Does otosclerosis affect the dimensions of the facial canal and cochlear aquaduct?

PURPOSE: Our aim was to evaluate the relationship of the dimensions of the facial canal (FC) and cochlear aqueduct (CA) in otosclerosis (OS) with the type and severity of OS. METHODS: Two radiologists retrospectively evaluated temporal bone high-resolution computed tomography (HRCT) images obtained from 48 healthy individuals and 94 OS patients between January 2015 and July 2020. In the study group, the CA width, funnel base width, and funnel length, in addition to the FC transverse length, were measured in the axial plane. The CA length was measured in the coronal plane on HRCT images. The FC craniocaudal length was measured in the same plane as the fissula ante fenestram (FAF) in coronal reformatted HRCT images. Grading of OS was based on otosclerotic plaque density and new bone formation extending toward the tympanic cavity at the FAF level. RESULTS: In the OS patients, the CA width and FC craniocaudal and FC transverse diameters were significantly decreased on both sides compared to those in the control group (p < 0.001). In fenestral OS, the FC craniocaudal and transverse widths on both sides were statistically significantly lower than the FC widths in the control group (p < 0.0001). A statistically negative correlation was found in the FC craniocaudal (r = - 0.831/- 0.818) and transverse (r = - 0.742/- 0.750) measurements on both sides in accordance with an increase in the otosclerotic plaque density (p < 0.0001). CONCLUSION: The presence of narrowing in the FC and CA adjacent to the FAF supports the role of autoimmunity theory in the etiology of OS.

Why did we encounter gusher in a stapes surgery case? Was it enlarged medial aperture of the cochlear aqueduct?

BACKGROUND AND PURPOSE: Preoperative prediction of cerebrospinal fluid (CSF) gusher is important for stapes surgery. According to the current opinion settled among otologists and radiologists, the issues of whether enlarged cochlear aqueduct might be a cause of CSF gusher in stapes surgery and which segment of the aqueduct should be taken into account to diagnose enlarged cochlear aqueduct in computerized tomography (CT) are controversial. The case we encountered led us to hypothesize that enlarged cochlear aqueduct might cause CSF gusher in stapes surgery and that shape and diameter of medial aperture of the cochlear aqueduct are important in this prediction. METHODS AND RESULTS: Enlarged medial aperture of the cochlear aqueduct with a shape differed from that of the other side was retrospectively diagnosed in thin-slice CT in a patient who had been undergone middle ear and stapes surgery for conductive hearing loss. This finding went unnoticed in preoperative CT. In the small fenestra stapedotomy operation, CSF gusher occurred through opening in the ill-defined, fixed and thickened stapes footplate. A piece of temporalis fascia and reshaped incus were appropriately placed which stopped the gusher. Re-evaluation of preoperatively taken CT showed that anterior-posterior and superior-inferior diameters of the medial aperture were 11.7 mm and 2.87 mm in CSF gusher side versus 2.95 mm and 1.88 mm on the other side, respectively. Its shape in gusher side differed from that of the other side. CONCLUSION: This report is the first to show video-documented CSF gusher in a patient with enlarged medial aperture of the cochlear aqueduct. It appears to be plausible to propose that these findings have to change the otologists' and radiologists' perspective to the cochlear aqueduct. It can be deduced that difference in shapes of the medial aperture in both sides might be an indicator of potential CSF gusher.

[The significance of microanatomy of the round window in terms of cochlear implantation]. / Znachenie mikroanatomii okna ulitki dlya provedeniya kokhlearnoi implantatsii.

Sensoneural hearing loss is a polyetiological disease, which is often a secondary reflection of systemic pathology and is associated with damage of the cochlea and auditory nerve receptors. An important point in the surgical stage of cochlear implantation is the introduction of an implant active electrode into the cochleostomy spiral channel through the cochleostoma or round window. However, the issue of intra-cochlear structures surgical trauma in such surgical intervention seems to be very important, as it may reduce the success of subsequent rehabilitation. Therefore, the study of the anatomy of the round window and adjuscent areas was the objective of this work.

Micro-CT study of the human cochlear aqueduct.

OBJECTIVE: The anatomic structure of the cochlear aqueduct (CA) in human temporal bone specimens was observed using micro-computed tomography (CT). MATERIALS AND METHODS: Micro-CT scanning of 18-µm-thick slices was performed on 30 slides of human temporal bone specimens to observe the CA structure and its relationship with its surroundings. The length, internal and external apertures, and the narrowest width of the CA were measured. The differences in CAs were compared between high jugular bulb (HJB) specimens and normal specimens. RESULTS: A large number of CA images were acquired using Micro-CT scanning, which clearly displayed the basic anatomic structures, stereotactic localizations, and adjacent relationships of the CAs. The whole course of a CA was 12.31 ± 3.60 mm, the diameter of the internal aperture was 465 ± 242 µm, the diameter of the external aperture was 2.88 ± 1.06 mm, the narrowest diameter was 601 ± 335 µm, the diameter of the opening of inferior cochlear vein (ICV) was 151 ± 50 µm, the distance between the internal aperture and ICV was 270 ± 197 µm, and the distance between the inferior margin of the internal acoustic meatus (IAM) and the top most part of the external aperture of the CA was 6.783 ± 2.15 mm. No bony obstruction of the CA or CA enlargement was observed in the specimens. A total of 28 CAs had one accompanying bony canal in the surroundings. The length and travelling of the CA were not affected by the level of the jugular bulb (JB). The variation of the travelling of the ICV was larger than that of the CA. CONCLUSION: Micro-CT adequately displayed the bony CA canal and provided a new method for anatomical studies of the CA and a basis for functional studies.

Hearing loss in hydrocephalus: a review, with focus on mechanisms.

While neither hydrocephalus nor cerebrospinal fluid (CSF) shunt placement is traditionally considered in the differential diagnosis of hearing loss, there is substantial evidence that CSF circulation and pressure abnormalities can produce auditory dysfunction. Several indirect mechanisms may explain association between hydrocephalus and hearing loss, including mass effect, compromise of the auditory pathway, complications of prematurity, and genetically mediated hydrocephalus and hearing loss. Nevertheless, researchers have proposed a direct mechanism, which we term the hydrodynamic theory. In this hypothesis, the intimate relationship between CSF and inner ear fluids permits relative endolymphatic or perilymphatic hydrops in the setting of CSF pressure disturbances. CSF is continuous with perilymph, and CSF pressure changes are known to produce parallel perilymphatic pressure changes. In support of the hydrodynamic theory, some studies have found an independent association between hydrocephalus and hearing loss. Moreover, surgical shunting of CSF has been linked to both resolution and development of auditory dysfunction. The disease burden of hydrocephalus-associated hearing loss may be large, and because hydrocephalus and over-shunting are reversible, this relationship merits broader recognition. Hydrocephalic patients should be monitored for hearing loss, and hearing loss in a patient with shunted hydrocephalus should prompt further evaluation and possibly adjustment of shunt settings.

Cochlear aqueduct revisited: A histological study using human fetuses.

BACKGROUND AND AIM: The cochlear aqueduct (CA) connects between the perilymphatic space of the cochlea and the subarachnoid space in the posterior cranial fossa. The study aimed to examine 1) whether cavitation of the CA occurs on the subarachnoid side or the cochlear side and 2) the growth and/or degeneration of the CA and its concomitant vein. METHODS: We examined paraffin-embedded histological sections from human fetuses: 15 midterm fetuses (crown-rump length or CRL, 39-115 mm) and 12 near-term fetuses (CRL, 225-328 mm). RESULTS: A linear mesenchymal condensation, i.e., a likely candidate of the CA anlage, was observed without the accompanying vein at 9-10 weeks. The vein appeared until 15 weeks, but it was sometimes distant from the CA. At 10-12 weeks, the subarachnoid space (or the epidural space) near the glossopharyngeal nerve rapidly protruded into the CA anlage and reached the scala tympani, in which cavitation was gradually on-going but without epithelial lining. However, CA cavitation did not to occur in the anlage. At the opening to the scala, the epithelial-like lining of the CA lost its meningeal structure. At near-term, the CA was often narrowed and obliterated. CONCLUSION: The CA develops from meningeal tissues when the cavitation of the scala begins. The latter cavitation seemed to reduce tissue stiffness leading, to meningeal protrusion. The so-called anlage of CA might be a phylogenetic remnant of the glossopharyngeal nerve branch. A course of cochlear veins appears to be determined by a rule different from the CA development.

Cochlear Aqueduct Morphology in Superior Canal Dehiscence Syndrome.

The cochlear aqueduct (CA) connects the scala tympani to the subarachnoid space and is thought to assist in pressure regulation of perilymph in normal ears, however, its role and variation in inner ear pathology, such as in superior canal dehiscence syndrome (SCDS), is unknown. This retrospective radiographic investigation compared CA measurements and classification, as measured on flat-panel computerized tomography, among three groups of ears: controls, n = 64; anatomic superior canal dehiscence without symptoms (SCD), n = 28; and SCDS, n = 64. We found that in a multinomial logistic regression adjusted for age, sex, and BMI, an increase in CA length by 1 mm was associated with a lower odds for being in the SCDS group vs. control (Odds ratio 0.760 p = 0.005). Hierarchical clustering of continuous CA measures revealed a cluster with small CAs and a cluster with large CAs. Another multinomial logistic regression adjusted for the aforementioned clinical covariates showed an odds ratio of 2.97 for SCDS in the small CA cluster as compared to the large (p = 0.004). Further, no significant association was observed between SCDS symptomatology-vestibular and/or auditory symptoms-and CA structure in SCDS ears. The findings of this study lend support to the hypothesis that SCDS has a congenital etiology.

Hyrtl's fissures in cochlear implant surgery.

This case study presents a rare anatomical anomaly complicating cochlear implantation in the form of patent periotic ducts and Hyrtl's (tympanomeningeal) fissures. Hyrtl's fissures are transient anatomical conduits which normally ossify by the 24th week of gestation. Their persistence may cause inadvertent insertion of the cochlear implant electrode into this channel and prevent a successful outcome. This case study and a review of the relevant literature highlights the importance of recognizing this rare anomaly which is easily missed on preoperative imaging.

Exploratory tympanotomy in sudden sensorineural hearing loss for the identification of a perilymphatic fistula - retrospective analysis and review of the literature.

OBJECTIVE: The diagnostic value of exploratory tympanotomy in sudden sensorineural hearing loss remains controversial. This study and review were performed to identify the incidence of perilymphatic fistula in patients with sudden sensorineural hearing loss. The effectiveness of tympanotomy for sealing of the cochlear windows in cases with perilymphatic fistula was evaluated. METHODS: A search in common databases was performed. Overall, 5034 studies were retrieved. Further, a retrospective analysis on 90 patients was performed. RESULTS: Eight publications dealing with tympanotomy in patients with sudden sensorineural hearing loss were identified. In 90 patients diagnosed with sudden sensorineural hearing loss and undergoing exploratory tympanotomy, 10 patients (11 per cent) were identified with a perilymphatic fistula, and this corresponds to the results obtained from our review (13.6 per cent). CONCLUSION: There was no significant improvement after exploratory tympanotomy and sealing of the membranes for patients with a definite perilymphatic fistula.

High-Resolution Computed Tomography of the Inner Ear: Effect of Otosclerosis on Cochlear Aqueduct Dimensions.

OBJECTIVES: The cochlear aqueduct is a bony duct connecting the scala tympani with the subarachnoid space. Given the pathophysiology of otosclerosis, including bone resorption and new bone deposition, we hypothesize that the cochlear aqueduct in otosclerotic ears is narrowed. METHODS: A retrospective review of patients with otosclerosis who have undergone high-resolution computed tomography (HRCT) of the temporal bone was completed. The control cohort included 20 patients with the diagnosis of noise-induced hearing loss, without the diagnosis of otosclerosis. Uniform measurements of cochlear aqueduct dimensions were performed using the axial plane. RESULTS: The otosclerosis cohort included 25 males and 52 females with mean age of 52.2 ± 17.6 years. The control group included 10 males and 10 females with mean age of 64.0 ± 18.5 years. The mean cochlear aqueduct length, width mid canal, aperture base, aperture widest diameter, and funnel diameter in millimeters were 12.19 ± 1.66, 0.68 ± 0.28, 4.21 ± 1.67, 3.23 ± 1.47, and 2.70 ± 1.05 in the ears with otosclerotic foci and 11.57 ± 1.66, 0.69 ± 0.29, 2.56 ± 1.59, 2.77 ± 1.67, and 2.58 ± 1.03 in control group, respectively. Statistical difference was seen in length of cochlear aqueduct, aperture base, and aperture widest diameters (P = .017, <.001, .007). CONCLUSIONS: The length of the cochlear aqueduct and the funnel width are statistically longer in the otosclerotic population compared to control. The width of the cochlear aqueduct is not statistically different.

Pathophysiology of sensorineural hearing loss in jugular foramen paraganglioma.

OBJECTIVES/HYPOTHESIS: Pathologic involvement of the inferior cochlear vein is a mechanism of sensorineural hearing loss in patients with jugular foramen paraganglioma. STUDY DESIGN: Retrospective case-control study. METHODS: The presenting audiograms, magnetic resonance imaging, and computed tomography were reviewed in 46 subjects with jugular foramen paragangliomas. Four-frequency bone conduction average was compared between the tumor and nontumor ears in each subject to establish the presence of sensorineural hearing loss. Imaging findings for each subject were recorded. Univariate and multivariate statistical analyses were performed to determine which radiographic features were associated with sensorineural hearing loss. Hearing data were analyzed as a continuous variable and as a categorical variable. RESULTS: Twenty subjects (43.4%) had a bone-conduction pure-tone asymmetry of greater than 15 dB. Inferior cochlear vein involvement was identified in 19 of the 20 (95%) subjects with sensorineural hearing loss. Inferior cochlear vein involvement was found to be a statistically significant predictor of sensorineural hearing loss using univariate and multivariate analyses. Other imaging findings that were statistically significant predictors of sensorineural hearing loss include Glasscock-Jackson stage, Fisch-Mattox stage, hypoglossal canal involvement, jugulo-carotid spin erosion, and petrous carotid canal erosion. CONCLUSIONS: Involvement of the inferior cochlear vein appears to be a plausible mechanism for sensorineural hearing loss in patients with jugular foramen paraganglioma. LEVEL OF EVIDENCE: 4 Laryngoscope, 129:67-75, 2019.

Limits on normal cochlear 'third' windows provided by previous investigations of additional sound paths into and out of the cat inner ear.

While most models of cochlear function assume the presence of only two windows into the mammalian cochlea (the oval and round windows), a position that is generally supported by several lines of data, there is evidence for additional sound paths into and out of the inner ear in normal mammals. In this report we review the existing evidence for and against the 'two-window' hypothesis. We then determine how existing data and inner-ear anatomy restrict transmission of sound through these additional sound pathways in cat by utilizing a well-tested model of the cat inner ear, together with anatomical descriptions of the cat cochlear and vestibular aqueducts (potential additional windows to the cochlea). We conclude: (1) The existing data place limits on the size of the cochlear and vestibular aqueducts in cat and are consistent with small volume-velocities through these ducts during ossicular stimulation of the cochlea, (2) the predicted volume velocities produced by aqueducts with diameters half the size of the bony diameters match the functional data within ±10 dB, and (3) these additional volume velocity paths contribute to the inner ear's response to non-acoustic stimulation and conductive pathology.

[Possible reasons for cerebrospinal fluid gusher in cochlear implantation with inner ear abnormality].

Objective: To discuss the possible reasons for cerebrospinal fluid (CSF) gusher in cochlear implantation (CI) with inner ear abnormality. Method: A retrospective analysis was performed on 340 cases who underwent CI from January 2013 to December 2016 in Division of Otology, Otorhinolaryngology Hospital, the First Affiliated Hospital of Zhengzhou University. Among them, 96 cases had inner ear abnormalities. Imaging examinations were performed on these patients, and classification of inner ear malformation was done according to the results. Results: Among the cases with inner ear abnormality, 9.4% (9/96) suffered from CSF gusher during CI. The inner ear abnormalities were found to be as follows: 3 cases had incomplete partition type Ⅰ; 1 case had incomplete partition type Ⅰ with semicircular canal dysplasia; 1 case had common cavity deformity; 1 case had enlarged vestibular aqueducts and common cavity deformity; 2 cases had Mondini deformity. All of these cases had bony defect in the fundus of the internal acoustic meatus observed on CT scans. Another case was type 1 cochlear aqueduct with round window aplasia. Conclusions: Defects in the modiolus or fundus of the internal acoustic meatus is the main reason for CSF gusher during CI. A patent cochlear aqueduct is another possible reason.

Otic Barotrauma Resulting from Continuous Positive Airway Pressure: Case Report and Literature Review.

BACKGROUND: Obstructive sleep apnea (OSA) is a growing problem affecting millions of people in the United States. The prevalence of OSA has risen drastically in the past few decades concurrently with the increasing prevalence of obesity. Subsequently, there has been an ever-increasing rise in the use of continuous positive airway pressure (CPAP) devices. While using CPAP devices may lead to many adverse effects, the majority of these effects are described as relatively benign. CASE REPORT: We describe the detailed clinical course and outcome for a patient with otic barotrauma as a result of excessive self-titration of CPAP therapy in an in-home setting. We also discuss the pathophysiology of otic barotrauma and present a review of current literature on the topic. CONCLUSION: While the benefits of CPAP are clear, we must take into account the rare but possible effects on ear structure and function. Many studies describe an increase in middle ear pressure with the use of CPAP, but few describe the effects of this increased pressure on the middle ear, such as the otic barotrauma described in this case. Given the increased prevalence of OSA, it is important to understand the risks associated with CPAP therapy.

Resolution of sudden sensorineural hearing loss following a roller coaster ride.

We report a case of sudden unilateral sensorineural hearing loss of sudden onset during an aeroplane flight, which completely resolved during a roller coaster ride at Alton Towers theme park. A review of the literature concerning sudden idiopathic sensorineural hearing loss and spontaneous resolution are discussed. Initially, pure-tone audiometry showed a profound sensorineural hearing loss in the right ear and mild sensorineural hearing loss in the left ear (of note, the hearing was normal prior to the episode). Following resolution of the patient's symptoms during a roller coaster ride, pure-tone audiometry showed normal hearing thresholds in both ears. Sudden sensorineural hearing loss is a symptom of cochlear injury and the mechanism of the patient's symptoms was attributed to a patent cochlear aqueduct.