During middle ear endoscopy, patients frequently experience vertigo. We theorized that this effect is secondary to heat produced by the scope. We evaluated two Hopkins rods and two fiberoptic scopes to assess the temperature elevation at the lateral semicircular canal (LSCC) of temporal bones and in a live canine model. These results were compared to the results of a standard 44 degrees C water caloric. We demonstrated in both models that the temperature rise at the LSCC increased relative to the scope diameter and that the Hopkins rods produced the same or greater heating effect than a warm caloric. Direct exposure of the thermocouple to the light produced a greater temperature elevation. We conclude that endoscopes produce sufficient heat to induce caloric stimulation of the LSCC. Care should be exercised to prevent the possibility of thermal injury.
The biomechanics of arytenoid adduction surgery are not well understood. An excised canine larynx model was used to study the effects of variable suture tension on glottal configuration and on vocal fold tension (at the midfold and the vocal process). Arytenoid adduction both medializes the vocal fold and closes a posterior glottal chink. Vocal fold tension at the midfold did not vary significantly with suture tension. As suture tension increased to approximately 100 g, vocal fold tension at the vocal process also increased. Beyond 100 g of suture tension, vocal fold tension at the vocal process did not increase. We conclude that the effects of suture tension on the resistance to lateral movement are different at the midfold compared to the vocal process. Procedures for surgical rehabilitation of vocal fold paralysis should address the biomechanical subunits of the larynx individually in order to achieve optimum results.
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