Limitation of High Pitch Sound Perception in Nontumor Patients with Auditory Brainstem Implantation / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Auditory brainstem implantation (ABI) is another option for hearing rehabilitation in non-neurofibromatosis type 2 patients who cannot undergo cochlear implantation (CI). However, the average performance of ABI is worse than that of CI. We analyzed the psycho-electrical parameters of each electrode and psycho-acoustic response to different frequency sounds in nontumor patients with ABI. SUBJECTS AND METHOD: Sixteen patients with ABI from July 2008 to May 2013 were included in the study. They were followed up for 4 to 56 months. Among them, 12 were prelingual deaf with a narrow internal auditory canal or cochlear ossification. The remaining four were post-lingual deaf adults with severely ossified cochleae. We analyzed the electrical parameters [impedance, threshold level (T level), and dynamic range] of each of the 12 electrodes. We also evaluated the sound field pure-tone threshold, Ling 6 sound detection-identification test (Ling 6 test), and pitch ranking data of these patients. RESULTS: The impedance, T level, and dynamic range did not significantly differ among electrodes. However, the pure-tone threshold to sound field stimulation was elevated in the high tone area, where more variables were found than in the low frequency area. Patients could not identify /S/ and /Sh/ sounds in the Ling 6 test. The mean T level and the dynamic range of the three highest pitch-perceiving electrodes in each patient was higher and narrower, respectively, than those of the three lowest pitch-perceiving electrodes. CONCLUSION: The nontumor patients with ABI have difficulty perceiving high pitch sound. More sophisticated penetrating type electrodes and, if possible, bimodal stimulation with CI, could be considered.

A case report of narrow internal auditory canal: Parasagittal reconstruction / 대한이비인후과학회지

A narrow internal auditory canal(IAC) is a malformation of the temporal bone, which is defined as IAC diameter of only 1-2mm in high resolution computed tomography(HRCT). This syndrome is known to be caused by aplasia or hypoplasia of the vestibulocochlear nerve. We present a case of unilateral narrow IAC which was diagnosed by HRCT. The aplasia of vestibulocochlear nerve was confirmed using MRI with parasagittal reconstruction images. The IAC was composed of two separate canals, one of which had facial nerve and the other an empty space by aplasia of the vestibulocochlear nerve.