Purpose: There are specific frequency hearing losses such as c4-dip(2kHz loss) in otosclerosis and c5-dip(4kHz loss) in case of noise induced hearing loss. The c3-dip(1kHz loss), however, is seldom mentioned in clinical field. We found a group of patient with 1 kHz hearing loss fortuitiously and report it with review of literature.
Method: Tertiary academic referral center-based retrospective chart review and review of audiogram was done. Otologic history, audiogram, diagnosis, occupation, history of noise exposure were reviewed with chart and telephone interview. We compared the c3-dip group with 98 patients of c5-dip group(4kHz hearing loss group).
Results: Thirty one patients met the criteria of 1kHz audiometric notch. There are eleven males and 20 female with mean age of 40.6 years old. The pure tone threshold of 1kHz was 37.97 dB and the hearing threshold was 22.38 dB with other frequencies. Tinnitus was most the common complaints of c3-dip group compared with c5-dip group. The most common diagnoses of the c3-dip group were sudden sensorineural hearing loss(n = 8) and idiopathic tinnitus(n = 8). Female patients and unilateral cases were more common in c3-dip group than c5-dip group. Ear fullness was the more common symptom in c3-dip group than c5-dip group. The duration of occupation-related noise exposure was longer in c5-dip group than c3-dip group. The history of head or ear trauma was more frequent in c3-dip group than c5-dip group.
Conclusion: We defined a new clinical entity of 1 kHz hearing loss group as c3-dip group.