Full etiologic spectrum of pediatric severe to profound hearing loss of consecutive 119 cases

Abstract

Determining the etiology of severe-to-profound sensorineural hearing loss (SP-SNHL) in pediatric subjects is particularly important in aiding the decision for auditory rehabilitation. We aimed to update the etiologic spectrum of pediatric SP-SNHL by combining internal auditory canal (IAC)-MRI with comprehensive and state-of-the-art genetic testings. From May 2013 to September 2020, 119 cochlear implantees under the age of 15 years with SP-SNHL were all prospectively recruited. They were subjected to genetic tests, including exome sequencing, and IAC-MRI for etiologic diagnosis. Strict interpretation of results were made based on ACMG/AMP guidelines and by an experienced neuroradiologist. The etiology was determined in of 65.5% (78/119) of our cohort. If only one of the two tests was done, the etiologic diagnostic rate would be reduced by at least 21.8%. Notably, cochlear nerve deficiency (n = 20) detected by IAC-MRI topped the etiology list of our cohort, followed by DFNB4 (n = 18), DFNB1 (n = 10), DFNB9 (n = 10) and periventricular leukomalacia associated with congenital CMV infection (n = 8). Simultaneous application of state-of-the-art genetic tests and IAC-MRI is essential for etiologic diagnosis, and if lesions of the auditory nerve or central nerve system are carefully examined on an MRI, we can identify the cause of deafness in more than 65% of pediatric SP-SNHL cases.

Figure 1

Three major abnormalities related to pediatric SP-SNHL as seen in IAC-MRI. Images on the left side show abnormal findings, while normal findings are on the right. (a) Cochlear nerve deficiency: Cochlear nerve is not observed in the internal auditory canal (arrow). (b) Enlarged vestibular aqueduct with incomplete partition type 2: Vestibular aqueduct is enlarged and conical in shape (arrowhead), and the interscalar septum is not present (dotted arrow). (c) Periventricular leukomalacia: Ventriculomegaly with irregular margins of the bodies of the lateral ventricles and loss of periventricular white matter are observed.

Figure 2

Systematic etiologic diagnostic flowchart used in our study. First line screening using internal auditory canal MRI in tandem with molecular screening of prevalent variants enables etiologic identification in 58.0% of subjects. Subsequent in-depth genetic testing elucidates molecular etiology in 9 more subjects (7.6%), leaving 41 subjects etiologically undiagnosed.