Occlusion of the semicircular canal using argon laser

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.

[Variants of treatment of the head direction at the festulars of the labi-rint of inflammatory genesis]

PURPOSE

To analyze the effectiveness of various methods of treating dizziness with fistulas of the labyrinth (FL) of inflammatory genesis. An analysis of the surgical treatment of 216 patients with chronic suppurative otitis media (CSOM) with cholesteatoma complicated by FL using a variety of FL treatment methods is presented. All patients underwent a debridement operation on the middle ear or revision of the postoperative cavity: in 48 patients with a matrix of cholesteatoma in situ on the fistula, in 109 patients with matrix removal followed by plastic repair or FL filling with various autotissues, in 59 patients with matrix conservation, plastic removal or filling FL and SLD labyrinth. In the last two groups, filling of a semicircular canal (SC) defect was performed in 33 patients, and mastoidoplasty - in 47.

CONCLUSION

All used FL treatment techniques are effective in the treatment of peripheral vestibular disorders. Careful treatment of SC fistula after removal of all pathological conditions in the absence of active inflammation and the appointment of hormone therapy in the postoperative period are the main factors in preserving the functions of the labyrinth in any surgical technique. Filling of the lumen of the SC and mastoidoplasty in patients with CSOM with FL can eliminate peripheral dizziness.

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.

Triple Semicircular Canal Occlusion in Guinea Pigs with Endolymphatic Hydrops

HYPOTHESIS

Triple semicircular canal occlusion will eliminate rotatory stimulation to the vestibular peripheral system (as it blocks endolymphatic fluid movement) and therefore release rotatory vertigo attack. This surgery is safe in ears with endolymphatic hydrops.

BACKGROUND

Semicircular canal occlusion has been used as an alternative treatment of intractable benign paroxysmal positional vertigo with varied success. Triple semicircular canal occlusion in animal models blocks the responses of the semicircular canals to rotation and spares cochleae and the otolithic apparatus. This result suggests that triple semicircular canal occlusion is a prospective method in vertigo management for patients with Ménière's disease. However, the effectiveness and safety of triple semicircular canal occlusion has not been fully evaluated in ears with endolymphatic hydrops.

METHODS

Endolymphatic hydrops was established in 20 guinea pigs by endolymphatic sac obliteration. Triple semicircular canal occlusion was performed in 12 of them 120 days after endolymphatic hydrops surgery, whereas 8 others were killed for morphologic observation to confirm endolymphatic hydrops. Auditory and vestibular functions were monitored from the time before endolymphatic hydrops until 1 month after triple semicircular canal occlusion. Endolymphatic hydrops and canal occlusion were confirmed by morphologic observation.

RESULTS

Successful establishment of endolymphatic hydrops was indicated by mild elevation of the auditory brainstem response threshold and tentative asymmetry in nystagmus. Endolymphatic hydrops was confirmed by cochlear morphology in all eight animals that were killed 120 days after endolymphatic hydrops surgery. After triple semicircular canal occlusion, all 12 animals showed spontaneous nystagmus with a slow component toward the side that had been operated on, head tilt, rotated walking, and tentative asymmetry in rotatory nystagmus. The static symptoms disappeared within 1 month after triple semicircular canal occlusion. Caloric nystagmus was only slightly reduced after endolymphatic hydrops as compared with the contralateral ears but could not be elicited at all after triple semicircular canal occlusion. No significant elevation in auditory brainstem response threshold was found after triple semicircular canal occlusion. The canal occlusion and endolymphatic hydrops were confirmed in all surgical ears.

CONCLUSION

Triple semicircular canal occlusion is effective for eliminating the response of semicircular canals to rotation and caloric stimulation and is safe in ears with endolymphatic hydrops. Also, the static compensation to the disequilibrium is quick and complete. These results suggest that triple semicircular canal occlusion should be an option for controlling rotatory vertigo in Ménière's disease.

Surgery of the inner ear with hearing preservation: serial histological changes

OBJECTIVES/HYPOTHESIS

Surgery of the inner ear can result in hearing preservation under certain conditions, but the mechanisms responsible for hearing preservation or loss are not well understood. The specific aim of the study is to examine histological sections obtained at different time intervals after varying degrees of surgical entry into the inner ear, to understand how the cochlea is protected. The hypothesis is that internal partitioning occurs.

STUDY DESIGN

Histologic examination of guinea pig inner ears by light microscopy.

METHODS

Guinea pigs underwent lateral semicircular canal transection and plugging, ampullectomy, or vestibulotomy, and tone-burst auditory brainstem response thresholds at 2, 8, and 24 kHz were measured at intervals before and after surgery. Animals were killed after 1, 3, 7, or 21 or more days, and temporal bones were examined histologically.

RESULTS

The histological response to surgical trauma consists of fibrosis and varying amounts of inflammation near the site of surgical entry. Cochlear hair cells are nearly always preserved, even when hearing loss occurs. Extension of the inflammatory response to the cochlea is associated with greater degrees of hearing loss.

CONCLUSION

The guinea pig inner ear is capable of withstanding surgical trauma to the semicircular canals and vestibule without complete loss of cochlear function. Fibrosis creates an effective partition between the site of surgical entry and the rest of the inner ear. Cochlear preservation might be enhanced if the inflammatory response can be contained.

Early histopathologic changes after lateral semicircular canal transection and occlusion in guinea pigs

Occlusion of the semicircular canals has been used in otoneurologic and skull base surgeries with preservation of hearing. In order to understand the role of occlusion in hearing preservation, we observed early histopathologic changes of the lateral semicircular canal following transection and occlusion in guinea pigs. After surgery, the membranous endolymphatic canal was collapsed, and its torn ends were sealed by intramural bone dust in the bony semicircular canal. On the first postoperative day, the endolymphatic canal was expanded to its normal shape, and the sealing at the torn ends was maintained by the bone dust. These findings suggest that occlusion after semicircular canal injuries, by making blind ducts in the membranous endolymphatic canal, is important for the preservation of postoperative hearing.

Argon laser irradiation to the semicircular canal

In order to elucidate the effects of argon laser irradiation on the lateral semicircular canal of the guinea pig, the vestibular labyrinth was histologically studied after irradiation, using the conventional celloidin method. Irrigation of the external meatus with ice water was used to evaluate the function of the semicircular canal by recording caloric nystagmus. When irradiation was performed, a laser probe was approximated to the lateral canal, 0.5 to 1 mm away from the surface of the canal. Each time, power applied was 1.0 W on the dial of the laser machine. The duration of irradiation was 0.5 s. The lateral canal was irradiated one to 15 times. Twenty-five to 87 days after irradiation, the temporal bones were fixed in Heidenhein-Susa solution, removed, and subjected to celloidin processing. The irradiated bony wall of the lateral canal demonstrated charring. Lucent areas were observed around and under the charred area. The semicircular duct showed shrinkage with disappearance of the trabecular mesh. New bone formation was observed along the endosteum of the irradiated area. The lateral canal was completely occluded by ossification with or without fibrosis when sufficient energy was applied. The anterior and posterior canals were normal. Caloric tests using 5 mL of ice water for 5 s failed to elicit nystagmus on the irradiated side.