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

Idiopathic sudden sensorineural hearing loss: A review focused on the contribution of vascular pathologies

Idiopathic sudden sensorineural hearing loss (ISSNHL) is characterized by abruptly appearing hearing loss, sometimes accompanied by vertigo. Vascular pathologies (e.g., cochlear ischemia, or cochlear infarction) are one of the most likely causes of ISSNHL. This review aims to present current understanding of inner ear anatomy, clinical features of ISSNHL, and its treatment strategies. The labyrinthine artery is the only end artery supplying blood to the inner ear, and it has three branches: the anterior vestibular artery, the main cochlear artery, and the vestibulo-cochlear artery (VCA). Occlusion of the VCA can be caused by a variety of factors. The VCA courses through a narrow bone canal. ISSNHL is usually diagnosed after excluding retrocochlear pathologies of sudden sensorineural hearing loss (SSNHL), such as vestibular schwannoma. Therefore, a head MRI or assessing auditory brainstem responses are recommended for patients with SSNHL. Severe SSNHL patients with high CHADS2 scores, an index of stroke risk, have a significantly lower rate of vestibular schwannoma than severe SSNHL patients with low CHADS2 scores, suggesting that severe ISSNHL in individuals at high risk of stroke is caused by vascular impairments. Intralabyrinthine hemorrhage causes SSNHL or vertigo, as in ISSNHL. The diagnosis of intralabyrinthine hemorrhage requires careful interpretation of MRI, and a small percentage of patients diagnosed with ISSNHL may in fact have intralabyrinthine hemorrhage. Many studies have reported an association between ISSNHL and atherosclerosis or cardiovascular risk factors (e.g., diabetes mellitus, hypertension, dyslipidemia and cardiovascular disease), and subsequent risk of stroke in patients with ISSNHL may be elevated compared to controls. Increased hearing level on the healthy ear side, high Framingham risk score, high neutrophil-to-lymphocyte ratio, high platelet-to-lymphocyte ratio, and severe white matter lesions may be poor prognostic factors for patients with ISSNHL. The association between thrombosis-related genes and susceptibility to ISSNHL has been reported in many studies (e.g., coagulation factor 2, coagulation factor 5, plasminogen activator inhibitor-1, platelet-associated genes, a homocysteine metabolism-related enzyme gene, endothelin-1, nitric oxide 3, phosphodiesterase 4D, complement factor H, and protein kinase C-eta). Treatment of ISSNHL with the aim of mitigating the vascular impairment in the inner ear includes systemically administered steroids, intratympanic steroid injections, hyperbaric oxygen therapy, prostaglandin E1, defibrinogenation therapy, and hydrogen inhalation therapy, but there is currently no evidence-based treatment for ISSNHL. Breakthroughs in the unequivocal diagnosis and treatment of ISSNHL due to vascular impairment are crucial to improve quality of life.

Doing more with less: Realistic stereoscopic three-dimensional anatomical modeling from smartphone photogrammetry

Traditional teaching methods struggle to convey three-dimensional concepts effectively. While 3D virtual models and virtual reality platforms offer a promising approach to teaching anatomy, their cost and specialized equipment pose limitations, especially in disadvantaged areas. A simpler alternative is to use virtual 3D models displayed on regular screens, but they lack immersion, realism, and stereoscopic vision. To address these challenges, we developed an affordable method utilizing smartphone-based 360° photogrammetry, virtual camera recording, and stereoscopic display (anaglyph or side-by-side technique). In this study, we assessed the feasibility of this method by subjecting it to various specimen types: osteological, soft organ, neuroanatomical, regional dissection, and a dedicated 3D-printed testing phantom. The results demonstrate that the 3D models obtained feature a complete mesh with a high level of detail and a realistic texture. Mesh and texture resolutions were estimated to be approximately 1 and 0.2 mm, respectively. Additionally, stereoscopic animations were both feasible and effective in enhancing depth perception. The simplicity and affordability of this method position it as a technique of choice for creating easily photorealistic anatomical models combined with stereoscopic depth visualization.

The variations of osseous structure of the ınternal acoustic canal: an anatomical study

OBJECTIVES

The internal acoustic meatus is an osseous canal that connects the inner ear to the posterior cranial fossa. It is located in the petrous portion of the temporal bone. A thin cribriform osseous plate known as the fundus is situated at the lateral end of the canal. This study assesses the structural and numerical variations of the fundus formations.

METHODS

Fifty-four temporal bones of unknown gender and age were examined with the surgical microscope.

RESULTS

The temporal bones analyzed were 46.2% right-sided and 53.7% left-sided. Only one temporal bone had two parallel transverse crests, while three had a single anterior crest that split into two branches posteriorly. The number of foramina at the transverse crest varied, with 29.6% having none, 48.1% having a single foramen, and 22.2% having several foramina. An anterior crest structure was seen in 53.7% of the temporal bones, with 5% having a slightly constricted entry to the facial canal. In cases with a single nerve foramen, 48.1% had one, while 51.8% had more than one, including examples with three or four foramina. A crest was found between the foramina of the single nerve in 7% of patients. Furthermore, a crest between the saccular nerve foramen and the high fiber foramina was seen in 25.9% of cases, and 5% had two saccular nerve foramina.

CONCLUSION

We think that revealing the anatomical, structural and numerical variations in the fundus will be useful in explaining the disease-symptom relationship.

LEVEL OF EVIDENCE

Level 4.

Sudden unilateral audiovestibular loss due to acute labyrinthine haemorrhage can be missed on early MRI brain sequences: case report

Background

Labyrinthine haemorrhage is a rare vascular disorder often presenting with the triad of acute vertigo, sudden sensorineural hearing loss and tinnitus. There are minimal reports on imaging progression over the acute period.

Index case

A woman in her mid-40s presented with acute vertigo, sudden left-sided hearing loss and tinnitus, consistent with acute unilateral audiovestibular loss. Left peripheral vestibular hypofunction was confirmed acutely on video head impulse testing, and pure tone audiometry showed a profound left sensorineural hearing loss. An MRI brain including diffusion-weighted imaging within 24 hours was normal. Delayed MRI brain and internal acoustic canal after 7 days demonstrated increased 3D fluid-attenuated inversion recovery and T1 signal throughout the left cochlea and semicircular canals, without contrast enhancement. This was consistent with labyrinthine haemorrhage. She received early oral prednisone followed by three doses of intratympanic dexamethasone. At 12 months follow-up the patient remained profoundly deaf, however, balance and vestibular symptoms improved with early vestibular physical rehabilitation.

Conclusion

We report a case of acute labyrinthine haemorrhage missed on an early MRI brain sequence. This diagnosis should be considered in presentations of acute audiovestibular loss, and delayed MRI including internal auditory canal sequences may be important for diagnosis.

Prognosis of vestibular dysfunction in idiopathic sudden sensorineural hearing loss with vertigo: a prospective cohort study

BACKGROUND

Approximately 28%-57% of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) have an acute vertigo attack and probable vestibular dysfunction; however, the prognosis of vestibular function in these patients remains unclear.

METHODS

A prospective cohort study of patients with ISSNHL and vertigo was conducted to evaluate the prognosis of vestibular function, especially the roles of peripheral vestibular restoration and central compensation, in patients with ISSNHL and vertigo. Clinical data were recorded at baseline and at 60 days from onset in participants with unilateral ISSNHL with vertigo. Enrolment occurred from May 1, 2019 to May 1, 2022 in the outpatient clinics and inpatient departments of the Eye and ENT Hospital of Fudan University in Shanghai. The primary outcome measure was the recovery rate of vestibular function 60 days after onset as assessed by vestibular function tests, including caloric tests, cervical and ocular vestibular-evoked myogenic potential tests (cVEMP, oVEMP), video head impulse tests (vHIT), and sensory organization tests (SOT). The secondary outcome measure was the recovery of subjective evaluations in vestibular dysfunction (the dizziness handicap inventory [DHI], and the visual analogue scale for vertigo [VAS-V]) and hearing assessments (pure-tone audiometry [PTA]).

RESULTS

Overall, 86 patients were recruited, with an average duration of disease of 11.7 days and follow-up time of 60.7 days. Vestibular function was significantly improved (p < 0.05) after 60 days. The recovery rates were 100% for anterior semicircular canal (ASC), 56% for posterior semicircular canal (PSC), 41% for horizontal semicircular canal (HSC), 28% for saccule, and 23% for utricle. The recovery of vestibular function was not significantly related to changes in DHI (p = 0.245), VAS-V score (p = 0.509), or hearing outcome (p = 0.390).

CONCLUSIONS

Restoration of peripheral vestibular sensory input and central vestibular compensation can occur during the course of ISSNHL with vertigo. The otolith organs are at a higher risk of being affected and have worse recovery than the semicircular canals. Incomplete and in-process restoration of vestibular dysfunction may perturb and delay the establishment of central compensation for balance. Neither hearing outcomes nor subjective vestibular symptoms are related to recovery from vestibular dysfunction.

TRIAL REGISTRATION

ClinicalTrials.gov (identifier NCT03951584).

Influence of the Electrode Array Design on Incidence of Vertigo Symptoms and Vestibular Function After Cochlear Implantation

PURPOSE

To evaluate if a specific type of cochlear implant (CI) electrode array (EA) reveals higher rates/prevalence of vestibular symptoms and to characterize their respective relationship to intracochlear position and objective vestibular function.

METHODS

This retrospective study included 71 cochlear implantations in patients older than 18 years. The electrode position within the cochlea, electrode insertion angle, and cochlear coverage were determined from postoperative multiplanar reconstructed cone-beam computed tomography scans. All device manufacturers were represented. Data related to preoperative and postoperative PTA as well as vestibular symptoms in the preoperative and postoperative stages were collected from the patient's records.

RESULTS

Twelve of the 71 (16.9%) CI patients experienced vertigo symptoms in the early postoperative period. In 5 (7.0%) patients, the vertigo complaints lasted until the time of the first activation (5-6 weeks postoperative). Postoperative onset of vestibular symptoms was more often seen in patients receiving lateral wall (LW)/straight EAs (19%) compared to perimodiolar/precurved EAs (7%), but this was only a trend and no statistical significance was observed. Moreover, preoperative pathologic caloric responses (CRs) better predicted the postoperative onset of vestibular symptoms.

CONCLUSION

The preoperative consideration of a complicated CI-induced vertigo is important in the counseling particularly of elderly patients. We identified some risk factors for post-CI vertigo that should be considered in the patient's counseling: preoperative pathologic CRs, the extent of surgical trauma, and possibly the use of an LW EA, regardless of the length.

Post-COVID-19 Syndrome: Audiometric Findings in Patients with Audiological Symptoms

Since the SARS-CoV-19 pandemic, the possibility of audiological involvement by this virus has been speculated without being able to generate a true cause-effect relationship. The objective of this observational, descriptive cross-sectional study is to describe the audiometric findings of post-COVID-19 patients with audiological symptoms. A sample of 47 patients with a diagnosis of COVID-19 infection was included: The age range was between 18 and 50 years old, the mean age was 37.0 years with a standard deviation of ±8.3 years, and 32 patients (68.1%) were female and 15 male patients (31.9%). Patients were recruited by the Otolaryngology service at Civil Fray Antonio Mayor Hospital from September 2020 to December 2022. Tonal audiometry was performed in a window of no more than 3 months from the onset of symptoms. The Chi-square test was used and odds ratios (OR) were established to associate the variables of post-COVID-19 audiological symptoms and the prevalence of hearing loss. A 95% confidence interval (CI) and statistical significance were considered of p ≤ 0.05. The audiological symptoms presented a prevalence of 74.4% for a sensation of ear fullness, 59.6% for tinnitus, and 51.1% for a sensation of hearing loss.

Anatomical Variations of the Human Cochlea Using an Image Analysis Tool

Understanding cochlear anatomy is crucial for developing less traumatic electrode arrays and insertion guidance for cochlear implantation. The human cochlea shows considerable variability in size and morphology. This study analyses 1000+ clinical temporal bone CT images using a web-based image analysis tool. Cochlear size and shape parameters were obtained to determine population statistics and perform regression and correlation analysis. The analysis revealed that cochlear morphology follows Gaussian distribution, while cochlear dimensions A and B are not well-correlated to each other. Additionally, dimension B is more correlated to duct lengths, the wrapping factor and volume than dimension A. The scala tympani size varies considerably among the population, with the size generally decreasing along insertion depth with dimensional jumps through the trajectory. The mean scala tympani radius was 0.32 mm near the 720° insertion angle. Inter-individual variability was four times that of intra-individual variation. On average, the dimensions of both ears are similar. However, statistically significant differences in clinical dimensions were observed between ears of the same patient, suggesting that size and shape are not the same. Harnessing deep learning-based, automated image analysis tools, our results yielded important insights into cochlear morphology and implant development, helping to reduce insertion trauma and preserving residual hearing.

Cardiovascular risk factors among patients with acute unilateral inner ear hypofunction: A case-control study

Objectives

To assess the prevalence of cardiovascular risk factors (CVRFs) and their impact on acute unilateral inner ear hypofunction (AUIEH), including acute unilateral peripheral vestibulopathy (AUPVP), sudden sensorineural hearing loss (SSNHL) and acute unilateral audiovestibular hypofunction (AUAVH).

Methods

One hundred and twenty-five patients consecutively diagnosed with AUPVP, SSNHL or AUAVH and 250 sex- and age-matched controls were included. Cases presented a mean age of 58.6 ± 14.7 years and included 59 women and 66 men. The correlation between CVRFs (high blood pressure [HBP], diabetes mellitus [DM], dyslipidemia [DLP], cardiocerebrovascular disease [CCVD]) and AUIEH was assessed by multivariate conditional logistic regression analysis.

Results

A higher prevalence of CVRFs was identified in patients than in controls (30 individuals with DM, 53 with HBP, 45 with DLP and 14 with a previous history of CCVD, p < .05). A significantly elevated risk of AUIEH was found in patients with two or more CVRFs (adjusted odds ratio [OR] 5.11; 95% CI 2.23-11.70). Previous CCVD individually predicted AUIEH (OR 8.41; 95% CI 2.36-29.88). Subgroup analysis showed the same tendency for AUPVP and SSNHL.

Conclusion

Acute unilateral inner ear hypofunction patients presented significantly more CVRFs than controls, and the presence of two or more CVRFs was associated with AUIEH. Future studies evaluating vascular risk in AUIEH may include AUPVP and SSNHL patients from the same source population to better characterize risk profiles that can indicate a vascular origin.

Level of Evidence

3b.

Inner ear organoids: progress and outlook, with a focus on the vascularization

The inner ear is a complex organ that encodes sound, motion, and orientation in space. Given the complexity of the inner ear, it is not surprising that treatments are relatively limited despite the fact that, in 2015, hearing loss was the fourth leading cause of years lived with disability worldwide. Inner ear organoid models are a promising tool to advance the study of multiple aspects of the inner ear to aid the development of new treatments and validate drug-based therapies. The blood supply of the inner ear plays a pivotal role in growth, maturation, and survival of inner ear tissues and their physiological functions. This vasculature cannot be ignored in order to achieve a truly in vivo-like model that mimics the microenvironment and niches of organ development. However, this aspect of organoid development has remained largely absent in the generation of inner ear organoids. The current review focuses on three-dimensional inner ear organoid and how recent technical progress in generating in vitro vasculature can enhance the next generation of these models.

Cervical and Ocular Vestibular Evoked Myogenic Potential Recovery in Susac Syndrome: A Case Report

Purpose:

Susac syndrome (SS) is a rare autoimmune disorder that affects the brain and the retina and causes unilateral or bilateral sensorineural hearing loss. Although vestibular dysfunction is reported in SS, limited information is available underlying the vestibular pathophysiology.

Method:

The diagnosis of SS was established based on symptoms and diagnostic tools such as magnetic resonance imaging and fundus fluorescein angiography. The audiovestibular evaluation was done on the seventh day of admission (Session 1) into the emergency unit, whereas the second and third evaluations were done at 3-month (Session 2) and 8-month (Session 3) follow-ups after discharge, respectively. The audiovestibular test battery consisted of routine audiological tests, auditory brainstem response, and vestibular evoked myogenic potentials (VEMPs; both cervical and ocular).

Results:

We found unilateral sensorineural hearing loss and absent cervical VEMPs(cVEMPs) when testing the left ear during Session 1. In the following sessions, the unilateral hearing loss did not recover; however, cVEMPs were present bilaterally. The ocular VEMPs showed an increase in amplitude during Sessions 2 and 3.

Conclusions:

SS can selectively disrupt auditory and vestibular structures. It may present with unique findings of audiovestibular tests. A detailed audiovestibular evaluation may be essential in patients with SS.

Supplemental Material:

https://doi.org/10.23641/asha.21513843

Three-Dimensional High-Resolution Temporal Bone Histopathology Identifies Areas of Vascular Vulnerability in the Inner Ear

OBJECTIVES

Hypothesized causes of vestibular neuritis/labyrinthitis include neuroinflammatory or vascular disorders, yet vascular disorders of the inner ear are poorly understood. Guided by known microvascular diseases of the retina, we developed 2 hypotheses: (1) there exist vascular vulnerabilities of artery channels in cases of hypothetical nerve swelling for the superior, inferior, and vestibulocochlear artery and (2) there are arteriovenous crossings that could compromise vascular flow in disease states.

METHODS

Two fully mounted and stained temporal bones were used to render three-dimensional reconstructions of the labyrinth blood supply. Using these maps, areas of potential vascular compression were quantified in 50 human temporal bones.

RESULTS

Although inner ear arteries and veins mostly travel within their own bony channels, they may be exposed (1) at the entrance into the otic capsule, and (2) where the superior vestibular vein crosses the inferior vestibular artery. At the entry into the otic capsule, the ratio of the soft tissue to total space for the superior vestibular artery was significantly greater than the inferior vestibular artery/cochleovestibular artery (median 44, interquartile range 34-55 vs. 14 [9-17], p < 0.0001).

CONCLUSIONS

Three-dimensional reconstruction of human temporal bone histopathology can guide vascular studies of the human inner ear. Studies of retinal microvascular disease helped identify areas of vascular vulnerability in cases of hypothetical nerve swelling at the entrance into the otic capsule and at an arteriovenous crossing near the saccular macula. These data may help explain patterns of clinical findings in peripheral vestibular lesions.

Vascular mechanisms in acute unilateral peripheral vestibulopathy: a systematic review

Acute unilateral peripheral vestibulopathy (AUPVP) is a frequent cause of vestibular loss. Several aetiologies have been proposed, but the exact mechanism remains unknown. The aim of this study is a systematic analysis of the literature evaluating the vascular aetiology of AUPVP. A systematic literature search was performed in PubMed, Cochrane Library and Embase, including articles published from January 1^st, 2010 to November 30^th, 2020. Two reviewers independently selected articles investigating a link between AUPVP and vascular disease. The following information was extracted: year of publication, country, level of evidence, assessed vascular risk factors and number of patients. A total of 450 articles was obtained. Eleven articles were retained with 100% agreement between the two reviewers. In a pooled population of 805 patients, the main results were the higher neutrophil to lymphocyte ratio and higher prevalence of vascular risk factors among AUPVP patients. A meta-analysis was not performed because the studies were too heterogeneous in terms of methodology. Indirect arguments for vascular mechanisms in AUPVP were found. These findings indicate that larger prospective well-controlled studies are needed to clarify the vascular aetiology of AUPVP.

Synchrotron Radiation-Based Reconstruction of the Human Spiral Ganglion: Implications for Cochlear Implantation

OBJECTIVE

To three-dimensionally reconstruct Rosenthal's canal (RC) housing the human spiral ganglion (SG) using synchrotron radiation phase-contrast imaging (SR-PCI). Straight cochlear implant electrode arrays were inserted to better comprehend the electro-cochlear interface in cochlear implantation (CI).

DESIGN

SR-PCI was used to reconstruct the human cochlea with and without cadaveric CI. Twenty-eight cochleae were volume rendered, of which 12 underwent cadaveric CI with a straight electrode via the round window (RW). Data were input into the 3D Slicer software program and anatomical structures were modeled using a threshold paint tool.

RESULTS

The human RC and SG were reproduced three-dimensionally with artefact-free imaging of electrode arrays. The anatomy of the SG and its relationship to the sensory organ (Corti) and soft and bony structures were assessed.

CONCLUSIONS

SR-PCI and computer-based three-dimensional reconstructions demonstrated the relationships among implanted electrodes, angular insertion depths, and the SG for the first time in intact, unstained, and nondecalcified specimens. This information can be used to assess stimulation strategies and future electrode designs, as well as create place-frequency maps of the SG for optimal stimulation strategies of the human auditory nerve in CI.

Cochleo-facial corridor to the vestibule and fundus of the internal auditory canal through oval window: a minimal invasive and cochlea sparing approach

PURPOSE

This cadaveric work aimed to test the effectiveness of a modified surgical corridor (ExpTSA: expanded transcanal supracochlear approach) developed for anatomic cochlear preservation in selected vestibular schwannoma patients necessitating to perform cochlear implantation for appropriate cases to achieve the best outcome.

METHODS

The ears of 10 cadavers (at mean age 75.70 ± 13.75 years, range 45-92 years) were dissected from the external auditory canal (EAC) to the internal auditory canal by ExpTSA under the guidance of a microscope and endoscope. All stages of the surgical process were recorded step by step and evaluated morphometrically.

RESULTS

The vestibular base was successfully reached in all ears without damaging the cochlear morphology and facial nerve. The vestibular base was 23.33 ± 2.02 mm away from the entrance (external orifice) and 10.26 ± 1.33 mm from the exit (internal orifice) of EAC. The oval window and vestibular base were measured to be 2.94 ± 1.05 mm and 5.87 ± 1.24 mm deep from the facial nerve, respectively. The normal areas of the oval window, the exit and entrance of EAC were found as 2.90 ± 0.81 mm², 42.52 ± 13.66 mm², and 110.73 ± 25.32 mm², respectively. After ExpTSA procedure, the areas of the oval window (11.04 ± 2.83 mm²), the exit (122.45 ± 20.41 mm²) and entrance (167.49 ± 30.94 mm²) of EAC were expanded approximately 280%, 188%, and 50%, respectively.

CONCLUSION

The ExpTSA may be performed for accessing to the vestibule and fundus of IAC for tumor removal of intravestibular schwannoma patients (with or without fundus involvement) with unserviceable hearing, preserving the cochlear morphology.

Association Between Microvascular Retinal Signs and Age-Related Hearing Loss in the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS)

Importance

Given that age-related hearing loss is highly prevalent and treatable, understanding its causes may have implications for disease prevention.

Objective

To investigate whether microvascular retinal signs are associated with age-related hearing loss attributable to a hypothesized underlying shared pathologic entity involving microvascular disease.

Design, Setting, and Participants

The Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS) is a community-based prospective cohort study of 15 792 men and women aged 45 to 64 years at baseline. The ARIC-NCS participants returned for a fifth clinic visit in 2011-2013 and a sixth clinic visit in 2016-2017. Participants were recruited from 4 US communities (Washington County, Maryland; Forsyth County, North Carolina; Jackson, Mississippi; and Minneapolis suburbs, Minnesota). Participants included a subset of the ARIC-NCS cohort with complete covariate data who underwent retinal fundus photography at visit 5 (2011-2013) and completed hearing assessment at visit 6 (2016-2017) (N = 1458). Overall, 453 participants had diabetes; of those, 68 had retinopathy. Of 1005 participants without diabetes, 42 had retinopathy.

Exposures

Microvascular retinal signs included retinopathy, arteriovenous (AV) nicking, and generalized arteriolar narrowing measured using the central retinal arteriolar equivalent (CRAE).

Main Outcomes and Measures

Hearing was measured using the better-hearing ear pure-tone average (PTA) of air conduction speech thresholds (0.5, 1, 2, and 4 kHz). Multivariable-adjusted linear and ordered logistic regression was used to estimate the association between microvascular retinal signs and age-related hearing loss to describe the precision of the estimates and provide a plausible range for the true association.

Results

After full adjustment among 1458 individuals in the analytic cohort (mean [SD] age, 76.1 [5.0] years [age range, 67-90 years]; 825 women [56.6%]; 285 black [19.5%]), the difference in PTA per dB hearing level in persons with and without retinopathy was 2.21 (95% CI, -0.22 to 4.63), suggesting that retinopathy is associated with poorer hearing, although the width of the 95% CI prevents definitive conclusions about the strength of the observed association. Restricting the analysis to participants without diabetes, the difference in PTA associated with retinopathy was even greater (4.14; 95% CI, 0.10-8.17 dB hearing level), but the large width of the 95% CI prevents definitive conclusions about the association. In analyses quantifying the mean differences in hearing thresholds at individual frequencies by retinopathy status, the estimates trended toward retinopathy being associated, contrary to expectation, with better high-frequency hearing. At 8 kHz, the estimated difference in hearing thresholds in persons with retinopathy vs those without was -4.24 (95% CI, -7.39 to -1.09).

Conclusions and Relevance

In this population-based study, an association between the presence of microvascular retinal signs and hearing loss was observed, suggesting that retinopathy may have the potential to identify risk for hearing loss in persons without diabetes. The precision of these estimates is low; therefore, additional epidemiologic studies are needed to better define the degree of microvascular contributions to age-related hearing loss.

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.

Vascular Supply of the Human Spiral Ganglion: Novel Three-Dimensional Analysis Using Synchrotron Phase-Contrast Imaging and Histology

Human spiral ganglion (HSG) cell bodies located in the bony cochlea depend on a rich vascular supply to maintain excitability. These neurons are targeted by cochlear implantation (CI) to treat deafness, and their viability is critical to ensure successful clinical outcomes. The blood supply of the HSG is difficult to study due to its helical structure and encasement in hard bone. The objective of this study was to present the first three-dimensional (3D) reconstruction and analysis of the HSG blood supply using synchrotron radiation phase-contrast imaging (SR-PCI) in combination with histological analyses of archival human cochlear sections. Twenty-six human temporal bones underwent SR-PCI. Data were processed using volume-rendering software, and a representative three-dimensional (3D) model was created to allow visualization of the vascular anatomy. Histologic analysis was used to verify the segmentations. Results revealed that the HSG is supplied by radial vascular twigs which are separate from the rest of the inner ear and encased in bone. Unlike with most organs, the arteries and veins in the human cochlea do not follow the same conduits. There is a dual venous outflow and a modiolar arterial supply. This organization may explain why the HSG may endure even in cases of advanced cochlear pathology.

Histopathological changes to the peripheral vestibular system following meningitic labyrinthitis

OBJECTIVE

While cochlear ossification is a common sequalae of meningitic labyrinthitis, less is known about the effects of meningitis on peripheral vestibular end organs. Herein, we investigate histopathologic changes in the peripheral vestibular system and cochlea in patients with a history of meningitic labyrinthitis.

METHODS

Temporal bone (TB) specimens from patients with a history of meningitis were evaluated and compared to age-matched controls. Specimens were evaluated by light microscopy and assessed for qualitative changes, including the presence of vestibular and/or cochlear endolymphatic hydrops, presence and location of inflammatory cells, new bone formation, and labyrinthitis ossificans; and quantitative changes, including Scarpa's ganglion neuron (ScGN) and spiral ganglion neuron (SGN) counts.

RESULTS

Fifteen TB from 10 individuals met inclusion and exclusion criteria. Presence of inflammatory cells and fibrous tissue was found in 5 TB. Of these, evidence of labyrinthitis ossificans was found in 2 TB. In the peripheral vestibular system, mild to severe degeneration of the vestibular membranous labyrinth was identified in 60% of cases (n = 9 TBs). There was a 21.2% decrease (range, 3%-64%) in the mean total count of ScGN in patients with meningitis, compared to age-matched controls. In the cochlea, there was a 45% decrease (range, 25.3%-80.9%) in the mean total count of SGN compared to age-matched controls (n = 14 TBs).

CONCLUSIONS

Otopathologic analysis of TB from patients with a history of meningitic labyrinthitis demonstrated distinct peripheral vestibular changes. Future research may help to delineate potential mechanisms for the observed otopathologic changes following meningitis.

LEVEL OF EVIDENCE

N/A.

Investigations of the Microvasculature of the Human Macula Utricle in Meniere's Disease

The integrity and permeability of the blood labyrinthine barrier (BLB) in the inner ear is important to maintain adequate blood supply, and to control the passage of fluids, molecules and ions. Identifying the cellular and structural components of the BLB, the vascular endothelial cells (VECs), pericytes, and the perivascular basement membrane, is critical to understand the pathophysiology of the inner ear microvasculature and to design efficient delivery of therapeutics across the BLB. A recent study of the normal and pathological ultrastructural changes in the human macula utricle microvasculature demonstrated that the VECs are damaged in Meniere’s disease (MD), and further studies identified oxidative stress markers (iNOS and nitrotyrosine) in the VECs. Using fluorescence microscopy, the microvasculature was studied in the macula utricle of patients diagnosed with MD that required transmastoid labyrinthectomy for intractable vertigo (n = 5), and patients who required a translabyrinthine approach for vestibular schwannoma (VS) resection (n = 3). Normal utricles (controls) were also included (n = 3). VECs were identified using rabbit polyclonal antibodies against the glucose transporter-1 (GLUT-1) and pericytes were identified using mouse monoclonal antibodies against alpha-smooth muscle actin (α-SMA). Immunofluorescence (IF) staining was made in half of the utricle and flat mounted. The other half was used to study the integrity of the BLB using transmission electron microscopy (TEM). GLUT-1-IF, allowed delineation of the macula utricle microvasculature (located in the stroma underneath the sensory epithelia) in both MD and VS specimens. Three sizes of vessels were present in the utricle vasculature: Small size (<15 μm), medium size (15–25 μm) and large size >25 μm. α-SMA-IF was present in pericytes that surround the VECS in medium and thick size vessels. Thin size vessels showed almost no α-SMA-IF. AngioTool software was used for quantitative analysis. A significant decreased number of junctions, total vessel length, and average vessel length was detected in the microvasculature in MD specimens compared with VS and control specimens. The deeper understanding of the anatomy of the BLB in the human vestibular periphery and its pathological changes in disease will enable the development of non-invasive delivery strategy for the treatment of hearing and balance disorders.

The Human Endolymphatic Sac and Inner Ear Immunity: Macrophage Interaction and Molecular Expression

Background: The endolymphatic sac (ES) is endowed with a multitude of white blood cells that may trap and process antigens that reach the inner ear from nearby infection-prone areas, it thus serves as an immunologic defense organ. The human ES, and unexpectedly the rest of the inner ear, has been recently shown to contain numerous resident macrophages. In this paper, we describe ES macrophages using super-resolution structured fluorescence microscopy (SR-SIM) and speculate on these macrophages' roles in human inner ear defense. Material and Methods: After ethical permission was obtained, human vestibular aqueducts were collected during trans-labyrinthine surgery for acoustic neuroma removal. Tissues were placed in fixative before being decalcified, rapidly frozen, and cryostat sectioned. Antibodies against IBA1, cytokine fractalkine (CX3CL1), toll-like receptor 4 (TLR4), cluster of differentiation (CD)68, CD11b, CD4, CD8, and the major histocompatibility complex type II (MHCII) were used for immunohistochemistry. Results: A large number of IBA1-positive cells with different morphologies were found to reside in the ES; the cells populated surrounding connective tissue and the epithelium. Macrophages interacted with other cells, showed migrant behavior, and expressed immune cell markers, all of which suggest their active role in the innate and adaptive inner ear defense and tolerance. Discussion: High-resolution immunohistochemistry shows that antigens reaching the ear may be trapped and processed by an immune cell machinery located in the ES. Thereby inflammatory activity may be evaded near the vulnerable inner ear sensory structures. We speculate on the immune defensive link between the ES and the rest of the inner ear.