Otosclerosis: its modern surgical management *

Introduction Valsalvais attributedwith the first description of ankylosisof the stapesin a deaf patient in 1741'. However,it was JosephToynbeewho, a hundred years later, related this pathologic entity to a clinical onefrequently seen with an hereditaryhistory and the classicsyndromeof paracusis(paradoxic hearing improvement in backgroundnoise)'. It is now knownthatotosclerosisis adisorder confined to the labyrinthine bone and stapes and seen only inhumans.The clinical presentation is oneof conductiveor mixed conductive and sensorineuralhearing loss occurring after the secondor third decadeof life and more commonly in females. The disease is rare in negroid races anduncommonin Asians. It is mostly seen inCaucasians, causinghearingloss in one to two per centof the population, although there is evidenceof approximatelya 10 per cent overall incidence from temporal bonestudies. The pattern of inheritance is autosomal dominantwith incompletepenetranceand variable expressivity'. Pathologically, the normal boneof the otic capsuleis replacedwith boneof increasedthickness,vascularityand cellularity. In 'clinical otosclerosis' (ie, otosclerosiscausing deafness), the ovalwindow is the mostcommon site of involvement, and as the lesionprogresses, thestapesbecomesfixed, causingthe conductivehearingloss. In the late 19thcentury, a numberof European otologists reported stapes mobilisation and evenstapesremovalto alleviatethe hearing loss of stapesankylosis", However, such proceduresfell into disreputeuntil reintroducedby Rosen in the 1950s. From 1913, a different form of surgical treatmentwasappliedthe fenestrationoperation. This consistedof the creationof a third window into the labyrinth, over the lateral semicircularcanal,which allowedmovementof the labyrinthine fluids in responseto sound, thus by-passingthe fixed stapes in the oval