Classification and Current Management of Inner Ear Malformations

Abstract

Morphologically congenital sensorineural hearing loss can be investigated under two categories. The majority of congenital hearing loss causes (80%) are membranous malformations. Here, the pathology involves inner ear hair cells. There is no gross bony abnormality and, therefore, in these cases high-resolution computerized tomography and magnetic resonance imaging of the temporal bone reveal normal findings. The remaining 20% have various malformations involving the bony labyrinth and, therefore, can be radiologically demonstrated by computerized tomography and magnetic resonance imaging. The latter group involves surgical challenges as well as problems in decision-making. Some cases may be managed by a hearing aid, others need cochlear implantation, and some cases are candidates for an auditory brainstem implantation (ABI). During cochlear implantation, there may be facial nerve abnormalities, cerebrospinal fluid leakage, electrode misplacement or difficulty in finding the cochlea itself. During surgery for inner ear malformations, the surgeon must be ready to modify the surgical approach or choose special electrodes for surgery. In the present review article, inner ear malformations are classified according to the differences observed in the cochlea. Hearing and language outcomes after various implantation methods are closely related to the status of the cochlear nerve, and a practical classification of the cochlear nerve deficiency is also provided.

Otopathology in CHARGE syndrome

“… The right internal auditory canal was small in size, but the cochlear nerve aperture appeared normal in size. The left temporal bone showed an even more underdeveloped cochlea with only one turn (ie, the basal turn), consistent with cochlear hypoplasia type IV . The left cochlear nerve aperture was markedly stenotic (Figure 1C).…”

“…The round window was normal with a patent round window niche (Figure 2B). The right cochlea had two complete turns (cochlear hypoplasia type IV) . The lower basal turn demonstrated the full complement of outer and inner hair cells with a normal appearing organ of Corti (Figure 2C).…”

“…The round window and round window niche were normal and patent (Figure 3B). The cochlea was very hypoplastic (cochlear hypoplasia type III, Figure 3C), with only one turn (ie, the basal turn). The lower basal turn showed a fully formed organ of Corti and an empty osseous spiral lamina, whereas the upper basal turn demonstrated vestigial development of a middle/second turn with duplicated organs of Corti and tectorial membranes (Figure 3D,E).…”

Variations in the Size and Shape of Human Cochlear Malformation Types

“…As per literature reports, approximately 20% of the sensorineural hearing loss (SNHL) population have some degree of malformed cochlear–vestibular anatomy (Sun et al ; Sennaroğlu and Bajin ). Enlarged vestibular aqueduct syndrome (EVAS), incomplete partition (IP) Types I, II (Mondini's), III (X‐linked), cochlear hypoplasia (CH), common cavity (CC), and cochlear aplasia (CA) were the most widely reported malformation types (Sennaroglu and Saatci ).…”

“…As a result, supporting preplanning tool like OtoPlan (http://www.otoplan.ch) is now European Confirmity marked and is in clinical application (Lovato and de Folippis ) assisting clinicians in measuring the cochlear size and choosing the cochlear implant (CI) electrode accordingly. Though abnormal anatomy cochleae were studied enough with the help of 2D radiographic images (Sennaroglu and Saatci ; Sun et al ; Sennaroğlu and Bajin ), only limited number of reports (Hara et al ; Liu et al ; Booth et al ) are available bringing most of the widely recognized malformation types especially in three‐dimensional (3D) format in knowing the variation in its size and shape.…”