Abstract
The outcome of cochlear implantation (CI) in patients with cochlear nerve deficiency (CND) is variable, resulting in a wide range of speech perception performance, from degrees of environmental sound perception to conversation without lip-reading. Twenty-five cochlear implantees with CND were enrolled retrospectively to determine the factors correlated with CI outcome in patients with CND and to develop a predictive model for CI outcome. CI outcome was evaluated using the Categories of Auditory Performance (CAP) score at 2 years after CI. Patients with negative auditory brainstem response (ABR) showed a significantly lower CAP score than those with positive ABR (2.5 ± 1.7, 4.8 ± 0.7; p = 0.001). The area ratio of vestibulocochlear nerve (VCN) to facial nerve (FN) at the cerebellopontine angle on magnetic resonance images was positively correlated with CI outcome (p < 0.001). With multiple regression analysis, a predictive equation accounting for 66% of variance of CAP score at 2 years after CI was {bf{deduced}}:{bf{CAP}},{bf{score}}{boldsymbol{=}}{bf{0.7}}{boldsymbol{+}}{bf{1.9}}{boldsymbol{ast }}{boldsymbol{(}}{bf{ABR}}{boldsymbol{)}}{boldsymbol{+}}{bf{1.2}}{boldsymbol{ast }}(frac{{boldsymbol{V}}{boldsymbol{C}}{boldsymbol{N}}}{{boldsymbol{F}}{boldsymbol{N}}}). We found that preoperative ABR and area ratio of VCN to FN at the cerebellopontine angle could predict CI outcome in patients with CND. Preoperative counselling based on our predictive model might be helpful to determine treatment modality for auditory rehabilitation and which ear to implant.
Highlights
facial nerve (FN) preoperative ABR and area ratio of vestibulocochlear nerve (VCN) to FN at the cerebellopontine angle could predict cochlear implants (CI) outcome in patients with cochlear nerve deficiency (CND)
It has been reported that the hearing threshold and word recognition score of unilateral deafness may be related to the size of bony cochlear nerve canal, which is associated with CND8,9
ABR response was selected as an independent factor for Categories of Auditory Performance (CAP) score at 2 years after CI in multiple regression analysis, and it did not show any correlation with the grade of internal auditory canal (IAC) (p = 0.38, chi-square), aplasia/hypoplasia (p = 0.89, chi-square), and the area ratio of VCN to FN at cerebellopontine angle (CPA) (p = 0.33, M-W U test)
Summary
Cochlear nerve deficiency (CND) is one of the various causes of hearing loss. It includes cochlear nerve aplasia, absence of cochlear nerve (CN) in internal auditory canal (IAC), and cochlear nerve hypoplasia, which refers to small-sized cochlear nerve in IAC. CND is the most common cause of unilateral congenital sensory nerve impairment It is found in approximately 25–48% of patients with unilateral hearing loss[4,5,6]. It has been reported that the hearing threshold and word recognition score of unilateral deafness may be related to the size of bony cochlear nerve canal, which is associated with CND8,9. Augmentation with other communication skills[16,17], and approximately 10–20% of them use sign language alone without any speech
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