**2. Investigations used to support the diagnosis of Meniere's disease**

As of now, no single test can claim to make a reliable diagnosis of Meniere's disease; rather it is based on a complete history with a detailed description of the pattern of disease presentation, supported by quantitative testing.

In 1972, a diagnostic criterion for Meniere's disease was proposed by American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and till date, it has been revised twice in the years 1985 and 1995 [5].

The latest criteria used for diagnosis of Meniere's disease are the one proposed by AAO-HNS in the year 1995 [5].

AAO-HNS (1995) also introduced a staging system for cases of definite Meniere's disease. Staging is based solely on hearing, which is the most readily measurable variable and most closely related to the natural history of the disease [17].

Stages 1 and 2 are considered representative of early reversible disease that is susceptible to remission, whereas stages 3 and 4 are considered fixed or not reversible.

A good classic history with the criteria as outlined by AAO-HNS is adequate for diagnosing a case of Meniere's disease.

#### **2.1. Pure tone audiometry (PTA).**

PTA is the elementary investigation for reaching at a diagnosis and following up the patient during the course of treatment. A four-tone average of 0.5, 1, 2 and 3 kHz has been adopted in the guidelines of AAO-HNS (1985, 1995), and a change of 10 dB or more in PTA or a greater than 15% change in word recognition score is considered a clinically significant change during diagnosis and treatment [5].

Pure tone audiometry is the primary tool applied by the clinicians to ascertain hearing thresholds of the patient. It is used to document the degree and type of auditory impairment. These elements along with shape of the audiogram lay the ground for designing and implementing a line of treatment. This investigation is principally used in adults and grown-up children as PTA is dependent on patient's cooperation and his/her response to the pure tone signals [7].

Pure tone audiometry has assumed an established role in diagnosis of hearing impairment. Pre-calibrated pure tones are presented to the patient in sound-treated chambers. Circumaural headphones, insert phones and bone oscillators are used to deliver these tones to patient to determine air-conduction and bone-conduction thresholds across a frequency range from 250 to 8000 Hz. The thresholds are recorded in terms of decibel HL. Specific algorithms are available to determine need for masking the non-test ear when asymmetrical hearing presents the risk of cross hearing. Procedures and formulae are available to calculate the initial masking levels needed both for air-conduction and for masking levels to determine masked thresholds. The thresholds so detected are plotted on an audiogram using standardized symbols. Air-conduction thresholds tell about the degree, and bone-conduction thresholds convey type of hearing loss.

Apart from the degree of hearing loss, the pattern of audiogram tells about the type of hearing loss, whether it is conductive, sensorineural or mixed. Pure tone audiometry is regarded by some as initial screening test of choice for audiological dysfunction [18].

Staging of Definite Meniere's disease may be done in all the patients on the basic degree of hearing loss.


The hearing loss in Meniere's disease is unilateral in about 70–85% of cases. However, the incidence of bilaterality increases with the duration of the disease, reaching about 40% after 15 years [19].

Audiograms are performed at different points during the course or progression of disease, and the hearing loss shows a fluctuating pattern. During the initial stages of the disease, if the PTA is performed after an episode has subsided, the audiogram may look to be normal. As the patient continues to experience more and more attacks, some degree of hearing loss tends to persist in between the attacks. However, in the later stages of the disease, the hearing loss establishes as non-fluctuating and permanent [20].

In the early stages of Meniere's disease, the characteristic audiometric configuration is a rising curve, that is, as the frequency increases, the hearing loss decreases. This contour has also been called a "reverse slope" audiogram, since high-frequency losses are by far the most frequent pattern in the hearing-impaired population. Word recognition (discrimination) has been reported in some studies as poor as 32%. Although mid- and high-frequency sensitivity tends to be good in the early stages, as the disease progresses, these frequencies become involved, leaving the patient with a "flat" audiometric configuration. The hearing loss may progress to a profoundly impaired degree as the disease process continues. However, the degree of hearing loss seldom exceeds a 70 dB average [21].

There is no classical audiogram pattern that can be used to identify Meniere's disease. However, there are certain features that have been commonly observed. These include:


**2. Investigations used to support the diagnosis of Meniere's disease**

tion, supported by quantitative testing.

closely related to the natural history of the disease [17].

remission, whereas stages 3 and 4 are considered fixed or not reversible.

in the years 1985 and 1995 [5].

a case of Meniere's disease.

**2.1. Pure tone audiometry (PTA).**

ing diagnosis and treatment [5].

of hearing loss.

in the year 1995 [5].

74 Up to Date on Meniere's Disease

As of now, no single test can claim to make a reliable diagnosis of Meniere's disease; rather it is based on a complete history with a detailed description of the pattern of disease presenta-

In 1972, a diagnostic criterion for Meniere's disease was proposed by American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and till date, it has been revised twice

The latest criteria used for diagnosis of Meniere's disease are the one proposed by AAO-HNS

AAO-HNS (1995) also introduced a staging system for cases of definite Meniere's disease. Staging is based solely on hearing, which is the most readily measurable variable and most

Stages 1 and 2 are considered representative of early reversible disease that is susceptible to

A good classic history with the criteria as outlined by AAO-HNS is adequate for diagnosing

PTA is the elementary investigation for reaching at a diagnosis and following up the patient during the course of treatment. A four-tone average of 0.5, 1, 2 and 3 kHz has been adopted in the guidelines of AAO-HNS (1985, 1995), and a change of 10 dB or more in PTA or a greater than 15% change in word recognition score is considered a clinically significant change dur-

Pure tone audiometry is the primary tool applied by the clinicians to ascertain hearing thresholds of the patient. It is used to document the degree and type of auditory impairment. These elements along with shape of the audiogram lay the ground for designing and implementing a line of treatment. This investigation is principally used in adults and grown-up children as PTA is dependent on patient's cooperation and his/her response to the pure tone signals [7]. Pure tone audiometry has assumed an established role in diagnosis of hearing impairment. Pre-calibrated pure tones are presented to the patient in sound-treated chambers. Circumaural headphones, insert phones and bone oscillators are used to deliver these tones to patient to determine air-conduction and bone-conduction thresholds across a frequency range from 250 to 8000 Hz. The thresholds are recorded in terms of decibel HL. Specific algorithms are available to determine need for masking the non-test ear when asymmetrical hearing presents the risk of cross hearing. Procedures and formulae are available to calculate the initial masking levels needed both for air-conduction and for masking levels to determine masked thresholds. The thresholds so detected are plotted on an audiogram using standardized symbols. Air-conduction thresholds tell about the degree, and bone-conduction thresholds convey type

• The audiogram may be "flat," upward sloping or downward sloping.

In a study of 211 consecutive patients with classic Meniere's disease, the audiological pattern was flat in 42%, peaked type in 32%, downward sloping in 19% and rising in 7% patients [22].

In a study conducted in our department, 31 patients of either sex between the age group of 18 and 65 years presenting with history of attacks of vertigo, accompanied with tinnitus, sensorineural hearing loss and aural fullness were selected randomly; 64% of these patients had either a flat audiometric graph or a low-frequency hearing loss as evidenced by downward sloping audiometric pattern. In this study, in 18 patients, the duration of symptoms was less than 12 months. In these 18 patients, 29 ears were affected; of these, 45% ears had rising or peak type of audiograms. Further analysis of the audiometric pattern in this study revealed that in patients with sudden onset of symptoms, 50% ears showed either a rising or a peak type of graph. On the contrary, among those patients with gradual onset of symptoms, 76% ears showed a flat or sloping type of graph. This correlates with the findings of a study which concluded that rising or peak audiograms appear more commonly in patients with disease of short duration [23].

In a study comprising of 111 patients with Meniere's disease, pure tone and speech audiometry was performed. The affected ears showed reduced hearing in both the modalities. An objective classification method used to determine audiogram shape indicated that affected ears more frequently show "low" or "low + high" hearing losses. The study concluded that shape of hearing loss does not depend on duration of affection of disease [24].

#### **2.2. Short increment sensitivity index test (SISI)**

It is a useful test in distinguishing between cochlear and retro-cochlear lesion. It determines the capacity of a patient to detect a brief 1 dB increment at a 20 dB supra-threshold tone (called carrier tone) in various frequencies (preferably at 1000 and 4000 Hz). If SISI score is above 70%, it is considered as positive SISI and pathology lies in the cochlea. If SISI score is <30%, it is negative SISI and here pathology lies elsewhere than inner ear [18].

On the basis of PTA report, all the patients suffering from sensorineural hearing loss may further be subjected to glycerol test.

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

The assumption that an increase in endolymph volume, with its effect on labyrinthine membrane behavior producing in part, the hearing loss and vestibular deficit in Meniere's disease has led to the administration of dehydrating agents like glycerol. The goal is to reduce the volume abnormalities in inner ear and produce a measurable change in response that is improvement in behavioral audiometric test scores.

Glycerol, a potent osmolar agent, elevates osmotic pressure of the liquid in which it is dissolved. In the cochlear context, upon administration to a patient it lowers the volume of membranous labyrinth. Animal studies in which endolymphatic hydrops was induced surgically, responded to glycerol through intracellular and extracellular edema. The increased secretion of glycoproteins following administration of glycerol induces endolymph flow into endolymphatic sac. Thus, glycerol promotes the absorption of endolymph both in radial and in longitudinal directions [25]. This is a simple and rapid method that provides information on the cochlear response to the osmotic changes produced by glycerol in the inner ear.

Glycerol is administered orally to patients to reduce fluid abnormalities in the inner ear. It affects hearing temporarily (for a few hours), the results of which are measured by audiogram.

#### **2.4. Method of glycerol test**

sensorineural hearing loss and aural fullness were selected randomly; 64% of these patients had either a flat audiometric graph or a low-frequency hearing loss as evidenced by downward sloping audiometric pattern. In this study, in 18 patients, the duration of symptoms was less than 12 months. In these 18 patients, 29 ears were affected; of these, 45% ears had rising or peak type of audiograms. Further analysis of the audiometric pattern in this study revealed that in patients with sudden onset of symptoms, 50% ears showed either a rising or a peak type of graph. On the contrary, among those patients with gradual onset of symptoms, 76% ears showed a flat or sloping type of graph. This correlates with the findings of a study which concluded that rising or peak audiograms appear more commonly in patients with disease of

In a study comprising of 111 patients with Meniere's disease, pure tone and speech audiometry was performed. The affected ears showed reduced hearing in both the modalities. An objective classification method used to determine audiogram shape indicated that affected ears more frequently show "low" or "low + high" hearing losses. The study concluded that

It is a useful test in distinguishing between cochlear and retro-cochlear lesion. It determines the capacity of a patient to detect a brief 1 dB increment at a 20 dB supra-threshold tone (called carrier tone) in various frequencies (preferably at 1000 and 4000 Hz). If SISI score is above 70%, it is considered as positive SISI and pathology lies in the cochlea. If SISI score is <30%, it

On the basis of PTA report, all the patients suffering from sensorineural hearing loss may

The assumption that an increase in endolymph volume, with its effect on labyrinthine membrane behavior producing in part, the hearing loss and vestibular deficit in Meniere's disease has led to the administration of dehydrating agents like glycerol. The goal is to reduce the volume abnormalities in inner ear and produce a measurable change in response that is improve-

Glycerol, a potent osmolar agent, elevates osmotic pressure of the liquid in which it is dissolved. In the cochlear context, upon administration to a patient it lowers the volume of membranous labyrinth. Animal studies in which endolymphatic hydrops was induced surgically, responded to glycerol through intracellular and extracellular edema. The increased secretion of glycoproteins following administration of glycerol induces endolymph flow into endolymphatic sac. Thus, glycerol promotes the absorption of endolymph both in radial and in longitudinal directions [25]. This is a simple and rapid method that provides information on

Glycerol is administered orally to patients to reduce fluid abnormalities in the inner ear. It affects hearing temporarily (for a few hours), the results of which are measured by audiogram.

the cochlear response to the osmotic changes produced by glycerol in the inner ear.

shape of hearing loss does not depend on duration of affection of disease [24].

is negative SISI and here pathology lies elsewhere than inner ear [18].

**2.2. Short increment sensitivity index test (SISI)**

further be subjected to glycerol test.

ment in behavioral audiometric test scores.

**2.3. Glycerol test**

short duration [23].

76 Up to Date on Meniere's Disease

The patients are advised to report empty stomach on the day of investigation. PTA test is performed before the administration of glycerol and then patient is administered a solution of 86% of glycerol (1.5 mg/kg of body weight) dissolved in equal volume of physiological saline.

Pure tone audiometry is then repeated at 1, 2 and 3 hours of glycerol administration.

The glycerol test is regarded as positive:


In the study conducted at our department (whose results have yet to be published), only those patients were included who had definite Meniere's disease based on the AAO-HNS criteria. All these patients were subjected to glycerol testing to determine their suitability for administration of hydrochlorothiazide. In this study, 74% of patients had a positive glycerol test.

Another study has reported its experience of using the glycerol test in 122 patients with combination of sensorineural hearing loss, tinnitus or vestibular symptoms, in which endolymphatic hydrops was considered a possibility. Fifty percent of patients ultimately were found to have endolymphatic hydrops and positive test [28].

In a study of series of 95 patients with Meniere's disease, 47% were found to have a positive glycerol dehydration test. Yet another study reported that 60% of patients with Meniere's disease have positive tests. This study also noted that positive tests were found only in ears with Meniere's disease [29]. In another study, intravenous administration of glycerol was performed instead of oral administration. Positive results were obtained in 50% (15 out of 30) of patients 1 hour after administration. The positive ratio was same as oral glycerol test [30]. Thus, the results of glycerol testing in our study are comparable with other studies. The relatively higher percentage of positive glycerol test in our study could be due to the fact that subjects included in our study met the criteria of "definite Meniere's disease" as laid down by AAO-HNS. In our study, the results of administration of hydrochlorothiazide to patients who tested positive on glycerol testing indicate an across the board improvement in symptoms of Meniere's disease at the end of follow-up. Thus, it may be concluded that glycerol testing in patients with "definite Meniere's disease" as assessed by AAO-HNS criteria is a good idea to select patients who will respond to administration of osmotic diuretics.

Most patients may suffer headache and nausea after drinking the glycerol for post-glycerol audiometric evaluation, which usually subsides after few hours.

## **3. Speech audiometry**

The objective of speech audiometry testing is to measure patient's ability to identify speech stimuli, to confirm results of pure tone audiometry and to rule out the presence of nonorganic hearing loss or retro-cochlear pathology.

The battery of speech audiometry tests includes speech detection threshold (SDT), speech recognition threshold (SRT) and word recognition score (WRS).

Word recognition test scores are often plotted on a graph. A point on this graph represents the percentage words correctly repeated by the patient at a specified intensity level from completed standardized list of words. Cochlear pathology tends to demonstrate a "plateau effect," reaching a ceiling of performance at <100% and no improvement in the score despite a rise in intensity.
