The effect of CO ₂ and KTP laser on the cat saccule and utricle

Objectives/Hypothesis: To assess the potential carbon dioxide (CO ₂) and potassium-titanyl-phosphate (KTP) laser-related trauma to the saccule and utricle in a cat model. Study Design: Basic science experiment utilizing cat model. Methods: Twelve adult male cats were divided into two groups-CO ₂ and KTP-to assess the potential saccule and/or utricle trauma with direct discharge of laser energy into the vestibule after the stapes was removed. Both groups were subdivided to assess the effects with acute sacrifice and three-month survival. Bone conduction auditory brain-stem response thresholds were used to monitor auditory function. Clinical observation was used to monitor vestibular function. The temporal bones were harvested, processed, and stained with hematoxylin and eosin (H&E) in all animals with the uninvolved side serving as the control. Results: None of the animals demonstrated changes in bone conduction auditory brain-stem responses. None of the animals in the survival group demonstrated clinical vestibular dysfunction. Saccular and utricular wall rupture was observed in all animals sacrificed acutely. None of the saccular and utricular wall ruptures were of a size and location that could be attributed to laser trauma, and none of the saccular and utricular wall ruptures were associated with neuroepithelial trauma. Conclusions: There is no evidence of a difference between the CO ₂and KTP laser in potential laser-related trauma. Using bone-conducting auditory brain-stem response thresh old and clinical monitoring of vestibular function, there was no evidence of clinical auditory or vestibular dysfunction. The histologic evidence of saccular and utricular wall rupture is more consistent with stapes extraction trauma than laser-related trauma.