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Head and Neck Imaging

Vestibulocochlear nerve, congenital anomalies

Aplasia or hypoplasia of the vestibulocochlear nerve is a possible cause of sensorineural hearing loss or congenital deafness, and can be visualized by acquiring thin-section (submillimetric) gradient-echo MR images through the internal auditory canal (Fig.1). Based on MR and clinical findings and embryological considerations, a classification in 3 types has been suggested (Table 1).

Vestibulocochlear nerve, congenital anomalies, Table 1. Congenital anomalies of the vestibulocochlear nerve (Table after Casselman JW, Offeciers FE, Govaerts PJ, Kuhweide R, Geldof H, Somers T, D'Hont G: Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging. Radiology 1997, 202: 773-781)

Type 1Aplasia of the vestibulocochlear nerve, associated with stenosis of the internal auditory canal
Type 2Common vestibulocochlear nerve with aplasia or hypoplasia of the cochlear branch, with (type 2A) or without (type 2B) labyrinthine malformation
Type 3Common vestibulocochlear nerve with aplasia or hypoplasia of the vestibular branch(es) (hypothetical type, not yet reported)

(editorial note: A-B, C-E, D-F are corresponding figures (right versus left) and should be mounted symmetrically).

RH

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Fig.1

Patient with deaf right ear. Axial T2-weighted gradient-echo images through internal auditory canal show normal vestibulocochlear nerve (arrowheads) on left side (b), but no such a nerve on the right side (a). Parasagittal reconstructions, perpendicular on internal auditory canals, show normal facial and vestibulocochlear nerve (arrowhead) in left cerebellopontine angle (e), with normal appearance of the nerve within the left internal auditory canal (f). On the right side only the facial nerve is visible in the cerebellopontine angle (c) and internal auditory canal (d). The right IAC is narrower than the left one. 1 = cochlear nerve; 2 = inferior vestibular nerve; 3 = superior vestibular nerve; 4 = facial nerve; fl = flocculus.
Vestibulocochlear nerve, congenital anomalies, Fig.1 (a)
Vestibulocochlear nerve, congenital anomalies, Fig.1 (b)
Vestibulocochlear nerve, congenital anomalies, Fig.1 (c)
Vestibulocochlear nerve, congenital anomalies, Fig.1 (d)
Vestibulocochlear nerve, congenital anomalies, Fig.1 (e)
Vestibulocochlear nerve, congenital anomalies, Fig.1 (f)