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Audiological Findings of Prolonged Ménière's Disease
Auris ' Nasus' Larynx (Tokyo) 17, 157-163 (1990)
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE Hideji OKUNO, M.D.* and Isamu WATANABE, M.D.**
*Department of Otolaryngology and ** Professor emeritus, Tokyo Medical & Dental University, School of Medicine, Tokyo, Japan
As Meniere's disease progresses, the fluctuations becomes less marked and the hearing level gradually declines. In the more established and advanced stages of the disease, a permanent and progressive hearing loss develops. It has been reported, however, that hearing acuity in some patients with Meniere's disease significantly improved after having had the disorder for many years. Such observation suggests that the inner ear pathology in late stages of Meniere's disease may not be necessarily irreversible. The purpose of this investigation was to assess whether or not various audiological evaluations including EcochG may be of value in predicting the irreversibility of hearing deficit in patients suffering from advanced stages of Meniere's disease. The audiological studies included pure tone audiogram, SISI test, Bekesy audiometry, glycerol (or urea) test, speech discrimination test, and electrocochleography. A combination of the recruiting type of response in the EcochG and the narrowing of the tracing width of continuous sound in the Bekesy pattern seemed to be indicative for irreversible hair cell damages. Patients who had a low score in the speech discrimination test as well as an absence of ABR response were suspected of having retrocochlear lesions. Our investigations suggest that the irreversibility of hearing impairment inpatients with later stages of Meniere's disease may be predicted to some extent in the use of various audiological evaluations including the EcochG. Meniere's disease is characterized by vertigo, hearing loss, and pressure in the involved ear. Each of the symptom has two common features, namely discontinuity and variability in intensity. Early in the course of the disease, deafness is primarily sensorineural in character and fluctuating. Late in the disease, when Received for publication January 8, 1990 This paper was presented at the 43rd Annual Meeting of the Canadian Society of Otolaryngology-Head & Neck Surgery, held in Tronto on April 30th to May 3rd, 1989. 157
H. OKUNO and I. WATANABE
158
fluctuation decreases and function of the inner ear is progressively destroyed, vertiginous attack subsides and a permanent hearing loss develops, which is usually at about 50-60 dB HL with flat or downward slope type in audiogram (FRIBERG, STAHLE, and SVEDBERG, 1984). In some patients, however, improvement in hearing may occur after a prolonged period of steady hearing deficit, suggesting that cochlear pathology in late stages of Meniere's disease may not be necessarily of an irreversible process (UEMURA, 1976). In this paper, an attempt has been made to determine whether or not various audiological evaluations including electrocochleogram may be of value in predicting the reversibility of hearing impairment in patients suffering from prolonged Meniere's disease. MATERIALS AND METHODS
Subjects consisted of 12 ears from 11 patients who were diagnosed as having Meniere's disease according to the criteria established for Meniere's disease by Meniere's disease Research Committee of Japan (WATANABE, 1980). Of these patients, 12 ears which met the following conditions were selected for this study: 1) duration of the disease ranging from three to 30 years, 2) hearing thresholds at about 60 dB with a flat or downward slope pattern in audiogram, and 3) absence of fluctuation of hearing at least for a period of 6 months prior to this study (see Table 1). Although most of these patients still experienced vertigo to some extent, the vertiginous attacks were of mild disequilibrium in nature rather than definitive spells when this evaluation was made. The 12 patients were sorted into four groups: A, B, C, and D. Group A, B, and C consisted of patients with bilateral disease, and subjects in group D were those of unilateral involvement. Among the patients with bilateral disease, Table 1. Objects of this study. * Tinnitus loundness were subjectively rated according to the scoring (0: very quie-4: very loud) by the standard method for tinnitus examination in 1984. Case
Side
Years
Sex
Duration
Vertigo
Tinnitus*
HM YH OH KA
R L R L
58 38 67 53
CS CS CS CS
14 years ( 1) ( 9) 3 11 (30) (30) 4
2 1 0
TH
R L
51
~
20 20
C
WS OS
L L
56 69
~ ~
30 6
+ + + + + + + +
~ CS ~ CS
6
4 8 3
+
D
IS AK OT TK
A
B
R
43
L
72
L L
66 55
+ + +
2 2 2 3 3
3 4
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
159
those in the group A had nearly total deafness in either ear due to advanced stage of Meniere's disease or labyrinthectomy; those in the group B had an approximately similar degree of hearing loss in both ears; subjects among the group C presented an early stage of the disease in one ear. Audiological evaluation carried out included electrocochleography and glycerol (or urea) tests as well as conventional pure tone, speech discrimination tests, SISI tests, and Bekesy audiograms. The electrocochleography (EcochG) was recorded in the external ear canal using a silver electrode. Click (0.125 ms rectangular pulse) of an intensity of 115 dB peSPL was applied as an acoustic stimulation. Responses were obtained at click rates of 10 per s. For further evaluation of the configuration of compound action potential, inter stimulus interval (lSI) were changed from 10 to 100 per s. Results obtained were analyzed according to YOSHIE'S description for electrocochleographic classification of sensorineural defects (1976). RESULTS
The audiograms of 12 ears selected for this study (see Fig. I) were characteristically of fiat or downward slope pattern, with their thresholds being at about 60 dB HL. The SISI tests gave a score higher than 80 % in all the ears tested. The Bekesy audiometry showed a type II in 11 ears and a type I in 1 ear; its width of continuous sound was more than 3 dB in 9 ears and less than 2 dB in 2 ears (Fig. 2). The glycerol test was positive only in 2 patients. The speech discrimination scores ranged from 35 to 90 %, the word intelligibility curves (speech discrimination curve) being normal except for 3 ears which showed rollover curve (Fig. 3). The results of EcochG were described as: broad response in 5 ears, complex re-10
o
10 20
30 40 50
- ---
"~
60 70 80 0 100
""':--
""
/,
=< =-:"--
.-/
~
~
"" ---...
D<"
L.
~
~
~ ~
.;:/ ~ .......
11 0 125
250
500
1000
2000
4000
Frequency in Hertz (Hz)
Fig. 1. Pure tone audio grams of 12 ears.
8000
H. OKUNO and I. WATANABE
160
Fig. 2. Representative Bekesy audiogram of type II. Width of tracing of continuous sound is more than 3 dB (upper trace) in 9 case and less than 2 dB (lower trace) in 2 cases. % 100'-~--~--~~~ i --~--~--~~----------'
. ,-._- -~.-.--j-! -.--.--; .
...... ....
.:0 V)
~
50
.i
c
j
i!E :E i2i2
_J
I. _. [I.-
~
co
0
f.
o
10
MDIII.Il tll111SIOlO
1001 en PC 1.
20
30
SPEECH SOUND LEVEL
Fig. 3. Speech discrimination curves of 12 ears.
sponse in 5 ears, and recruiting response in 2 ears. Confirmed by altering the lSI, the broad and complex responses were found to be composed of action potential (AP) and summating potential (SP). The recruiting response showed two types: normal latency of AP and delayed latency (Fig. 4). The results of all the investigations performed were summarized in Table 2. COMMENTS
Fluctuation in hearing, one of the characteristic findings of Meniere's disease, is rather uncommon iIi late stages of the disease. However, in some patients a significant improvement of hearing loss occurred after having had Meniere's disease with a steady hearing deficit for many years (UEMURA, 1976). Therefore,
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
161
~~ 1 ms
~ Fig. 4. EcochG: broad response, complex response, recruiting response with normal latency, recruiting response with delayed latency, and normal ear's response, from top to bottom, respectively.
Table 2. Summarized table of 12 ears. * Tinnitus loundness were subjectively rated according to the scoring (0: very quiet-4: very loud) by the standard method for tinnitus examination in 1984. Case
HM
Side Years Sex
Duration Tinnitus·
SISI
Bekesy (width) II (4) II (5) II (5) II (4)
1/
Urea test
EcochG
R L R L
58 38 67 53
3 3 3 3
14 years ( 1) ( 9) 3 (30) 11 (30) 4
0 1
Positive Positive Positive Positive
R L
51
~
20 20
2 2
Positive Positive
WS OS
L L
56 69
~ ~
30 6
2 3
Positive
/ /
Recruiting Broad
IS AK OT TK
R L L L
43 72 66 55
~
6 4 8 3
3 3 1 4
Positive Positive Positive Positive
II (5) II (2) II (5) II (5)
Complex Recruiting Complex Complex
YK OH KA TH
3 ~
3
2
II (5) II (2)
+ +
Broad Complex Complex Broad Broad Broad
162
H. OKUNO and I. WATANABE
it would be of great benefit to come up with an objective method of assessing the potential reversibility of hearing impairment in advanced stage of Meniere's disease. Our investigations performed here represented audiological findings consistent with advanced stage of Meniere's disease, indicating basically dysfunction ofthe cochlea alone. Of the 12 ears affected with the disorder, the narrowing of the tracing width of continuous sound in the Bekesy tracing and recruiting type of EcochG were observed in two ears from two patients (WS, AK). This "narrowing" of width of the Bekesy tracing was considered to be an indication of a reduced difference limen for intensity at threshold. The recruiting type of the EcochG has been described as sensory unit loss as well as irreversible lesions (YOSHIE, 1976). Such observations suggest irreversible process of the inner ear with severe hair cell damage in the two subjects studied here. One of them (AK) was the oldest of all the patients and the other (WS) had the longest history of the disorder (30 years) in the group. As for the result of EcochG, the other 10 subjects showed the broad or complex response. YOSHIE (1976) described the two basic types of abnormal pattern of EcochG in sensorineural hearing losses, that is sense-organ malfunction type (broad response) and subtractive loss type (recruiting response). Moreover, he mentioned the mixed type (complex response), in which broad and recruiting response were mixed with each other in any combination. In our series, complex response were seemed to be mainly composed of negative SP according to the result of changing lSI. A combination of low speech discrimination score and an absence of ABR response was found in two patients (IS, HM), both of whom had the type II Bekesy pattern and a high score of SISI test. SATOH, SUZUKI, YAHATA, KIMURA, and HATSUSHIKA (1985), in his study of five patients with essentially retrocochlear lesion, reported that a considerably low score in the speech discrimination test based on the result of pure tone audiogram, a broad AP in EcochG and an absence of ABR response were among the characteristic features associated with the retrocochlear disease. In his paper he believed that the most peripheral part of the auditory nerve was involved with the lesion. Describing pathological findings of patients with advanced Meniere's disease who had a downward slope pattern in the audiogram and a low score in the speech discrmination test, NADOL and THORNTON (1987) made a point of the decreased number of synapses of afferent neurons in the ear affected with the disorder. These published studies suggested that there were also irreversible process in the last two patients in our series who had a low score in the speech discrimination test and who had no response in ABR. Osmotic loading test, an indicator of endolymphatic hydrops, has been effective in the assessment of the potential reversibility of the hearing deficit in the early stage of Meniere's disease. Although there were two patients who demonstrated a positive result in glycerol test in this series, neither of them improved
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
163
their hearing loss. Glycerol dehydration test may be of little value in predicting reversibility of hearing deficit associated with advanced stage of Meniere's disease. The number of patients studied here may not be large enough to propose an objective method to aid in differentiation of reversible from irreversible lesion. However, our investigation brings about a prospect that may lead to a challenge in the assessment of the hearing acuity in later stages of Meniere's disease. The authors wish to express their deep gratitude to Nobuhiro Tokuta, M.D., F.A.CS., for giving helpful criticism during the preparation of this paper.
REFERENCES FRIBERG, U., STAHLE, J., and SVEDBERG, A.: The natural course of Meniere's disease. Acta Otolaryngol. Suppl. 406: 72-77, 1984. NADOL, J. B., and THORNTON, A. R.: Ultrastructural findings in a case of Meniere's disease. Ann. Otol. Rhinol. Laryngol. 96: 449-453, 1987. SATOH, T., SUZUKI, R., YAHATA, N., KIMURA, R., and RATSUSHIKA, S.: Audiological findings in patients with essential retrocochlear lesions. Audiol. Jpn. 28: 758-771, 1985. UEMURA, T.: Treatment for the Meniere's disease. Oto-Rhino-Laryngol. Tokyo 19: 386, 1976. WATANABE, I.: Meniere's disease-With special emphasis on epidemiology, diagnosis and prognosis. ORL 42: 20-45, 1980. YOSHIE, N.: Electrocochleographic classification of sensorineural defects: Pathological pattern of the cochlear nerve compound action potential in man. In Electrocochleography (Ruben, R. J., Elberling, C, and Salmon, G., eds.), University Park Press, Baltimore/London/ Tokyo, 1976.
Request reprints to:
Dr. R. Okuno, Department of Otolaryngology, Tokyo Medical & Dental University, 5-45, Yushima l-chome, Bunkyo-ku, Tokyo 113, Japan
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE Hideji OKUNO, M.D.* and Isamu WATANABE, M.D.**
*Department of Otolaryngology and ** Professor emeritus, Tokyo Medical & Dental University, School of Medicine, Tokyo, Japan
As Meniere's disease progresses, the fluctuations becomes less marked and the hearing level gradually declines. In the more established and advanced stages of the disease, a permanent and progressive hearing loss develops. It has been reported, however, that hearing acuity in some patients with Meniere's disease significantly improved after having had the disorder for many years. Such observation suggests that the inner ear pathology in late stages of Meniere's disease may not be necessarily irreversible. The purpose of this investigation was to assess whether or not various audiological evaluations including EcochG may be of value in predicting the irreversibility of hearing deficit in patients suffering from advanced stages of Meniere's disease. The audiological studies included pure tone audiogram, SISI test, Bekesy audiometry, glycerol (or urea) test, speech discrimination test, and electrocochleography. A combination of the recruiting type of response in the EcochG and the narrowing of the tracing width of continuous sound in the Bekesy pattern seemed to be indicative for irreversible hair cell damages. Patients who had a low score in the speech discrimination test as well as an absence of ABR response were suspected of having retrocochlear lesions. Our investigations suggest that the irreversibility of hearing impairment inpatients with later stages of Meniere's disease may be predicted to some extent in the use of various audiological evaluations including the EcochG. Meniere's disease is characterized by vertigo, hearing loss, and pressure in the involved ear. Each of the symptom has two common features, namely discontinuity and variability in intensity. Early in the course of the disease, deafness is primarily sensorineural in character and fluctuating. Late in the disease, when Received for publication January 8, 1990 This paper was presented at the 43rd Annual Meeting of the Canadian Society of Otolaryngology-Head & Neck Surgery, held in Tronto on April 30th to May 3rd, 1989. 157
H. OKUNO and I. WATANABE
158
fluctuation decreases and function of the inner ear is progressively destroyed, vertiginous attack subsides and a permanent hearing loss develops, which is usually at about 50-60 dB HL with flat or downward slope type in audiogram (FRIBERG, STAHLE, and SVEDBERG, 1984). In some patients, however, improvement in hearing may occur after a prolonged period of steady hearing deficit, suggesting that cochlear pathology in late stages of Meniere's disease may not be necessarily of an irreversible process (UEMURA, 1976). In this paper, an attempt has been made to determine whether or not various audiological evaluations including electrocochleogram may be of value in predicting the reversibility of hearing impairment in patients suffering from prolonged Meniere's disease. MATERIALS AND METHODS
Subjects consisted of 12 ears from 11 patients who were diagnosed as having Meniere's disease according to the criteria established for Meniere's disease by Meniere's disease Research Committee of Japan (WATANABE, 1980). Of these patients, 12 ears which met the following conditions were selected for this study: 1) duration of the disease ranging from three to 30 years, 2) hearing thresholds at about 60 dB with a flat or downward slope pattern in audiogram, and 3) absence of fluctuation of hearing at least for a period of 6 months prior to this study (see Table 1). Although most of these patients still experienced vertigo to some extent, the vertiginous attacks were of mild disequilibrium in nature rather than definitive spells when this evaluation was made. The 12 patients were sorted into four groups: A, B, C, and D. Group A, B, and C consisted of patients with bilateral disease, and subjects in group D were those of unilateral involvement. Among the patients with bilateral disease, Table 1. Objects of this study. * Tinnitus loundness were subjectively rated according to the scoring (0: very quie-4: very loud) by the standard method for tinnitus examination in 1984. Case
Side
Years
Sex
Duration
Vertigo
Tinnitus*
HM YH OH KA
R L R L
58 38 67 53
CS CS CS CS
14 years ( 1) ( 9) 3 11 (30) (30) 4
2 1 0
TH
R L
51
~
20 20
C
WS OS
L L
56 69
~ ~
30 6
+ + + + + + + +
~ CS ~ CS
6
4 8 3
+
D
IS AK OT TK
A
B
R
43
L
72
L L
66 55
+ + +
2 2 2 3 3
3 4
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
159
those in the group A had nearly total deafness in either ear due to advanced stage of Meniere's disease or labyrinthectomy; those in the group B had an approximately similar degree of hearing loss in both ears; subjects among the group C presented an early stage of the disease in one ear. Audiological evaluation carried out included electrocochleography and glycerol (or urea) tests as well as conventional pure tone, speech discrimination tests, SISI tests, and Bekesy audiograms. The electrocochleography (EcochG) was recorded in the external ear canal using a silver electrode. Click (0.125 ms rectangular pulse) of an intensity of 115 dB peSPL was applied as an acoustic stimulation. Responses were obtained at click rates of 10 per s. For further evaluation of the configuration of compound action potential, inter stimulus interval (lSI) were changed from 10 to 100 per s. Results obtained were analyzed according to YOSHIE'S description for electrocochleographic classification of sensorineural defects (1976). RESULTS
The audiograms of 12 ears selected for this study (see Fig. I) were characteristically of fiat or downward slope pattern, with their thresholds being at about 60 dB HL. The SISI tests gave a score higher than 80 % in all the ears tested. The Bekesy audiometry showed a type II in 11 ears and a type I in 1 ear; its width of continuous sound was more than 3 dB in 9 ears and less than 2 dB in 2 ears (Fig. 2). The glycerol test was positive only in 2 patients. The speech discrimination scores ranged from 35 to 90 %, the word intelligibility curves (speech discrimination curve) being normal except for 3 ears which showed rollover curve (Fig. 3). The results of EcochG were described as: broad response in 5 ears, complex re-10
o
10 20
30 40 50
- ---
"~
60 70 80 0 100
""':--
""
/,
=< =-:"--
.-/
~
~
"" ---...
D<"
L.
~
~
~ ~
.;:/ ~ .......
11 0 125
250
500
1000
2000
4000
Frequency in Hertz (Hz)
Fig. 1. Pure tone audio grams of 12 ears.
8000
H. OKUNO and I. WATANABE
160
Fig. 2. Representative Bekesy audiogram of type II. Width of tracing of continuous sound is more than 3 dB (upper trace) in 9 case and less than 2 dB (lower trace) in 2 cases. % 100'-~--~--~~~ i --~--~--~~----------'
. ,-._- -~.-.--j-! -.--.--; .
...... ....
.:0 V)
~
50
.i
c
j
i!E :E i2i2
_J
I. _. [I.-
~
co
0
f.
o
10
MDIII.Il tll111SIOlO
1001 en PC 1.
20
30
SPEECH SOUND LEVEL
Fig. 3. Speech discrimination curves of 12 ears.
sponse in 5 ears, and recruiting response in 2 ears. Confirmed by altering the lSI, the broad and complex responses were found to be composed of action potential (AP) and summating potential (SP). The recruiting response showed two types: normal latency of AP and delayed latency (Fig. 4). The results of all the investigations performed were summarized in Table 2. COMMENTS
Fluctuation in hearing, one of the characteristic findings of Meniere's disease, is rather uncommon iIi late stages of the disease. However, in some patients a significant improvement of hearing loss occurred after having had Meniere's disease with a steady hearing deficit for many years (UEMURA, 1976). Therefore,
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
161
~~ 1 ms
~ Fig. 4. EcochG: broad response, complex response, recruiting response with normal latency, recruiting response with delayed latency, and normal ear's response, from top to bottom, respectively.
Table 2. Summarized table of 12 ears. * Tinnitus loundness were subjectively rated according to the scoring (0: very quiet-4: very loud) by the standard method for tinnitus examination in 1984. Case
HM
Side Years Sex
Duration Tinnitus·
SISI
Bekesy (width) II (4) II (5) II (5) II (4)
1/
Urea test
EcochG
R L R L
58 38 67 53
3 3 3 3
14 years ( 1) ( 9) 3 (30) 11 (30) 4
0 1
Positive Positive Positive Positive
R L
51
~
20 20
2 2
Positive Positive
WS OS
L L
56 69
~ ~
30 6
2 3
Positive
/ /
Recruiting Broad
IS AK OT TK
R L L L
43 72 66 55
~
6 4 8 3
3 3 1 4
Positive Positive Positive Positive
II (5) II (2) II (5) II (5)
Complex Recruiting Complex Complex
YK OH KA TH
3 ~
3
2
II (5) II (2)
+ +
Broad Complex Complex Broad Broad Broad
162
H. OKUNO and I. WATANABE
it would be of great benefit to come up with an objective method of assessing the potential reversibility of hearing impairment in advanced stage of Meniere's disease. Our investigations performed here represented audiological findings consistent with advanced stage of Meniere's disease, indicating basically dysfunction ofthe cochlea alone. Of the 12 ears affected with the disorder, the narrowing of the tracing width of continuous sound in the Bekesy tracing and recruiting type of EcochG were observed in two ears from two patients (WS, AK). This "narrowing" of width of the Bekesy tracing was considered to be an indication of a reduced difference limen for intensity at threshold. The recruiting type of the EcochG has been described as sensory unit loss as well as irreversible lesions (YOSHIE, 1976). Such observations suggest irreversible process of the inner ear with severe hair cell damage in the two subjects studied here. One of them (AK) was the oldest of all the patients and the other (WS) had the longest history of the disorder (30 years) in the group. As for the result of EcochG, the other 10 subjects showed the broad or complex response. YOSHIE (1976) described the two basic types of abnormal pattern of EcochG in sensorineural hearing losses, that is sense-organ malfunction type (broad response) and subtractive loss type (recruiting response). Moreover, he mentioned the mixed type (complex response), in which broad and recruiting response were mixed with each other in any combination. In our series, complex response were seemed to be mainly composed of negative SP according to the result of changing lSI. A combination of low speech discrimination score and an absence of ABR response was found in two patients (IS, HM), both of whom had the type II Bekesy pattern and a high score of SISI test. SATOH, SUZUKI, YAHATA, KIMURA, and HATSUSHIKA (1985), in his study of five patients with essentially retrocochlear lesion, reported that a considerably low score in the speech discrimination test based on the result of pure tone audiogram, a broad AP in EcochG and an absence of ABR response were among the characteristic features associated with the retrocochlear disease. In his paper he believed that the most peripheral part of the auditory nerve was involved with the lesion. Describing pathological findings of patients with advanced Meniere's disease who had a downward slope pattern in the audiogram and a low score in the speech discrmination test, NADOL and THORNTON (1987) made a point of the decreased number of synapses of afferent neurons in the ear affected with the disorder. These published studies suggested that there were also irreversible process in the last two patients in our series who had a low score in the speech discrimination test and who had no response in ABR. Osmotic loading test, an indicator of endolymphatic hydrops, has been effective in the assessment of the potential reversibility of the hearing deficit in the early stage of Meniere's disease. Although there were two patients who demonstrated a positive result in glycerol test in this series, neither of them improved
AUDIOLOGICAL FINDINGS OF PROLONGED MENIERE'S DISEASE
163
their hearing loss. Glycerol dehydration test may be of little value in predicting reversibility of hearing deficit associated with advanced stage of Meniere's disease. The number of patients studied here may not be large enough to propose an objective method to aid in differentiation of reversible from irreversible lesion. However, our investigation brings about a prospect that may lead to a challenge in the assessment of the hearing acuity in later stages of Meniere's disease. The authors wish to express their deep gratitude to Nobuhiro Tokuta, M.D., F.A.CS., for giving helpful criticism during the preparation of this paper.
REFERENCES FRIBERG, U., STAHLE, J., and SVEDBERG, A.: The natural course of Meniere's disease. Acta Otolaryngol. Suppl. 406: 72-77, 1984. NADOL, J. B., and THORNTON, A. R.: Ultrastructural findings in a case of Meniere's disease. Ann. Otol. Rhinol. Laryngol. 96: 449-453, 1987. SATOH, T., SUZUKI, R., YAHATA, N., KIMURA, R., and RATSUSHIKA, S.: Audiological findings in patients with essential retrocochlear lesions. Audiol. Jpn. 28: 758-771, 1985. UEMURA, T.: Treatment for the Meniere's disease. Oto-Rhino-Laryngol. Tokyo 19: 386, 1976. WATANABE, I.: Meniere's disease-With special emphasis on epidemiology, diagnosis and prognosis. ORL 42: 20-45, 1980. YOSHIE, N.: Electrocochleographic classification of sensorineural defects: Pathological pattern of the cochlear nerve compound action potential in man. In Electrocochleography (Ruben, R. J., Elberling, C, and Salmon, G., eds.), University Park Press, Baltimore/London/ Tokyo, 1976.
Request reprints to:
Dr. R. Okuno, Department of Otolaryngology, Tokyo Medical & Dental University, 5-45, Yushima l-chome, Bunkyo-ku, Tokyo 113, Japan