Temperature Measurements of the Semicircular Canal During Green Laser Irradiation of the Canal: A Preliminary Study.

BACKGROUND: Laser irradiation of the semicircular canal (SCC) is a good treatment for intractable benign paroxysmal positional vertigo. However, there were few reports on the temperature changes during laser irradiation. OBJECTIVE: To measure the internal temperature of the SCC and vestibule during green laser irradiation of the SCC and investigate morphologic changes using human temporal bones. METHODS: After the lateral SCC was blue-lined, a thermocouple was inserted into the SCC through a hole made in the canal wall. Another thermocouple was inserted into the vestibule through the oval window. Green laser was irradiated to the lateral canal wall. After the irradiation, the tissues were inspected as paraffin using HE staining. RESULT: The internal temperature of the SCC rose from 33 ° to 52 °C by a single laser irradiation of 1.5 W × 2 seconds and 82 °C by a single laser irradiation of 1.7 W × 3 seconds to the canal wall with a black spot. Continuous laser irradiation of 1.5 W × 3 seconds, 10 times resulted in a temperature rise of 92 °C from 33 °C. Throughout the whole experiments, temperatures within the vestibule were unchanged. Histopathology showed that the irradiated areas of the lateral canal wall were partially deficient with or without carbonization after single irradiation. By continuous laser irradiations, the SCC bony wall showed a peroration of 40 µm in diameter with carbonized edges. CONCLUSIONS: Green laser irradiation of the SCC produced char formation with perforation in the canal wall. High temperatures within the SCC were recorded for a short period of less than 30 seconds. However, the vestibule didn't show temperature changes.

A 3-Dimensional Model of the Human Round Window Membrane.

OBJECTIVES: The round window membrane (RWM) is small in size, making it difficult to clarify its shape and structure. The authors examined a 40x magnified 3-dimensional model of the human RWM to clarify its morphologic aspects and characteristics. METHODS: An RWM specimen was obtained from an archival, formalin-fixed, decalcified, left temporal bone of an 84-year-old female cadaver. The data obtained by laser scanning microscopy were input into a 3-dimensional printer. After a model of the RWM was created, the following features were examined: striae on the surfaces, curvatures, thickness, and areas. Cross sections of the original specimen were made for histological observations. RESULTS: The contour of this RWM model was approximately elliptic, with a saddle shape. When illuminated from the scala tympani side, the surface facing the fossula exhibited dark anterior and clear posterior portions. A borderline appeared where the 2 portions were bound along the short axis of the ellipse. This borderline was identified as the line of inflection. Collagen fibers were shown to run parallel to the borderline in the posterior portion but were fanned out in the anterior portion. CONCLUSIONS: The magnified 3-dimensional model clarified gross anatomy and characteristics of the RWM. It is good teaching material for small tissues, such as the RWM.

Hydrops of the organ of Corti.

OBJECTIVES: The authors would like to confirm a fluid pathway from the scala tympani to the organ of Corti, and to observe its morphological changes. METHODS: A staining solution for succinic dehydrogenase was perfused with phenazine methosulfate in the scala tympani of living guinea pigs (n = 5) under deep anesthesia. After fixation, the cochleas were eventually embedded in epon. Sections were observed under a light microscope. RESULTS: Blue-stained tissue is indicative of the pathway taken by the solution. The staining solution entered the organ of Corti through Hensen-Deiters' slit. The slit widened and Hensen's cells were pushed laterally. A new space was formed medial to Hensen's cells. Cortilymphatic hydrops developed. CONCLUSION: The Hensen-Deiters' slit is a pathway of a certain staining solution from the scala tympani to inside the organ of Corti of the guinea pig. The influx of the fluid pushes Hensen's cells laterally and upward, resulting in a formation of hydrops of the organ of Corti or cortilymphatic hydrops. The hydrops is observed in animals with experimental perilymphatic fistula and with viral labyrinthitis. At the end stage of the hydrops, only the surface of the organ of Corti remains as a thin layer without any cellular elements.

Laser irradiation of the semicircular canal: occlusion of the canal or duct.

The aim of this study was to evaluate the effects of argon laser irradiation of the semicircular canals using computed tomography (CT) images and to examine the basis for laser treatment for benign paroxysmal positional vertigo (BPPV). CT images of the posterior canal were evaluated postoperatively in a patient with intractable BPPV, in whom the unilateral posterior and lateral semicircular canals were irradiated with an argon laser. In addition, bootstrap analysis of 20 patients with normal CT findings of the temporal bone was performed and previous experimentally obtained histologic findings were compared. Cross-sections of the posterior canals of 20 patients were found to show no difference in size between the right and left sides. The laser-irradiated posterior canal became narrower than that on the non-irradiated healthy side in our patient. There was a discrepancy between the CT images and experimentally obtained histologic findings that showed complete occlusion of the canal. CT images of a patient with severe vertigo demonstrated that argon laser irradiation to the blue-lined semicircular canals did not occlude the canal of the corresponding areas, while the canal of the guinea pig histologically showed complete obstruction with new bone after irradiation with the same energy (1.5 W, 0.5 s, spot size: around 200 µm in diameter). The patient has been free from vertigo for 16 years. Marked constriction of the semicircular duct corresponding to the irradiated area appeared to be effective in treating intractable BPPV.

Pathogenesis of cytomegalovirus-associated labyrinthitis in a guinea pig model.

Cytomegalovirus infects fetuses through the placenta, resulting in various congenital disorders in newborns, including hearing loss. We developed a monoclonal antibody to guinea pig cytomegalovirus (GPCMV) that was available for immunohistochemistry, and investigated the expression of the GPCMV antigen in animal models of direct and congenital infections. Injection of GPCMV, directly to the inner ear, increased the sound pressure level and resulted in labyrinthitis with severe inflammation. Immunohistochemistry detected GPCMV-infected cells mainly in the scala tympani, scala vestibule and spinal ganglion, but rarely in the cochlear duct. Injection of GPCMV to 5-week pregnant guinea pigs resulted in severe labyrinthitis in fetuses. Immunohistochemistry detected GPCMV-infected cells in the perilymph area and spinal ganglion, but not in the endolymph area, including hair cells. These data suggest that the virus spreads via the perilymph and neural routes in the inner ear of both models of direct and congenital infections.

Effect of single-drug treatment on idiopathic sudden sensorineural hearing loss.

OBJECTIVES: In order to evaluate the effect of a medical administration for the sudden deafness patients, single-drug treatment for idiopathic sudden sensorineural hearing loss (ISSHL) was assessed at multi-centers participating in the Acute Severe Hearing Loss Study Group sponsored by the Ministry of Health, Labor and Welfare of Japan. METHODS: The subjects consisted of ISSHL patients who were (1) 20 years of age or older, (2) diagnosed within 2 weeks after the onset of hearing loss, (3) showing a mean hearing level of 40-90 dB at five frequencies from 250 to 4000 Hz, (4) previously untreated, and (5) with normal for age in hearing of the opposite ear. The drugs used in this study were ATP, alprostadil, hydrocortisone and amidotrizoate, which were administered intravenously, and beraprost sodium and betamethasone, which were given orally. Two drugs were assigned to each center, one of which was selected according to the code hidden in envelopes and administered for 1 week. The treatment after the single-drug administration was conducted at the discretion of each center. The hearing gain and recovery rate at 1 week after the initiation of single-drug treatment and at 1 month or over when the hearing level was fixed, were evaluated based on the criteria for hearing recovery prepared by the Acute Severe Hearing Loss Study Group. RESULTS: There was no statistically significant difference in the recovery rate among drugs either at 1 week after the initiation of single-drug treatment or at the time of fixed hearing level. At the time when the hearing level was fixed, a statistically significant difference in the complete recovery rate was detected only between amidotrizoate and beraprost sodium. CONCLUSION: From these results, we could not find any specific drugs recommended for ISSNHL. In evaluating the effect of the drugs, however, several problems in the clinical trial for ISSHL should be considered.

Argon laser irradiation of the semicircular canal in two patients with benign paroxysmal positional vertigo.

The results of long-term follow-up after surgical treatment of two patients with intractable benign paroxysmal positional vertigo are reported. Argon laser irradiation of the blue-lined posterior and lateral semicircular canals in one patient, and of only the posterior canal in the other was performed seven and six years ago, respectively. Argon laser irradiation was carried out 10 times in succession three mm along the canal to occlude it. The power applied each time was 1.5 W on the dial of the laser device for 0.5 sec. Relief of vertigo was noted on the second post-irradiation day. There has been no recurrence of vertigo in these patients.