Labyrinthitis Ossificans: On the Mechanism of Perilabyrinthine Bone Remodeling

Ovariectomized Rat Model and Shape Variation in the Bony Labyrinth

Postmenopausal osteoporosis is a serious concern in aging individuals, but has not been explored for its potential to alter the shape of the inner ear by way of increased remodelling in the otic capsule. The otic capsule, or bony labyrinth, is thought to experience uniquely limited remodelling after development due to high levels of osteoprotegerin. On this basis, despite the widespread remodelling that accompanies osteoporosis, we hypothesize that both the shape and volume of the semicircular canals will resist such changes. To test this hypothesis, we conducted three-dimensional geometric morphometric shape analysis on microcomputed tomographic data collected on the semicircular canals of an ovariectomized (OVX) rat model. A Procrustes ANOVA found no statistically significant differences in shape between surgery and sham groups, and morphological disparity testing likewise found no differences in shape variation. Univariate testing found no differences in semicircular volume between OVX and control groups. The range of variation in the OVX group, however, is greater than in the sham group but this difference does not reach statistical significance, perhaps because of a combination of small effect size and low sample size. This finding suggests that labyrinthine shape remains a tool for assessing phylogeny and function in the fossil record, but that it is possible that osteoporosis may be contributing to intraspecific shape variation in the bony labyrinth. This effect warrants further exploration at a microstructural level with continued focus on variables related to remodelling. This article is protected by copyright. All rights reserved.

Aminoglycoside- and glycopeptide-induced ototoxicity in children: a systematic review

Background

Ototoxicity has been reported after administration of aminoglycosides and glycopeptides.

Objectives

To identify available evidence for the occurrence and determinants of aminoglycoside- and glycopeptide-related ototoxicity in children.

Materials and methods

Systematic electronic literature searches that combined ototoxicity (hearing loss, tinnitus and/or vertigo) with intravenous aminoglycoside and/or glycopeptide administration in children were performed in PubMed, EMBASE and Cochrane Library databases. Studies with sample sizes of ≥50 children were included. The QUIPS tool and Cochrane criteria were used to assess the quality and risk of bias of included studies.

Results

Twenty-nine aminoglycoside-ototoxicity studies met the selection criteria (including 7 randomized controlled trials). Overall study quality was medium/low. The frequency of hearing loss within these studies ranged from 0%–57%, whereas the frequency of tinnitus and vertigo ranged between 0%–53% and 0%–79%, respectively. Two studies met the criteria on glycopeptide-induced ototoxicity and reported hearing loss frequencies of 54% and 55%. Hearing loss frequencies were higher in gentamicin-treated children compared to those treated with other aminoglycosides. In available studies aminoglycosides had most often been administered concomitantly with platinum agents, diuretics and other co-medication.

Conclusions

In children the reported occurrence of aminoglycoside/glycopeptide ototoxicity highly varies and seems to depend on the diagnosis, aminoglycoside subtype and use of co-administered medication. More research is needed to investigate the prevalence and determinants of aminoglycoside/glycopeptide ototoxicity. Our results indicate that age-dependent audiological examination may be considered for children frequently treated with aminoglycosides/glycopeptides especially if combined with other ototoxic medication.

Imaging of labyrinthine fistula after repair with bone pate

OBJECTIVES/HYPOTHESIS

To demonstrate imaging of labyrinthine fistula due to cholesteatoma and illustrate outcome following repair with bone pate.

STUDY DESIGN

Retrospective review.

METHODS

Patients with labyrinthine fistula due to cholesteatoma were identified, and pre- and postoperative imaging was assessed. Method of repair was recorded. The fistula site was examined for patency and bone density after repair.

RESULTS

Twenty-nine fistulae were seen in a cohort of 375 cholesteatoma cases (8%). Preoperative computed tomography (CT) imaging for fistula detection showed sensitivity of 96% and specificity of 90%. The lateral semicircular canal was the most common site of dehiscence occurring in all cases. Facial nerve dehiscence is observed in 91% of fistula cases and stapes erosion in 69%. Severe hearing loss was present preoperatively in four (14%) cases. Bone pate was used to repair the fistula with CT-documented restoration of the otic capsule in 11/13 cases with postoperative imaging. When bone pate was not used, the otic capsule defect persisted.

CONCLUSIONS

Spontaneous repair of the otic capsule following treatment of cholesteatoma is expected to be an uncommon occurrence. Repair of the fistula with bone can result in long-lasting restoration of the otic capsule.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1643-1648, 2018.