Dimensions of the human vestibular and tympanic scalae.

The cochlear scalae provide a practical access route for the insertion of cochlear implant electrodes. A microanatomical study was carried out on 25 human temporal bones obtained from cadavers. These bones were dissected with the aid of an operation microscope, in which their perilymphatic spaces were filled with coloured latex and further prepared in a formalin stain. Each of the rubber moulds was removed from the osseous matrix using standard otosurgical equipment, and subsequently cut into 1 mm segments. The height and width of the vestibular and tympanic scalae were measured. The results, presented in diagrams, indicate that the vestibular scala is less prominent than the tympanic scala in the basic and middle coil of the cochlea and in the upper coil, they display greater dimensions which could serve as a place for electrode insertion in cochlear implant procedures. In addition, the vestibular and tympanic scalae present alternate dominance in their width and height as corroborated by the calculated coefficients. The results obtained in this study supplement our knowledge of the anatomy of the cochlea thus far lacking a full investigation of the scalae, and could serve as a basis for other studies dealing with the physiology of the organs of hearing.