I received a couple of patients with reverse-sloping hearing loss and it provoked writing this article. Read more to learn more about this type of hearing loss and the challenges that your audiologist might face in fitting your hearing aids.
For the vast majority of people with hearing loss, the problem starts at high frequencies. That means that the patient has no or only little hearing problems with low frequencies, starts having some hearing loss at mid-frequencies, and the worst hearing loss is usually recorded at high frequencies.
On the other hand, a patient with reverse-sloping hearing loss has good high-frequency hearing but has some hearing difficulty in the mid-range and the biggest hearing impairment is at the low frequencies (see below).
What are the common health issues resulting in reverse-sloping hearing loss?
Reverse-sloping hearing loss is not very common. It can be caused by
Meniere's disease,
Genetic condition,
Sudden sensorineural hearing loss, or
a cardiovascular condition.
The patient with reverse-sloping hearing loss feels that s/he needs more volume to hear better, often hears female voices better than male voices,
What are the challenges of fitting hearing aids for patients with reverse-sloping hearing loss?
There are multiple connected challenges when fitting hearing aids to people with reverse sloping:
Less natural sound - As you can guess the patient needs amplification in the low-frequency range, hence the ear canal needs to be fully occluded to be able to pump enough energy to compensate for the loss. Sealing the ear canal off by power domes or earmoulds will force us to amplify the mid and high frequencies for the patient too, what he or she has no problem hearing naturally.
Occlusion - As a result of sealing the ear canal off and a high level of amplification in the low-frequency range the patient will experience occlusion, or simply hear his or her voice loud and artificial.
Perception of sound - It might take some time and effort to find the optimum individual fitting for the patient. Some may perceive sound better and achieve better speech intelligibility with power domes, while some may get better results with canal earmould and vice versa. There seems not to be a one-size-fits-all approach for fitting the hearing aids for patients with this type of hearing loss.
How can the fitting of hearing aids be optimized for people with reverse-sloping hearing loss?
There are a few techniques to optimize the fitting for patients with reverse-sloping hearing loss:
Hearing aids apps could help the patient to optimize the setting of the hearing aids on the go. After 2-3 weeks the audiologist can collect the information in a rehab session and make these personal settings permanent in the hearing aids settings.
Often the REM setting of a reverse-sloping prescription needs to be altered based on the patient's feedback and his/her tolerance to occlusion. I found that REM often amplifies the low range beyond the patient's tolerance. Something that needs to be corrected manually anyway.
Is there a specific type or model of hearing aids more suitable than others for reverse-sloping hearing loss?
Not really. In my experience, the majority of the patients with reverse sloping hearing loss are fitted with earmould and behind-the-ear type hearing aids. But virtually any type of hearing aid could work well if the SPL power limitation of the hearing aid satisfies the level of loss in low frequencies. Patients with narrow ear canals are likely to need eartip or earmould to hold the P or HP receiver in the canal. generally speaking, I rather keep patients away from the ITE and ITC hearing aids as there may be little room to alter the acoustics of the shell.
How does ageing impact reverse-sloping hearing loss?
Hearing loss due to ageing can start at about age 50 and the sign of it is the difficulty of one in hearing high frequencies. In the case of patients with reverse-sloping the ageing will impair their ability to hear high frequencies and it can work in a way to make their hearing loss profile almost flat. This is not a bad outcome, but unfortunately in my experience, the same health issues that caused the reverse-sloping hearing loss often persist and push the thresholds of the low frequencies even further down during the ageing process.
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