Dissection of temporal bone by Mondini
Illustration of the cochlea by Mondini
Who was the first to describe the inner ear anomaly in the medical history? That is C. Mondini (1729–1803) in Italy. Professor H. Edamatsu of Toho University of Medicine in Tokyo investigated and reported Mondini’s article in Latin .
In 1791, Mondini wrote the Latin article entitled Anatomica Surdi Nati Sectio . It became the first report of the dissection of the temporal bone in an 8 year-old boy with congenital deafness and reported the anatomical findings of the inner ear anomaly. Mondini’s original paper is a historical one for ontological researchers, but it has been difficult, indeed rather impossible, to read for a long time. We fortunately had the chance to review the original copy of the paper.
The summary of Mondini’s report described several conditions: there was a large opening of the vestibular aqueduct, labyrinth fluid was escaping from the enlarged vestibular aqueduct, and the cochlea consisted of only one and a half turns, among others. According to his paper, the common cavity is not an inner ear anomaly of the Mondini type. Currently, recent progress in three-dimensional imaging can detect and visualize the fine and detailed structure of the inner ear. Therefore, imaging diagnosis is able to discriminate Mondini anomalies from other types.
In 1904, Alexander described incomplete development of the bony and membranous labyrinth with basal turn only and interscalar septum in the upper turns resulting gross distention of the endolymphatic sac .
In modern age, Mondini’s anomaly of the inner ear is variously modified and misinterpreted. However, we should return the Mondini’s original article.
1.1.2 The Nineteenth Century: “Temporal Bone Histology”
In 1863, Michel reported complete lack of development of the inner ear . Later, in 1964, Jorgensen et al.  and, in 1971, Black et al.  described agenesis of the labyrinth in temporal bone pathology.
In 1892, Scheibe described the malformation limited to the cochlea and saccule with membranous cochlea-saccular aplasia and normal bony labyrinth .
In 1965, Shuknecht et al. suggested the concept of cochlea-saccular degeneration in congenital deafness .
1.1.3 The Twentieth Century: “X-ray and CT of Temporal Bone”
X-ray polytome and CT scan and MRI developed new classification of inner ear malformation and cochlear nerve deficiency. Development of cochlear implants has needed precise anatomical structure of cochlea for insertion of electrodes into cochlear turns.
In 1987, Jackler et al. proposed congenital malformation of the inner ear: a classification based on embryogenesis in Table 1.1 and Fig. 1.3 . This classification was proposed by polytomes or CT scans considering embryogenesis of cochlea and vestibular end organs.
Classification of congenital malformation of the inner ear 
A. With an absent or malformed cochlea
1. Complete labyrinthine aplasia (Michel deformity): no inner ear development
2. Cochlear aplasia: no cochlea, normal or malformed vestibule and semicircular canals
3. Cochlear hypoplasia: small cochlear bud, normal or malformed vestibule, and semicircular canals
4. Incomplete partition: small cochlea with incomplete or no interscalar septum, normal or malformed vestibule, and semicircular canals
5. Common cavity; cochlea and vestibule form a common cavity without internal architecture; normal or malformed semicircular canals
B. With a normal cochlea
1. Vestibule-lateral semicircular canal dysplasia; enlarged vestibule with a short, dilated lateral semicircular canal; remaining semicircular canals are normal
2. Enlarged vestibular aqueduct; accompanied by normal semicircular canals, normal or enlarged vestibule
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1.1.4 The Twenty-First Century: “High-Resolution CT and MRI of the Temporal Bone”
Multichannel cochlear implants have been introduced in order to recover hearing in deaf children and adults in the world since 1980. This hearing technology is epoch-making in hearing science. Indication of cochlear implant has been extended to more difficult cases with inner ear malformation or cochlear nerve deficiency.
In 2002, Sennaroglu and Saatci proposed a new classification of cochleovestibular malformation. This new classification is based on embryogenesis of labyrinth, vestibular end organs, cochleovestibular nerve, and inner auditory canal and images of CT scans. Before decision of cochlear implantation, this classification is worldwidely used (Figs. 1.4 and 1.5) .
Schematic representation of the normal cochlea and cochlea malformations . (a) Normal cochlea, midmodiolar section MO modiolus, CA cochlear aperture, B basal turn, M middle turn, A apical turn, arrowheads = interscalar septa. (b) Normal cochlea, inferior section passing through the round window niche (RWN). Arrowhead interscalar septum between middle and apical turns. (c) Cochlear aplasia with normal vestibule. (d) Cochlear aplasia with enlarged vestibule. (e) Common cavity. (f) Incomplete partition type I (IP-I). (g) Incomplete partition type II (IP-II). (h) Incomplete partition type III (IP-III). (i) Cochlear hypoplasia, bud type (type I). (j) Cochlear hypoplasia, cystic cochlea type (type II) (hypoplasia (type II)). (k) Cochlear hypoplasia, with less than 2 turns (type III) (hypoplasia (type III))
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