Global, regional, and national prevalence of hearing loss from 1990 to 2019: A trend and health inequality analyses based on the Global Burden of Disease Study 2019.

As a severe public health issue, hearing loss has caused an increasingly disease burden, especially in the elderly population. Hearing loss may inevitably induce asymmetric hearing, which makes it difficult for elderly individuals to locate sound sources, therefore resulting in increased postural instability and falling risk. To emphasize the public health emergence of hearing loss, we investigated the temporal trend of prevalence of hearing loss over the last 30 years and further predicted its changes in the next 20 years, decomposed the trend according to demographic factors and epidemiological changes, and quantified the cross-country healthy inequalities, using the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019. In 2019, there were more than 140 million cases of hearing loss worldwide, a 93.89% increase from 70 million cases in 1990. The age-standardized rate (ASR) also increased with an estimated annual percentage change of 0.08% per year. Population growth and aging are the major drivers contributing to the changes, accounting for 60.83% and 35.35%. Of note, the contribution of aging varies showing a gradual increasing trend with sociodemographic index (SDI) elevating. Also notable, there were significant health inequalities across 204 countries and territories, with slope index of inequality rising over time. Projection of the global burden of hearing loss from 2020 to 2040 indicated progressive increases in both case number and ASR. These reflect the heavy disease burden of hearing loss that needed more targeted and efficient strategies in its prevention and management.

Mechanisms of Hearing Loss in a Guinea Pig Model of Superior Semicircular Canal Dehiscence.

Defective acoustic transmission in the cochlea is closely related with various auditory and vestibular symptoms. Among them, semicircular canal dehiscence (SCD) with a defective semicircular bone is typical. Currently, the pathogenesis of SCD is usually explained by the third window hypothesis; however, this hypothesis fails to explain the variability in the symptoms and signs experienced by superior SCD (SSCD) patients. We evaluated the mechanism of hearing loss in a guinea pig model of bony dehiscence with various sizes and locations along the superior semicircular canal. Auditory brainstem responses (ABRs) and laser Doppler velocimetry were used to measure hearing loss and vibration changes before and after fenestration, as well as after restorative patching. ABR thresholds at low frequencies (e.g., 1000 Hz) increased after fenestration and decreased back to the normal range after we repaired the defect. Energy leakage from the surgically introduced third window was detected in the range of 300-1500 Hz, accompanied by increased vibration at the umbo, stapes head, and the dehiscence site, while decreased vibration was observed at the round window membrane in the same frequency range. After the patching procedure, the deviant vibrations were recovered. The degree of postfenestration energy leakage was proportional to the size of fenestration and the proximity of the fenestration site to the oval window. These results suggest that the bony fenestration of the superior semicircular canal mimics the hearing loss pattern of patients with SSCD. The decrease in perilymph wave impedance likely accounts for the auditory changes.

Effect of Endolymphatic Hydrops on Sound Transmission in Live Guinea Pigs Measured with a Laser Doppler Vibrometer.

Objective. This study aimed at describing the mechanism of hearing loss in low frequency and the different dynamic behavior of the umbo, the stapes head, and the round window membrane (RWM) between normal guinea pigs and those with endolymphatic hydrops (EH), using a laser Doppler vibrometer (LDV). Methods. Cochlear sections were stained with hematoxylin and eosin (HE) to evaluate the hydropic ratio (HR). Auditory brainstem responses (ABR) and whole-mount immunostaining were measured. Displacement of the umbo, stapes head, and RWM in response to ear-canal sound was evaluated using a LDV. Results. Mean HR values in EH model of all the turns are larger than the control group. The ABR threshold of the EH group was significantly higher than that of the control. Strong positive correlation was found between HR at apical turn and ABR threshold elevation at 1000 Hz and at subapical turn and ABR threshold elevation at 2000 Hz. FITC-phalloidin immunostaining of the cochlear basilar membrane in the apical, subapical, and suprabasal turns showed missing and derangement stereocilia of third-row outer hair cells. The umbo, stapes head, and RWM displacement in ears with EH was generally lower than that of normal ears. The EH-induced differences in stapes head and RWM motion were significant at 0.5 kHz. Conclusion. The LDV results suggested that the higher inner ear impedance in EH affected the dynamic behavior of the two opening windows of the cochlea and then reduced the vibration of the ossicular chain by increasing the afterload, resulting in acoustic dysfunction. The vibration reduction mainly occurred at low frequencies, which has related with the morphology changes of the apical and subapical turns in EH model.

[Multi-center study of clinical treatment on the flat type of sudden hearing loss].

OBJECTIVE: To investigate the effect of different treatment options for the flat type of sudden hearing loss. METHODS: Prospective, multi-center clinical study was carried out using internationally used standardized clinical research method. Patients with the flat type of sudden hearing loss between 18 and 65 years old, within two weeks duration, and without any medical treatment were recruited. Treatment options were randomly selected according to the designed random table. RESULTS: From August 2007 to October 2011, 402 patients with the flat type of sudden hearing loss who met the criteria (account for 39.26% of the total number of patients) from the 33 hospitals were collected; the total effective rate was 82.59%, and no significant difference was detected between different treatments, (χ(2) = 10.95, P = 0.28). In the 402 cases, 139 were cured (34.58%); 118 were markedly improved (29.35%); 75 were effective (18.66%); 70 were invalid (17.41%). CONCLUSIONS: The therapeutic efficacy of flat type of sudden hearing loss overall is good; the treatment of improving the inner ear blood rheology and/or reducing blood fibrinogen has clinical significance; the therapeutic efficacy of using glucocorticoid systemically is good as well; there is no obvious difference between combination and single medication.

A clinical study of microcirculatory disturbance in Chinese patients with sudden deafness.

CONCLUSION: Cochlear microcirculation disturbance is closely associated with sudden deafness. OBJECTIVES: To investigate the relationship between cochlear microcirculation and sudden deafness. SUBJECTS AND METHODS: Clinical laboratory parameters (clinical chemistry, hemorheology, hematology, and hemostasis determinations) were studied in 86 patients with sudden deafness and 30 healthy control subjects. RESULTS: The levels of total cholesterol (TCH), triglyceride (TG), and lipoprotein A were significantly higher in patients with sudden deafness than in control subjects. Plasma viscosity, ratio viscosity of whole blood, reduced viscosity of whole blood, high and low shear relative viscosity of whole blood, index of red blood cells transmutation, and fibrinogen level in the plasma of patients with sudden sensorineural hearing loss (SSNHL) were also significantly elevated in comparison with those in control subjects. White-collar workers with psychological and behavioral abnormalities tend to suffer from sudden deafness.

[Anatomical landmarks of skull base and safety of the skull base surgery].

OBJECTIVE: In order to improve the safety of skull base surgery and to completely resect the skull base tumors, the anatomical landmarks of skull base were studied. METHODS: 29 cases of skull base surgery were performed between 1992 and 2002, and their clinical data were retrospectively analysed. The anatomical landmarks of cranial base, such as comb, pterygoid process, spine of temporal bone, styloid process, and internal caroid artery, were analysed in preoperative diagnosis and operative treatment of various kinds of skull base tumors. RESULTS: In the early stages, because of lacking the knowledge of anatomical landmarks of the skull base, the surgery lasted longer, part of skull base tumors remained and operative blood lose was much more than that in later stage. In the later stage, no operative death and severe complications were found in 26 cases which underwent various kinds of skull base surgery. The survival rates at 3 and 5 years were 72.2% and 35.7% respectively for malignant tumors. CONCLUSIONS: Comb, pterygoid process, spine of temporal bone, styloid process, internal caroid artery and their adjacent structures were important anatomical landmarks for operative treatment of anterior, middle and lateral cranial base tumors. It was important to know the anatomical landmarks to ensure the safety of the skull base surgery.