Harvest of Vestibular End-Organs under Physiologic Conditions during Labyrinthectomy

This protocol describes a new technique for harvesting human inner ear tissue during labyrinthectomy using an underwater technique. We are using this technique to better understand inner ear disorders, such as Meniere's disease. Human inner ear diseases are difficult to study because the human inner ear is encased in dense bone. Previous studies have primarily relied upon post-mortem tissue analysis or high resolution imaging. This protocol offers a new means of directly studying human inner ear tissue. The inner ear is kept under physiologic conditions using balanced salt solution. Additionally, the underwater technique and increased magnification afforded by the endoscope allow for the easy visualization of the membranous labyrinth, aiding in atraumatic dissection.

[Instructor] To begin, perform mastoidectomy and submerge the mastoid cavity in a balanced salt solution. And visualize the labyrinth using a zero degree endoscope with a lens cleaning sheath irrigation system. Then irrigate the mastoid cavity with balanced salt solution to wash away blood and improve visualization of the labyrinth. Using the endoscope for visualization, carefully drill away the otic capsule bone. Under balanced salt solution, after entering the dome of the lateral semi-circular canal, follow it anteriorly until its ampullae are identified. Enter the superior semi-circular canal, and follow it medially to its ampullae. Then cut the lateral semi-circular canal duct sharply to facilitate removal. Next, employing a rosen needle, elevate the horizontal and superior semi-circular canal ampullae off the crista. Harvest the required structures and place all tissues in balanced salt solution. Remove the bone between the horizontal and posterior semicircular canal ampullae to expose the vestibule. Elevate and remove the macula while maintaining the fluid level. Finally, sharply elevate and remove the saccule from the spherical recess and place the tissue samples in balanced salt solution on ice. The human utricle and lateral and superior canal ampullae were harvested intact with minimal trauma. Immunofluorescent labeling showed intact type one vestibular hair cells in the utricle. Hair cell density was recorded at 82 cells per 10,000 square micrometers.