What is Asymmetric Nerve Hearing Loss

Given my last blog article regarding an ENT who got sued for not doing an MRI after audiogram showing an asymmetric hearing loss, the question that should be on everybody's mind is what IS asymmetric nerve hearing loss on a hearing test?

I am sad to report that there is no clear consensus on what is asymmetric nerve hearing loss.

First of all, at its most basic definition, asymmetric nerve hearing loss is when hearing is worse in one ear when compared with the opposite ear due to nerve damage.

Technically, hearing should decrease equally on both sides over time, but when one side gets worse faster than the other, it can cause concern because:

1) A tumor can be pressing against the nerve causing it to slowly fail faster than the other ear's nerve which is not compressed.
2) There is a loud noise history with asymmetric exposure to the ears. One example is hunting with a rifle where the left ear would repetitively get noise-induced damage from the gunshot in a right-handed shooter.
3) Bad luck

The conflict is at what point is an asymmetry considered significant enough to warrant a workup which may include an MRI scan of the head and/or auditory brainstem response (ABR)? Also, for a given patient history, a physician/patient may elect to recheck hearing bi-annually to monitor for asymmetric progression rather than pursue workup immediately (further studies being pursued only if asymmetry progresses over time).

Is asymmetry defined as 1 decibel difference between ears? Is it 50 decibel difference?

Even if the decibel difference is agreed upon, than over what frequencies? All of them or just a few of the frequencies?

So for the purposes of a "medically" significant asymmetric nerve hearing loss, the definition must define not only HOW big the difference in hearing loss is present between ears but also at what frequencies.

In one paper, it is 15 decibels at just 3000 Hz.

In another paper, it is 20 decibels at any two adjoining frequencies (or 15 decibels at two adjoining frequencies between 2000 and 8000 Hz).

Get this... even when criteria is defined, one study found substantial disagreement among five expert judges on what hearing tests they considered showed asymmetry.

Even insurance companies are jumping into the fray in what they considered significant enough to warrant covering the MRI scan. At one point when I ordered an MRI scan of the head for what I thought was a significant asymmetry found in one patient's hearing test, the insurance company denied the test citing "that there needed to be other neurological deficits PLUS the asymmetry seen on hearing test before MRI scan would be authorized".

I personally pursue further workup using the 20 decibel difference at two adjoining frequencies OR 30 decibel at one frequency.

Assuming medically significant asymmetric hearing loss has been defined and is present...

What are the chances of something bad going on (i.e., tumor) when an MRI scan of the head is ordered for asymmetry found on hearing test?

Less than 10% (depending on study, can be as low as 1-4%).

Given such a low positive yield on testing, why even pursue a MRI scan?

Because of defensive medicine to avoid being named in a lawsuit if the affected patient just happens to be within that 10% found to have an acoustic neuroma.

Indeed, in one study, 40% of ENTs stated medico-legal concerns factored into their decision to get an MRI scan of the head.

ENT Sued for Malpractice for Hearing Loss Due to Acoustic Neuroma

A patient has sued an ENT for failing to workup an asymmetric sensorineural hearing loss (nerve hearing loss greater in one ear compared to the opposite ear) that allegedly deviated from standard of care that ultimately led to permanent hearing damage and facial paralysis.

Since January 2008, the plaintiff saw the defendant ENT who performed 3 audiograms that revealed an asymmetric sensorineural hearing loss. In 2010, the plaintiff suffered a sudden sensorineural hearing loss at which time an MRI scan of the head was performed revealing a "large" acoustic neuroma (benign tumor of the hearing nerve).

Resection of this tumor resulted in a visible facial droop, permanent hearing loss, and cognitive deficits due to partial removal of brain tissue.

According to plaintiff, had the ENT performed MRI scan when asymmetric sensorineural hearing loss was first detected (presumably back in 2008), he never would have suffered from these defects.

Read about the case here.

Normally, if and when asymmetric sensorineural hearing loss is first detected, some type of workup is typically performed (auditory brainstem response and/or MRI scan of the head) unless there are extenuating factors present in the history. Such extenuating factors include old age and/or significant loud noise history that may lead to asymmetric hearing loss such as shooting (which often causes left greater than right nerve damaged hearing loss in right-handed shooters).

Apparently THREE audiograms were performed over time. If there was progressive worsening of the asymmetric sensorineural hearing loss, than MRI should have been performed and/or at the very least an auditory brainstem response testing (ABR). IF the audiograms showed stable asymmetry over time, it can be argued that absolutely no further workup is needed.

The key question in this case is had the defendant ENT obtained an MRI in 2008 when asymmetric sensorineural hearing loss was first detected, the acoustic neuroma would have been discovered earlier thereby preventing the permanent hearing loss he later suffered in 2010 along with facial paralysis and cognitive defects that occurred after surgical resection.

A couple problems with this line of reasoning:

1) Acoustic neuromas grow at a rate of 1mm per year on average. As such, if the acoustic neuroma was large in 2010... it most certainly was large in 2008 being only 2mm smaller.
2) As such, surgical resection of the "large" acoustic neuroma had it been performed in 2008 probably would have resulted in the same outcome of permanent hearing loss, facial paralysis, and cognitive defects.

Furthermore, had the MRI been performed back in 2008 revealing the tumor, the options that would have been presented to the defendant patient would be:

1) Surgery
2) Radiation
3) Observe

Given it is established that the acoustic neuroma was large even in 2008, any type of intervention whether surgery or radiation, most certainly would put at risk the facial nerve which runs alongside the acoustic neuroma. Permanent facial paralysis and hearing loss most certainly is not an uncommon outcome after intervention.

One could even argue that in all likelihood, ALL the defendants current complaints would have occurred 2 years more quickly had the MRI scan of the head and subsequent intervention been performed.

Observation would have only lead to the current sequence of events.

As such, did malpractice occur?

I don't think so.

Should the defendant ENT have ordered the MRI scan of the head back in 2008 when an audiogram he obtained showed the asymmetric sensorineural hearing loss?

Probably though this might be debatable depending on patient's prior noise history and exact audiogram findings. Most definitely if the audiograms revealed a progressive worsening of the asymmetry over time. Most likely not if the audiograms remained the same over time.

Would knowing there was an acoustic neuroma present in 2008 have changed the patient's ultimate outcome?

Probably not.

Source:
Couple sues physician for medical malpractice. The West Virginia Record 7/10/12

Katie Couric Gets a Hearing Test

On July 10, 2012, Katie Couric reported on a personal story during which she obtained a hearing test.

In a modern society like the United States, there are many sources for hearing loss with our alarms, lawn-mowers, and loud music.

As the article correctly pointed out, damage due to loud noises is due to two factors: loudness and duration.

The louder something is, the shorter time of exposure before hearing damage can occur. The quieter something is, the longer a person can listen before suffering noise-induced hearing loss.

Otherwise, hearing aids may be in your future... even if you are in your 20s or 30s!

Source:
Am I Going Deaf? Yahoo News 7/10/12