Fumiro Suga

Histopathological observations of presbycusis.

Temporal bone histopathology of 17 aged patients who had spontaneous and gradually progressive bilateral sensorineural hearing losses associated with aging was studied. Six cases in the present material showed the gradually sloping audiometric curve; nine cases, abrupt high tone hearing loss; and two cases, the flat audiometric curve. The most prominent histopathological change in the inner ear was a decrease in the population of the spiral ganglion cells. However, diffuse senile atrophy was also often seen in the organ of Corti and the stria vascularis. A positive correlation between the degree of arteriosclerosis and the degree of sensorineural degeneration in the cochlea was not obtained in the present cases. Also, the correlation was not found to be consistent between the type of the audiometric curve and the localization of lesions in the sensory, the neural or the vascular elements in the cochlea. Our observations show that a certain type of audiometric curve does not necessarily indicate a lesion in a specific cochlear element.

Inner Ear Degeneration in Acoustic Neurinoma

The temporal bones of three cases of acoustic neurinoma are described to illustrate histopathological features of inner ear lesions due to chronic partial obstruction of blood circulation by the tumor in the internal auditory meatus. Degenerative changes in the inner ear due to acoustic neurinoma were evaluated and compared with changes in the opposite ear. The main pathological findings in the inner ear which were attributed to the tumor were degeneration of nerve fibers and of ganglion cells, degeneration of the stria vascularis, degeneration of the tectorial membrane, fibrosis and ossification of a semicircular canal. Fairly good preservation of sensory cells was observed in the presence of total degeneration of nerve fibers and ganglion cells and subtotal degeneration of the stria vascularis.

Temporal Bone Histopathology of Osteopetrosis

The histopathology of the temporal bone of an eight and one-half-year-old girl with osteopetrosis (Albers-Schönberg disease) was studied to evaluate the pathogenesis of its frequent complications in hearing and facial nerve function. The patient was blind and had acute otitis media, but facial paralysis was not noted. Although the size of the temporal bone pyramid was markedly increased due to enormously thickened periosteal layer, changes in the endosteal and endochondral layers were less marked. Exostotic growth of periosteal bone was seen in the middle ear wall, and the tympanic cavity appeared to be narrowed. At the oval window region, the facial nerve was pushed down towards the stapes due to extreme overgrowth of periosteal bone of the epitympanum, and the superstructure of the stapes was imbedded deeply into the dislocated facial nerve and had strongly compressed it. Although the footplate was free from ankylosis, the crus of the stapes appeared to be immobilized because it was lodged in the facial nerve. Such changes appeared to be the pathogenesis of one form of facial nerve paralysis and conductive hearing loss associated with osteopetrosis.

Labyrinthitis Ossificans Due to Chronic Otitis Media

Histopathology of two cases of unilateral labyrinthitis ossificans in the presence of bilateral chronic suppurative otitis media is presented. In both cases, ossification and fibrosis were limited to the scala tympani of the lower basal turn, apparently due to inflammation entering through the round window membrane. The round window was occluded by new bone and fibrous tissue presumably resulting in a conductive hearing loss in addition to the conductive loss due to middle ear lesions. Degeneration of the hair cells of the organ of Corti was limited to the lower basal turn where ossification and fibrosis occurred.