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LOW-FREQUENCY SENSORINEURAL HEARING LOSS

Timothy C. Hain, MD Hearing Page Page last modified: May 31, 2017

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There are many patterns of hearing loss. Generally clinicians group them along several axes; sensory vs conductive; the severity axis -- mild vs moderate vs. profound; the time axis -- sudden vs progressive vs chronic, and the frequency spectrum that is affected. Roughly speaking, the frequency patterns of hearing loss are divided up into: Low-frequency, mid-frequency, high-frequency, notches, and flat. There are also combinations of the above -- mainly the "peaked", or perhaps inverse-cookie bite, which is a mixture of low and high-frequency, sparing mid-frequency.

Some common audiogram shapes are shown below:

 

Normal
Normal audiogram -- threshold of 0. Noise Notch

 

Examples of other abnormal hearing patterns are shown below

low frequency cookie high flat
Low frequency (Meniere's) Middle (or "cookie bite") centered on 1K High-frequency loss, beginning at 8K Flat hearing loss in both ears, R is worse.

Here we are discussing only low-frequency sensorineural hearing loss. This group appears to be distinct in demographic features from the more common "sudden hearing loss" that affects all frequencies (flat), or just high frequencies. (Yoshida et al, 2017).

As an overview, low frequency (or tone) sensorineural hearing loss (LF SNHL or LT SNHL) is unusual, and mainly reported in Meniere's disease as well as related conditions such as low CSF pressure. There are a few "one-off" reports in central conditions such as Susacs, vertebrobasilar insufficiency, just old age, and periventricular leukomalacia. There is a large literature about genetic causes, mainly in Wolfram's syndrome ( diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), probably because it is relatively easier to publish articles about genetic problems.

Causes of low-frequency sensorineural hearing loss.

General papers:

Asakuma (1999) reported 241 patients with acute low-tone SNHL. These patients were largely young females. He defined LTSNH as that the sum of the three low frequencies (125, 250, 500) was more than 100 dB, and the sum of the 3 high frequencies (2, 4, 8) was less than 60 dB.

Jun et al suggested prognosis in SHL was better for low-tone hearing loss. This seems reasonable enough.

Le Prell et al (2011) suggested that low frequency hearing loss was detected in 2.7% of normal college student's ears. We are dubious that this has any significance. We think it is probably just "noise".

Oishi et al (2010) suggested that about half of patients with LTSNHL developed high or flat hearing loss within 10 years of onset.

Meniere's disease: Starts with a low-tone SNHL

Meniere's
2014 2015
Early low-tone SNHL Progression of hearing 1 year later

The new international criteria for Meniere's disease require observation of a low-tone SNHL. To us, this seems a little overly stringent, compared to the earlier 1995 AAO criteria that just required any kind of hearing loss, but criteria are better than no criteria.

Belinchon et al (2011) reported that Meniere's disease show an "inherent upward sloping configuration", after correction for patient's age, at all points. Brannstrom et al (2008) reported that Meniere's patients fluctuate at low-tones.

Gatland et al (1991) reported fluctuation in hearing at low frequencies with dialysis was common, and suggested there might be treatment induced changes in fluid or electrolyte composition of endolymph (e.g. part of the hydrops story).

Rahko et al (1990) suggested that "in Meniere's disease the whole cochlear sensory area is affected, and that the damage caused by Meniere's disease advances simultaneously in all parts of the cochlea." We disagree ourselves - - in Meniere's, hearing loss starts at low frequencies. Furthermore, we don't see that hearing loss automatically means cochlear damage either.

Although OAE's are generally obliterated in patients with hearing loss > 30 dB, for any mechanism other than neural, this is not always the case in the low-tone SNHL associated with Meniere's disease.

Meniere's
menieres audio lowtone oae
Audiogram (classic early Meniere's) High-resolution OAE, same patient, same day. The distance between red and black line is a measure of the strength of the OAE. This patient has excellent OAE's at low frequencies.

The lack of universal correspondence between audios and OAE's in low-tone SNHL in at least some patients with Meniere's, suggests that the mechanism of hearing loss may not always be due to cochlear damage. We have also encountered patients with "miraculous recoveries" of hearing in Meniere's, again suggesting that in some patients, the cochlea must be still intact. Where might the injury be ? One wonders if these patients reflect a different (perhaps better prognosis mechanism). There is a small amount of evidence that LTSNHL may be central (see below). Could these patients have brainstem hearing loss ?

Of course, in a different clinical context, one might wonder if the patient with the discrepancy between OAE and audiogram might be pretending to have hearing loss. We would strongly doubt this, but it is possible.

Genetic causes of low-tone sensorineural hearing loss.

Papers are easy to publish about genetic hearing loss conditions, so the literature is somewhat oversupplied with these. That being said, genetic conditions should not be your first thought when you encounter a patient with LTSNHL. If there is a family history you should be thinking about this.

Central lesions as causes of low tone sensorineural hearing loss.

Spinal fluid pressure as a cause of low tone sensorineural hearing loss

There are an immense number of reports of LTSNHL after spinal anesthesia and related conditions with low CSF pressure. One would wonder if looking for LTSNHL shouldn't be part of the protocol for diagnosis.

Fog et al (1990) reported low frequency hearing loss in patients undergoing spinal anesthesia where a larger needle was used. This is likely part of the story with hydrops and low spinal fluid pressure.

Age

Gates et al (1991) suggested that low tone deterioration with age was due to "strial atrophy or other intracochlear processes". We do sometimes observe mysterious low-tone deterioration in older people. We do not know why.

Medications:

Horner et al (1997) reported that lithium causes low frequency hearing loss in guinea pig. We are dubious that this has any applicability to humans and we have never seen a patient with lithium toxicity with any LFSNHL. Guinea pigs may be special.

SCD

Kanaan et al reported a single case of low tone SNHL with bilateral SCD. SCD stands for superior canal dehiscence. We have observed this occasionally ourselves, but of course, the usual pattern is a conductive hyperacusis.

Pregnancy:

Kenny reported a case of sudden LTSNHL after delivery. We find this somewhat plausible as pregnancy and delivery might be associated with spinal anesthesia, with changes in collagen, and with gigantic changes in hormonal status. That being said, it is very rare to encounter any substantial change in hearing after pregnancy.

Zoster hearing loss zoster oae
Low tone hearing loss 6 years post Herpes Zoster on the right Sweep OAE done 1 year after Herpes Zoster on the right. Note preserved low frequencies.

 

Neural ?

We have encountered a patient, about 50 years old, with a low-tone sensorineural hearing loss that occurred in the context of a herpes zoster infection (Ramsay-Hunt). Her hearing improved, and remained stable for 5 years thereafter. OAE testing was intact at low frequency. This may be a neural type LTSNHL. There is very little written about hearing loss in Ramsay Hunt.

Treatment of LTSNHL

LTSNHL is generally viewed as either a variant of Meniere's disease or a variant of sudden hearing loss, and the same medications are used. The most common ones are diuretics and steroids. According to Im et al (2016), prognosis was excellent (in their uncontrolled study). We suspect prognosis would be equally good without any treatment.

According to Sato et al (2017), female gender, younger age, low-grade hearing loss, and a shorter interval between onset and initial visit were significantly predictive of a good prognosis. Most of these observations are rather obvious -- less hearing loss, being younger, and not having a long history of being deaf already are naturally associated with better prognosis. The main surprise is female gender. Perhaps this relates to a different distribution of mechanism (e.g. more migraine in females).

REFERENCES

Copyright May 31, 2017 , Timothy C. Hain, M.D. All rights reserved. Last saved on May 31, 2017