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Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging.
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1997
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The study introduces vestibulocochlear nerve aplasia/hypoplasia as a potential cause of hearing loss and demonstrates that MR imaging can diagnose this condition in patients with congenital or unexplained sensorineural hearing loss. High‑resolution 0.7‑mm 3DFT‑CISS MR imaging with parasagittal reconstructions in two planes was used to visualize the vestibulocochlear nerve and its branches, allowing comparison with normal inner ears. Aplasia of the vestibulocochlear nerve was found in two patients with normal labyrinths but severe internal auditory canal stenosis, and a common VCN lacking the cochlear branch was observed bilaterally in two patients with congenital labyrinth malformations.
To introduce aplasia or hypoplasia of the vestibulocochlear nerve (VCN) as a possible cause of hearing loss and to identify the magnetic resonance (MR) imaging characteristics of this entity.In seven patients with congenital deafness or unexplained sensorineural hearing loss, MR imaging enabled diagnosis of aplasia or hypoplasia of the VCN. Axial (0.7-mm) three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) images and parasagittal reconstruction images perpendicular on the course of the VCN were obtained. Twenty normal inner ears were also studied; their findings were compared with those of the patients.The facial nerve and inferior and superior vestibular and cochlear branches of the VCN were identified on the MR images in the 20 normal inner ears. Aplasia of the VCN was detected in two patients with normal labyrinths but with a severe stenosis of the internal auditory canal. A common VCN with absence of the cochlear branch was found bilaterally in two patients with a congenital malformation of the labyrinth. This entity, which can occur with or without associated labyrinthine malformation, should be confirmed in two planes.