Epithelial cysts in the human vestibular apparatus

Decoding Age-Linked Masseter Vestibular Evoked Myogenic Potential Changes in Healthy, Aging Individuals

PURPOSE

The primary objective of this study was to assess how age influences masseter vestibular evoked myogenic potential (mVEMP) parameters by utilizing 500-Hz tone burst stimuli delivered through air conduction.

METHOD

The study involved 110 participants ranging from 15 to 60 years of age, grouped into five categories, all of whom had no previous issues related to their vestibular system. The participants were exposed to 500-Hz tone burst stimuli at 125 dB SPL through ER-3A inserts. These stimuli were presented to one ear at a time, with alternating polarity. A Tukey's honestly significant difference test was conducted to compare rectified and unrectified amplitude, along with latencies (P11 and N21) and the asymmetric ratio across all age groups. Additionally, a multivariate analysis of variance was performed to assess the impact of sex on the study variables.

RESULTS

All 110 participants (220 ears) in the study provided mVEMP responses, encompassing 100% of the subjects. The results revealed a significant reduction in both amplitude and latency extension for the P11 and N21 peaks. Interestingly, P11 latency was also prolonged in the youngest participants (Group 1), suggesting ongoing maturation of the system even beyond the age of 16 years. Moreover, a significant sex difference was observed in the P11 latencies. However, there were no substantial sex differences (p > .05) in N1 peak latency, peak-to-peak amplitude, rectified amplitude, and asymmetric ratio.

CONCLUSIONS

Changes in structure occur due to degeneration, and the quantity of vestibular sensory hair cells gradually diminishes with age. The rate of decline is faster in semicircular canals compared to end organs, as observed by Merchant et al. (2000). Following a linear degeneration starting at the age of 40 years, a continuous reduction in sensory cells and primary neurons takes place until approximately 40% of vestibular sensory cells are lost by the age of 75 years and insufficient maturation can lead to prolonged peaks and reduced amplitudes compared with those that are considered normal. Therefore, it is crucial to consider the age of the participants when making diagnoses and incorporate relevant correction factors based on age-related reference data.

Characterizing the impact of advancing age on 500 Hz tone-burst evoked ocular-vestibular evoked myogenic potentials

PURPOSE

Ageing is process that brings about steady decline in most of the systems, and vestibular system is no different. Although the effects of advancing age on the functioning of the semicircular canals and saccule has been well explored, its impact on the utricle remains the least studied component. While some researchers have investigated the effect of advancing age on the utricular functioning by virtue of studying ocular-vestibular evoked myogenic potentials (oVEMP), the use of smaller sample sizes would hamper the generalization of their results. Therefore, the present study aimed at investigating the effect of advancing age on oVEMP using a substantially larger sample size than the predecessors.

METHODS

A total of 480 individuals in the age range of 10-70 years were used as participants and were divided into six age groups, each one defined as a decade. Contralateral oVEMPs were elicited by 500-Hz tone-bursts and averaged over 200 sweeps to obtain the final waveform.

RESULTS

There was a significant decline in the response rates, prolongation of latencies and reduction of peak-to-peak amplitude of oVEMP with increasing age after 50 years (p < 0.05). However, there was no significant difference among the age groups until 50 years of age on any of these parameters (p > 0.05). Further, there was no significant change in inter-aural amplitude difference ratio with increasing age (p > 0.05).

CONCLUSION

The results of the study confirm significant impact of the ageing process on oVEMP after the age of 50 years and, therefore, age appropriate norms should be considered when using oVEMP for investigating utricular functioning in an individual, especially after the age of 50 years.

Vestibular sensory epithelia in patients with acoustic neurinoma

The human vestibular sensory epithelia of the macula utriculi were examined ultrastructurally in 13 cases with acoustic neurinoma. The sensory epithelia were fairly well preserved, with several morphological changes such as lipofuscin granules, intraepithelial cysts, pyknosis, vacuoles, laminated structures, banded structures and degeneration of subepithelial myelinated nerves evident. The pathological significance of these findings was discussed. There were thickened irregular membrane formations in spaces between the nerve calyces and type I hair cells which might be related to acoustic neurinoma. Some type I hair cells were incompletely surrounded by nerve calyces. The neck regions of these cells received direct contact from the efferent nerve endings.

Light and electron microscopic study of vestibular sensory epithelia in 17 cases with acoustic neurinoma

Vestibular sensory epithelia were studied histologically and ultrastructurally in 17 cases with acoustic neurinoma (AN). The superior vestibular nerve (SVN) near the fundus was also histologically studied in 5 of these 17 cases. Histologically, severe fibrotic change of the vestibular sensory epithelia was found in 1 case, and severe fibrotic change of the SVN was also found in this case. Intra-epithelial cysts were found at the edge of the utricular sensory epithelia in 2 cases. The cysts consisted of the transitional epithelium and were filled with the darkly stained substances. Ultrastructurally, abnormal accumulation of darkly stained masses within the nerve ending and abnormal accumulation of the fibrillar material below the normal basal lamina were frequently observed. These morphological changes described above were regarded as the pathological changes due to AN. In addition, the relationship among the histologic changes, ultrastructural changes and clinical data were fully investigated, and some histologic and ultrastructural changes were regarded as artifacts or age-related changes.

Pathology of peripheral vestibular disorders in the elderly

A clinical classification of vertigo commonly seen in the elderly and caused by peripheral vestibular disorders is illustrated by case reports and temporal bone histopathology. The classification includes inducible transient vertigo and noninducible protracted vertigo. The peripheral vestibular pathology includes abnormalities of sensory, neural, and mechanical structures and is often asymmetric. The pathogenesis of these disorders is often speculative, but includes degenerative, infectious, neoplastic, and vascular insults to the vestibular labyrinth.

Ultrastructural aspects of the human peripheral vestibular system

The sensory epithelia from the membranous labyrinths of 4 patients were examined by transmission electron microscopy. The distribution ratio of type 1 to type 2 cells was recorded, compared for each sensory area and correlated with age. An ultrastructural assessment confirmed generalized patterns consistent with autolytic and preparation artefact, viz. calyceal dilatation, cytoplasmic protrusions and some sensory hair loss. More specific features, i.e. lipofuscin accumulation, membrane-bound inclusions and neural degeneration were consistent with pre-mortem pathological change. In 2 patients, total nerve fibre counts of 15,766 and 19,741 were obtained. Total fibre counts correlated with the sensory cell density of the innervated areas. Differential counts of the superior and inferior vestibular nerves suggested that there was a reduced number of fibres in the superior division of both patients, in comparison with established normative data. Morphometric analysis of the constituent fibre diameters revealed a skewed distribution with a modal value of 6 microns for both patients.

Inner ear anomalies in two cases of trisomy 18

Two cases of trisomy 18 in which temporal bone defects were limited to the inner ears are described. Several abnormalities were present that have not been described previously in this syndrome. The first case involved a 1-month-old female infant who died of congenital heart defects. Cochlear nerve fibers were absent on the left side, with near-normal innervation on the right. Although the organ of Corti was present bilaterally, some of the outer hair cells were deformed, having small rounded cell bodies unsupported by Deiters' cells. On the right, similar abnormal cells were found in the tunnel of Corti. Vestibular defects in this case included reduced nerve supply of the left saccular macula, cysts in the superior and posterior cristae, and absence of the utriculoendolymphatic valve. The second case involved a newborn male infant with multiple congenital anomalies. The major cochlear defect was a deformity of the stria vascularis. In the lower apical turn, the stria was adherent to Reissner's membrane and extended beneath it into scala media. Large capillaries, which ran freely suspended in scala vestibuli, entered the upper portion of the stria. Severe atresia of the lateral and posterior semicircular ducts was found in the vestibular apparatus.

Quantitative study of human Scarpa's ganglion and vestibular sensory epithelia

Methods for counting vestibular ganglion cells and determining the densities of hair cells and intraepithelial basophilic inclusions (IBI) in samples of cross-sectioned vestibular sensory epithelia are described. Data obtained by means of these methods in vestibular sensory epithelia and Scarpa's ganglia in individual temporal bones from subjects at different ages are presented. Both vestibular hair cells and nerve cells in Scarpa's ganglia are found numerically reduced in ears of aged individuals. Changes in the vestibular sensory epithelia appear to precede those seen in Scarpa's ganglion. The incidence of intraepithelial basophilic inclusions correlates with degeneration in the respective vestibular sensory epithelia. There are no striking differences in hair cells densities of the different vestibular sense organs of the same ear and from subjects at about the same age.

Influence of age on results of vestibular function tests. Review of literature and presentation of caloric test results

Following a bibliographic review of currently known, age-dependent morphological and functional changes of the vestibular and auditory system, results are presented of our investigations concerning the influence of age on the outcome of the caloric test on 102 healthy subjects from six age groups ranging between the ages of 11 and 70 years. They prove, without any doubt, that the absolute values of nystagmic parameters in the caloric test are dependent upon age; but not in such a way that the intensity of reaction decreases with advancing age. On the contrary, they indicate that in awake, healthy subjects of middle and late middle-age, the most intensive reactions occur (maximum slow phase velocity, maximum amplitude, maximum frequency, total number of beats). In addition, based on the statistical analysis, it seems probable that the extent of the side difference of excitability depends upon age. Individuals in their middle years show side differences to a considerably lesser degree than children and elderly subjects. These represent findings which, to our knowledge, are reported here for the first time. Provided our results gain further substantiation, standard values for a true quantitative evaluation of the caloric test could only be determined as in the audiometric functional tests on the basis of larger test series of healthy subjects belonging to different age groups.

Macula utriculi in four cases with Meniere's disease

Four patients suffering from Meniere's disease were labyrinthectomized. Maculae utriculi were removed and studied by electron microscopy. The neuro-epithelia from all four patients appeared fairly normal, considering the age of the patients. However, two types of degenerative change, which could be related to the inner ear disorder, could be distinguished. One was vacuolation of the sensory cell cytoplasm, followed by pycnosis of the nucleus and cell death. The other was cystic degeneration. This started with localized separations between the sensory cell and the nerve chalice. These separations developed into a single cystic cavity. A few large intra-epithelial cysts were found, probably representing the final stage of the cystic degenerative process.