Isolated Traumatic Dislocation of the Malleus into the External Auditory Canal.

We report a rare case of isolated malleus dislocation into the external auditory canal with lateralized intact tympanic membrane following a head trauma. The patient was a 63-year-old woman who presented at the outpatient department of our institute with hearing loss of 10 years' duration after a bicycle accident. During physical examination of the patient, total dislocation of the malleus-like bony structure into the external auditory canal on the right side was observed. In the computed tomography scan, an isolated malleus dislocation with intact incus-stapes articulation was identified. The patient was successfully treated with endoscopic exploratory tympanotomy and partial ossicular replacement prosthesis. The isolated malleus dislocation can rarely occur after trauma. A careful diagnostic step through history, physical examination, and temporal bone computed tomography scan are needed to confirm this rare condition.

Changes of incudostapedial joint angle in stapedotomy: does it impact hearing outcomes?

PURPOSE: The aims of this article are: (1) is there an ideal incudostapedial joint (ISJ) angle after stapedotomy? (2) is there any difference between pre- and postoperative ISJ angle? and (3) what is the significance of the ISJ angle in postoperative hearing outcomes? METHODS: Forty six ears from 39 different adult patients (28 women and 11 men; 21 left and 25 right ears) with a mean age of 39 years with clinical otosclerosis who underwent stapedotomy between May 2017 and May 2019 were retrospectively registered, including seven bilateral surgery cases. ISJ angle and intravestibular depth of the stapes prosthesis were measured from multiple planar reconstruction-computed tomography images and the length of the prosthesis was measured during surgery. Relationships between the ISJ angle parameters and postoperative hearing outcomes and parameters of the prosthesis were analyzed. RESULTS: The mean ISJ angle was 93.3° ± 8.8° preoperatively and 101.9° ± 6.3° postoperatively, increasing by 8.6° during stapedotomy (p < 0.01). There were weak and negative correlations between ISJ angle changes and postoperative air conduction gains at frequencies ≤1 kHz and bone conduction gains at 0.5 kHz. When the postoperative ISJ angle changed more than 20°, the success rate of the procedure decreased to 0%. CONCLUSION: The stapedotomy operation increased the ISJ angle. The success of postoperative auditory outcomes had more to do with the ISJ angle change than the value of the angle itself, indicating there is no universal ideal ISJ angle that surgeons should aim for during stapedotomy.

Isolated Incudostapedial Cholesteatomas: Unique Radiologic and Surgical Features.

OBJECTIVES: Congenital cholesteatomas originate from epithelial tissue present within the middle ear in patients with an intact tympanic membrane, no history of otologic surgery, otorrhea, or tympanic membrane perforation. They are diagnosed by a pearl-like lesion on otoscopy and computed tomography (CT) scan showing an expansile soft-tissue mass. We describe a series of patients with no prior otologic history presenting with progressive unilateral conductive hearing loss and normal otoscopy. The CT scans showed ossicular erosion without obvious soft-tissue mass. Surgery confirmed incudostapedial erosion found to be cholesteatoma. In this study, we characterize the clinical course of patients diagnosed with isolated incudostapedial cholesteatoma (IIC) and review possible pathologic mechanisms. METHODS: Retrospective review of IIC cases treated by the Department of Pediatric Otolaryngology, Rady Children's Hospital, San Diego, 2014 to 2020. Data included patient demographics, clinical features, imaging, surgical findings, and audiologic data. RESULTS: Five patients were diagnosed with IIC (3 [60%] female; mean age at presentation 10.7 years [range 5.5-16.0]). All patients presented with postlingual unilateral conductive hearing loss and normal otoscopy without any past otologic history; delay in diagnosis ranged from 4 months to several years. The CT scans showed ossicular chain erosion with an absent long process of the incus and/or stapes superstructure. All patients underwent middle ear exploration, revealing a thin layer of cholesteatoma in the incudostapedial region, confirmed by histopathology. Mean preoperative speech reception threshold was 55 dB and improved to a mean of 31 dB in the 4 patients who underwent ossicular chain reconstruction. CONCLUSION: Isolated incudostapedial cholesteatoma should be included as a possible etiology in pediatric patients with insidious onset of unilateral conductive hearing loss with normal otoscopy, unremarkable otologic history, and a CT scan showing ossicular abnormality/disruption without notable middle ear mass. These patients should be counseled preoperatively regarding the possibility of cholesteatoma and should undergo middle ear exploration with possible ossiculoplasty.

Stability of the standard incus coupling of the Carina middle ear actuator after 1.5T MRI.

Limited data is available concerning the safety of active middle ear implants (AMEI) during Magnetic Resonance Imaging (MRI). Measurements in temporal bones are the gold standard for preclinical assessment of device safety. In this study the coupling stability of an actuator as used in a fully implantable AMEI was determined in temporal bones. Eleven temporal bones were implanted with the actuator according to the manufacturer's surgical guidelines. The actuator was coupled on the incus short process as recommended for sensorineural hearing loss. Temporal bones were exposed 10 times to the MRI magnetic field by entering the MRI suite in a clinically relevant way. Computed Tomography (CT) images were acquired before and after the experiment to investigate the risk of actuator dislocation. Based on the electrical impedance of the actuator, the loading of the actuator to the incus was confirmed. Relative actuator displacement was determined on the CT images by comparing the initial with the final actuator position in 3D space. Impedance curves were analyzed after each exposure to check the loading of the actuator to the ossicles. Analysis of CT images with a 0.30.6 mm in-plane resolution indicate no actuator displacement. The maximum detected change in impedance for all actuators was 8.43 Ω at the actuator's resonance frequency. Impedance curves measured when the actuator was retracted from the short process after the experiment still indicate the presence of a clear resonance peak. No actuator displacement or dislocation could be detected in the analysis of CT images and the measured impedance curves. Impedance curves obtained when the actuator was retracted from the incus short process still show a clear resonance peak, indicating the device is still functional after the MRI exposures.

Characterization of mechanical behaviour of healthy and injured human incus by eigenfrequency evaluation.

The usage of finite element method techniques gives a possibility to replace time-consuming experiments or imitate physical process in the ear by numerical simulation. Especially, the research of spatial motion of ossicular chain in the middle ear is of high interest for the oto-surgeons and engineers. It is known that the most affected bone from the ossicular chain is the incus. After the cholesteatoma operation and tympanoplasty, the affected incus is removed or sacrificed; thus, the possibility of transducing noise lays on the stapes, new titanium or other material prosthesis. In this case, the affected incus was removed because of the cholesteatoma that was lying in front of it in the tympanic cavity. The removed incus with the affected long process passed micro-computed tomography. The computer-aided design systems allowed redesigning a 'healthy' incus with an intact long process. In this way, it was possible to evaluate the influence of damaged long process of incus in the vibrational analysis. This article analyses the problems of mechanical behaviour of injured and healthy human incus. The numerical simulation has demonstrated that the features of healthy incus and analysed injured incus do not differ significantly, especially at low (about 500 Hz) frequencies. It explains why there is no impact of cholesteatoma on hearing for a long time in the audiogram.

The Sensitivity of the cVEMP Test in Detecting A Superior Semicircular Canal Dehiscence and the Influence of a Coexisting Incudal Lysis: A Case Report.

In this case report, the air-conducted cervical vestibular evoked myogenic potentials (AC cVEMP) test was only sensitive for the left superior semicircular canal dehiscence (SCD), even though the contralateral SCD was of equal length (2.5 mm). Furthermore, a lysis of the processus lenticularis incudis caused a real conductive hearing loss in the left ear. A diminished left AC cVEMP was thus expected, but the opposite was shown (increased corrected amplitude, lowered detection threshold). The patient only experienced hearing loss, so middle ear surgery was performed to repair the lysis. The postoperative AC cVEMP showed a further "uncovering" of the SCD with increased corrected amplitude on the left but no vestibular symptoms. The significance of an SCD should be interpreted with caution, even when the AC cVEMP and the imaging are significant. Furthermore, AC cVEMPs should not be considered as evidence for the absence or presence of conductive hearing loss.

Radiological-audiological correlation in type II tympanoplasty with glass ionomer cement.

AIM: To assess the CT scan aspect of cement bridges used to repair incudostapedial joint discontinuity (ISD) and correlate these observations to audiometric data over time. MATERIAL AND METHODS: A retrospective study in 12 patients with cement rebridging for ISD compared pre- and post-operative pure-tone average thresholds, Hounsfield units (HU), and bridge size and position on postoperative CT scans. RESULTS: Mean pre- and post-operative air-bone gap (ABG) was 24.5 and 16dB, respectively. HU did not vary over time post-surgery, with no significant correlation between HU and time to postoperative CTnscan up to 24months (p=0.219). However, a "suggestive" correlation was found between postoperative ABG and HU (p=0.004, r=-0.7). High cement density correlated with good functional outcome: HU <500 indicating functional failure and >1000 indicating ABG closure. CONCLUSION: Immediate cement polymerization quality (high HU) was stable over time and a marker of ossiculoplasty success, correlating with good functional outcome. Particular care should be taken in preparing the cement, and solidification needs to be on dry mucosa-free ossicles.

High-resolution imaging of the human incudostapedial joint using synchrotron-radiation phase-contrast imaging.

The incudostapedial joint (ISJ) of the middle ear is important for proper transmission of sound energy to the cochlea. Recently, the biomechanics of the ISJ have been investigated using finite-element (FE) modelling, using simplified geometry. The objective of the present study was to investigate the feasibility of synchrotron-radiation phase-contrast imaging (SR-PCI) in visualising the ISJ ultrastructure. Three human cadaveric ISJs were dissected and scanned using SR-PCI at 0.9 µm isotropic voxel size. One of the samples was previously scanned at 9 µm voxel size. The images were visually compared and contrast-to-noise ratios (CNRs) were calculated (of both bone and soft tissues) for quantitative comparisons. The ISJ ultrastructure as well as adjacent bone and soft tissues were clearly visible in images with a 0.9 µm voxel size. The CNRs of the 0.9 µm images were relatively lower than those of the 9 µm scans, while the ratio of bone to soft tissue CNRs were higher, indicating better discernibility of bone from soft tissue in the 0.9 µm scans. This study was the first known attempt to image the ISJ ultrastructure using an SR-PCI scanner at submicron voxel size and results suggest that this method was successful. Future studies are needed to optimise the contrast and test the feasibility of imaging the ISJ in situ. LAY DESCRIPTION: The human middle ear consists of the eardrum, three small bones (the malleus, incus and stapes) and two joints connecting the bones (the incudostapedial joint and the incudomallear joint). The role of the middle ear is to amplify and transfer sound energy to the cochlea, the end organ of hearing. The incudostapedial joint (ISJ) of the middle ear is a synovial joint which is important for proper transmission of sound energy to the cochlea. Similar to other synovial joints it consists of meniscus, fluid and articulating surfaces. Recently, the biomechanics of the ISJ have been investigated using computational models, using grossly simplified geometry. Synchrotron radiation phase contrast imaging (SR-PCI) is a high-resolution imaging technique used to visualise small structures in three dimensions. The objective of the present study was to investigate the feasibility of using SR-PCI in visualising the ISJ ultrastructure. Three human cadaveric ISJs were dissected and scanned using SR-PCI at 0.9 µm isotropic voxel size. One of the samples was previously scanned at 9 µm voxel size. The images were both qualitatively and quantitatively compared. This study was the first known attempt to image the ISJ ultrastructure using an SR-PCI scanner at submicron voxel size and results suggest that this method was successful. Future studies are needed to optimise the contrast and feasibility of imaging the ISJ in situ.

Incus Necrosis and Blood Supply: A Micro-CT and Synchrotron Imaging Study.

BACKGROUND: Incus necrosis is a common complication following stapes surgery and is associated with impaired microcirculation. The objective of this study was to investigate the vascular anatomy of the human incus by using light microscopy, micro-computed tomography (micro-CT), and synchrotron phase-contrast imaging (SR-PCI) for a novel three-dimensional (3D) analysis of the middle ear, mucosal folds, major vascular pathways, and intraosseous vascular bone channels. METHODS: One-hundred-and-fifty temporal bones from the Uppsala collection were analyzed under light microscopy. Twenty temporal bones underwent high-resolution micro-CT scanning, and an additional seven specimens underwent SR-PCI at the Canadian Lightsource in Saskatoon, Canada. One of these specimens was from an individual who had undergone stapes surgery. Data were processed with volume-rendering software to create 3D reconstructions using scalar opacity mapping for bone transparency, cropping, and soft tissue analyses. RESULTS: Micro-CT and SR-PCI with 3D rendering revealed the extensive vascular plexus within the un-decalcified incus bone communicating with the exterior surface. The relationship between the vessels, lenticular process, and incudostapedial joint were clearly observed. SR-PCI allowed for histologic-level detail while preserving the specimen and its 3D relationships. CONCLUSION: SR-PCI with 3D reconstructions confirmed the main vascular supply to the lenticular process along the intraosseous lenticular vessels. This is the first synchrotron analysis of a patient having undergone stapes surgery, and it suggests that incus necrosis associated with stapes surgery may be caused by a disruption of the lenticular blood flow induced by the prosthesis loop, and not by strangulation of mucosal vessels as has been previously described.

Stapes Prosthesis Length: One Size Fits All?

BACKGROUND: The insertion of the stapes piston into the vestibule provides the physical basis for a successful stapedotomy. In routine clinical practice, two different ways to handle prosthesis length are performed: (1) an individualized measurement of the stapes prosthesis length or (2) a standard prosthesis length for all cases. OBJECTIVE: The objective of this study was to compare both ways of handling prosthesis length and the effect of these methods on insertional prosthesis depth. MATERIAL AND METHOD: We retrospectively evaluated 39 patients after performing a stapedotomy for radiologically estimated vestibular stapes prosthesis insertion depth. The individual measured length data were hypothetically changed to a standard length of 4.75, 5, 5.25, and 5.5 mm, and the insertion depths were compared. RESULTS: The individually measured prosthesis lengths led to an insertion depth between 0.2 and 1.6 mm (mean 0.74 mm). The ratio of insertion depth/vestibular depth was between 8 and 59.1% (mean 26.6%). The different assumed standard lengths led to different rates of the vestibulum positions and possible bony contacts at the vestibulum floor. CONCLUSION: The individual measurement led to a zero rate of the vestibulum positions of stapes prosthesis pistons with a low insertion depth/vestibular depth ratio.

Conductive hearing loss with a "dry middle ear cleft"-A comprehensive pictorial review with CT.

Conductive hearing loss (CHL) commonly results from middle ear fluid and inflammation (otitis media). Less commonly in patients with CHL, the middle ear cleft is well aerated or 'dry' with absence of soft tissue or fluid clinically and on imaging. There are numerous causes for this but they can be clinically challenging to diagnose. This pictorial review aims to illustrate and discuss the CT features of both common and less common causes of CHL in patients with a "dry middle ear cavity".

Neuroimaging findings in Emanuel Syndrome.

Emanuel syndrome is a rare inherited chromosomal abnormality caused by an unbalanced translocation of chromosomes 11 and 22. Clinically, Emanuel syndrome is characterized by a wide spectrum of congenital anomalies, dysmorphisms, and developmental disability often confused with other similar syndromes. Outside of genetic testing, diagnosis remains challenging and current literature on typical radiologic findings is limited. We present classic neuroimaging findings of Emanuel syndrome consistent with prior literature including microcephaly, microretrognathia, external auditory canal stenosis, and cleft palate; and also introduce the additional maxillofacial anomaly of dysplastic middle ear ossicles, to our knowledge not previously described in the literature. Recognition of findings leading to earlier diagnosis of Emanuel syndrome may improve outcomes and quality of life for patients and their families.

Three-dimensional force analysis of surgical manipulations at the long process of the incus.

PURPOSE: Surgical manipulation with application of inappropriate force may damage middle ear structures leading to hearing loss. This work analyzes the forces applied in simulated otosurgical exercises in a laboratory set-up by measuring the spatial components of applied forces with objective assessment criteria. With these criteria, the individual force characteristics applied by the surgeon can be quantified and an objective feedback can be given about their surgical maneuvers. METHODS: A natural size model of the human incus was mounted on a load cell to measure the spatial forces in all three directions during different manipulation tasks performed under the microscope by ten surgeons from our department having different levels of experience in otosurgery. The motions of the incus model and the instrument tip were recorded simultaneously with a video camera. RESULTS: Independent of surgical experience, a three-dimensional force pattern could be detected with components transverse to the desired force directions. The measured forces applied by trainees showed larger variations in magnitude, in spatial distribution and in temporal course than those applied by experienced surgeons. A better repeatability of identical tasks, constancy of force patterns and low peak force values could be seen in the group of experienced surgeons. CONCLUSIONS: The laboratory system presented in this study using simultaneous video and 3-D force registration allows the objective assessment of surgical manipulations, e.g., at the long process of the incus. Training with video and force feedback provides information about surgical techniques and skill development of surgeons and has the potential to shorten the learning curve and to diminish intra-operative risks to patients.

Predictable prosthesis length on a high-resolution CT scan before a stapedotomy.

OBJECTIVE: (1) To assess the correlation between preoperative high-resolution CT (HRCT) imaging measurement from the long process of the incus to the footplate and the length of intraoperative selected prosthesis. (2) To determine if HRCT has a predictive value of prolapsed facial nerve during stapedotomy. MATERIALS AND METHODS: We evaluated in our tertiary care center, in a retrospective case series, 94 patients undergoing primary stapedotomy. Preoperative temporal bone HRCT scans were reformatted in the plane of the stapes to measure on the same section the distance between the long process of the incus and the footplate. Measurement was performed by otolaryngology resident and neurotologist. We analyze the interobserver correlation and the mean length measured on the HRCT to the selected prosthesis size intraoperatively. RESULTS: Mean HRCT measurement of the incus long process/footplate distance assessed by the otolaryngology resident and neurotologist was 4.34 and 4.38 mm, respectively. Interobserver correlation was statistically significant [intraclass correlation coefficient (ICC) of 0.679 (p < 0.001)]. Mean selected prosthesis length intraoperatively was 4.36 mm. Correlation between the mean selected length prosthesis and the mean HRCT measurement was also statistically significant [ICC of 0.791 (p < 0.001)]. Postoperatively, a statistical improvement was shown in air conduction (p < 0.001), bone conduction (p < 0.001) and air-bone gap reduction (p < 0.001). 2 cases of facial nerve covering one-half of the oval window were identified by HRCT and confirmed intraoperatively. CONCLUSION: HRCT is a valuable tool to predict preoperatively the length of the stapedotomy prosthesis. Moreover, it might be helpful to identify a potential prolapsed facial nerve, to confirm the diagnosis of otosclerosis and to rule out other abnormalities. Ultimately, it may optimize the stapedotomy procedure planning.

3D morphometric analysis of the human incudomallear complex using clinical cone-beam CT.

Human middle ears show large morphological variations. This could affect our perception of hearing and explain large variation in experimentally obtained transfer functions. Most morphological studies focus on capturing variation by using landmarks on cadaveric temporal bones. We present statistical shape analysis based on clinical cone beam CT (CBCT) scans of 100 patients. This allowed us to include surface information on the incudomallear (IM) complex (joint, ligaments and tendon not included) of 123 healthy ears with a scanning resolution of 150 µm and without a priori assumptions. Statistical shape modeling yields an average geometry for the IM complex and the variations present in the population with a high precision. Mean values, variation and correlations among anatomical features (length of manubrium, combined length of malleus head and neck, lengths of incus long and short process, enclosing angles, ossicular lever ratio, incudomallear angle, and principal moments of inertia) are reported and compared to results from the literature. Most variation is found in overall size and the angle between incus and malleus. The compact representation provided by statistical shape modeling is demonstrated and its benefits for surface modeling are discussed.

Congenital anomalies of the incudostapedial joint.

OBJECTIVE: To describe congenital anomalies of the incudostapedial joint (ISJ) and to discuss the possible unique embryogenesis of the ISJ based on the two anomalies that were encountered. SETTING: Tertiary care medical center. SUBJECTS AND METHODS: Retrospective review of the medical records of all patients with ISJ anomalies. RESULTS: Four patients presented with congenital hearing loss. Upon further workup, we observed a preserved incudostapedial joint (ISJ) with deficiencies of the incus and stapes in three cases. Our fourth case demonstrated the inverse pattern of the congenital anomalies in which the ISJ was missing with an intact proximal incus and stapes crura. Three patients opted for surgical intervention with improvement in hearing. One case preferred hearing amplification over surgery. CONCLUSION: Isolated ISJ malformations are uncommon potential causes of congenital conductive hearing loss. Although numerous patterns of ossicular anomalies have been reported in the literature, our case series is the first to demonstrate both the absence of the ISJ in one patient and the presence of the ISJ in the presence of missing stapes crura and incus body in other patients. Though limited by the small number of cases, the inverse relationship of the single case compared to the three other cases, suggests a possible independent embryological development pathway for the ISJ. Therefore, an embryological explanation of the defects should be considered. Additionally, surgical intervention can improve hearing outcomes for patients with isolated ISJ anomalies.