Endolymphatic hydrops as a cause of audio-vestibular manifestations in relapsing polychondritis

Secondary autoimmune immune ear disease (AIED): a systematic review and meta-analysis on vestibular manifestations of systemic autoimmune and inflammatory disorders

Secondary autoimmune inner ear disease (AIED) is often bilateral and asymmetric in patients presenting with audiovestibular symptoms due to a systemic autoimmune disease. This systematic review and meta-analysis are aimed at identifying and highlighting patterns in prevalence of vestibular dysfunction, symptom presentation, and diagnostic methods in extant literature by combining clinical context from case reports with quantitative analyses from cohort studies. Screening of articles by title, abstract, and full text was completed by four reviewers (K.Z., A.L., S.C., and S.J.). In this study, we grouped secondary AIED and systemic autoimmune diseases by pathophysiologic mechanism: (1) connective tissue disease (CTD), (2) vasculitides (VAS), (3) systemic inflammatory disorders (SID), and (4) other immune-mediated disorders (OIMD). The search for AIED disease identified 120 articles (cohorts and case reports) that met the final inclusion criteria. All 120 were included in the qualitative review, and 54 articles were included for meta-analysis. Of these 54 articles, 22 included a control group (CwC). Ninety individual cases or patient presentations from 66 articles were included for analysis in addition to the 54 cohort articles. Secondary AIED does not have a diagnostic algorithm for managing vestibular symptoms. The management of audiovestibular symptoms requires close collaboration between otolaryngologists and rheumatologists to preserve end-organ function of the ear. To improve our ability to understand the impact on the vestibular system, vestibular clinicians need to develop a standardized reporting method. Clinical presentation should frequently be paired with vestibular testing to contextually investigate symptom severity and provide higher quality care.

A Genetic Murine Model of Endolymphatic Hydrops: The Phex Mouse

Animal models of endolymphatic hydrops (ELH) provide critical insight into the pathophysiology of Meniere's disease (MD). A new genetic murine model, called the Phex mouse, circumvents prior need for a time and cost-intensive surgical procedure to create ELH. The Phex mouse model of ELH, which also has X-linked hypophosphatemic rickets, creates a postnatal, spontaneous, and progressive ELH whose phenotype has a predictable decline of vestibular and hearing function reminiscent of human MD. The Phex mouse enables real-time histopathologic analysis to assess diagnostic and therapeutic interventions as well as further our understanding of ELH's adverse effects. Already the model has validated electrocochleography and cervical vestibular evoked myogenic potential as useful diagnostic tools. New data on caspase activity in apoptosis of the spiral ganglion neurons may help target future therapeutic interventions. This paper highlights the development of the Phex mouse model and highlights its role in characterizing ELH.

A mouse model with postnatal endolymphatic hydrops and hearing loss

Endolymphatic hydrops (ELH), hearing loss and neuronal degeneration occur together in a variety of clinically significant disorders, including Meniere's disease (MD). However, the sequence of these pathological changes and their relationship to each other are not well understood. In this regard, an animal model that spontaneously develops these features postnatally would be useful for research purposes. A search for such a model led us to the Phex Hyp-Duk mouse, a mutant allele of the Phex gene causing X-linked hypophosphatemic rickets. The hemizygous male (Phex Hyp-Duk/Y) was previously reported to exhibit various abnormalities during adulthood, including thickening of bone, ELH and hearing loss. The reported inner-ear phenotype was suggestive of progressive pathology and spontaneous development of ELH postnatally, but not conclusive. The main focuses of this report are to further characterize the inner ear phenotype in Phex Hyp-Duk/Y mice and to test the hypotheses that (a) the Phex Hyp-Duk/Y mouse develops ELH and hearing loss postnatally, and (b) the development of ELH in the Phex Hyp-Duk/Y mouse is associated with obstruction of the endolymphatic duct (ED) due to thickening of the surrounding bone. Auditory brainstem response (ABR) recordings at various times points and histological analysis of representative temporal bones reveal that Phex Hyp-Duk/Y mice typically develop adult onset, asymmetric, progressive hearing loss closely followed by the onset of ELH. ABR and histological data show that functional degeneration precedes structural degeneration. The major degenerative correlate of hearing loss and ELH in the mutants is the primary loss of spiral ganglion cells. Further, Phex Hyp-Duk/Y mice develop ELH without evidence of ED obstruction, supporting the idea that ELH can be induced by a mechanism other than the blockade of longitudinal flow of endolymphatic fluid, and occlusion of ED is not a prerequisite for the development of ELH in patients.