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Objective: To determine features of hypoplasia and aplasia of the vestibulocochlear nerve (VCN) in combination with inner ear malformations (IEMs)., Methods: Index cases were retrospectively selected from all IEMs collected since 1995. CT and MRI data were reviewed by two neuroradiologists. The number and thickness of visible nerves in the cerebellopontine angle cistern and inside the internal auditory canal (IAC) were analysed., Results: MR images for 176 patients with IEMs were analysed. Labyrinthine aplasia and otocyst deformity showed 100% correlation, and IAC malformations exhibited 92% correlation with VCN aplasia. Cochlear aplasia, complete aplasia of the semicircular canals, severe cochlear hypoplasia, common cavity, incomplete partition type 1 and mild cochlear hypoplasia showed decreasing degrees of correlation with hypoplasia of the VCN. The remaining types of IEM did not demonstrate VCN hypoplasia., Conclusions: Certain forms of IEM show 100% correlation with hypoplasia or aplasia of the VCN, while others correlate less strongly and some do not usually exhibit VCN hypoplasia. MRI should always be carried out for those forms often correlated with VCN hypoplasia., Key Points: Vestibulocochlear nerve deficiency can be strongly suspected in certain inner ear malformations • Bony cochlear aplasia and cochlear nerve aplasia are strongly correlated • In semicircular canal aplasia, hypoplasia of the vestibular nerve can be found • Before cochlear implantation, the type of any IEM should be fully understood.

Objectives: Pontine tegmental cap dysplasia (PTCD) is a rare congenital malformation. Clinical and imaging findings in 3 patients and the authors' experience with bilateral cochlear implantation in 1 patient are described., Study Design: Retrospective review., Setting: Two tertiary medical centers., Subjects and Methods: Three patients were evaluated by an otolaryngologist and underwent magnetic resonance imaging (MRI) of the temporal bones and brain. High-resolution computed tomography (CT) scanning of the temporal bones was performed in 2 patients. Imaging findings of the brain, the presence and course of resolvable cranial nerves, the membranous labyrinth, and internal auditory canals were reviewed. Clinical data were reviewed., Results: All patients demonstrated typical brain characteristics of PTCD. Mild, bilateral cochlear dysplasia was noted in 2, and all had a normal vestibular labyrinth. The cochleovestibular nerves were universally absent bilaterally. The facial nerves were subjectively deficient bilaterally in 1 patient, unilaterally in the second patient, and normal in the third. An accessory canal for the seventh cranial nerve, referred to as a duplicated internal auditory canal, was present in all patients. Auditory brainstem response testing revealed profound bilateral sensorineural hearing loss in all of the patients; none suffered facial weakness. A single patient underwent bilateral cochlear implantation with only minimal response., Conclusion: The authors report 3 cases of PTCD with emphasis on imaging of the seventh and eighth cranial nerves and clinical neurotologic findings. All patients manifested duplicated internal auditory canals, a previously unreported finding in PTCD. Bilateral profound sensorineural hearing loss is due to absence of the cochleovestibular nerve. Prognosis for cochlear implantation is poor.

Background: Otologic manifestations are one of the most consistent findings of CHARGE syndrome found in more than 90%. Since genetic analysis of the CHD7 gene has rarely been performed in previous reports dealing with ear abnormalities, the genotypic spectrum of CHD7 mutations was analyzed in deaf patients with CHARGE syndrome, and the clinical considerations concerning auditory rehabilitation were investigated., Methods: Nine Korean patients with CHARGE syndrome showing profound hearing loss and semicircular canal aplasia were included. All 38 exons of CHD7 were analyzed by direct sequencing. For splice site variations, in silico and exon-trapping analyses were performed to verify the pathogenicity of nucleotide variations. Clinical features and the outcome of auditory rehabilitation were also analyzed., Results: Eight of 9 patients revealed alterations of the CHD7 gene including 3 frameshift, 2 nonsense, 2 splice site, and 1 missense mutations. Five of 9 patients were clinically diagnosed as atypical CHARGE syndrome but demonstrated various mutations of the CHD7 gene. One familial case showed intra-familial variability. Radiologic findings suggesting cochleovestibular nerve deficiency were identified in most of the patients. Of the 8 patients who underwent cochlear implantation, 5 patients demonstrated favorable outcome. Larger diameter of the cochleovestibular nerve on imaging and absence of severe mental retardation were factors related to better outcome after cochlear implantation rather than the type of CHD7 mutations. Auditory brainstem implantation was performed in two patients who did not benefit from cochlear implantation., Conclusions: Genetic analysis of the CHD7 gene should be performed in cases with semicircular canal aplasia even when other typical features of CHARGE syndrome are absent. For auditory rehabilitation in CHARGE syndrome, cochlear implantation should be strongly recommended in selected cases with favorable prognostic factors. Auditory brainstem implantation may be a viable option in patients with CHARGE syndrome who have failed to benefit from cochlear implantation.

Introduction: The anatomy of the nerves in the human internal auditory canal (IAC) has been reported by a number of authors, and there are some differences among the viewpoints of the literatures. With the development of the microsurgery and endoscopic surgery in the IAC, the study of the topographical relationship of the nerves in the human IAC becomes more and more important. The purpose of this study was to investigate the anastomosis and topographical relationship of the nerves in the human IAC., Methods: In this study, we dissected 30 human temporal bones from 15 heads, and examined the topographical relationship and the anastomosis of the nerves in human IAC., Results: (1) In 11 out of 30 cases (37%), the facial nerve is anterosuperior to the vestibulocochlear nerve through the whole IAC; and for the remaining 19 cases (63%), the facial nerve rotates anteroinferiorly at an angle ranging from 30 degrees to 90 degrees , which is in the same direction as that of the cochlear. (2) Vestibulofacial nerve anastomosis occurs in 25 cases (83%), of which 67% appears near the porus acusticus, and of which 33% appears between the lateral and intermedial portion of IAC. The diameter was about 0.5-1 mm. (3) Vestibulocochlear anastomosis occurs in 24 cases (80%) among which, some brush-like nerve fiber bundles of the cochlear nerve were seen to enter the acculus proprius directly in 13 cases. Transverse vestibulocochlear anastomosis in the fundus of internal acoustic meatus occurred in 15 cases, including two cases with more anastomosis. No vestibulocochlear nerve anastomosis was found in six cases in this study., Conclusions: Our study shows that the Vestibulofacial nerve anastomosis and the vestibulocochlear nerve anastomosis do exist, and some variations appear due to individual differences. The appearance of the facial and vestibulocochlearnerves is variable but follows certain consistent patterns.

This study documents morphologic alterations in the spiral ganglion and Scarpa's ganglion from gamma-aminobutyric acid A (GABA(A)) receptor beta(3) subunit null mutant mice. The ganglion cells of the mutant mice were hypoplastic in hematoylin&eosin-stained sections. Hypoplasia was observed at every location of the spiral ganglion and Scarpa's ganglion except the apical cochlear turn. Calretinin immunostaining demonstrated a selective hypoplasia of calretinin-negative cells at every location of spiral and Scarpa's ganglion cells, while the soma area of calretinin-positive cells was not affected by the gene deletion. Meanwhile, in the spiral ganglion of both wild type and knockout mice, there were apical to basal gradients in the soma size and the proportion of calretinin-positive cells. The absence of statistically significant hypoplasia in hematoylin&eosin sections through the apical turn of the cochlea can be explained by the relatively higher proportion of calretinin-positive ganglion cells, which were unaffected by the gene deletion. These findings suggest that GABA(A) receptor isoforms containing the beta(3) subunit may play an important role in the development and differentiation of non-calyceal terminals of Scarpa's ganglion cells and type II and smaller type I spiral ganglion cells.

Vestibular receptors and ganglia of homozygous Bronx waltzer (bv/bv) mice were investigated by scanning and transmission electron microscopy at various stages between 3 days and 90 days after birth. Scanning electron microscopy revealed that there was already a considerable lack of hair bundles in the maculae utriculi, as well as in the cristae ampullares by the 3rd day after birth. During development, the growth of the remaining hair bundles was observed but the most of them exhibited morphological abnormalities. Transmission electron microscopy revealed early degeneration of sensory cells followed by delayed maturation of the remaining sensory cells. The sensory cells which seem unaffected displayed immature features in adult animals. In type I hair cells, the calyces were incomplete, contacts between the cell and the afferent calyces were immature and synaptic bodies persisted. In some type II hair cells, there was an abnormal overabundance of afferent nerve endings, which implies that these type II cells could be immature type I cells. Immature features were also observed in the vestibular ganglia, particularly the absence of the myelin sheath around the perikarya. We discuss the relationship between these vestibular morphogenetic abnormalities and those described in the cochlear system.

We suggest a new explanation for the lack of auditory response to electric stimulation in children with cochlear implants: the very narrow internal auditory canal, 1 to 2 mm in diameter, and the probable absence of the cochlear nerve. This defect can be seen on high-resolution computed tomographic x-ray studies and may represent aplasia of the auditory-vestibular nerve. We report on eight children with this anomaly, three of whom have received implants and failed to respond with a sensation of sound. Identification of this problem on screening x-ray films is a contraindication to cochlear implantation for auditory stimulation.