Predilection of otosclerotic foci related to the bone turnover in the oticcapsule

Using multiple fluorochrome lagging of eight mongrel dogs and a newly estab lished methodology of measuring bone turnover (BTO) in the otic capsule, it has previously been demonstrated that BTO in the canine otic capsule is hi ghly reduced close to the perilymphatic spaces (PLS) compared to the normal level of BTO in the periphery. Reanalysis of these data shows that this in hibition of BTO is far more pronounced around the cochlea and vestibule tha n around the semicircular canals. Similar tendencies are seen for the numer ical density and mean label area of the bone remodelling units. with increa sing distance to the PLS, these patterns are weakened, but still recognizab le. In otosclerosis, foci of abnormal bone deposition are particularly freq uent around the oval and round windows and in the cochlear capsule, i.e. wh ere inhibition of bone remodelling is most prominent. A surpassing (or fail ure) of this pronounced inhibition must precede the tumultuous but delimite d osteogenesis of otosclerosis. Otosclerosis may be a deviation of the norm al BTO process in an osteometabolically abnormal site, perhaps initiated as an osteogenetic response to abnormal stress exposure.