Surgical Labyrinthectomy of the Rat to Study the Vestibular System.

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including surgical or chemical labyrinthectomy and vestibular neurectomy. Surgical labyrinthectomy is a relatively simple, reliable, and rapid method. Here, we describe the surgical technique for rat labyrinthectomy. A postauricular incision is made under general anesthesia to expose the external auditory canal and the tympanic membrane, after which the tympanic membrane and the ossicles are removed without the stapes. The stapes artery, which is located between the stapes and the oval window, is a vulnerable structure and must be preserved to obtain a clear surgical field. A hole to fenestrate the vestibule is made with a 2.1-mm drill bur superior to the stapes. Then, 100% ethanol is injected through this hole and aspirated several times. Meticulous dissection under a microscope and careful bleeding control are essential to obtain reliable results. Symptoms of vestibular loss, such as nystagmus, head tilting, and a rolling motion, are seen immediately after surgery. The rotarod or rotation chair test can be used to objectively and quantitatively evaluate the vestibular function.