Hiroshi Kajikawa

Tympanoplasty with and without mastoidectomy for non-cholesteatomatous chronic otitis media.

Objectives: Cases of non-cholesteatomatous chronic otits media (COM) were reviewed to determine whether mastoidectomy is helpful when combined with tympanoplasty for these conditions. Study design: A retrospective analysis of 251 ears with non-cholesteatomatous COM operated on by one surgeon (Y.M.) in an 11-year period was conducted. Methods: Patients in group A (n = 147) were treated by tympanoplasty with mastoidectomy. Patients in group B (n = 104) were operated on without mastoidectomy. Results: Graft success rates were 90.5% in group A and 93.3% in group B. There was no statistically significant difference. Graft success rates of discharging ears were 90.0% in group A and 85.7% in group B. Graft success rates of dry ears were 90.7% in group A and 94.4% in group B. There was no statistically significant difference between discharging ears and dry ears. The rates of the postoperative air–bone gap within 20dB were 81.6% in group A and 90.4% in group B, without a statistically significant difference. Conclusions: Mastoidectomy is not helpful in tympanoplasty for non-cholesteatomatous COM, even if the ear is discharging.

Expression of neurite outgrowth factor and gicerin during inner ear development and hair cell regeneration in the chick

Several cell adhesion molecules are expressed in the developing inner ear. The present study focused on gicerin, a novel member of the immunoglobulin superfamily, in an attempt to improve our understanding of the development and regeneration of chick inner ear. Gicerin is known to homophilically interact with itself and to bind to neurite outgrowth factor (NOF). The data collected herein show that gicerin is highly expressed in auditory epithelium and acoustic ganglion during early embryogenesis. The immunoreactivity of gicerin in the auditory epithelium decreases more rapidly than that in the acoustic ganglion as the mature hair cells become distinguishable. At the post-hatch stage, the expression of gicerin is not observed. In contrast, NOF was expressed on the basement membranes around the auditory epithelium, and in the acoustic ganglion during development and after birth, but not in the auditory epithelium. Following noise damage, gicerin is transiently re-expressed on the damage receptor epithelium when active cell proliferation is observed in the epithelium. This positive reaction immediately disappears as immature short hair cells appear. These results suggest that gicerin may be associated with cell proliferation in the auditory epithelium, and play a role in neurite extension of the acoustic ganglion cells in conjunction with NOF.

Effects of antibiotic nasal nebulizer treatments on the auditory sensory epithelium in guinea pigs

The effects of antibiotics administered by intramuscular injection or nasal inhalation on the auditory sensory epithelium of guinea pigs were examined using auditory brainstem response (ABR), scanning and transmission electron microscopy. The threshold of the ABR increased, and auditory hair cells were severely damaged in guinea pigs treated with gentamycin, an antibiotic of the aminoglycoside group, administered by intramuscular injection at a dose of 400 mg/kg/day for 2 weeks. On the other hand, the threshold of the ABR was unchanged, and auditory hair cells remained intact, in guinea pigs treated with gentamycin or cefmenoxime, an antibiotic of the cephem group, administered by nasal inhalation for 30 min/day for 3 weeks. This finding suggests that antibiotic nasal nebulizer treatment is safe, while aminoglycoside antibiotic intramuscular injection is very dangerous to the auditory sensory epithelium.