Implication of bony cochlear nerve canal on hearing in patients with congenital unilateral sensorineural hearing loss.

This study was designed to evaluate the dimensions of the bony cochlear nerve canal (BCNC) in congenital unilateral sensorineural hearing loss (USNHL) patients with normal inner ears, and to analyze the correlation between BCNC and hearing status. Medical records and temporal bone computed tomography (TBCT) findings of 380 patients who visited Seoul National University Hospital between January 1999 and December 2007 were reviewed retrospectively. The length and width of the BCNC at the fundus of the internal auditory canal were measured in millimeters based on the axial view of TBCT for three ear groups: normal inner ears of control group subjects (group A, 179 ears), normal inner ears on the contralateral side of USNHL patients (group B, 201 ears), and the affected inner ears in USNHL (group C, 201 ears). The mean values of length and width in group C (0.79 ± 0.36 and 1.58 ± 0.83 mm, respectively) were significantly smaller than those in group A (1.07 ± 0.10 and 2.38 ± 0.28 mm, respectively; p < 0.001) and group B (1.04 ± 0.23 and 2.33 ± 0.39 mm, respectively; p < 0.001). The receiver operating characteristic curves for BCNC were conducted to estimate the cutoff values from which the proportions of profound hearing loss increased, compared to those of mild to severe hearing loss. The areas under the curve were 0.487 ± 0.044 (p = 0.781) and 0.622 ± 0.041 (p = 0.011) for length and width, respectively. The cutoff value of width with a sensitivity of 90% for profound USNHL was 1.16 mm in otherwise normal inner ears. Clinicians would be recommended to take a close look at BCNC as one of the possible causes of hearing loss in otherwise normal inner ears of USNHL on TBCT.

Jang JH ，Kim JH ，Yoo JC ，Kim CH ，Kim MS ，Chang SO ，Oh SH ，Lee JH ... -  《-》

Cochlear nerve deficiency and associated clinical features in patients with bilateral and unilateral hearing loss.

Nakano A ，Arimoto Y ，Matsunaga T 《-》

Proportion of bony cochlear nerve canal anomalies in unilateral sensorineural hearing loss in children.

The aim of this study was to characterize the various bony anomalies of the inner ear in patients with unilateral sensorineural hearing loss using high-resolution temporal bone computed tomography and establish the relationship between hearing and the diameter of the bony cochlear nerve canal. We performed a retrospective review of 51 patients (mean age 11 years, range 0-20 years, 27 boys, 24 girls) who were diagnosed with unilateral sensorineural hearing loss with an audiogram. Coronal and axial diameter of the inner ear structures, including the internal auditory canal, bony cochlear nerve canal, and each turn of the cochlea and semicircular canals, were measured with high-resolution temporal bone computed tomography. The mean values (± 2 standard deviations) were calculated and compared between sensorineural hearing loss and normal ears, and between narrow bony cochlear nerve canal and normal bony cochlear nerve canal ears. Bony cochlear nerve canal atresia/stenosis was defined as a value less than 1.4mm in axial images. The diameter of the bony cochlear nerve canal was significantly smaller in sensorineural hearing loss ears than in normal ears (p<.05). Associated inner ear anomalies, such as IAC stenosis (24%), cochlear hypoplasia (7-17%), and narrow semicircular canal bony island (8%) were only observed in the narrow bony cochlear nerve canal group. This group also showed statistically significant, severe to profound hearing loss compared to the normal bony cochlear nerve canal group (p<.05, R(2)=12.8%). Most (57%) of the unilateral sensorineural hearing loss ears had bony cochlear nerve canal stenosis/atresia and this group showed associated inner ear anomalies. When the diameter of the bony cochlear nerve canal was less than 1.4mm, pure tone audio averages were more than 70 dB HL in most ears.

Yi JS ，Lim HW ，Kang BC ，Park SY ，Park HJ ，Lee KS ... -  《-》

Bony cochlear nerve canal stenosis and speech discrimination in pediatric unilateral hearing loss.

To examine the relationship between bony cochlear nerve canal (BCNC) width, degree of hearing loss, and speech discrimination in children with unilateral sensorineural hearing loss (USNHL). Retrospective chart review (case-control study). Audiometric database was cross-referenced with radiologic database at pediatric tertiary care facility to identify children with USNHL and temporal bone computed tomography. BCNC widths were measured independently by two radiologists blinded to affected ear. Regression analyses investigated associations among variables. One hundred and sixty children with USNHL had temporal bone imaging. Mean BCNC width was significantly smaller in affected ears, P = 0.0001. Narrower width was associated with more severe hearing loss, P = 0.01. Among children who had narrower cochlear nerve canals in affected ears compared to unaffected ears, smaller width was associated with lower speech discrimination score, P = 0.03. Increasing asymmetry in BCNC width between affected and unaffected ears was associated with poorer discrimination scores, P = 0.02. Among ears with asymmetrically smaller cochlear nerve canals, a 1-mm reduction in cochlear canal width between the normal and affected ear was associated with 30.4% lower word recognition score percentage in the affected ear, P = < 0.001. There is a significant association between BCNC stenosis and impaired speech discrimination, independent of degree of hearing loss. Further investigation is needed to determine whether BCNC stenosis is a poor prognostic factor for auditory rehabilitation.

Purcell PL ，Iwata AJ ，Phillips GS ，Paladin AM ，Sie KC ，Horn DL ... -  《-》

High prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss.

Radiological and genetic examination has recently advanced for diagnosis of congenital hearing loss. The aim of this study was to elucidate the prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss (USNHL) for better management of hearing loss and genetic and lifestyle counseling. We conducted a retrospective study of charts and temporal bone computed tomography (CT) findings of 69 consecutive patients 0-15 years old with USNHL. In two cases, genetic examination was conducted. Of these patients, 66.7% had inner-ear and/or internal auditory canal malformations. The prevalence of malformations in infants (age <1 year) was 84.6%, which was significantly higher than that in children 1-15 years old (55.8%; p<0.01). Almost half of the patients (32; 46.4%) had cochlear nerve canal stenosis; 13 of them had cochlear nerve canal stenosis alone, and in 19 it accompanied other malformations. Internal auditory canal malformations were observed in 22 subjects (31.8%), 14 (20.3%) had cochlear malformations, and 5 (7.2%) had vestibular/semicircular canal malformations. These anomalies were seen only in the affected ear, except in two of five patients with vestibular and/or semicircular canal malformations. Two patients (2.9%) had bilateral enlarged vestibular aqueducts. Mutations were found in SLC26A4 in one of the two patients with bilateral large vestibular aqueducts. The prevalence of a narrow internal auditory canal was significantly higher in subjects with cochlear nerve canal stenosis (50.0%) than in subjects with normal cochlear nerve canals (11.1%; p<0.01). There were no correlations between the type and number of malformations and hearing level. The prevalence of inner-ear and/or internal auditory canal malformations detected by high-resolution temporal bone CT in children with USNHL was very high. Radiological and genetic examination provided important information to consider the pathogenesis and management of hearing loss. Temporal bone CT should be recommended to children with USNHL early in life. SLC26A4 mutation also should be examined in cases with bilateral enlarged vestibular aqueduct.

Masuda S ，Usui S ，Matsunaga T 《-》