Clinical and audiological characteristics of 1000Hz audiometric notch patients

Among the hearing loss patients, we can confirm that the hearing loss of the specific frequency decreases, such as the 2000Hz notch in otosclerosis and the 4000Hz notch (c5-dip) in noise-induced hearing loss. The 1000Hz notch (c3-dip), however, is rarely studied. We fortuitously encountered a group of patients with a 1kHz hearing loss and report it with a review of the literature.

Otological history, audiogram, diagnosis, occupation, and history of noise exposure were reviewed from charts and telephone interview, and compared between c3-dip and c5-dip patients (n=98).

Thirty-one patients (mean age: 46.2years) demonstrated 1kHz hearing loss; these included 11 males. The pure-tone threshold was 37.97dB at 1kHz and the average threshold was 22.38dB at other frequencies. In the c3-dip group, tinnitus was the most common complaint, while sudden sensorineural hearing loss and idiopathic tinnitus (n=8 each) were the most common diagnoses. Female patients and unilateral cases were more common in the c3-dip than in the c5-dip group, and ear fullness was more common in the c3-dip group than in the c5-dip group. The duration of occupation-related noise exposure was longer in the c5 group, and head or ear trauma was more frequent in the c3-dip group.

We have defined a new clinical entity of 1kHz hearing loss in patients, defined as the c3-dip, which was clinically and audiologically distinct from the c5-dip. Further study is needed to clarify this new entity of hearing loss.