Is ‘otosclerosis’ a misnomer?

By Kenneth H. Brookler, MD, MS Presented at the Otolaryngology Historical Society Meeting, September 22, 2014 Otosclerosis was first described as ankylosis of the stapes by Antonio Maria Valsalva in 1704 and continued by Joseph Toynbee in 1857 in his Museum Catalogue. Adam Politzer, MD, in Washington, DC, in 1893 gave a paper titled “Peculiar Affection of the Labyrinthine Capsule as a Frequent Cause of Deafness.” On the same program was Lawrence Turnbull, MD, who described “progressive or proliferous sclerosis” as a non-suppurative disease of the middle ear for which he performed an operation he termed “otosclerectomy.” In an 1897 publication, regarding the term “otosclerosis,” Dr. Politzer preferred the term “capsulitis labyrinthi,” but understood that it had gained acceptance and in the 1901 edition of his textbook a chapter for the first time titled “Otosclerosis” was included. Gray’s Anatomy in 1917, “Otosclerosis: Idiopathic Degenerative Deafness,” first introduced that the term “otosclerosis” is a misnomer. S.R. Guild, MD, in the 1944 paper “histologic otosclerosis” in post mortem histopathology makes the case for otic capsule otosclerosis without oval window findings. He did not support the idea that otosclerosis begins in the fissula ante fenestram. In 1953, a paper attributed to Dr. Guild was called upon to defend the 1944 paper where he indicated that otosclerosis could not produce a “nerve” hearing loss. He was willing to concede this as possible. The discussion at this meeting began the concept of “cochlear otosclerosis.” Temporal bone imaging evolved so that a “radiologic otosclerosis” diagnosis could be reached and computerized tomography had matured by 2000 to almost overlay the equivalent slice histopathology. The routine use of CT applied to many clinical otologic conditions revealed otic capsule disorders that were classified as otosclerosis but without oval window involvement. In 1968, Barry Anson, MD, in describing the embryology of the otic capsule said: “Arrest in development may occur in another, importantly, in the region of the fissula ante fenestram”… where sometimes “a chondral mass persists even through infancy, in the fissular tract.” “This is the predictive site for the occurrence of otosclerosis … cartilage may be the precursor of otosclerosis.” Ruth Gussen, MD, in 1968 said: “The histologic structure of the labyrinthine capsule is usually considered to be normal unless otosclerotic bone is present replacing portions of the original capsule. An area of predilection for otosclerotic involvement is definitely agreed upon within the fissula ante fenestram. However, otosclerotic foci also develop within the capsule with no relation to this area of predilection.” Because of her basic premise she failed to recognize that osteoclasts and osteoblasts in the otic capsule could result from a different origin. A century since the term otosclerosis was coined molecular biology of bone, especially “osteoclastogenesis,” explains the underlying mechanisms of bone physiology and pathology. In 2005, osteoprotegerin (OPG) and TNF-α along with a lacuno-canalicular network were identified in the otic capsule. Simultaneously, the effect of TNF-α on hair cells was described. In 2014, sodium fluoride was found to induce apoptosis in cultured rat chondrocytes. On August 1, 2014, stapedectomy stapes fragments osteoblasts were cultured and examined for rate of proliferation, degree of mineralization, and adhesiveness compared to osteoblasts cultured from normal bone specimens for orthopedic. They were found to proliferate slower, mineralize greater, and had more adhesive properties that the normal cultures osteoblasts and these properties could be reversed to normal with the addition of a bisphosphonate. FISSULA ANTE FENESTRAM IS THE ORIGIN OF THE PROCESS PRODUCING FIXATION OF THE STAPES: begins with recruitment of chondrocytes in the fissula ante fenestram to become osteoblasts, followed by the signaling between osteoblasts and osteoclasts as the process migrates over the oval window, as evidenced in histopathology. OTIC CAPSULE DEMINERALIZATION: (previously described as histologic otosclerosis) is an independent osteoclast-osteoblast-osteocyte, TNFα family cytokine driven disorder without fixation of the stapes. Questions to be considered: Is the term otosclerosis relevant or a misnomer today? Should “otosclerosis” be reserved for the observed presence in the oval window at surgery or on imaging? In the absence of oval window evidence, should otic capsule demineralization be otherwise characterized? Understanding the origin of the oval window pathology and the recent research, should sodium fluoride and bisphosphonates be considered in the medical management of the hearing loss? Since otosclerosis is clearly a misnomer should there be a movement to eliminate it from the daily nomenclature of otology? Do these findings suggest a potential variety of otic capsule disorders requiring more research and the development of a meaningful classification?