![]() This dysplasia is more difficult to identify within the current classification system. i, j Patient 4: in this patient a foreshortened cochlea and a cystic appearance of the vestibular system is seen without enlargement of the vestibular aqueduct ( black arrow). On a 3D T2 TSE MR image the enlarged endolymphatic duct and sac are well seen ( white arrows). The modiolus is deficient ( white arrowhead). g, h Patient 3 shows a classic Mondini malformation (incomplete partition type II) consisting of a cochlea with a normal basal turn, but confluent middle and apical turn ( black arrow), a widened vestibule (V) and an enlarged vestibular aqueduct (VA) (the normal size of the VA is 1–1.5 mm at its midpoint and generally does not exceed the size of the SCC). This has been classified as a cystic cochleovestibular dysplasia (incomplete partition type I). The vestibule also shows pronounced enlargement. e, f Patient 2: on axial CT images of this deaf child, a widened cochlea without a modiolus renders a cystic appearance of the cochlea. There is no development of the cochlea anteriorly hence this developmental anomaly can be classified as a cochlear aplasia. On the left, axial ( b, c) and coronal ( d) CT shows an IAC bending posteriorly towards a cystic dilated vestibular system. The internal auditory canal (IAC) is also absent. On the right ( a) axial CT shows a small cyst in place of the cochleovestibular system, corresponding to labyrinthine aplasia. a- d Patient 1: a 6-month-old girl presenting with congenital deafness has bilateral congenital malformations of the labyrinth on CT. The endolymphatic duct is connected to the saccule and courses through a bony canal-the vestibular aqueduct-to form the endolymphatic sac in the posterior fossa (Figs. The vestibule harbours the oval window the stapes footplate is attached to the oval window. The vestibular system is located posterior to the cochlea and contains the vestibule with the saccule and utricle and three semicircular canals which are oriented perpendicular to each other. The cochlea is connected to the middle ear by the round window. ![]() The modiolus containing the spiral ganglion can, however, be visualised in the centre of the cochlea. The scala media, containing the organ of Corti and filled with endolymph, cannot be visualised separately with current imaging systems. These scalae are connected to each other at the apical tip of the cochlea (helicotrema) and they contain perilymph. Within each turn the cochlea is divided into the scala tympani and scala vestibuli by the osseous spiral lamina. The normal cochlea consists of two-and-a-half turns separated by interscalar septae. The inner ear comprises the cochlea, the vestibular system and the endolymphatic duct and sac. The display slice thickness should not exceed 1.5 mm. Contiguous or overlapping sections from the superior most mastoid air cells to the stylomastoid foramen should be obtained with the gantry angle parallel to the infraorbital-meatal line. With multidetector CT, images can be reconstructed in any desired plane, obviating the need for direct coronal scanning. Temporal bone CT should consist of both axial and coronal images. MRI will render supplementary information on the fine intralabyrinthine structures. CT forms an ideal means to evaluate the bony details of the otic capsule and labyrinth and will also allow evaluating the course of the facial nerve canal and eventual associated anomalies of middle ear structures and the external auditory canal. In patients requiring anaesthesia, these exams should be planned in one session. These techniques render complementary information. Imaging of the inner ear is performed with computed tomography (CT) and/or magnetic resonance imaging (MRI).
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