Asymmetric Hearing Loss
Asymmetric hearing loss is hearing loss in which the two ears differ meaningfully in degree, configuration, or type. Rather than both ears showing a similar pattern on the audiogram, one ear is measurably poorer than the other. Asymmetry can involve a difference in the overall level of hearing loss (for example, moderate loss in one ear and mild loss in the other), a difference in which frequencies are most affected, or a difference in how well speech is understood at a given volume.
Some degree of asymmetry between ears is common and does not always require further investigation. However, a significant or unexplained asymmetry, particularly when one ear shows poor word recognition scores out of proportion to its threshold level, or when asymmetric sensorineural hearing loss is accompanied by tinnitus or balance symptoms on one side, warrants investigation to rule out retrocochlear causes. Vestibular schwannoma and other conditions affecting the auditory nerve can produce a characteristic pattern of unilateral or asymmetric hearing loss that warrants MRI of the internal auditory canals.
In hearing aid fitting, asymmetric hearing loss influences device selection and programming. Each device must be programmed independently to match the hearing profile of that ear. Asymmetry also affects the audiologist's recommendation regarding bilateral versus monaural fitting and whether additional devices such as a CROS system are appropriate.
