Acute hyperfibrinogenemia impairs cochlear blood flow and hearing function in guinea pigsin vivo

The Role of Fibrinogen, Homocysteine and Metabolic Syndrome's Alterations in Sudden Sensorineural Hearing Loss (SSHL): A Narrative Review

Fibrinogen and homocysteine (HCY) are molecules known to play a role in vascular homeostasis, and their blood levels are often elevated in patients with metabolic syndrome. Recent evidence suggests that sudden sensorineural hearing loss (SSHL) may have a vascular origin. This has led many authors to advocate that fibrinogen, homocysteine, and metabolic syndrome (MetS) may play a direct role in SSHL. The aim of this brief review is to examine the role and influence of these molecules and MetS on the mechanisms of SSHL. Elevated fibrinogen levels have been associated with a worse prognosis in SSHL, possibly due to increased blood viscosity and decreased blood flow. Similarly, HCY has been associated with vascular damage, particularly in hyperhomocysteinemia, although the exact association with SSHL remains controversial. MetS has been demonstrated to function both as a causative factor and as a contributor to poorer recovery in cases of SSHL. However, although some studies suggest a possible role for these biomarkers and MetS in the prognosis and treatment of SSHL, specific therapeutic and preventive strategies based solely on these factors have yet to be developed. Given their potential role in prognosis and treatment and the global epidemic of metabolic syndrome, this issue needs to be analyzed comprehensively. Thus, further quality studies need to be conducted, even though it is difficult to determine the actual impact of MetS on the development of SSHL, as it is a multifactorial disease affecting multiple organs.

Randomized, placebo-controlled study on efficacy, safety and tolerability of drug-induced defibrinogenation for sudden sensorineural hearing loss: the lessons learned

PURPOSE

Disturbance of cochlear microcirculation is discussed as final common pathway of various inner ear diseases. Hyperfibrinogenemia causing increased plasma viscosity is a possible factor for a critical reduction of cochlear blood flow that might lead to sudden sensorineural hearing loss (SSHL). The aim was to determine the efficacy and safety of drug-induced defibrinogenation by ancrod for SSHL.

METHODS

Double-blind, randomized, placebo-controlled, multicenter, parallel group, phase II (proof-of-concept) study (planned enrollment: 99 patients). Patients received an infusion of ancrod or placebo (day 1) followed by subcutaneous administrations (day 2, 4, 6). Primary outcome was the change in pure tone audiogram air conduction average until day 8.

RESULTS

The study was terminated early due to slow recruiting (31 enrolled patients: 22 ancrod, 9 placebo). A significant improvement of hearing loss was registered in both groups (ancrod: - 14.3 dB ± 20.4 dB, - 39.9% ± 50.4%; placebo: - 22.3 dB ± 13.7 dB, - 59.1% ± 38.0%). A statistically significant group-difference was not detected (p = 0.374). Placebo response of 33.3% complete and 85.7% at least partial recovery was observed. Plasma fibrinogen levels were reduced significantly by ancrod (baseline: 325.2 mg/dL, day 2: 107.2 mg/dL). Ancrod was tolerated well, no adverse drug reaction was of severe intensity, no serious adverse events occurred.

CONCLUSION

Ancrod reduced fibrinogen levels that support its mechanism of action. The safety profile can be rated positively. Since the planned number of patients could not be enrolled, no efficacy conclusion can be drawn. The high rate of placebo response challenges clinical trials for SSHL and needs to be considered in future investigations. Trial registrations This study was registered in the EU Clinical Trials Register, EudraCT-No. 2012-000066-37 at 2012-07-02.

Comorbidities and laboratory changes of sudden sensorineural hearing loss: a review

Sudden sensorineural hearing loss (SSNHL) is defined as an abrupt hearing loss of more than 30 dB in three contiguous frequencies within 72 h. It is an emergency disease requiring immediate diagnosis and treatment. The incidence of SSNHL in Western countries' population is estimated between 5 and 20 per 1,00,000 inhabitants. The etiology of SSNHL remains unknown. Due to the uncertainty of the cause of SSNHL, at present, no specific treatment targets the cause of SSNHL, resulting in poor efficacy. Previous studies have reported that some comorbidities are risk factors for SSNHL, and some laboratory results may provide some clues for the etiology of SSNHL. Atherosclerosis, microthrombosis, inflammation, and the immune system may be the main etiological factors for SSNHL. This study confirms that SSNHL is a multifactorial disease. Some comorbidities, such as virus infections, are suggested to be the causes of SSNHL. In summary, by analyzing the etiology of SSNHL, more targeting treatments should be used to achieve a better effect.

[Analysis of coagulation state in sudden deafness patients with total deafness and vertigo]

Objective:To analyze the coagulation status and prognosis of sudden deafness patients with total deafness accompanied by vertigo, and to provide basis for improving the treatment of this disease. Methods:From January 2017 to December 2020, 33 patients with total deafness and vertigo sudden deafness who were hospitalized in the Department of Otolaryngology Head and Neck Surgery, Hebei Provincial People's Hospital were selected as the research group. During the same period, 33 cases of low frequency type, full frequency type, total deafness and 26 cases of high frequency type were treated as control group.Thirty-three cases of inpatients without history of middle ear and inner ear diseases were treated as normal control group. The levels of fibrinogen（FIB）, D-Dimer（D-D）, Prothrombin Time（PT）, Activated Partial Thrombin Time（APTT） between the research group and the control group were analyzed, and the therapeutic effects of different types of sudden deafness patients were analyzed. Results:FIB and D-D of total deafness with vertigo were 2.50（2.11, 2.95）and 0.27（0.16, 0.51） respectively, which were higher than 2.31（1.92, 2.50） and 0.17（0.12, 0.21） of normal group. APTT was 25.2（23.1, 28.1）, lower than 27.3（26.4, 29.7） in the normal group, the differences were statistically significant（P<0.01）. ② FIB of total deafness with vertigo was 2.50（2.11, 2.95）, which was higher than that of low frequency group 2.37（1.81, 2.68）. D-D was 0.27（0.16, 0.51）, higher than low frequency group 0.16（0.12, 0.25）, high frequency group of 0.13（0.11, 0.23）, the whole frequency group 0.16（0.11, 0.28）, total of 0.18（1.45, 0.30）. APTT was 25.75±3.18/25.2（23.1, 28.1）, lower than 27.72±2.22 in low frequency group and 26.7（25.8, 28.7） in full frequency group, with statistical significance（P<0.05）. ③ The total deafness with vertigo group had the worst curative effect（ineffective rate was 63.6%）, and the low frequency group had the best curative effect（recovery rate was 75.8%）. The difference of curative effect among different types of sudden deafness groups was statistically significant（P<0.05）. Conclusion:Hypercoagulability and thrombosis may be one of the influencing factors of total sudden deafness. The hypercoagulable state of sudden deafness patients with total deafness and vertigo is more serious than that of total deafness and other types of sudden deafness, and the prognosis is the worst.

Cannabinoid Receptor 2 Agonism is Capable of Preventing Lipopolysaccharide Induced Decreases of Cochlear Microcirculation - A Potential Approach for Inner Ear Pathologies

HYPOTHESIS

The ability of JWH-133, an agonist at the cannabinoid receptor 2, to abrogate the effects of lipopolysaccharide on cochlear microcirculation was investigated.

BACKGROUND

Cochlear inflammation and subsequent impairment of microcirculation is part of numerous pathologies affecting inner ear function, including suppurative labyrinthitis, noise trauma, and sudden sensorineural hearing loss. One way of causing cochlear inflammation is exposing the cochlea to lipopolysaccharide, a bacterial endotoxin.

METHODS

Twenty Dunkin-hartley guinea pigs were divided into four groups of five animals each. Two groups received topic treatment with JWH-133 and two received treatment with placebo. One group that had been treated with JWH-133 and one with placebo were then exposed to lipopolysaccharide or placebo, respectively. Cochlear microcirculation was quantified before, in between and after treatments by in vivo fluorescence microscopy.

RESULTS

Significantly different changes in cochlear blood flow were only seen in the group that was treated with placebo and subsequently lipopolysaccharide. Every other group showed no significant change in cochlear blood flow.

CONCLUSION

JWH-133 is capable of abrogating the effects of lipopolysaccharide on cochlear microcirculation. It may therefore be clinical interest in treating numerous inflammation associated cochlear pathologies.

Sudden sensorineural hearing loss during pregnancy: etiology, treatment, and outcome

OBJECTIVE

To analyze the etiologies, treatments, and outcomes of sensorineural hearing loss (SSNHL) during pregnancy.

STUDY DESIGN

Retrospective chart review of 25 pregnant patients treated for SSNHL between January 2012 and September 2019. Forty-nine age matched non-pregnant women with severe and profound hearing loss diagnosed with SSNHL during the same period served as controls. Data were recorded on age, symptoms, onset of hearing loss, audiometric results, treatments, and outcomes.

RESULTS

The mean age was 29.6 years (range 23-38 years). Intratympanic steroids (ITS) were administered in 15 (60.0%) pregnant women with SSNHL. Three women were treated with postauricular steroids only, while another woman was treated with intravenous ginkgo leaf extract and dipyridamole. The remaining six women received no medications. More than half (8/15, 53.3%) of pregnant women with SSNHL receiving ITS experienced hearing improvement. Pregnant women with profound hearing loss who received no medication had no hearing improvement. Most pregnant women with SSNHL (12/15, 80.0%) had higher fibrinogen levels than controls (mean values 3.77±0.71 g/L and 2.54±0.48 g/L, respectively).

CONCLUSION

Fibrinogen could be a risk factor for SSNHL during pregnancy. ITS may benefit pregnant women with severe and profound SSNHL.

Lipopolysaccharide decreases cochlear blood flow dose dependently in a guinea pig animal model via TNF signaling

OBJECTIVE

To evaluate the effect of Lipopolysaccharide (LPS), a bacterial endotoxin on cochlear microcirculation, and its mode of action.

METHODS

Twenty-five Dunkin-Hartley guinea pigs were divided into five groups of five animals each. After surgical preparation, cochlear microcirculation was quantified by in vivo fluorescence microscopy. Placebo or LPS (1 mg, 10 µg, and 100 ng) was applied topically, and microcirculation was measured before and twice after application. A fifth group was pretreated with etanercept, a tumor necrosis factor (TNF) antagonist, and afterward the lowest LPS concentrations that yielded significant results (10 µg) were applied.

RESULTS

In the groups that had been treated with 1 mg and 10 µg LPS, a significant drop in cochlear microcirculation was observed after 30 (.791 ± .089 Arbitrary Units (AU), compared to baseline, and .888 ± .071AU) and 60 (.756 ± .101 AU and .817 ± .124 AU, respectively) minutes. The groups that had been treated with 100 ng LPS and that had been pretreated with etanercept showed no significant change in cochlear blood flow compared to placebo.

CONCLUSION

Lipopolysaccharide shows a dose-dependent effect on cochlear microcirculation; this effect can already be observed after 30 min. Pretreatment with etanercept can abrogate this effect, indicating that TNF mediates the effect of LPS on cochlear microcirculation.

Biomarkers Suggesting Favorable Prognostic Outcomes in Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is a medical emergency, making detailed examination to determine possible causes and early treatment important. However, etiological examinations in SSNHL do not always reveal a cause, and several factors have been found to affect treatment outcomes. Various studies are being performed to determine the prognosis and effects of treatment in patients who experience sudden hearing loss, and to identify biomarkers associated with this condition. Embase, PubMed, and the Cochrane database were searched using the key words SSNHL, prognostic, and biomarker. This search identified 4 articles in Embase, 28 articles in PubMed, and 36 in the Cochrane database. Of these 68 articles, 3 were duplicates and 37 were unrelated to the research topic. After excluding these articles, the remaining 28 articles were reviewed. Factors associated with SSNHL were divided into six categories: metabolic, hemostatic, inflammatory, immunologic, oxidative, and other factors. The associations between these factors with the occurrence of SSNHL and with patient prognosis were analyzed. Low monocyte counts, low neutrophil/lymphocyte ratio (NLR) and monocyte/high-density lipoproteins (HDL) cholesterol ratio (MHR), and low concentrations of fibrinogen, platelet glycoprotein (GP) IIIa, and TNF-α were found to be associated with good prognosis. However, these factors alone could not completely determine the onset of and recovery from SSNHL, suggesting the need for future basic and clinical studies.

Analysis of Clinical and Laboratory Findings of Idiopathic Sudden Sensorineural Hearing Loss

Idiopathic sudden sensorineural hearing loss (ISSNHL) is an emergency disease requiring immediate diagnosis and treatment. The incidence of ISSNHL in the Western countries’ population was estimated to 5–20 per 100,000 inhabitants. The etiology of ISSNHL remains unknown. Its pathogenesis is most often suggested to be due to a disturbed microcirculation and infection. Previous studies have reported that comorbidities, including hypertension, diabetes mellitus (DM), and hyperfibrinogenemia are risk factors of ISSNHL. This study aimed at investigating the clinical characteristics, laboratory parameters and comorbidities of patients with ISSNHL. Our study suggests that the annual incidence of ISSNHL in China mainland is 19 per 100 000. The clinical characteristics and prevalence of comorbidities of ISSNHL patients are different according to age distribution and hearing results. Moreover, the patients with vertigo, hypertension, DM and high TG suffered more often from severe hearing loss compared with the counterparts. This indicates that the cardiovascular and metabolic diseases (hypertension and hyperlipidemia) appeared to be closely associated with the occurrence and severity of ISSNHL.

Serum Fibrinogen as a Prognostic Factor in Sudden Sensorineural Hearing Loss: A Meta-analysis

OBJECTIVE

High blood viscosity has been proposed as a mechanism for sudden sensorineural hearing loss (SSNHL); however, the relationship between blood markers of fibrinolysis or coagulation and severity or prognosis of SSNHL is still unclear. The aim of this study is to investigate the relationship between serum fibrinogen and SSNHL.

DATA SOURCES

PubMed and Scopus were searched for English language articles using the following keywords: SSNHL, sudden hearing loss, sudden deafness, idiopathic hearing loss or idiopathic sensorineural hearing loss, and fibrinogen.

STUDY SELECTION

The articles in the study related to SSNHL and provided data about the serum fibrinogen level.

DATA EXTRACTION

The data included patient profiles, fibrinogen level, recovery, and treatment modality.

DATA SYNTHESIS

Nineteen articles were selected. The aggregated data were analyzed using the random effect model. Two articles that included the fibrinogen level with recovery rates were analyzed for the relationship between the fibrinogen level and recovery.

CONCLUSIONS

The average fibrinogen level was 318 ± 8.5 mg/dl (mean ± standard error, within normal range). There was no difference in the fibrinogen level between SSNHL patients and the control group. The fibrinogen level of the recovery group was lower than that of the no recovery group. This showed that a high fibrinogen level was associated with poor prognosis, and it could be related to the severity of the pathological change rather than being the cause of the SSNHL. SSNHL includes various pathologies; therefore, the appropriate therapy should be selected based on each condition.

Cochlear Capillary Pericytes

Capillary pericytes in the cochlea of mammals are-compared to pericytes in other tissues, like the CNS-relatively poorly researched. To begin with, there is still a considerable debate as to whether the very last precapillary arterioles should-due to their contractile properties-may be considered to be pericytes.However, cochlear capillary pericytes have shifted into the center of attention in the past decade. Most mammals show a considerable number of pericytes in the stria vascularis of the cochlea-up to 1300 in a mouse alone. This high number may be explained by the observation that cochlear capillary pericytes may be differentiated into different subgroups, depending on the immune markers that are expressed by them. Corresponding with these subpopulations, cochlear pericytes fulfill three core functions in the physiology of the cochlea: Formation of the intrastrial blood-fluid barrier-Pericytes monitor the ion, fluid, and nutrient household and aid in the homeostasis thereof. Regulation of cochlear blood flow-By contraction on relaxation, pericytes contribute to the regulation of cochlear blood flow, a paramount function parameter of the cochlea. Immune response-Pericytes actually contribute to the immune response in inflammation of the cochlea. Due to these central roles in the physiology of the cochlea, pericytes actually play a major role in numerous cochlear pathologies, including, but not limited to, sudden sensorineural hearing loss, acoustic trauma, and inflammation of the cochlea.

Cochlear Pericytes Are Capable of Reversibly Decreasing Capillary Diameter In Vivo After Tumor Necrosis Factor Exposure

OBJECTIVE

The aim of this work was to evaluate the effect of tumor necrosis factor (TNF) and its neutralization with etanercept on the capability of cochlear pericytes to alter capillary diameter in the stria vascularis.

METHODS

Twelve Dunkin-Hartley guinea pigs were randomly assigned to one of three groups. Each group was treated either with placebo and then placebo, TNF and then placebo, or TNF and then etanercept. Cochlear pericytes were visualized using diaminofluorescein-2-diacetate and intravasal blood flow by fluorescein-dextrane. Vessel diameter at sites of pericyte somas and downstream controls were quantified by specialized software. Values were obtained before treatment, after first treatment with tumor necrosis factor or placebo and after second treatment with etanercept or placebo.

RESULTS

Overall, 199 pericytes in 12 animals were visualized. After initial treatment with TNF, a significant decrease in vessel diameter at sites of pericyte somas (3.6 ±4.3%, n = 141) compared with placebo and downstream controls was observed. After initial treatment with TNF, the application of etanercept caused a significant increase (3.3 ±5.5%, n = 59) in vessel diameter at the sites of pericyte somata compared with placebo and downstream controls.

CONCLUSION

We have been able to show that cochlear pericytes are capable of reducing capillary diameter after exposition to TNF. Moreover, the reduction in capillary diameter observed after the application of TNF is revertible after neutralization of tumor necrosis factor by the application of etanercept. It seems that contraction of cochlear pericytes contributes to the regulation of cochlear blood flow.

A sustained increase of plasma fibrinogen in sudden sensorineural hearing loss predicts worse outcome independently

OBJECTIVES

A number of etiologies of idiopathic sudden sensorineural hearing loss (ISSNHL) have been proposed. Vascular disturbance is one cause of ISSNHL and has been reported to be associated with fibrinogen. We aimed to determine whether hyperfibrinogenemia is associated with poor outcome and whether a serial change in fibrinogen level is associated with outcome.

METHODS

Twenty-two patients with ISSNHL were enrolled. We compared the levels of fibrinogen in ISSNHL groups classified as improved and non-improved according to improvement of hearing. Blood samples were also collected from patients who visited the emergency room with coronary heart disease (CHD) as the control group.

RESULTS

Initial fibrinogen level was significantly different between the non-improved and improved ISSNHL group (350.63±87.20 vs. 310.71±81.06. The improved ISSNHL group showed a "surge phenomenon", in which fibrinogen started to decrease at day 5 and increased at day 26. In the non-improved group, fibrinogen remained elevated throughout the course of therapy.

CONCLUSION

It is important to measure not only the initial fibrinogen level but also to monitor its change throughout the course of therapy in order to predict the outcome of ISSNHL.

The evaluation of cochlear functions in Familial Mediterranean Fever

Familial Mediterranean Fever (FMF) is a progressive disease characterized by chronic inflammation, which also has negative effects on cochlear functions and hearing levels. We investigated whether the cochlear functions and hearing levels of FMF patients were different than healthy controls and also evaluated the relationship of hearing levels with the age at diagnosis, duration without treatment, and inflammation and lipid parameters in this study. A total of 60 patients diagnosed with FMF and 48 age, gender and body mass index (BMI)-matched healthy controls were included in the study. The hemogram, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and lipid parameters of the subjects were studied and they all underwent pure tone audiometry and Transient evoked otoacoustic emission tests after an otologic examination. The hearing levels of the FMF group were significantly higher than those of the control group. The TEOAE signal/noise (S/N) ratios were similar in both groups. A positive relationship was present between the audiometric test results and the age, BMI, low-density lipoprotein and triglyceride levels and a negative relationship with the high-density lipoprotein levels. A negative relationship was present between the TEOAE S/N ratios and the age of the patients, duration without treatment, lipid parameters, inflammation markers and the creatinine level. FMF patients are exposed to chronic inflammation and this can influence their hearing levels. The age at diagnosis, duration without treatment, chronic inflammation, unfavorable lipid parameters, and obesity can affect hearing tests negatively.

Prognostic predictors of sudden sensorineural hearing loss in defibrinogenation therapy

CONCLUSIONS

Defibrinogenation therapy rather than corticosteroids therapy should be chosen for patients specifically with profound hearing loss and with initial high fibrinogen.

OBJECTIVES

Corticosteroids therapy is the standard treatment for sudden sensorineural hearing loss (SSNHL) and prognostic factors by this therapy were reported. Defibrinogenation therapy is one of the treatment options for SSNHL. Aims of this study were to identify prognostic factors and correlative markers with hearing improvement in treating SSNHL by defibrinogenation therapy.

METHODS

During the early phase of the study, consecutive 61 patients were treated by defibrinogenation therapy with batroxobin (50 units), whereas corticosteroids (500 mg/day of hydrocortisone tapered by 9 days) were used for consecutive 64 patients during the late phase. Blood data that could predict a complete recovery were identified. Coagulation/fibrinolysis markers correlated with hearing improvement by defibrinogenation therapy were investigated.

RESULTS

Although there were no overall differences in hearing improvement between the two therapies, recovery rate in profound hearing loss patients was better in defibrinogenation therapy. In patients who showed complete recovery, serum fibrinogen level before treatment was significantly higher in the defibrinogenation group than the corticosteroid group. Responses of several fibrinolysis markers to defibrinogenation therapy evaluated by post-/pre-values were negatively correlated with hearing improvement.

Two-photon microscopy allows imaging and characterization of cochlear microvasculature in vivo

Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of 90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR) of 3.3±1.7. Mean diameter in vivo was 16.5±6.0 μm for arterioles and 8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with 12.2±1.6 μm and 6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001 and P=0.022, two-way ANOVA). Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.

Prognostic impact of standard laboratory values on outcome in patients with sudden sensorineural hearing loss

Background

Aim of the present study was to evaluate prognostic factors, in particular standard laboratory parameters, for better outcome after idiopathic sudden sensorineural hearing loss (SSNHL).

Methods

Using a retrospective review, 173 patients were included presenting between 2006 and 2009 with unilateral SSNHL, ≥30 dB bone conduction in three succeeding frequencies between 0.125 to 8 kHz in pure tone audiometry (PTA), and a time interval between first symptoms and diagnostics ≤ 4 weeks. Hearing gain of <10 dB versus ≥10 dB in the affected ear in 6PTA values was the primary outcome criterion. Univariate and multivariate statistical tests were used to analyze predictors for better outcome.

Results

The initial hearing loss was 50.6 ± 27.2 dB. The absolute hearing gain was 15.6 ± 20.1 dB. Eighty-one patients (47%) had a final hearing gain of ≥10 dB. Low-frequency hearing loss (p <0.0001); start of inpatient treatment <4 days after onset (p = 0.018); first SSNHL (versus recurrent SSNHL, p = 0.001); initial hearing loss ≥ 60 dB (p < 0.0001); an initial quick value lower than the reference values (p = 0.040); and a pretherapeutic hyperfibrinogenemia (p = 0.007) were significantly correlated to better outcome (≥10 dB absolute hearing gain). Multivariate analysis revealed that first SSNHL (p = 0.004), start of treatment <4 days after onset (p = 0.015), initial hearing loss ≥ 60 dB (p = 0.001), and hyperfibrinogenemia (p = 0.032) were independent prognostic factors for better hearing recovery.

Conclusion

Better hearing gain in patients with hyperfibrinogenemia might be explained by the rheological properties of the applied therapy and supports the hypothesis that SSNHL is caused in part by vascular factors.