Chiaki Tago

Cochlear and renal pathology in the autoimmune strain mouse.

This study was designed to investigate the role of immunologic mechanisms in sensorineural hearing disorders and the relationship between inner ear and renal disorders. Autoimmune strain (NZB/kl) mice, in which autoimmune disease can be spontaneously induced, were used in this study. The mice were tested for acoustic brain stem responses, cochlear and renal disorders, and circulating immune complex serology by means of enzyme immunoassay. Pathologic studies consisted of observation of tissue changes following hematoxylin and eosin staining and indirect immunofluorescence staining under light microscopy. Compared to controls, the hearing was impaired in NZB/kl mice. Indirect fluorescence staining showed immunoglobulin G deposits in the stria vascularis. There was a correlation between the degree of hearing impairment and the severity of stria vascularis lesions. The NZB/kl mouse can provide a model for sensorineural hearing disorders secondary to immunologic disorders.

Mechanisms of Hearing Disturbance in an Autoimmune Model Mouse NZB/kl

A subline of the NZB mouse, NZB/kl, was found to develop severe hearing disturbances at high frequency sound at the age of 4 to 6 months. Deposition of IgG was observed on the capillary wall of the stria vascularis of the mice, but the concentration of circulating immune complex did not seem to be correlated to the deposition. Electron microscopic examination revealed that the capillaries had a thick basement membrane, and in severe cases the membrane contained foamy structures of various size. In some cases the base membrane was so thick that the capillary lumen was narrowed, and the intermediate cells seemed to be damaged. No pathological findings were found in other inner ear tissues. These results suggest that the changes in the stria vascularis were possibly caused by an autoimmune mechanism which resulted in hearing disturbance.

HLA associations in otosclerosis in Japanese patients

Otosclerosis is a disease of the otic capsule that is caused by abnormal resorption and redeposition of bony tissue. Sixty-two unrelated Japanese patients exhibiting clinical otosclerosis were typed for HLA-A, -B,-C antigens. Twenty-one of the patients were also typed for DR antigens. The frequency of HLA-Aw33 was significantly higher in otosclerosis patients than in the control group (24.2% vs 9.5%). This finding suggests that the presence of HLA-Aw33 antigens may be related to an increased susceptibility to otosclerosis or to its clinical outcome.

Factors Affecting Improvement of Hearing After Stapes Surgery

Presently, stapedectomy and stapedotomy are common techniques for improving hearing defects secondary to otosclerosis. Ninety-two consecutive cases with otosclerosis were analyzed on the postoperative hearing gain. The degree of postoperative hearing gain was affected by many factors, such as sex, age, preoperative bone conduction at high frequencies, and preoperative A-B gap at speech frequencies. The age of patients did not affect the postoperative hearing gain, while sex, preoperative bone conduction, and preoperative A-B gap at speech frequencies influenced postoperative hearing gain.

Improvement in Hearing and Incidence of Complications Following Three Types of Stapes Surgery

We reviewed the records of 80 patients who had undergone stapes surgery over the past 10 years and who had been followed for more than 6 months at Nagoya University Hospital. They were divided into three groups: those who received total stapedectomy using a wire loop (29), those who received a large fenestra stapedotomy using a 0.6 mm Teflon wire piston (39), and those who received a small fenestra stapedotomy using a 0.3 mm Teflon piston (12). The decline in the air conduction threshold and closure of the air-bone (A-B) gap were used as indices of postoperative improvement in hearing. The postoperative elevation of bone conduction threshold at 4 and 8 kHz was used as an index of inner ear damage caused by the surgery. The postoperative hearing improvement at four speech frequencies between the three types of stapes surgery did not differ significantly. At 4 and 8 kHz, postoperative bone conduction was elevated significantly in the patients who received total stapedectomy as compared with those who underwent a large or small fenestra stapedotomy.

A Case of Extensive Cholesteatoma to the Base of The Skull

We report a rare case of cholesteatoma that invaded deeply into the base of the skull. The patient was a 64-year-old male with a longstanding history of left otorrhea. From the CT scan, extensive destruction of the left temporal, occipital, sphenoid, and atlas bone was found. In spite of extensive resection of the necrotic bone, destruction of the bone spread deeply into the entire skull base bone, resulting in death from respiratory arrest. In the pathological examination, we found a large amount of keratinized debris and proliferative squamous epithelium in the base of the skull. We concluded that the cause of this rapid, extensive invasion is due to the fact that 1) original character of the epithelium of this cholesteatoma was vigorously proliferative, 2) during the long course and operations, this epithelium and abundant debris broke into the bone in a complicated fashion, was adjacent to the bone, and destroyed the bone directly, 3) infection and pressure at the base of the skull without drainage and abundant debris from the epithelium itself stimulated the epithelial proliferation and bond resorption.