Analysis of 4 kHz Notch Audiogram as a Sign of Noise Induced Hearing Loss / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: In this study, we tried to study the criteria and characteristics of patients with noise-induced hearing loss by analyzing the pure tone audiogram such as "C5 dip" or "4 kHz notch". SUBJECTS AND METHOD: Out of 553 patients who complained of tinnitus and hearing loss, medical examination by interview, physical examination, hearing test, brain MRI and survey of tinnitus were performed from January 2010 to December 2012, targeting 81 patients who underwent pure tone hearing test. We analyzed the clinical characteristics of 81 patients with the exception of systemic disease or a history of otologic disease, conductive hearing loss, and vestibular schwannomas. Patients consisted of 70 men and 11 women (34 persons on both sides, 31 persons on right side, and 16 persons on left side), with an average of 48.1+/-12.9 years. 4 kHz notch-type sensorineural hearing loss was compared with contralateral hearing. RESULTS: The audiogram of 4 kHz notch was analyzed, and the results were as follows; 0.5 kHz (11.2+/-9.9 dB HL), 1 kHz (13.2+/-9.9 dB HL), 2 kHz (19.4+/-15.4 dB HL), 3 kHz (38.1+/-18.7 dB HL), 4 kHz (49.3+/-16.2 dB HL), 8 kHz (27.2+/-16.2 dB HL). Among all frequencies of 4 kHz notch audiogram, there was no significant hearing loss in 0.5 kHz and 1 kHz, but significant hearing loss was noted in higher frequencies (paired t-test, p>0.05). The contralateral ear showed a ski-slope hearing loss in about half of the patients. CONCLUSION: Remarkable points of the 4 kHz notch audiogram analysis, known as a typical characteristic of noise-induced hearing loss, were as follows; First, there was hearing loss of about 50 dB HL at 4 kHz. Second, the hearing threshold was improved to about 30 dB HL at 8 kHz. Third, the 4 kHz-notch audiogram showed a significant hearing loss in a high-pitched tone of over 2 kHz, but otherwise there were no significant hearing loss observed in 0.5 kHz and 1 kHz. Fourth, even if there were no symptoms, contralateral ear can still show the ski-slope type of hearing loss.

A Longitudinal Study of Frequency Specific Electrical Stimulation Levels in Cochlear Implant Users / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The purpose of the study was to evaluate the changes in electrical stimulation levels, i.e. threshold (T) levels, comfortable (C) levels, dynamic range (DR), and electrode impedance values (EIVs) during the first year in cochlear implant users. SUBJECTS AND METHOD: The maps of 49 cochlear implant users (at least 1 year mapping), using the Nucleus device, were examined at the time of initial connection, and at 6 and 12 months post-initial stimulation. T levels, C levels, DR and EIVs were analyzed according to three frequency levels. RESULTS: During the first 6 months of implant use, C levels and DR increased significantly whereas T levels were stable. EIVs of current carrying electrodes decreased significantly from the connection to the 12-month visit. The changes of electrical stimulation levels did not differ among three frequency levels during the entire follow-up. CONCLUSION: During the first 6 months of implant use, C levels and DR increased significantly. Thus, an appropriate mapping in the first 6 month is critical to setup hearing capacity in implant users. The mapping should be performed under the best communication environment between the audiologist and the patient, and it makes correct setting of T levels from the initial connection period.