Abstract
We aimed to compare the diagnostic yield between temporal bone computed tomography (TBCT) and internal auditory canal MRI (IAC MRI) for the etiologic diagnosis of children with congenital single-sided deafness (SSD) and the evaluation of cochlear implant (CI) candidacy. In the original cohort, 24 subjects with congenital SSD were enrolled and underwent both TBCT and IAC MRI. We recruited an additional 22 consecutive infants with congenital SSD (the supplementary cohort) and evaluated in particular the cochlear nerve (CN) integrity using IAC MRI. Cochlear nerve deficiency (CND) was classified as ‘absent’, ‘small’, and ‘indeterminate’ via mutual comparison between optical and parameters based on the MRI results. The most common etiologies were CND in the original cohort (19 out of 24). Notably, accurate evaluations of CN status (‘small CN’ = 2, ‘indeterminate CN’ = 2), inner ear malformations, and brain abnormalities were possible only with MRI. The ‘indeterminate CN’ tended to be more frequently detected in SSD ears than in unaffected ears. MRI appeared to be more accurate than TBCT in a meticulous differentiation of CN, which is crucial for the selection of appropriate CI candidacy among congenital SSD children. Additionally, we introduced the novel concept of ‘indeterminate CN’, of which the causal relationship with SSD awaits confirmation.
Highlights
Single-sided deafness (SSD), known as a form of profound unilateral sensorineural hearing loss (USNHL), is a specific condition characterized by the total loss of functional hearing ability (>90 dB) in the poorer ear and pure-tone average hearing threshold of ≤20 decibels hearing level (dB HL) to 4 kHz inclusively in the better ear [1]
A cochlear nerve deficiency (CND) that coincides with a narrow bony cochlear nerve canal is a frequently encountered anatomical abnormality accounting for the etiology of USNHL/SSD [10]
The lateral semicircular canal (LSCC) dysplasia was identified in one subject who showed a normal IAC and a narrow BCNC
Summary
Single-sided deafness (SSD), known as a form of profound unilateral sensorineural hearing loss (USNHL), is a specific condition characterized by the total loss of functional hearing ability (>90 dB) in the poorer ear and pure-tone average hearing threshold of ≤20 dB HL to 4 kHz inclusively in the better ear [1]. Radiological evaluation for USNHL may be an especially efficient step because anatomical abnormalities in the inner ear and cochlear nerve are common, accounting for approximately 35% of all USNHL cases; based on imaging studies, the incidence of anatomical abnormalities seems to be dependent on the severity of hearing loss [5]. A substantial improvement after cochlear implantation (CI) was reported in children with acquired SSD [6] and in limited early implanted (before 18 months old) prelingual congenital SSD cases with an intact cochlear nerve (CN) [7,8,9]. Implantation within a ‘critical’ period for a favorable outcome from congenital or prelingual SSD cases might prevent aural preference with a reorganization of auditory pathway, leading to binaural development [7,8,9]. Thorough and robust radiological evaluation of CN integrity within the critical period is important
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