Venous communications of the cochlea after acute occlusion of the vein of the cochlear aqueduct

Cochlear implantation impairs intracochlear microcirculation and counteracts iNOS induction in guinea pigs

Introduction

Preservation of residual hearing remains a great challenge during cochlear implantation. Cochlear implant (CI) electrode array insertion induces changes in the microvasculature as well as nitric oxide (NO)-dependent vessel dysfunction which have been identified as possible mediators of residual hearing loss after cochlear implantation.

Methods

A total of 24 guinea pigs were randomized to receive either a CI (n = 12) or a sham procedure (sham) by performing a cochleostomy without electrode array insertion (n = 12). The hearing threshold was determined using frequency-specific compound action potentials. To gain visual access to the stria vascularis, a microscopic window was created in the osseous cochlear lateral wall. Cochlear blood flow (CBF) and cochlear microvascular permeability (CMP) were evaluated immediately after treatment, as well as after 1 and 2 h, respectively. Finally, cochleae were resected for subsequent immunohistochemical analysis of the iNOS expression.

Results

The sham control group showed no change in mean CBF after 1 h (104.2 ± 0.7%) and 2 h (100.8 ± 3.6%) compared to baseline. In contrast, cochlear implantation resulted in a significant continuous decrease in CBF after 1 h (78.8 ± 8.1%, p < 0.001) and 2 h (60.6 ± 11.3%, p < 0.001). Additionally, the CI group exhibited a significantly increased CMP (+44.9% compared to baseline, p < 0.0001) and a significant increase in median hearing threshold (20.4 vs. 2.5 dB SPL, p = 0.0009) compared to sham after 2 h. Intriguingly, the CI group showed significantly lower iNOS-expression levels in the organ of Corti (329.5 vs. 54.33 AU, p = 0.0003), stria vascularis (596.7 vs. 48.51 AU, p < 0.0001), interdental cells (564.0 vs. 109.1 AU, p = 0.0003) and limbus fibrocytes (119.4 vs. 18.69 AU, p = 0.0286).

Conclusion

Mechanical and NO-dependent microvascular dysfunction seem to play a pivotal role in residual hearing loss after CI electrode array insertion. This may be facilitated by the implantation associated decrease in iNOS expression. Therefore, stabilization of cochlear microcirculation could be a therapeutic strategy to preserve residual hearing.

Relationship between the drainage pattern of the dural venous sinuses and hearing recovery in patients with sudden sensorineural hearing loss

Although cochlear venous insufficiency has been considered to cause sudden sensorineural hearing loss (SSHL), there is insufficient clinical evidence to support this hypothesis. We sought to determine whether there is a correlation between draining patterns of the dural venous sinuses and the side of the affected ear in SSHL, as well as hearing recovery. The medical records of 109 patients diagnosed with unilateral SSHL were retrospectively reviewed. Magnetic resonance images and pure tone audiometry were performed in all patients. We measured the dominance of the inferior petrosal sinus (IPS) and transverse-sigmoid sinus (TS/SS) ipsilateral to the affected ear. Most patients were characterized by asymmetric venous drainage (IPS, 53.2%; TS/SS, 81.7%). The dominant side of the IPS or TS/SS was independent of the side of the affected ear for all patients in this study. However, in 35 patients with early recovery within 2 weeks, the dominant side of TS/SS was significantly associated with the side of the affected ear (p = 0.011). Moreover, the dominance of both the IPS and TS/SS influenced hearing outcomes at 3 months. Dominant TS/SS ipsilateral to the affected ear, particularly in the presence of ipsilateral hypoplastic IPS, is associated with a favorable hearing prognosis of SSHL.

Petrosal morphology and cochlear function in Mesozoic stem therians

Here we describe the bony anatomy of the inner ear and surrounding structures seen in three plesiomorphic crown mammalian petrosal specimens. Our study sample includes the triconodont Priacodon fruitaensis from the Upper Jurassic of North America, and two isolated stem therian petrosal specimens colloquially known as the Höövör petrosals, recovered from Aptian-Albian sediments in Mongolia. The second Höövör petrosal is here described at length for the first time. All three of these petrosals and a comparative sample of extant mammalian taxa have been imaged using micro-CT, allowing for detailed anatomical descriptions of the osteological correlates of functionally significant neurovascular features, especially along the abneural wall of the cochlear canal. The high resolution imaging provided here clarifies several hypotheses regarding the mosaic evolution of features of the cochlear endocast in early mammals. In particular, these images demonstrate that the membranous cochlear duct adhered to the bony cochlear canal abneurally to a secondary bony lamina before the appearance of an opposing primary bony lamina or tractus foraminosus. Additionally, while corroborating the general trend of reduction of venous sinuses and plexuses within the pars cochlearis seen in crownward mammaliaforms generally, the Höövör petrosals show the localized enlargement of a portion of the intrapetrosal venous plexus. This new vascular feature is here interpreted as the bony accommodation for the vein of cochlear aqueduct, a structure that is solely, or predominantly, responsible for the venous drainage of the cochlear apparatus in extant therians. Given that our fossil stem therian inner ear specimens appear to have very limited high-frequency capabilities, the development of these modern vascular features of the cochlear endocast suggest that neither the initiation or enlargement of the stria vascularis (a unique mammalian organ) was originally associated with the capacity for high-frequency hearing or precise sound-source localization.

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.

Human inner ear blood supply revisited: the Uppsala collection of temporal bone-an international resource of education and collaboration

BACKGROUND

The Uppsala collection of human temporal bones and molds is a unique resource for education and international research collaboration. Micro-computerized tomography (micro-CT) and synchrotron imaging are used to investigate the complex anatomy of the inner ear. Impaired microcirculation is etiologically linked to various inner ear disorders, and recent developments in inner ear surgery promote examination of the vascular system. Here, for the first time, we present three-dimensional (3D) data from investigations of the major vascular pathways and corresponding bone channels.

METHODS

We used the archival Uppsala collection of temporal bones and molds consisting of 324 inner ear casts and 113 macerated temporal bones. Micro-CT was used to investigate vascular bone channels, and 26 fresh human temporal bones underwent synchrotron radiation phase contrast imaging (SR-PCI). Data were processed by volume-rendering software to create 3D reconstructions allowing orthogonal sectioning, cropping, and soft tissue analyses.

RESULTS

Micro-CT with 3D rendering was superior in reproducing the anatomy of the vascular bone channels, while SR-PCI replicated soft tissues. Arterial bone channels were traced from scala vestibuli (SV) arterioles to the fundus, cochlea, and vestibular apparatus. Drainage routes along the aqueducts were examined.

CONCLUSION

Human inner ear vessels are difficult to study due to the adjoining hard bone. Micro-CT and SR-PCI with 3D reconstructions revealed large portions of the micro-vascular system in un-decalcified specimens. The results increase our understanding of the organization of the vascular system in humans and how altered microcirculation may relate to inner ear disorders. The findings may also have surgical implications.

Complications of Sigmoid Sinus Transvenous Occlusion for the Endovascular Treatment of Dural Arteriovenous Shunts with Emphasis on Inner Ear Dysfunction

OBJECTIVE

Embolization of cranial dural sinus arteriovenous fistulae with transvenous occlusion of the involved sinuses is an established strategy when the collateral brain drainage allows it. We aimed to investigate the frequency and types of complications after endovascular occlusion of the sigmoid sinus.

METHODS

From our database, we detected 52 endovascularly treated consecutive cases of cranial dural arteriovenous shunts involving the sigmoid sinus. The cases treated through the transvenous approach alone or combined with the transarterial one were analyzed retrospectively. Previously reported series and cases were reviewed and critically analyzed.

RESULTS

In 15 cases, a transvenous approach was used and in 4 combined a transvenous approach with a transarterial approach. Two patients (13.3%) both treated with the transvenous approach alone presented postoperatively with vertigo and hearing loss. In the first case, the sinus occlusion involved the whole sigmoid sinus, whereas in the second case the occlusion was restricted to a parallel channel posteriorly to the proximal segment of the sigmoid sinus. Magnetic resonance imaging and ear, nose, and throat investigations failed to elucidate the cause and pathomechanism of these symptoms. No other complications occurred.

CONCLUSIONS

Although the transvenous occlusion of the sigmoid sinus generally is a safe therapeutic option for the treatment of dural arteriovenous fistulae, inner ear dysfunction is still a possible complication. The combined analysis of the reported and our cases did not allow a plausible explanation of this complication and its pathomechanism remains obscure.

Hearing Outcomes after Surgical Drainage of Petrous Apex Cholesterol Granuloma

Objective This study aims to assess the hearing outcomes of patients undergoing surgical management of petrous apex cholesterol granuloma and to discuss the role of otic capsule-sparing approaches in drainage of petrous apex cholesterol granulomas. Design Retrospective case series. Setting Tertiary care medical center. Participants Eight patients underwent surgery for presumed or definitive cholesterol granuloma between 2002 and 2011 and met the inclusion criteria for this study. Main Outcome Measures Pre- and postoperative audiogram results as measured by pure tone thresholds and word recognition scores. Results Four patients (50%) demonstrated improvement in speech discrimination. One patient had an increase from 0 to 67% in word recognition scores. Four patients (50%) demonstrated worsening of pure tone thresholds, including two patients with anacusis. Conclusion Perilabyrinthine drainage of petrous apex cholesterol granulomas may result in hearing preservation or hearing improvement, even in the setting of otic capsule erosion. Patients should be counseled about the potential risk of significant hearing loss.

Chronic cerebrospinal venous insufficiency in Ménière disease

Objectives

The aim of this study was to focus on patients suffering from cochleo-vestibular disorder with and without Ménière disease (MD) in order to verify whether chronic cerebrospinal drainage abnormalities could play a role in the etiopathogenesis of endolymphatic hydrops.

Methods

Fifty-two volunteers were enrolled and subdivided into two groups: 24 definite MD and 28 not-MD. Both magnetic resonance venography imaging with contrast-enhanced imaging of the venous cerebrospinal system (MRV) and venous echo-color Doppler (ECD) were performed.

Results

MRV showed abnormalities in 83% of MD and 57% of not-MD subjects ( p < 0.001). Asymmetrical cervical venous flow, assessed by MRV, was confirmed by ECD in 62.5% of MD but in only 21.5% of not-MD subjects ( p<0.001).

Conclusion

Chronic cerebrospinal venous insufficiency might be the anatomical background, which provides a predisposing factor for the development of endolymphatic hydrops in MD patients.

Bilateral sudden sensorineural hearing loss and chronic venous cerebrospinal insufficiency: a case report

OBJECTIVES

We report a case of bilateral sudden sensorineural hearing loss (SSHL) in a patient suffering from chronic venous cerebrospinal insufficiency (CCSVI).

METHODS

Audiometric testing confirmed bilateral sensorineural hearing loss with hypoexcitability to caloric stimulation on the left side and echo-colour Doppler examination showed abnormal cerebral venous deficiency.

RESULTS

The patient's condition improved after 15 days following medical treatment.

CONCLUSIONS

CCSVI may explain the anatomical background which provides a predisposing factor for SSHL although further studies are needed to verify whether this observation is casual or coincidental.

Surgical planning and evaluation of implanting a penetrating cochlear nerve implant in human temporal bones using microcomputed tomography

OBJECTIVE

To develop a transmastoid-posterior tympanotomy approach for the implantation of a penetrating auditory prosthesis in the most distal portion of the cochlear nerve.

BACKGROUND

Animal studies suggest that penetrating cochlear nerve implants may overcome limitations of current cochlear implant systems. One step toward human implantation is the development of a suitable surgical approach.

METHODS

In computer-rendered 3-dimensional (3-D) models (based on micro-CT scans of 10 human temporal bones), we simulated trajectories through the most basal part of the cochlea that gave access to the most distal portion of the cochlear nerve with minimal damage to intracochlear structures. We determined their vectors with respect to the mid-modiolar axis and posterior round window edge and assessed if they intersected the chorda tympani nerve.

RESULTS

The typical vector obtained with these 3-D models ran in an anterosuperior direction, through the inferior part of the facial recess and anterior round window edge. In 7 of 10 temporal bones, this trajectory intersected the chorda tympani nerve. Based on the vectors, dummy probes were implanted in 3 of 10 temporal bones, and the need for chorda tympani removal was confirmed in accordance with the 3-D models. Postoperative micro-CT scans revealed that all probes were successfully implanted in the cochlear nerve, whereas the osseous spiral lamina and basilar membrane were preserved.

CONCLUSION

The vector for drilling and implantation found in this study can be used as a guideline for real-life surgery and, therefore, is another step toward the clinical implementation of cochlear nerve implants.

Disorders of cochlear blood flow

The cochlea is principally supplied from the inner ear artery (labyrinthine artery), which is usually a branch of the anterior inferior cerebellar artery. Cochlear blood flow is a function of cochlear perfusion pressure, which is calculated as the difference between mean arterial blood pressure and inner ear fluid pressure. Many otologic disorders such as noise-induced hearing loss, endolymphatic hydrops and presbycusis are suspected of being related to alterations in cochlear blood flow. However, the human cochlea is not easily accessible for investigation because this delicate sensory organ is hidden deep in the temporal bone. In patients with sensorineural hearing loss, magnetic resonance imaging, laser-Doppler flowmetry and ultrasonography have been used to investigate the status of cochlear blood flow. There have been many reports of hearing loss that were considered to be caused by blood flow disturbance in the cochlea. However, direct evidence of blood flow disturbance in the cochlea is still lacking in most of the cases.