Quantitative Study Of The Vestibular Sensory Epithelium In Cochleosaccular Dysplasia

Vestibular anomalies and dysfunctions in children with inner ear malformations: A narrative review

About 20% of children with congenital hearing loss present malformations of the inner ear. In the past few years much has been understood about the morphology and function of the anterior part of the labyrinth, since hearing loss may have a dramatic effect on the overall development of a child. Nowadays, for most of them, a chance for hearing rehabilitation is available, making hearing loss a treatable condition. The anomalies range from the lack of development of the whole inner ear to specific anomalies of isolated structures. Despite the frequent concomitant involvement of the posterior part of the labyrinth, this part of the inner ear is frequently neglected while discussing its morphology and dysfunction. Even though vestibular and balance function/dysfunction may have a significant impact on the global development of children, very little is known about these specific disorders in patients with inner ear malformations. The aim of this review is to summarize the available literature about vestibular anomalies and dysfunctions in children with inner ear malformations, discussing what is currently known about the topic.

Vestibular Imaging and Function in Patients With Inner Ear Malformation Presenting With Profound Hearing Loss

Objective

Vestibular impairment has been observed in patients with congenital hearing loss, but little is known about the vestibular anatomy and function of those in this group with inner ear malformations. This study aims to investigate the association between vestibulocochlear anatomy and vestibular function test results in children with inner ear malformations.

Study Design

Case series with chart review.

Setting

Pediatric patients with inner ear malformations presenting with bilateral profound hearing loss at a tertiary hospital from 1999 to 2017.

Methods

Ears were classified into subgroups based on anatomic abnormalities seen on computed tomography imaging. Cervical vestibular evoked myogenic potential (cVEMP), rotatory chair, and caloric test results were obtained and collated. Descriptive and inferential statistics were calculated.

Results

Of 82 ears, 29.3% had incomplete partition type II malformation, the most common type. The second-most common type was isolated vestibular organ anomaly (20.7%), which is not included in currently accepted categories. Most ears exhibited abnormal vestibular function. Abnormal vestibule volume was associated with a nonreactive cVEMP (P < .001). Radiologically abnormal lateral semicircular canals were associated with abnormal caloric and rotatory chair results (P < .001).

Conclusion

With a relatively large number of cases of isolated vestibular organ anomaly not only in our study but also in previous publications, we suggest that this category be added to the subsets of inner ear malformations. Abnormal vestibule volume was significantly associated with a nonreactive cVEMP finding. The majority of patients with hearing loss secondary to inner ear malformations have abnormal vestibular function test results.

Histopathologic Findings in Peripheral Vestibular System From Patients With Systemic Lupus Erythematosus: A Human Temporal Bone Study

HYPOTHESIS

We hypothesized that a pathologic condition exists in vestibular hair cells in human temporal bones from patients with systemic lupus erythematosus (SLE).

BACKGROUND

A significant association between sensorineural hearing loss and autoimmune disease has been reported. Patients with SLE also frequently have vestibular symptoms whose pathophysiologic mechanism is unclear.

METHODS

We examined 15 temporal bone samples from 8 patients with SLE, along with 21 samples from 17 age-matched healthy control patients. The samples were serially sectioned in the horizontal plane and stained with hematoxylin and eosin. Using differential interference contrast microscopy, we counted the number of type I and type II hair cells in the saccular macula, the utricular macula, and the cristae of the three semicircular canals; then, we calculated the hair cell density (cells per 0.01 mm).

RESULTS

The mean density of type I hair cells in our SLE group was significantly lower than in our control group in the saccular macula, in the utricular macula, and in the superior, lateral, and posterior semicircular canals. But in all five vestibular sensory epithelia, the mean density of type II hair cells did not significantly differ between our two groups. In our SLE group, the mean density of vestibular hair cells did not significantly correlate with the patient's age at death or with the duration of SLE.

CONCLUSION

Type I hair cells in peripheral vestibular organs are affected in patients with SLE. Our findings could provide a pathologic basis for the difficulty with balance experienced by patients with SLE.

Fgf10 expression patterns in the developing chick inner ear

The inner ear is a complex three-dimensional sensorial structure with auditory and vestibular functions. It originates from the otic placode, which invaginates, forming the otic vesicle; the latter gives rise to neurosensory and nonsensory elements of the adult membranous labyrinth. A hypothesis based on descriptive and experimental evidence suggests that the acquisition of discrete sensory patches during evolution of this primordium may be related to subdivision of an early pansensory domain. In order to gain insight into this developmental mechanism, we carried out a detailed analysis of the spatial and temporal expression pattern of the gene Fgf10, by comparing different markers of otic patterning and hair cell differentiation. Fgf10 expression labels a sensory-competent domain included in a Serrate-positive territory from which most of the sensory epithelia arise. Our data show that Fgf10 transcripts are present initially in a narrow ventromedial band of the rudimentary otocyst, extending between its rostral and caudal poles. During development, this Fgf10-expressing area splits repetitively into several separate subareas, creating six of the eight sensory organs present in birds. Only the lateral crista and the macula neglecta were initially Fgf10 negative, although they activated Fgf10 expression after their specification as sensory elements. These results allowed us to determine a timetable of sensory specification in the developing chick inner ear. The comparison of the expression pattern of Fgf10 with those of other markers of sensory differentiation contributes to our understanding of the mechanism by which vertebrate inner ear prosensory domains have arisen during evolution.

Peripheral Vestibular System in Down Syndrome

Objective. To evaluate the maturity of the peripheral vestibular system in Down syndrome by examining the number of Scarpa’s ganglion cells and the density of vestibular hair cells.

Study Design. Case-control study using human temporal bones.

Setting. Tertiary academic center, otopathology laboratory.

Subjects and Methods. Sixteen temporal bones from 8 patients with Down syndrome and 15 control temporal bones from 8 individuals with no history of otologic disease were selected. Hypoplasia of the lateral semicircular canal (LSC) and vestibule was investigated by measuring the dimensions of the structures. Scarpa’s ganglion cells were counted under light microscopy. The vestibular hair cells were counted in the LSC crista and the utricular and saccular maculae under differential interference contrast (Nomarski) microscopy and expressed as density.

Results. The patients with Down syndrome were divided into 2 groups: with and without LSC hypoplasia. The number of Scarpa’s ganglion cells and the density of vestibular hair cells were significantly smaller in both groups of patients with Down syndrome than in the control group. There was no significant difference in the number of Scarpa’s ganglion cells or the density of vestibular hair cells between the groups with and without LSC hypoplasia.

Conclusion. The peripheral vestibular system, including Scarpa’s ganglion cells and vestibular hair cells, is hypoplastic irrespective of the vestibular malformation in Down syndrome.

Histopathological morphometric study of cochleosaccular dysplasia in Dalmatian dogs

OBJECTIVE

To analyze temporal bones of deaf Dalmatian dogs from 5 days after birth to adulthood to better understand the pathogenesis of cochleosaccular dysplasia.

METHODS

This is an experimental animal histopathological temporal bone study that included two groups of temporal bones. Group I consisted of 41 temporal bones from deaf Dalmatian dogs and group II of 25 temporal bones from 15 "normal" aged-matched, hearing Black Labradors. Morphometric analysis included: stria vascularis and spiral ligament area measurements, and cell counts of spiral ganglion, Scarpa's ganglion, and hair cells of saccular macula.

RESULTS

The following findings were significantly less in deaf Dalmatian group compared to hearing Labradors: (1) cellular area of the stria vascularis in all cochlear turns; (2) cellular area of spiral ligament in the inferior part of the basal turn; (3) cellular density of spiral ganglion cells within segments III and IV; (4) number of Scarpa's ganglion cells; and (5) density of saccular hair cells types I and II. A borderline negative correlation was found between average density of spiral ganglion cells of segments III and IV and age in group I. Young deaf animals showed some cochlear hair cells, however in adult dogs all hair cells were replaced by supporting cells.

CONCLUSION

General pattern of cochleosaccular dysplasia is variable, even when only one etiology, the genetic one, is involved. The gradual degeneration of inner ear elements in the cochleosaccular degeneration might indicate that early intervention might be crucial to stop the progression of cochleosaccular dysplasia.