**2. Audiological evaluation**

Audiological testing includes pure tone audiometry, with highlights of bone conduction especially in acute episodes of this disease, glycerol test when hearing loss is documented, auditory brainstem response (ABR) and electrocochleography.

#### **2.1. Pure tone audiometry**

Pure tone audiometry is a subjective method of hearing evaluation. Patient must signalize the faintest sound he/she hears. Pure tone with specific frequencies is used (125, 250, 500, 1000, 2000, 4000, and 8000 Hz), based on the human normal hearing frequency range (20–20,000 Hz).

Sounds are presented both in air and bone conduction in order to have an accurate image of the hearing.

The result of the test is shown in a graph, a Cartesian system with frequency tested (in Hz) on horizontal axis and intensity (in dB HL) on the vertical one. Frequency varies between 125 and 8000 Hz and intensity between −10 and 120 dB (the latest represents the painful sensation, not an audible one = uncomfortable level). Based on patient's response, the least audible intensity (threshold) on each tested frequency is plotted.

Threshold notation is standardized internationally (ISO system) and colors as well: red for the right ear and blue for the left ear (**Figure 1**):


Normative for hearing thresholds (THR) were established based on nonotological history teenagers' responses decades ago and normal hearing stands for hearing thresholds between −10 and +20 dB on all frequencies, without differences between air and bone conduction (**Figure 2**).

Pure tone audiometry is the method of choice for hearing evaluation also in Menière's disease patients in [1, 2]. When hearing loss (HL) is permanent, Menière's disease patients experience

**Figure 1.** Standardized notation for hearing thresholds.

**Figure 3.** Low frequency sensorineural hearing loss in left ear.

important for counselling the patients regarding the disease long-term evolution and also for

Audiological testing includes pure tone audiometry, with highlights of bone conduction especially in acute episodes of this disease, glycerol test when hearing loss is documented, audi-

Pure tone audiometry is a subjective method of hearing evaluation. Patient must signalize the faintest sound he/she hears. Pure tone with specific frequencies is used (125, 250, 500, 1000, 2000, 4000, and 8000 Hz), based on the human normal hearing frequency range (20–20,000 Hz).

Sounds are presented both in air and bone conduction in order to have an accurate image of

The result of the test is shown in a graph, a Cartesian system with frequency tested (in Hz) on horizontal axis and intensity (in dB HL) on the vertical one. Frequency varies between 125 and 8000 Hz and intensity between −10 and 120 dB (the latest represents the painful sensation, not an audible one = uncomfortable level). Based on patient's response, the least audible intensity

Threshold notation is standardized internationally (ISO system) and colors as well: red for the

• Nose-opened brackets for bone conduction: "<" and ">" in unmasked condition and "["

Normative for hearing thresholds (THR) were established based on nonotological history teenagers' responses decades ago and normal hearing stands for hearing thresholds between −10 and +20 dB on all frequencies, without differences between air and bone conduction (**Figure 2**). Pure tone audiometry is the method of choice for hearing evaluation also in Menière's disease patients in [1, 2]. When hearing loss (HL) is permanent, Menière's disease patients experience

appropriate management of the disease.

tory brainstem response (ABR) and electrocochleography.

(threshold) on each tested frequency is plotted.

• Air conduction: "circle" for the right ear and "X" for the left ear

right ear and blue for the left ear (**Figure 1**):

**Figure 1.** Standardized notation for hearing thresholds.

and "]" in masked condition

**2. Audiological evaluation**

100 Up to Date on Meniere's Disease

**2.1. Pure tone audiometry**

the hearing.

sensorineural hearing loss (average of hearing THR on 0.5, 1, and 2 kHz greater than 20 dB), with pathological thresholds on low frequencies (**Figure 3**).

Cochlear sensorineural hearing loss (SNHL) is accompanied by recruitment, a phenomenon of increased loudness perception—above an increase threshold, higher intensity sounds are as loud to the hearing impaired person as for a normal hearing one and thus disturbing.

Some authors describe in Menière's disease patients a particular type of recruitment—hyper- or overrecruitment: loudness in the affected ear overtakes the normal ear at high intensities in [3–5].

When differences between air conduction thresholds in both ears exceed 40dB for supra-aural earphones or 55 dB when insert earphones are used, air conduction masking is mandatory for that specific frequency where this difference exists. For bone conduction, masking is mandatory whenever more than 10dB difference between bone and air conduction thresholds is present on that specific frequency. Bone conduction masking is essential in differentiating conductive and sensorineural hearing loss.

It is not unusual to have a conductive component of the hearing loss in Menière's disease acute phase—disturbances in endolymph metabolism lead to pressure variations at the round and oval window with secondary increases of impedances. High impedances diminish air transmission of the sounds, with consecutive cochlear conductive hearing loss (**Figure 4**). In these cases, middle ear test (tympanometry and acoustically evoked stapedius reflex) shows no impairment of the middle ear as cause of the conductive component of the hearing loss.

#### **2.2. Speech audiometry**

Besides pure tone audiometry, speech audiometry complements auditory evaluation. It is a more complex test, since evaluates the entire auditory pathway as hearing is a cortical process. Speech audiometry is also a subjective audiological test where the tested person has to repeat the heard stimuli—numbers, monosyllabic, disyllabic words, or sentences.

The result of the test is a Cartesian graphic with percentage of correct repeated stimuli on the vertical axis for each intensity tested and with intensity of the stimulus on the horizontal axis. For each intensity, a phonemic-balanced list of 10 stimuli (numbers, monosyllabic, disyllabic words, or sentences) is presented. These percentages draw a curve which crosses the 50% line at some specific intensity. This crossing represents the threshold of speech audiometry. For normal hearing, conductive or cochlear sensorial sensorineural hearing loss, this threshold must correlate with pure tone average ±7 dB (**Figure 5**).

**Figure 4.** Conductive (a) or mixed (b) hearing loss due to cochlear conductive hearing loss.

**Figure 5.** Speech audiometry.

Some authors describe in Menière's disease patients a particular type of recruitment—hyper- or overrecruitment: loudness in the affected ear overtakes the normal ear at high intensities in [3–5]. When differences between air conduction thresholds in both ears exceed 40dB for supra-aural earphones or 55 dB when insert earphones are used, air conduction masking is mandatory for that specific frequency where this difference exists. For bone conduction, masking is mandatory whenever more than 10dB difference between bone and air conduction thresholds is present on that specific frequency. Bone conduction masking is essential in differentiating conductive and

It is not unusual to have a conductive component of the hearing loss in Menière's disease acute phase—disturbances in endolymph metabolism lead to pressure variations at the round and oval window with secondary increases of impedances. High impedances diminish air transmission of the sounds, with consecutive cochlear conductive hearing loss (**Figure 4**). In these cases, middle ear test (tympanometry and acoustically evoked stapedius reflex) shows no impairment of the middle ear as cause of the conductive component of the hearing loss.

Besides pure tone audiometry, speech audiometry complements auditory evaluation. It is a more complex test, since evaluates the entire auditory pathway as hearing is a cortical process. Speech audiometry is also a subjective audiological test where the tested person has to repeat

The result of the test is a Cartesian graphic with percentage of correct repeated stimuli on the vertical axis for each intensity tested and with intensity of the stimulus on the horizontal axis. For each intensity, a phonemic-balanced list of 10 stimuli (numbers, monosyllabic, disyllabic words, or sentences) is presented. These percentages draw a curve which crosses the 50% line at some specific intensity. This crossing represents the threshold of speech audiometry. For normal hearing, conductive or cochlear sensorial sensorineural hearing loss, this threshold

the heard stimuli—numbers, monosyllabic, disyllabic words, or sentences.

**Figure 4.** Conductive (a) or mixed (b) hearing loss due to cochlear conductive hearing loss.

must correlate with pure tone average ±7 dB (**Figure 5**).

sensorineural hearing loss.

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**2.2. Speech audiometry**

If in cochlear sensorineural hearing loss of other etiology there is a good correlation (±7 dB) between pure tone and speech audiometry THR, in prolonged Menière's disease, some differences may appear.

Another parameter used in interpretation of the speech audiometry is the maxim of intelligibility/discrimination. It represents the highest percentage of correct repeated stimuli the patient obtains. For normal hearing or conductive hearing loss persons, 100% intelligibility is reached.

Sensorineural hearing loss induced distortions in audition which can limit the maximum of discrimination. Speech audiometry can draw attention on the estimated site of hearing loss, cochlear, or retrocochlear: in cochlear lesions, once the maximum score of discrimination is reached, it remains constant as higher intensities are tested. In retrocochlear sensorineural hearing loss an odd phenomenon occurs—as intensity increases, the patient understands less word (roll-over phenomenon).

#### **2.3. Glycerol test**

In patients with Menière's disease and permanent sensorineural HL, if low frequencies THR are greater than 40 dB, glycerol test is recommended. Since endolymphatic hydrops is the pathophysiological mechanism of the Menière's disease, oral administration of a hypertonic solution will extract liquids from tissues, including from the endolymphatic space. Thus, the endolymphatic pressure is diminished and hearing and vestibular sensorial epithelium recovers from increased pressure. The clinical effect of this restoration is improvement of both auditory and vestibular system function 2 h and 30 min after the ingestion, when both pure tone audiometry and speech audiometry are repeated.

Hearing improvement can be documented by pure tone audiometry and speech audiometry. An improvement of the THR on at least 10dB on three consecutive frequencies in pure tone audiometry and/or a more than 12% improvement of speech audiometry THR is considered

**Figure 6.** Positive glycerol test.

a positive glycerol test (**Figure 6**). Some authors consider this as an indication for diuretic treatment, since the endolymphatic system has the capacity to modify its pressure after oral administration of a hyperosmolar solution.

#### **2.4. Brainstem evoked response audiometry (BERA)/auditory brainstem response (ABR)**

ABR—is an objective electrophysiological audiological method that allows recording of the electrical activity evoked by neural activity in the auditory pathways, from the cochlea to the brainstem (lateral lemniscus) in Refs. [6, 7]. Surface electrodes are used in this far-field technique. Most commonly used acoustic stimulus is the click—a brief (0.1 ms) rectangular stimulus. Click-evoked ABR reflects hearing sensitivity in the frequency range of 1–4 kHz with a high correlation with pure tone audiometry threshold in this frequency domain, especially at 4 kHz where the stimulus' energy is maximum.

ABR is the first evoked potentials, with seven characteristic waves in the first 10 ms after click stimulation at high intensities: 70–90 dB normal hearing level (nHL). These waves were first described by Jewett, as response of different auditory pathway structures after acoustic stimulation:


**Figure 7.** Parameters used in ABR interpretation.

a positive glycerol test (**Figure 6**). Some authors consider this as an indication for diuretic treatment, since the endolymphatic system has the capacity to modify its pressure after oral

**2.4. Brainstem evoked response audiometry (BERA)/auditory brainstem response (ABR)**

ABR—is an objective electrophysiological audiological method that allows recording of the electrical activity evoked by neural activity in the auditory pathways, from the cochlea to the brainstem (lateral lemniscus) in Refs. [6, 7]. Surface electrodes are used in this far-field technique. Most commonly used acoustic stimulus is the click—a brief (0.1 ms) rectangular stimulus. Click-evoked ABR reflects hearing sensitivity in the frequency range of 1–4 kHz with a high correlation with pure tone audiometry threshold in this frequency domain, especially at

ABR is the first evoked potentials, with seven characteristic waves in the first 10 ms after click stimulation at high intensities: 70–90 dB normal hearing level (nHL). These waves were first described by Jewett, as response of different auditory pathway structures after acoustic

administration of a hyperosmolar solution.

**Figure 6.** Positive glycerol test.

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4 kHz where the stimulus' energy is maximum.

• wave I: proximal auditory nerve

• wave IV: superior olivar complex

• wave II: distal auditory nerve

• wave III: cochlear nuclei

• wave V: lateral lemniscus

stimulation:


First five are mostly used in interpretation of the BERA recordings. In Menière's disease patients, BERA is mandatory in order to rule out a retrocochlear etiology of the sensorineural hearing loss. Latencies, interpeak intervals and interaural differences of the latencies and interpeak intervals are the parameters used for this differential diagnosis (**Figure 7**).

In general, ABR exhibits a sensitivity of over 90% and a specificity of approximately 70–90%. Findings suggestive of retrocochlear pathology may include any one or more of the following:


#### **2.5. Electrocochleography**

Electrocochleography (ECochG) is an objective audiological test that measures the electrical potentials derived from the cochlear hair cells and the auditory nerve in [8–10]. These potentials are produced between an electrode on the cochlear promontory and an earlobe electrode, within a time frame of 5 ms after stimulation with alternative repetitive very short acoustic signals (click). Averaging of a large number of potentials (1000 sweeps) is needed in order to record the ECochG characteristic wave. Click is the most common stimuli used in ECochG due to its effect of very good synchronization of a large number of cochlear nerve fibers, mandatory for eliciting a measurable action potential. Click has an abrupt onset, very short duration and broad frequency spectra, thus stimulating a very large number of hair cells in the basal turn of the cochlea, where the speed of the travelling wave is the fastest.

Magnitude and quality of the response depends on the electrode type—transtympanic electrode fixed directly on the promontory gives the best recordings, but it is an invasive audiological investigation. Alternatively, with good clinical results are used extratympanic electrodes, place in the external auditory canal, as close as possible to the eardrum or on the eardrum itself.

Synchronization of the auditory nerve fibers after above-mentioned stimulation gives birth to global action potential. Its origin lies into the inner ear hair cells and cochlear nerve.

Global action potential consists of presynaptic and postsynaptic potentials (**Figure 8**).

The first one includes cochlear microphonic (CM) that originates in the outer cochlear hair cells and summating potential (SP) arising from the inner cochlear hair cells. Postsynaptic potentials, known as global action potential of the cochlear nerve, is generated by all cochlear nerve fibers, fired in synchrony by the acoustic stimulus.

In endolymphatic hydrops, due to the increased pressure in scala media, basilar membrane vibrates asymmetrical. These changes of the traveling wave lead to several dysfunctions: distorted cochlear microphonics, enlargement of the summating potential and broadening of the

**Figure 8.** Global action potential.

**Figure 9.** SP/AP amplitude ratio.

**2.5. Electrocochleography**

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wave is the fastest.

eardrum itself.

**Figure 8.** Global action potential.

Electrocochleography (ECochG) is an objective audiological test that measures the electrical potentials derived from the cochlear hair cells and the auditory nerve in [8–10]. These potentials are produced between an electrode on the cochlear promontory and an earlobe electrode, within a time frame of 5 ms after stimulation with alternative repetitive very short acoustic signals (click). Averaging of a large number of potentials (1000 sweeps) is needed in order to record the ECochG characteristic wave. Click is the most common stimuli used in ECochG due to its effect of very good synchronization of a large number of cochlear nerve fibers, mandatory for eliciting a measurable action potential. Click has an abrupt onset, very short duration and broad frequency spectra, thus stimulating a very large number of hair cells in the basal turn of the cochlea, where the speed of the travelling

Magnitude and quality of the response depends on the electrode type—transtympanic electrode fixed directly on the promontory gives the best recordings, but it is an invasive audiological investigation. Alternatively, with good clinical results are used extratympanic electrodes, place in the external auditory canal, as close as possible to the eardrum or on the

Synchronization of the auditory nerve fibers after above-mentioned stimulation gives birth to

The first one includes cochlear microphonic (CM) that originates in the outer cochlear hair cells and summating potential (SP) arising from the inner cochlear hair cells. Postsynaptic potentials, known as global action potential of the cochlear nerve, is generated by all cochlear

In endolymphatic hydrops, due to the increased pressure in scala media, basilar membrane vibrates asymmetrical. These changes of the traveling wave lead to several dysfunctions: distorted cochlear microphonics, enlargement of the summating potential and broadening of the

global action potential. Its origin lies into the inner ear hair cells and cochlear nerve. Global action potential consists of presynaptic and postsynaptic potentials (**Figure 8**).

nerve fibers, fired in synchrony by the acoustic stimulus.

action potential. Magnitude of the AP compared with SP (SP/AP ratio) is increased in endolymphatic hydrops (>30%). The SP/AP amplitude ratio has 50–60% sensitivity in Ménière's disease diagnosis and 95% specificity in Refs. [11, 12] (**Figure 9**).

Recently, an area ratio (**Figure 10**) seems to be a more sensitive parameter for detecting endolymphatic hydrops [13]. An increase of more than 2 of SP/AP area together with the increase of SP/AP amplitude ratio increases sensitivity and specificity in Menière's disease diagnosis to 92 and 83.9%, respectively [14]. Some EP machines enabled automatically measurement of the area ratio.

**Figure 10.** SP/AP area ratio (www.nervecenter.natus.com).
