Insights and Constraints: Understanding the Boundaries in Investigating Otosclerosis and Endolymphatic Hydrops Interaction.

Otosclerosis and endolymphatic hydrops (EH) are distinct inner ear pathologies that may coexist within the same temporal bone, creating diagnostic and therapeutic challenges. Their interaction remains controversial, with proposed mechanisms suggesting that otosclerotic involvement of the vestibular aqueduct or cochlear endosteum may obstruct endolymphatic flow, leading to secondary hydrops. This review summarizes current evidence on the coexistence, pathophysiology, diagnostic tools, and clinical implications of otosclerosis-associated EH. Histopathologic studies have demonstrated EH adjacent to otosclerotic foci involving the cochlear endosteum and the vestibular aqueduct, supporting a mechanical or metabolic interaction between both entities. Advances in magnetic resonance imaging, particularly gadolinium-enhanced 3D-fluid-attenuated inversion recovery (FLAIR) sequences, have allowed in vivo visualization of cochlear and vestibular hydrops, improving diagnostic accuracy and enabling earlier detection of mixed pathology. Clinically, affected patients often exhibit mixed or fluctuating hearing loss, tinnitus, and vertigo, suggesting both cochlear and vestibular compromise. Post-stapedectomy EH has also been described, likely secondary to altered perilymphatic pressure or microtrauma. Despite growing evidence supporting an association, the causal relationship remains uncertain - whether EH arises as a secondary consequence of otosclerosis or represents a concurrent process within a shared pathophysiological spectrum. The coexistence of EH and otosclerosis exemplifies the complexity of inner ear disorders, highlighting the need for integrated approaches combining imaging, audiovestibular testing, and histopathologic correlation. Multidisciplinary collaboration and longitudinal studies are essential to clarify underlying mechanisms, refine diagnostic criteria, and optimize management strategies for patients with combined otosclerotic and hydropic pathology.