Meanings of a double-notch audiogram

Area of Science:

• Audiology
• Occupational Health
• Ototoxicology

Background:

• Noise exposure is a significant risk factor for hearing loss.
• Standard audiological assessments typically identify noise-induced hearing loss in the higher frequency ranges.
• A less common 'double-notch' audiogram configuration has been observed in some noise-exposed individuals.

Purpose of the Study:

• To investigate the characteristics of patients presenting with a double-notch audiogram.
• To compare audiological findings in patients with double-notch audiograms to those without this configuration.
• To explore the potential causes and implications of the double-notch audiogram in noise-exposed individuals.

Main Methods:

• Retrospective analysis of audiological data from patients with a history of noise exposure.
• Identification of 27 patients (1.5%) with a double-notch audiogram configuration.
• Comparison of audiological findings, occupational history, and medical history with a control group of 50 patients without the double-notch pattern.

Main Results:

• The double-notch audiogram configuration was identified in a small percentage of noise-exposed patients.
• Analysis suggests that noise damage may also contribute to the low-frequency notch component of the double-notch pattern.
• The low incidence indicates a limited susceptibility to noise damage in the 500 Hz to 1 kHz region, in addition to the typical 3 to 6 kHz region.

Conclusions:

• The double-notch audiogram is a rare finding in noise-exposed individuals, suggesting specific susceptibility.
• Noise damage is implicated as a cause for both the low and high-frequency notches in this configuration.
• The double-notch pattern may be exacerbated by the release from inhibition of damaged auditory hair cells.