Early histopathologic changes after lateral semicircular canal transection and occlusion in guinea pigs

Hearing Outcomes of Transmastoid Plugging for Superior Canal Dehiscence Syndrome by Underwater Endoscopic Surgery: With Special Reference to Transient Bone Conduction Increase in Early Postoperative Period

OBJECTIVE

To investigate the influence on hearing of transmastoid plugging of the superior semicircular canal accompanied with membranous superior canal transection by underwater endoscopic ear surgery (UWEES) for the superior semicircular canal dehiscence syndrome.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Seven patients underwent plugging with membranous superior canal transection with UWEES from 2017 to 2019.

INTERVENTION

Bone conduction (BC) thresholds (250, 500, 1000, 2000, 4000 Hz) were repetitively examined in early postoperative period.

MAIN OUTCOME MEASURES

Subjective symptoms and pure-tone audiometry.

RESULTS

Transient BC threshold increase was detected in all cases in early postoperative period and hearing levels were ameliorated in 1 to 2 months. The mean maximum BC threshold elevations (dB) during the early postoperative period (within 1 mo) and the postoperative stable hearing period (after 2 mo) were 18.6 and 2.9 at 250 Hz, 24.3 and 8.6 at 500 Hz, 26.4 and 8.6 at 1000 Hz, 28.6 and 7.1 at 2000 Hz, and 30.0 and 0.8 (except for scale-out cases) at 4000 Hz. respectively. The mean maximum BC thresholds in the early period were significantly elevated compared with those in the stable period at each frequency (p < 0.01).

CONCLUSIONS

Hearing outcomes of transmastoid plugging with transection of the membranous superior canal by using UWEES were found favorable in a long-term follow-up. However, it caused transient reversible hearing loss in all cases. The BC increase in early postoperative period may not cause permanent hearing loss but improvement for the surgical technique may still be necessary.

[Variants of treatment of the head direction at the festulars of the labi-rint of inflammatory genesis]

PURPOSE

To analyze the effectiveness of various methods of treating dizziness with fistulas of the labyrinth (FL) of inflammatory genesis. An analysis of the surgical treatment of 216 patients with chronic suppurative otitis media (CSOM) with cholesteatoma complicated by FL using a variety of FL treatment methods is presented. All patients underwent a debridement operation on the middle ear or revision of the postoperative cavity: in 48 patients with a matrix of cholesteatoma in situ on the fistula, in 109 patients with matrix removal followed by plastic repair or FL filling with various autotissues, in 59 patients with matrix conservation, plastic removal or filling FL and SLD labyrinth. In the last two groups, filling of a semicircular canal (SC) defect was performed in 33 patients, and mastoidoplasty - in 47.

CONCLUSION

All used FL treatment techniques are effective in the treatment of peripheral vestibular disorders. Careful treatment of SC fistula after removal of all pathological conditions in the absence of active inflammation and the appointment of hormone therapy in the postoperative period are the main factors in preserving the functions of the labyrinth in any surgical technique. Filling of the lumen of the SC and mastoidoplasty in patients with CSOM with FL can eliminate peripheral dizziness.

Sensitivity of the cochlear nerve to acoustic and electrical stimulation months after a vestibular labyrinthectomy in guinea pigs

Single-sided deafness patients are now being considered candidates to receive a cochlear implant. With this, many people who have undergone a unilateral vestibular labyrinthectomy for the treatment of chronic vertigo are now being considered for cochlear implantation. There is still some concern regarding the potential efficacy of cochlear implants in these patients, where factors such as cochlear fibrosis or nerve degeneration following unilateral vestibular labyrinthectomy may preclude their use. Here, we have performed a unilateral vestibular labyrinthectomy in normally hearing guinea pigs, and allowed them to recover for either 6 weeks, or 10 months, before assessing morphological and functional changes related to cochlear implantation. Light sheet fluorescence microscopy was used to assess gross morphology throughout the entire ear. Whole nerve responses to acoustic, vibrational, or electrical stimuli were used as functional measures. Mild cellular infiltration was observed at 6 weeks, and to a lesser extent at 10 months after labyrinthectomy. Following labyrinthectomy, cochlear sensitivity to high-frequency acoustic tone-bursts was reduced by 16 ± 4 dB, vestibular sensitivity was almost entirely abolished, and electrical sensitivity was only mildly reduced. These results support recent clinical findings that patients who have received a vestibular labyrinthectomy may still benefit from a cochlear implant.

Sensorineural hearing loss: there is no correlation with isolated dysplasia of the lateral semi-circular canal on temporal bone CT

Background

Inner ear malformations may cause sensorineural hearing loss (SNHL). However, the correlation between the small lateral semi-circular canal (LSCC) and SNHL is controversial.

Purpose

To determine whether there is a correlation between the two using CT-based measurement.

Material and Methods

We retrospectively reviewed the high-resolution CT images of the temporal bone obtained from consecutive patients. A total 136 ears of 68 patients (25 men and 43 women; age range 20–85 years, mean 49.8 years) were included in this study. Patients who were clinically suspected to have otosclerosis were also excluded. Two radiologists independently measured the width and cross-sectional area of the bony island of LSCC. We evaluated the correlation between LSCC bone island width or cross-sectional area and hearing level in all cases using Pearson correlation co-efficients. In addition, we compared hearing levels among the patient group with normal-sized LSCC (≧mean-SD), small LSCC (<mean-SD) and very small LSCC (<mean-2SD) as defined by the width and cross-sectional area of the bony island using Student's t-test.

Results

A total 136 ears of 68 patients (25 men and 43 women; age range 20–85 years, mean 49.8 years) were included in this study. No significant correlation was shown between LSCC bony island width or cross-sectional area and hearing level (P > 0.05). No significant difference in hearing levels were found among groups of the normal-sized, small and very small LSCC (P > 0.05).

Conclusion

We conclude that there is no correlation between isolated small LSCC and SNHL.

Surgery of the inner ear with hearing preservation: serial histological changes

OBJECTIVES/HYPOTHESIS

Surgery of the inner ear can result in hearing preservation under certain conditions, but the mechanisms responsible for hearing preservation or loss are not well understood. The specific aim of the study is to examine histological sections obtained at different time intervals after varying degrees of surgical entry into the inner ear, to understand how the cochlea is protected. The hypothesis is that internal partitioning occurs.

STUDY DESIGN

Histologic examination of guinea pig inner ears by light microscopy.

METHODS

Guinea pigs underwent lateral semicircular canal transection and plugging, ampullectomy, or vestibulotomy, and tone-burst auditory brainstem response thresholds at 2, 8, and 24 kHz were measured at intervals before and after surgery. Animals were killed after 1, 3, 7, or 21 or more days, and temporal bones were examined histologically.

RESULTS

The histological response to surgical trauma consists of fibrosis and varying amounts of inflammation near the site of surgical entry. Cochlear hair cells are nearly always preserved, even when hearing loss occurs. Extension of the inflammatory response to the cochlea is associated with greater degrees of hearing loss.

CONCLUSION

The guinea pig inner ear is capable of withstanding surgical trauma to the semicircular canals and vestibule without complete loss of cochlear function. Fibrosis creates an effective partition between the site of surgical entry and the rest of the inner ear. Cochlear preservation might be enhanced if the inflammatory response can be contained.