Abnormal Tectorial Membranes in Sensorineural Hearing Loss: A Human Temporal Bone Study Hypothesis: This study evaluates the morphological changes of the tectorial membrane (TM) in conjunction with degeneration of hair cells, interdental cells, and presence of endolymphatic hydrops (EH) in sensorineural hearing loss (HL) in the human using histopathology techniques. Background: The TM plays an important role in mechanical transduction of acoustic energy, and pathology of the TM may result in HL. Methods: All temporal bone (TB) specimens from the Massachusetts Eye and Ear Otopathology Laboratory from patients with various causes of sensorineural HL and morphological abnormalities of the TM were evaluated. Cases with a history of cochlear trauma (other than acoustic trauma) and/or severe postmortem artifacts were excluded. The TBs were processed histologically, and the status of hair cells, supporting cells, interdental cells, presence of EH, and postmortem time were tabulated. Results: Two thousand two hundred ninety TBs from 1340 individuals were evaluated, and 164 of 748 TBs from the otological disorders in which the TM were abnormal, met the inclusion criteria. The most common disorders were idiopathic sudden deafness (57.1%), genetic etiology (53.7%), and ototoxicity (40.0%), as compared with cases with presbycusis (2.9%). EH was found in 33.3% of all cases with an identified abnormality of the TM. Abnormalities of the TM were 1) deformed, 2) shrunken, 3) detached from the limbus, 4) encapsulated, or 5) missing. Encapsulated, shrunken and missing patterns (36, 35, 31%, respectively) were the most common. Conclusion: A relative high prevalence of EH among disorders with TM abnormalities suggests a possible common pathophysiology in both. In addition, anatomic abnormalities of the TM may play a role in the pathophysiology of HL in these disorders. Address correspondence and reprint requests to Joseph B. Nadol, Jr., M.D., Otopathology Laboratory, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114; E-mail: joseph_nadol@meei.harvard.edu This work was supported by grant U-24DC013983 from the National Institute on Deafness and Other Communication Disorders (NIDCD). The authors disclose no conflicts of interest. Copyright © 2019 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company