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LESSON 141

The audiologist in sudden hearing loss

Year 2
Spring semester
Disorders of the Auditory and Vestibular Systems
Inner ear and retrocochlear disorders
Duration: 11:39

We explain the definition of sudden sensorineural hearing loss, the steps of a rapid audiological assessment, ruling out conductive loss, and why same-day referral to a physician matters. With examples, we cover the audiology-related key points of the 2019 AAO-HNSF guideline, follow-up audiograms and the factors that affect prognosis.

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Hello, and welcome to the AIHEAR Audiology Academy.
In this lesson we will learn about sudden sensorineural hearing loss and the audiologist's role in this emergency.
We will cover the definition, the steps of a rapid assessment, urgent referral and follow-up audiograms.
Sudden hearing loss is a drop in hearing over a short time, such as 72 hours, and it can affect one or both ears.
Sudden sensorineural hearing loss is the subgroup that is sensorineural and meets the audiometric criteria.
In the 2019 AAO-HNSF guideline, the most widely used criterion is a loss of 30 decibels or more at three or more consecutive frequencies.
Because the person's previous audiogram is often unknown, the loss is judged by comparison with the thresholds of the other ear.
According to the guideline, in about ninety percent of sudden sensorineural losses, no clear cause is found at presentation.
In the clinic, sudden losses under 30 decibels are also taken seriously; the definition is a shared language, not a lower limit.
Let us consider a purely example case: two days ago, on waking in the morning, the person noticed fullness and ringing in the left ear.
In this example, the right ear thresholds are within normal limits.
In the left ear, there is a moderate to moderately severe loss across all frequencies.
Masked bone-conduction thresholds overlap with air conduction, so the loss is sensorineural.
At three or more consecutive frequencies, the difference between the ears is well above 30 decibels.
This picture meets the criteria for sudden sensorineural hearing loss and calls for same-day referral to a physician.
The first complaint is often a feeling of fullness or blockage in the ear.
Because this complaint seems common and ordinary, both the person and health workers may dismiss it, and assessment may be delayed.
Tinnitus often accompanies sudden sensorineural loss and causes marked anxiety.
Some people also have dizziness or imbalance.
The loss is often noticed on waking in the morning, or develops over a few hours to a few days.
Sudden loss is often mistaken for a simple blocked ear, and the person may wait for days.
Yet treatment options are assessed by the physician early; the guideline especially stresses the first two weeks.
Deciding on the type and timing of treatment is the physician's responsibility, not the audiologist's.
In addition, though rarely, important causes such as vestibular schwannoma or stroke can lie behind a sudden loss.
So the audiologist's key task is to document the loss quickly and refer the person that day to an ear, nose and throat, or ENT, doctor.
Assessment starts with a brief, focused history: when did the loss start, in which ear, and are there other symptoms?
Otoscopy looks for conductive causes, such as impacted earwax or fluid in the middle ear.
In pure-tone audiometry, air- and bone-conduction thresholds are measured in both ears with the necessary masking.
Tympanometry shows the middle ear status; speech tests are added if possible.
As soon as the results are ready, the person is referred, with the findings, to an ENT physician the same day.
Being fast does not mean measuring less; an accurate first audiogram is the basis for all later comparisons.
The guideline's first recommendation is to distinguish whether a sudden loss is sensorineural or conductive.
Impacted earwax or middle ear fluid can also cause sudden blockage and reduced hearing.
If audiometry cannot be done right away, a tuning fork Weber test gives a clue: in sensorineural loss, sound goes to the better ear.
In conductive loss, the sound lateralizes toward the affected ear.
The definite distinction is made with masked bone-conduction thresholds and tympanometry.
Finding a conductive cause does not make a medical examination unnecessary, but it changes the content of the referral note.
In a severe unilateral loss, cross-hearing occurs easily, so air-conduction thresholds are measured with the necessary masking.
Because interaural attenuation for bone conduction is very low, bone thresholds are also confirmed with masking.
If possible, the speech recognition threshold, or SRT, and the word recognition score are also measured.
These scores document both the starting point and the assessment of recovery.
Tests such as acoustic reflexes and otoacoustic emissions give extra information, but they should not delay referral.
The audiogram is recorded with the date and even the time, because later follow-up measurements will be compared with this first value.
Let us summarize the audiology-related key points of the 2019 AAO-HNSF guideline update; the first step is to rule out conductive loss.
If the loss is bilateral, recurrent, or accompanied by neurologic findings, a different and more urgent assessment is needed.
The guideline recommends against routinely ordering a head computed tomography, or CT, at initial assessment.
It recommends evaluating for retrocochlear causes; the most sensitive method is magnetic resonance imaging, or MRI.
The auditory brainstem response, or ABR, or audiometric monitoring are also among the accepted options.
Treatment options and timing are assessed by the physician; the guideline stresses the early period, especially the first two weeks.
Follow-up audiometry is recommended at the end of treatment and within six months after treatment ends.
Counseling people with incomplete recovery about hearing aids and assistive technologies is also a strong recommendation.
Sudden loss in both ears at once raises the possibility of systemic or neurologic causes.
Recurrent episodes of sudden loss may point to other conditions, such as Meniere's disease.
Neurologic signs may accompany it, such as facial weakness, speech problems, sudden headache or marked loss of balance.
In such cases, because a life-threatening cause such as stroke is possible, the person is helped to reach emergency care without delay.
The audiologist should ask about these signs and state them clearly in the referral note.
A clinical tip: keep sudden sensorineural loss in mind for everyone who comes in saying their ear feels blocked.
If otoscopy is normal and the tympanogram is type A, the feeling of blockage may not come from the middle ear.
For such a person, do pure-tone audiometry the same day, and always measure bone conduction.
If you find a sensorineural loss, refer to a physician the same day, without putting the person in the appointment queue.
Follow-up measurements document recovery objectively; the thresholds of the healthy ear are also shown for comparison.
In this example, the first test of the left ear is shown by the blue line; measurements are always made with the same method and conditions.
In the follow-up test a few weeks later, the green line, the thresholds have improved clearly.
At 1000 Hz, the improvement is 30 decibels, but the thresholds are still clearly poorer than the right ear.
By the guideline, complete recovery means thresholds return to within about 10 decibels of the healthy ear, with a similar word score.
Improvement over 10 decibels that is not complete, as here, is partial recovery; change under 10 decibels is defined as no recovery.
According to the guideline, some of these losses recover on their own; studies have reported rates of about 32 to 65 percent.
The degree of loss matters; in severe and profound losses, the chance of complete recovery is lower.
The audiogram shape also guides us; losses limited to the low frequencies usually have a better course.
Vertigo at onset has been associated with a worse prognosis.
Older age is also associated with more limited recovery.
A longer time between symptom onset and assessment and treatment can also affect the outcome negatively.
If recovery is incomplete, tinnitus often remains the most bothersome complaint and calls for counseling.
Depending on remaining hearing, options such as hearing aids or CROS systems, which route sound to the other side, are considered.
A sudden one-sided loss can cause anxiety and insecurity; this emotional impact is also addressed in counseling.
A team approach, with the ENT physician and audiologist working together, makes the person's long-term follow-up easier.
The guideline also stresses that in some patients, the cause may emerge only during long-term follow-up.
Sudden sensorineural hearing loss is usually defined as a loss of 30 decibels or more at three consecutive frequencies, within 72 hours.
The first step is to rule out conductive loss, using masked air and bone conduction and tympanometry.
The audiologist documents the loss quickly and refers the person to a physician the same day; treatment is the physician's decision.
Follow-up audiograms document recovery at the end of treatment and within six months.
Test yourself: what is the audiologist's main role in sudden sensorineural hearing loss?
The correct answer is B: documenting the loss and referring the person to a physician the same day.
Because treatment options are assessed early by the physician, waiting or postponing the appointment is not appropriate.
In the next lesson, we will learn about Meniere's disease, with its fluctuating hearing loss and attacks of vertigo.
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Prerequisites

LESSON 134 Cochlear or retrocochlear?

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