: O presente estudo foi realizado para avaliar as diversas variações da anatomia da janela redonda e sua relação com as estruturas adjacentes, o que pode ser relevante para a cirurgia de implante coclear. Método: Trinta e cinco ossos temporais normais de cadáveres humanos frescos foram dissecados para avaliação da anatomia da janela redonda e sua relação com o nervo facial, canal carotídeo, fossa jugular e outras estruturas da caixa timpânica posterior. Os ossos dissecados foram fotografados com uma câmera digital de 18 megapixels e as imagens importadas para um computador para determinar diversos parâmetros, utilizando-se o software ScopyDoc versão 8.0.0.22, após a calibração adequada e com ampliação de 1×. Resultados: Quando o nicho da janela redonda se encontra posicionado posteriormente e inferiormente, a distância entre a janela redonda e o nervo facial vertical diminui, enquanto aquela com o nervo facial horizontal aumenta. Em tais casos, a distância entre a janela oval e a janela redonda também aumenta. A altura máxima da janela redonda em nosso estudo variou de 0,51 a 1,27 mm (média de 0,69 ± 0,25 mm). A largura máxima da janela redonda variou de 0,51 a 2,04 mm (média de 1,16 a 0,47 mm). A distância mínima média entre a janela redonda e o canal carotídeo foi de 3,71 ± 0,88 mm (variação de 2,79 a 5,34 mm) e entre a janela redonda e a fossa jugular, em nosso estudo, foi de 2,47 ± 0,9 mm (variação de 1,24 ± 4,3 mm). Conclusão: A distância da janela redonda a partir da janela oval e do nervo facial são parâmetros importantes para a identificação do difícil nicho da janela redonda. A modificação do desenho do eletrodo pode ser uma opção melhor do que o broqueamento das margens da janela redonda para a inserção dos eletrodos no implante coclear.

Applied anatomy of round window and adjacent structures of tympanum related to cochlear implantation.

INTRODUCTION: Various aspects of the round window anatomy and anatomy of posterior tympanum have relevant implications for designing cochlear implant electrodes and visualizing the round window through facial recess. Preoperative information about possible anatomical variations of the round window and its relationships to the adjacent neurovascular structures can help reduce complications in cochlear implant surgery. OBJECTIVE: The present study was undertaken to assess the common variations in round window anatomy and the relationships to structures of the tympanum that may be relevant for cochlear implant surgery. METHODS: Thirty-five normal wet human cadaveric temporal bones were studied by dissection for anatomy of round window and its relation to facial nerve, carotid canal, jugular fossa and other structures of posterior tympanum. The dissected bones were photographed by a digital camera of 18 megapixels, which were then imported to a computer to determine various parameters using ScopyDoc 8.0.0.22 version software, after proper calibration and at 1× magnification. RESULTS: When the round window niche is placed posteriorly and inferiorly, the distance between round window and vertical facial nerve decreases, whereas that with horizontal facial nerve increases. In such cases, the distance between oval window and round window also increases. Maximum height of the round window in our study ranged from 0.51-1.27mm (mean of 0.69±0.25mm). Maximum width of round window ranged from 0.51 to 2.04mm (mean of 1.16±0.47mm). Average minimum distance between round window and carotid canal was 3.71±0.88mm (range of 2.79-5.34mm) and that between round window and jugular fossa was 2.47±0.9mm (range of 1.24-4.3mm). CONCLUSION: The distances from the round window to the oval window and facial nerve are important parameters in identifying a difficult round window niche. Modification of the electrode may be a better option than drilling off the round window margins for insertion of cochlear implant electrodes.

Three-Tesla magnetic resonance imaging of the vestibular endolymphatic space: A systematic qualitative description in healthy ears.

BACKGROUND AND PURPOSE: A detailed knowledge of the normal Magnetic Resonance (MR) anatomy of the vestibular endolymphatic space (ES) could be useful to understand the linkage between endolymphatic hydrops (EH) and Ménière's disease (MD). Our aim was to describe the MR anatomy of the vestibular ES as depicted by MR imaging in healthy ears. METHODS: This report describes a single-center retrospective study. Three readers analyzed the healthy ears of 22 consecutive patients who had undergone MRI for unilateral sudden hearing loss. The readers described the vestibular ES based on a delayed post-contrast 3D-FLAIR sequence according to six well-defined planes, three oblique sagittal (lateral, intermediate and medial) planes and three axial (superior, intermediate and inferior) planes. RESULTS: On sagittal lateral and intermediate planes, we identified the SSC ampulla combined with the utricle in 22/22 ears. On the sagittal medial plane, the saccule was detectable in 15/22 (68%) ears, having a club shape with the long axis oriented cranio-caudally; in 7/22 (32%) ears, the saccule presented an oval/round shape that appeared more conspicuously on the axial intermediate plane. The ES occupied the half superior portion of the vestibule in 22/22 ears, never contacting the round and oval windows. On the axial plane, in 17/22 cases, the ES showed a Y-shaped arrangement, while in 5/22 ears (23%), the ES presented a more globular shape. CONCLUSION: MR imaging represents a valid tool to explore the in vivo anatomy of the vestibular ES and to highlight its variability in normal ears.

Oval Window Size and Shape: a Micro-CT Anatomical Study With Considerations for Stapes Surgery.

BACKGROUND: The oval window is an important structure with regard to stapes surgeries, including stapedotomy for the treatment of otosclerosis. Recent study of perioperative imaging of the oval window has revealed that oval window niche height can indicate both operative difficulty and subjective discomfort during otosclerosis surgery. With regard to shape, structures incorporated into the oval window niche, such as cartilage grafts, must be compatible with the shape of the oval window. Despite the clinical importance of the oval window, there is little information regarding its size and shape. METHODS: This study assessed oval window size and shape via micro-computed tomography paired with modern morphometric methodology in the fetal, infant, child, and adult populations. Additionally, the study compared oval window size and shape between sexes and between left- and right-sided ears. RESULTS: No significant differences were found among traditional morphometric parameters among age groups, sides, or sexes. However, geometric morphometric methods revealed shape differences between age groups. Further, geometric morphometric methods provided the average oval window shape and most-likely shape variance. CONCLUSION: Beyond demonstrating oval window size and shape variation, the results of this report will aid in identifying patients among whom anatomical variation may contribute to surgical difficulty and surgeon discomfort, or otherwise warrant preoperative adaptations for the incorporation of materials into and around the oval window.

Round and Oval Window Anatomic Variability: Its Implication for the Vibroplasty Technique.

OBJECTIVE: The objective of this study is to evaluate the anatomical variability of round and oval window regions and its relationship with their closest structures, to determine its implication on the fitting and stabilization of the middle ear implant Vibrant Soundbridge. METHODS: Variations of the anatomy of round and oval window regions were assessed in a total of 85 human dissected temporal bones. Afterward, we evaluated the adaptation and subsequent stabilization of the floating mass transducer (FMT) of the Vibrant Soundbridge in 67 cases in round window (RW) and in 22 cases in oval window (OW), and the influence that the variability of the different anatomical features examined had on this stabilization. We also assessed access and surgeon's view of the RW niche through the facial recess approach. RESULTS: Stabilization of the FMT in the RW was achieved in 53 (79%) of the 67 cases; we found that the less favorable anatomical conditions for stabilization were: membrane smaller than 1.5 mm, presence of a high jugular bulb and a narrow or very narrow RW niche. Frequently, two or more of these conditions happened simultaneously. In seven cases (22%) access to the RW through facial recess approach did not allow positioning the FMT in place. OW stabilization succeeded in 18 (82%) of the 22 cases. CONCLUSION: Round and oval window vibroplasty are difficult surgical techniques. To place the FMT directly on the OW may be easier as we do not have to drill the niche. In both regions there are some anatomical conditions that hinder fitting the FMT and even make it impossible. Once fitted, the main problem is to achieve good stabilization of the device.

Anomalous facial nerve in congenital stapes fixation.

OBJECTIVE: The aim of this article was to assess the prevalence and influence of anomalous facial nerves in patients undergoing surgery for congenital stapes anomalies. PATIENTS: The medical records of all patients who underwent surgery for congenital stapes fixation between January 1999 and December 2012 were retrospectively reviewed. An abnormal facial nerve was found in 7 ears in 5 patients (from a total of 62 ears). MAIN OUTCOME MEASURES: The patients' temporal bone computed tomography results, operation records, video clips, and preoperative and postoperative hearing tests were reviewed. RESULTS: Oval window atresia was found in all 7 ears, and the facial nerves in all 7 ears ran inferior medially over the atretic oval window niche. The atretic plate was fenestrated into the vestibule in the superior margin of the facial nerve. A piston wire was anchored to the long process of the incus in 3 ears, to the handle of the malleus in 3 ears, and attached to the tympanic membrane in 1 ear. The postoperative ABG at long-term follow-up was 13.1 dB (SD, 4.6 dB; range, 8.8-18.3 dB). No patient had postoperative facial weakness. CONCLUSION: An anomalous facial nerve was found in 11.2% of ears in patients undergoing surgery for congenital stapes fixation. Despite the anomalous course of facial nerves in these patients, vestibular fenestration was successful without facial nerve damage. The audiometric outcome at long-term follow-up was serviceable hearing for all cases.

Surgical anatomy of round window and its implications for cochlear implantation.

The objective of this work was to study the morphometry and morphology of the round window (RW) and its relationships with the internal carotid artery, jugular bulb (JB), facial nerve and oval window (OW). Fifty cadaveric temporal bones were microdissected to expose the medial wall of the middle ear. The areas around the RW were cleared and its shape, height and width were noted. Its distances from the carotid canal (CC), jugular fossa (JF), facial canal (FC), and OW were measured. Oval, round, triangular, comma, quadrangular, and pear shapes of RW were observed. The average height and width of the RW were 1.62 ± 0.77 mm and 1.15 ± 0.39 mm, respectively. There was a statistically significant correlation (r = 0.4, P < 0.01) between the height and width. The distances between the RW and the CC, JF, FC, and OW were in the ranges 4.39-11.05 mm, 0.38-8.65 mm, 2.99-6.3 mm, and 1.39-3.57 mm, respectively. In 8% of cases, the distance between the RW and the JF was <1 mm. There were no statistically significant differences with regard to age group, gender, or side. Electrode insertion can be challenging in cases where the height and width of the RW are <1 mm. The thin bone separating the roof of the JF from the RW (<1 mm in 8%) highlights a potential risk of injury to the JB during cochleostomy placement. This information could be useful for selecting cochlear implant electrodes in order to avoid potential risks to vital neurovascular structures during implant surgery.

The windows of the inner ear.

The oval and round windows of the inner ear are important structures for the transmission of sound and may be affected by a variety of disease entities. The anatomy of this small area is one that often causes the radiology trainee some difficulty, but there are certain disease states that can be easily diagnosed when knowing where and how to look. As this area is very important to the otologist in a variety of preoperative settings, accurate assessment of the windows and recognition of important and potentially complex intra-operative anomalies, will greatly aid our surgical colleagues.

Measurements of the position relationship between the inferior margin of the oval window and the endosteum of basal cochlear turn in histologic and HRCT study.

HYPOTHESIS: To identify the optimum and safe location histologically for drilling and fenestration on promontory inferior to the oval window in stapedectomy. The value of application of high-resolution computed tomography (HRCT) scanning and multiple-planar reconstruction (MPR) for this purpose is also assessed. METHODS: By means of histologic sections and HRCT scanning and MPR for coronal image, measurements were conducted on 3 perpendicular planes in temporal bone sections through the anterior, posterior, and midpoint of the inferior margin of the oval window, respectively. RESULTS: The promontory bone inferior to the posterior portion of the oval window is thickest, which has an average thickness of about 1.1 mm. The endosteum of the basal turn here is deepest under the promontory, which has an average height of about 0.2 mm above the plane of footplate, whereas the distance between the inferior margin of the oval window and the endosteum here is no more than 0.3 mm. The coincidence rate of the measurements by HRCT and histology is up to 90.5%. CONCLUSION: Relatively safe location for bone of the promontory removal should be restricted in the posterior portion inferior to the oval window, and the burr should be lifted laterally while drilling. Preoperative HRCT scanning and MPR for coronal image would offer a valuable reference to estimate the safe area for bone of the promontory removal in stapedectomy.

[Clinical significance and anatomical relationship between the inferior margin of oval window and the endosteum of basal cochlear turn].

OBJECTIVE: To investigate the safety range of drilling and fenestration on promontory inferior to the oval window in difficult stapedectomy via anatomical study of the relationship between the inferior margin of oval window and the endosteum of basal cochlear turn. METHODS: By means of histological sections, the distances between the inferior margin of oval window and different locations of endosteum of basal cochlear turn, the corresponding height of the projecting endosteum and the thickness of promontory bone, on three vertical sections through the anterior, posterior and midpoint of the inferior edge of oval window were measured respectively. RESULTS: The promontory bone inferior to the posterior point of the oval window was thickest, with an average thickness of about 1.1 mm. The endosteum of basal turn at this portion was lowest, with an average height of 0.2 mm. Furthermore, the shortest distance here between the inferior edge of oval window and the endosteum could be no more than 0.3 mm. CONCLUSION: Relatively safe location of drilling on promontory should be selected on promontory inferior to the posterior point of the oval window, with the direction of drilling outward and downward.

Effect of cochlear window fixation on air- and bone-conduction thresholds.

HYPOTHESIS: In the absence of patent cochlear windows, cochlear fluid inertia depends on the presence of a "third window" as a major component of the bone-conduction response. BACKGROUND: Studies have shown conflicting results regarding changes in air and bone conduction whenever, the round window, oval window, or both windows were occluded. METHOD: The study was performed in a tertiary university-affiliated medical center. Auditory brain responses to clicks and 1-kHz tone bursts delivered by air and bone conduction were tested in 5 adult-size fat sand rats. The round window membrane (total, 7 ears) was sealed with Super Glue, and auditory brain response testing was repeated. Thereafter, the stapes footplate was firmly fixated, and auditory brain responses were recorded for a third time. RESULTS: Round-window fixation induced a significant increase in air-conduction thresholds to clicks from 36.4 ± 0.9 to 69.3 ± 4.1 dB SPL, with no significant change in bone-conduction thresholds. When the stapes footplate was immobilized as well, air conduction increased by another 20 dB, on average, with no change in bone conduction. A similar deterioration was seen in response to 1 kHz stimulus. CONCLUSION: These findings support and complement earlier studies in the same animal model, suggesting that when the pressure outlet through the cochlear windows are abolished, still bone conduction displaces the cochlear partition probably because of a functioning "third window."

Variational anatomy of the human cochlea: implications for cochlear implantation.

HYPOTHESIS: To study variations in human cochlea anatomy with potential implications for cochlear implantation surgery. BACKGROUND: A comprehension of the anatomic variations of the human cochlea is essential for understanding the degree of surgical trauma induced by inserting various electrode arrays in cochlear implantation surgery. Variations in anatomy may also limit the potential for performing hearing preservation. METHODS: We studied 73 archival, nonselected, adult, corrosion casts of human inner ears. Anatomic reference points were constructed from photographic reproductions taken at different angles, and various dimensions were assessed using planimetry. Anatomic variants with particular clinical/surgical interests were pinpointed. RESULTS: Results showed that the human cochlea is individually shaped, varying greatly in dimensions ("fingerprint"). The outer cochlear wall length ranged from 38.6 to 45.6 mm with a mean length of 42.0 mm. The first turn represented 53% of the total length and ranged from 20.3 to 24.3 mm. The number of quadrants varied from slightly more than 8 to 12. The facial nerve canal ran in close proximity to the upper first turn explaining facial nerve excitement during stimulation of electrodes in this region in some instances. The internal diameter (height) of the cochlear tube in the first turn varied broadly (1.6-2.6 mm), occasionally with limited space for conventional implants. CONCLUSION: The human cochlea exhibits extensive anatomic variations. These variations will influence the location of cochlear implant arrays and affect the potential of hearing preservation surgery. Our results may explain the surgeon's difficulties sometimes to insert electrode arrays even in so-called "normal" cochleae.

[Useful imaging of the ear]. / Radio-anatomie utile de l'oreille.

Good anatomical knowledge is necessary to make an effective diagnosis in ear pathology. The purpose of this article is to summarize the main landmarks of the ear. Anatomic definitions of the external ear, middle ear, and bony labyrinth are described on routine spiral CT, and the anatomic definition of the membranous labyrinth and the cochleovestibular nerve on MRI is reviewed.

Locating the scala media in the fixed human temporal bone for therapeutic access: a preliminary study.

OBJECTIVE: To investigate the location of the scala media in relation to the round window niche in human temporal bones. DESIGN: Ten human temporal bones were investigated by radical mastoidectomy and promontory drill-out. SETTING: Temporal bone laboratory. OUTCOME MEASURES: The distance from the scala media to the anterior edge of the round window niche, measured by Fisch's stapedectomy measuring cylinders. RESULTS: The scala media was identified at the transection point of a vertical line 1.6 to 2.2 mm (mean=1.8 mm; standard deviation=0.2) anterior to the anterior edge of the round window niche and a horizontal line 0.2 mm inferior to the lower border of the oval window. CONCLUSION: This report demonstrates the point of entry into the scala media via the promontory in fixed temporal bone models, which may provide a site of entry for stem cells and gene therapy insertion.

Promontory drilling in stapedectomy: an anatomical study.

BACKGROUND: Anatomical variants such as an overhanging facial nerve or promontory can impede access to the footplate during stapedectomy. Drilling away bone from the cochlear promontory may be required. In the case of a floating or depressed footplate, it has been recommended that a "pothole" be drilled in the inferior margin of the oval window. There is little published information on the anatomy of the promontory with respect to these maneuvers. MATERIALS AND METHODS: Twenty temporal bones were studied. A series of measurements was made to assess how much bone may safely be removed without risking damage to the underlying cochlear endosteum and, hence, spiral ligament and stria vascularis. RESULTS: The bony promontory is thickest posteriorly, and here, the endosteum has least lateral projection. The promontory becomes thinner closer to the oval window. Moving anteriorly, the bone becomes thinner and the underlying endo steum more closely follows the bony contour. The stria vascularis and spiral ligament may be less than 0.2 mm inferior to the inferior margin of the oval window posteriorly. This distance is at least 0.3 mm at the midpoint of the footplate (range, 0.3-0.5 mm). CONCLUSION: Bone may be removed inferiorly to the posterior one-third of the footplate from lateral to a line that makes an angle of 35 degrees with the superoinferior axis of the footplate. In creating a "pothole" in the case of a floating or depressed footplate, the authors recommend that it be created at the midpoint of the inferior margin of the oval window and should not exceed 0.3 mm in diameter.

The topographical anatomy of the round window and related structures for the purpose of cochlear implant surgery.

The treatment of total deafness using a cochlear implant has now become a routine medical procedure. The tendency to expand the audiological indications for cochlear stimulation and to preserve the remnants of hearing has brought new problems. The authors have studied the topographical anatomy of the internal structures of the ear in the area where cochleostomy is usually performed and an implant electrode inserted. Ten human temporal bones were obtained from cadavers and prepared in a formalin stain. After dissection of the bone in the area of round and oval windows, the following diameters were measured using a microscope with a scale: the transverse diameters of the cochlear and vestibular scalae at the level of the centre of the round window and 0.5 mm anteriorly to the round window, the distance between the windows and the distances from the end of the spiral lamina to the centre of the round window and to its anterior margin. The width of the cochlear scala at the level of the round window was 1.23 mm, and 0.5 mm anteriorly to the round window membrane it was 1.24 mm. The corresponding diameters for the vestibular scala are 1.34 and 1.27 mm. The distances from the end of the spiral lamina to the centre of the round window and to its anterior margin are 1.26 and 2.06 respectively. The authors noted that the two methods of electrode insertion show a difference of 2 mm in the length of the stimulated spiral lamina. The average total length of the unstimulated lamina is 2.06 and 4.06 in the two situations respectively.

Sex differences in the middle ear of the bullfrog (Rana catesbeiana).

Impedance transformation by the middle ear of terrestrial vertebrates is considered to be a function of the ossicular lever apparatus, which increases force and decreases velocity at the stapes footplate relative to the tympanic membrane, and the ratio of tympanic membrane area to stapes footplate area (the area ratio), which increases pressure at the stapes. A recent vibrometric study has found that the velocity ratio between tympanic membrane and stapes footplate is higher in male bullfrogs (Rana catesbeiana) than in females. Although the tympanic membrane area is known to be larger in male bullfrogs, the area ratio has apparently never been compared between the sexes. The hypothesis that a lower area ratio in males helps to compensate for the higher velocity ratio was investigated by comparing tympanic membrane, stapes footplate and operculum areas in frogs of both sexes. Contrary to expectation, the difference in stapes footplate area between males and females is very small, and area ratios are considerably higher in males. Area ratios increase with increasing body size in both sexes. Operculum area does not differ between the sexes. The apparent difference in impedance transformation between male and female frogs might be necessary due to different inner ear impedances, or might reflect serious inadequacies in the conventional models of middle ear function.

Cochlear orientation and dimensions of the facial recess in cochlear implantation.

OBJECTIVE: To study the dimensions of the facial recess and the spatial relationship between the facial recess and the cochlea, using CT scanning in cochlear implantees. METHOD: In 29 cochlear implantees, preoperative CT scans of the temporal bone were compared with findings done at surgery. The dimensions of the facial recess and the relationship between the facial recess and the cochlea were both measured on a viewing station and classified on printed films by 3 blinded and independent reviewers. RESULTS: No significant relations could be found between either intuitive classification of facial recess width or electrode array insertion feasibility and the measurements with the viewing station. The 3 reviewers had large interobserver variability. In 5 cases, neither intuitive review of the CT scans nor viewing station measurements could predict any of the problems encountered during surgery. CONCLUSION: Our findings show that intuitive review was not reliable in classifying facial recess width. Viewing station measurements, in classifying the spatial relation between the facial recess and the cochlear basal turn, need a more detailed review in terms of the relationship with the operation direction and the orientation of the basal turn of the cochlea. Advanced imaging techniques, specifically multislice CT, might improve the diagnostic capabilities.