The Otosclerosis Problem: including Reports of Two Cases Pathologically Examined (Dalby Memorial Lecture): (Section...

The essential causative factor of otosclerosis is a gradually increasing defect in the vasomotor mechanism which governs the nutrition of the structures of the organ of hearing as a whole. The axon reflexes are, of course, included in this vasomotor mechanism, and the stimulus which excites the vasomotor mechanism is sound and sound alone. Consequently the vestibular apparatus and the semicircular canals are unaffected in otosclerosis.There is no evidence whatever of any defect in any of the endocrine glands or their secretions in otosclerosis. Neither is there any evidence of any defect in the bone metabolism of the body. On the contrary the subjects of otosclerosis are, apart from their deafness, perfectly normal individuals with ordinary average health.The deafness of otosclerosis bears very little relationship to the extent of the disease in the bone. The deafness may be very severe when the stapes is hardly fixed at all.The severity of the tinnitus bears no relationship at all to the extent of the disease in the bone.The extent of the change in the bone bears very little relationship to the duration of the disease.The extent of the changes in the bone appears to depend upon the age of onset of the disease. The earlier in life that the otosclerosis begins, the more extensive will the bone lesion become.The deafness of otosclerosis is to a large extent functional, and is the result of the insufficient supply of blood to all the nerve-structures concerned in the perception of sound.The preponderance of women as subjects of otosclerosis is the result of the greater instability of their vasomotor system and the more frequent disturbances to which it is exposed.The changes in the bone show a remarkable bilateral symmetry even to minute details. This symmetrical distribution is readily explained by the writer's view of the causative factor of otosclerosis. The vasomotor nerves governing the nutrition of the organ of hearing are anatomically symmetrical like other nerve-structures in the body. If, therefore, structural changes occur as a result of defective functioning of those nerves, such structural changes will naturally be bilaterally symmetrical in their distribution.