[Diagnosis of cochlear nerve foramen stenosis and atresia of the cochlear implantation].

Objective: To summarize methods on diagnosis of congenital cochlear nerve canal (CNC) stenosis or atresia and to report results of post-operation such as auditory electrophysiological test and speech test.

Method: Based on temporal bone HRCT and internal acoustic canal MRI, 27 bilateral congenital CNC stenosis/bony atresia cases were distinguished from 3 700 CI cases. Unilateral cochlear implantations were conducted above 27 cases. Post-operation tests such as auditory nerve response telemetry, EABR test, hearing threshold in sound field and speech recognition test were applied in the cases above.

Result: Incidence of CNC stenosis/bony atresia was observed at 0.73% (27 in 3700 CI cases). Impedance values were in the normal range accounting for 27 cases. Intro operative auditory nerve response telemetry were conducted accounting for 21 cases while 6 cases which were implanted with Combi40 + were not available for this test. Atypical ART response wave was observed for 14 cases, while no response for 7 cases. EABR test was completed in 27 cases within post-operation during 3 months and atypical EABR was identified in all cases. Hearing threshold in sound field was confirmed at 75 dB which was the average value of 500 Hz,1000 Hz,and 2000 Hz in all 27 cases. Speech recognition test result reached to both 65% (21 cases, simple finals test) and fewer than 10% (21 cases, simple initials test).

Conclusion: By temporal bone HRCT pre-operation, CNC stenosis/bony atresia can be diagnosed. According to both relatively poor auditory and speech test results, further research and discussion are requisite to identify CI indication among the cases above.