PT - JOURNAL ARTICLE AU - J.C. Benson AU - F. Diehn AU - T. Passe AU - J. Guerin AU - V.M. Silvera AU - M.L. Carlson AU - J. Lane TI - The Forgotten Second Window: A Pictorial Review of Round Window Pathologies AID - 10.3174/ajnr.A6356 DP - 2019 Dec 12 TA - American Journal of Neuroradiology 4099 - http://www.ajnr.org/content/early/2019/12/12/ajnr.A6356.short 4100 - http://www.ajnr.org/content/early/2019/12/12/ajnr.A6356.full AB - SUMMARY: The round window serves to decompress acoustic energy that enters the cochlea via stapes movement against the oval window. Any inward motion of the oval window via stapes vibration leads to outward motion of the round window. Occlusion of the round window is a cause of conductive hearing loss because it increases the resistance to sound energy and consequently dampens energy propagation. Because the round window niche is not adequately evaluated by otoscopy and may be incompletely exposed during an operation, otologic surgeons may not always correctly identify associated pathology. Thus, radiologists play an essential role in the identification and classification of diseases affecting the round window. The purpose of this review is to highlight the developmental, acquired, neoplastic, and iatrogenic range of pathologies that can be encountered in round window dysfunction.LOlabyrinthitis ossificansRWround window