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

Abstract

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.