CASES of congenital deafness which appear to be based on developmental defects of the internal ear have been grouped into four main types. These have been named after the investigators who described the essential pathologic changes and have been extensively discussed by Ormerod1; therefore they need be only briefly listed here: (1) Michel type, complete lack of development of the inner ear; (2) Mondini-Alexander type, development of only a single curved tube or a flattened and shortened cochlea with bony abnormalities which is coupled with an enlarged saccule and endolymphatic sac; (3) Bing-Seibenman type, normal bony labyrinth with a lack of development of both the pars inferior and superior membranous structures; (4) Scheibe type, normal bony labyrinth with malformation limited to the pars inferior (the cochleosaccular type). Even with the above classification there are several major problems in the assessment of pathology of congenital deafness.
The foremost of these