Acta Oto-Laryngologica
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Electronystagmographic Findings in 147 Patients with Acoustic Neuroma Yukihiro Okada, Masahiro Takahashi, Akira Saito & Jin Kanzaki To cite this article: Yukihiro Okada, Masahiro Takahashi, Akira Saito & Jin Kanzaki (1991) Electronystagmographic Findings in 147 Patients with Acoustic Neuroma, Acta OtoLaryngologica, 111:sup487, 150-156, DOI: 10.3109/00016489109130461 To link to this article: http://dx.doi.org/10.3109/00016489109130461
Published online: 08 Jul 2009.
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Date: 05 May 2016, At: 16:09
Acta Otolaryngol (Stockh) 1991; Suppl. 487: 150-156
Electronystagmographic Findings in 147 Patients with Acoustic Neuroma YUKIHIRO OKADA, MASAHIRO TAKAHASHI, AKIRA SAITO and JIN KANZAKI From the Department of Otolaryngology, Keio University School of Medicine, Tokyo 160, Japan
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Okada Y, Takahashi M, Saito A, Kanzaki J. Electronystagmographic findings in 147 patients with acoustic neuroma. Acta Otolaryngol (Stockh) 1991; Suppl 487: 150- 156. We report on the preoperative findings in 147 patients with surgically confirmed acoustic neuroma (AN). Gaze nystagmus, spontaneous nystagmus and positional nystagmus were present in 23.1%. 47.5% and 63.0% of the patient, respectively. Pathological findings in ETT, OKP and bithermal caloric test were found in 4 . 3 % , 45.3% and 77.0%, respectively. The ratio of pathological findings in ETT and OKP was larger in the large tumor group than in the small tumor group. Gaze nystagmus to both directions and direction-changing positional nystagmus were also found in the large tumor group. While the correlation between tumor size and CP% in caloric test was slightly significant (correlation coefficient, 0.52) in all 122 patients, it was more significant (correlation coefficient, 0.65) in 16 patients whose tumor origin was surgically confirmed to be the inferior vestibular nerve. These findings suggest that reduced caloric response is caused by compression of the nerve by tumor mass. On the other hand, 6 patients whose tumor originated from the superior vestibular nerve showed no significant correlation between CF% and tumor size. Key words: acoustic neuroma, ENG, caloric test, tumor size, tumor origin.
INTRODUCTION Only a limited number of electronystagmographic (ENG) findings is considered to be characteristic in acoustic tumor (AN) cases, and vestibular examinations such as the caloric test are thought to have less diagnostic value than CT and MR imaging or ABR. However, in certain cases ENG finding may be useful to determine the location of the tumor, i.e., the superior vestibular nerve or inferior vestibular nerve, and to evaluate the degree of CNS involvement. In this paper, we report on preoperative ENG findings in 147 patients with surgically confirmed AN and compare them with tumor size measured on CT films and surgical findings. SUBJECTS We studied 147 patients with AN who underwent examinations at Keio University Hospital between 1976 and 1988. Sixty-eight patients (46%) were male and 79 (54%) female. Age at the time of ENG examination ranged from 16 to 72 years, and the mean age was 46.5 years. METHODS ENG examinations for preoperative assessment of vestibular function consisted of tests of gaze nystagmus, spontaneous nystagmus, positional nystagmus, optokinetic pattern test (OKP), pendular eye tracking test (ETT), and bithermal caloric test (30°C and 44°C). Eye movements were recorded with a d.c. ENG with time constants of 3 s and 0.03 s. Gaze nystagmus was evaluated by frontal, 20" right lateral and 20" left lateral gaze. Spontaneous nystagmus was recorded with the eyes open in the dark and the eyes closed, with mental arithmetic in the spine position. Positional nystagmus was examined with the eyes open in
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Electronystugrnogruphy and AN
the dark at 6 head positions: frontal head position, right lateral head position, left lateral head position, head-hanging position, right lateral head-hanging position and left lateral head-hanging position. In ETT, patients were asked to track a light spot which moved horizontally and sinusoidally over a 40" amplitude across a flat screen which was placed 150 cm away from the patient. The OKP test was performed by using a Jung-type stimulator of 4"/s2 angular acceleration which reached maximum 120"/s. The bithermal caloric test was performed in the dark with the eyes open. In the test, 5 ml water at 30°C or 44°C was irrigated over a period of 10 s and pooled in the ear canal for 10 more s. Slow phase eye velocity was measured manually and caloric response (CP%) was calculated. CP% values exceeding 20% were considered pathological. The size of the tumor was decided by measuring the maximum diameter of the tumor shadow which protruded out of the internal auditory canal (IAC) on the CT films. Tumors confined within the IAC (IC tumor) were regarded as 0 mm in size. We analysed nystagmus of at least three successive beats in one direction as significant nystagmus on each nystagmus test. Similarly, eye tracking interrupted by 5 saccades during one cycle was diagnosed as pathological ETT, and optokinetic pursuit with apparently decreased pursuit velocity or abnormal fast phase as pathological OKP. We classified the findings of nystagmus tests into 3 grades, and tumor size, into 2 grades. Since there were several patients who did not undergo all of these examinations, the total patient number varied among the different ENG tests. RESULTS Nystagmus tests
Gaze nystagmus was found in 23.1% of the patients. Nystagmus to one direction was seen in 13.1% and nystagmus to both directions including Bruns nystagmus in 10.0%. Spontaneous nystagmus was found in 47.5%. Nystagmus to the intact side was seen in 34.5% and nystagmus to the affected side in 13.0%. For positional nystagmus, the rates of no nystagmus, direction-fixed positional nystagmus and direction-changing positional nystagmus were 37.0%, 55.0% and 8.O%, respectively. Caloric test
Caloric responses were classified into 4 grades according to values of CP%, i.e., normal response with CP% values of 20% or less (normal response group), slightly decreased response with CP% values of 21 -40% (slight CP group), moderately decreased response with CP% values of 41-60% (moderate CP group) and severely decreased response with CP% values larger than 60% (severe CP group). Normal response was found in 23.0% of the patients, slight CP in 21.3%, moderate CP in 19.7% and severe CP in 36.0%. ETT and OKP Normal findings on ETT and OKP were found in 55.7% and 54.7% of the patients, respectively. Pathological findings confined to one direction and those in both directions accounted for 11.5% and 32.8% on ETT, and 17.6% and 27.7% on OKP (Fig. 1). Relationship between ENG findings and tumor size Tumor size was divided into 20 mm or less and larger than 20 mrn. The results of these two groups on each ENG test are shown in Table I. The ratio of absence of nystagmus or normal findings was less in the large tumor group than in the small one. Gaze nystagmus to both
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Gaze Spontaneous Positional OKP
ETT Caloric test
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0
20
40
I
80
60
100%
Fig. I . The proportion of findings in ENG tests. 0:absence of nystagmus, normal finding (OKP, ETT) and CP% Q 20% (caloric test); 0:gaze nystagmus to one direction, spontaneous or positional nystagmus to the intact side, pathological finding gaze nystagmus in both confined to one direction (OKP, ETT) and slight CP (20% < CPA < 40%); 0: directions, spontaneous nystagmus to the affected side, direction-changing positional nystagmus, pathological finding in both directions (OKP, ETT) and moderate CP (40% < CP% < 60%); W : severe CP ( 60% < CP/u < 1OOo/o).
Table I. The ENGfindings in the large tumor group and the small tumor group Tumor size < 20 mm
Tumor size 2 21 mm
Findings
no.
Yo
no.
%
Average tumor size (mm)
Gaze nyst
Absence of nyst. Nyst. to one direction Nyst. to both directions
48 3 2
90.5%, 5.1% 3.8*h
52 14 11
61.5% 18.2% 14.3%1
23.1 39.1 38.2
Spontaneous nyst.
Absence of nyst. Nyst. to the intact side Nyst. to the affected side
35 16 4
63.5% 29.1% 7.4%i
38 32 14
45.2% 38.1% 16.1‘%1
23.1 30.0 36.4
Positional nyst.
Absence of nyst. Nyst. to one direction Direction changing nyst.
30 25 0
54.5% 45.5% 0.0Uh
21 51
\I
25.3% 61.5%) 13.2’Li
19.2 29.8 45.9
ETT
Normal finding Pathological finding to one direction Pathological finding to both directions
44
84.6%
29
36.8%
19.2
4
7.1%
11
13.9%
4
l.l”/u
39
49.3%
Normal finding Pathological finding to to one direction Pathological finding to both directions
31
82.2%
28
37.8%
6
13.4%
15
20.3%
2
4.4%
31
41.9%
Normal response Reduced response
24 30
44.4% 55.6%
4 64
6.1% 93.9%
OKP
Caloric test
37.1 20.5
36.1 10.6 30.5
Electronystugmography and A N
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Fig. 2. Relationship between tumor size and CP% in 122 cases. The correlation of coefficient was 0.52.
0
0
0
0
40 50 (1. c.) tumor size(mm)
10
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I I
20
30
60
directions was found in 11 patients of the large tumor group; their average tumor size was 52.0 mm. Direction-changing positional nystagmus was found in 11 patients in the large tumor group; their mean tumor size was 45.9 mm. Differences in the proportion of pathological findings between the small and large tumor groups were more marked for tests of ETT and OKP than other nystagmus tests. The average tumor size in patients with normal finding on ETT OKP (19.2 mm and 20.5 mm on ETT and OKP, respectively) was smaller than that in patients with pathological findings on these tests (37.1 mm and 36.1 mm, respectively). The proportion of normal response on the caloric test was larger in the small group than in the large one. While mean tumor size was 10.6mm in normal response group, it was 30.5 mm in slight, moderate and severe CP groups. The relationship between tumor size and CP% is shown in Fig. 2. The correlation coefficient was 0.52, indicating a slight correlation between tumor size and CPYO. Cuioric response und surgical findings
We compared the relationship between tumor size, caloric response and origin of tumor in 22 patients whose origin of tumor was confirmed during surgery. The tumor originated in the superior vestibular nerve in 6 of 22 patients, and in the inferior vestibular nerve in 16 patients. The correlation coefficient between caloric response and tumor size was 0.65 in the group whose origin was in the inferior vestibular nerve, higher than the value obtained for all 122 patients (0.52) (Fig. 2). Whereas 5 of 6 patients with tumor origin in the superior vestibular nerve showed abnormal caloric response, 10 of 16 patients with tumor origin in the inferior vestibular nerve presented CP%Ivalues within the normal range (20% or less) (Fig. 3). As regards the findings of small tumors within the internal auditory canal (IC tumor), while 6 of 7 patients with origin in the inferior vestibular nerve showed normal caloric response, 5 of 6 patients with origin in the superior vestibular nerve showed significantly decreased response. One of these 6 patients presented the highest value of CP% of the 22 patients whose origin of tumor was surgically confirmed.
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80.
5
0
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(I.
10
c.) tumor
15
20
size(mm)
00. Fig. 3: Relationship between
80 -
8 a
0 0
60-
0
40.
0
0 (b)
5
10
0
15 (1. C.) tumor size(mm)
0
tumor size and CPh in 22 cases whose origin of tumor was surgically confirmed. (a):In 16 patients whoses tumor originated from inferior vestibular nerve, the correlation of coefficient was 0.65 (upper figure); ( b ) : In 6 patients whose tumor originated from superior vestibular
20
DISCUSSION Gaze nystagmus, spontaneous nystagmus and positional nystagmus were present in 23.1%. 47.5% and 63.0%, respectively, of the patients in this study. According to previous reports, gaze nystagmus is observed in 40% ( I ) , spontaneous nystagmus in 9.4-40.0% ( I , 2, 3) and positional nystagmus in 21.5-70.0% of patients ( 1 , 3). The values in the present study seem to be almost equal to the reported values. The rates of occurrence of pathological findings in ETT and OKP (44.3% and 45.3%, respectively) were slightly higher than those in previous reports (4, 5). A significant decrease in caloric response (CPhhigher than 20%) was seen in 77% of the patients in this study, comparable to previously reported values (4-9). With respect to the relationship between tumor size and ENG findings, the ratio of pathological findings was apparently higher in the patient group with larger tumors than in the group with smaller tumors for all the tests examined. Two patients who showed Brunn's nystagmus and 11 patients who showed direction-changing positional nystagmus and appar-
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Electronystagmography and A N ent pathological findings on ETT and OKP belonged to the group with larger tumors. This finding suggests that space occupying lesions may have influenced the CNS, especially the brain stem. The severity of nystagmus findings increased as average tumor size increased (from absence of nystagmus or nystagmus confined to one direction or the the intact side, to nystagmus to both directions or to the affected side). The present study supports the idea that ENG examinations provide informations of CNS involvement in patients with AN, although they do not play a significant role in its diagnosis. Bergenius et al. reported a significant correlation between tumor size and caloric response (CF%) (4). We also found a slight correlation between the two in the present study, as shown in Fig. 2. The correlation was more significant in the group of 16 patients whose origin of tumor was confirmed, during surgery, to be the inferior vestibular nerve. On the other hand, in the group of 6 patients whose tumor originated in the superior vestibular nerve, no significant correlation was found. Even small tumors confined to the internal auditory canal presented high CP% values in the early stage of lesion, as reported by Fukaya et al. (10). Some reports have indicated that sensory epithelium in the vestibular end organs does not manifest damage in cases of AN (11, 12), suggesting that the vestibular dysfunction in AN patients is caused by impairment of the vestibular nerve function rather than inner ear lesions. If this were true in our cases, we can conclude that the reduced caloric response is caused by tumorization of the nerve in tumors originating in the superior vestibular nerve and that it results more from compression of the nerve by the tumor mass in cases of inferior vestibular nerve origin. On the other hand, there have been severat reports that dysfunction of the eighth nerve is caused by infiltration of the tumor onto the nerve, and others that reduced caloric response does not indicate a decrease in the number of vestibular nerve fibers ( 13, 14, 15). More information is needed to determine which hypothesis is correct regarding the mechanism that reduces caloric response. Despite the many possibilities, the present findings suggest that even a small tumor can cause a severe decline in caloric response in patients whose tumor originates in the superior vestibular nerve.
REFERENCES 1. Kirtane MV, Medikeri SB, Merchant SN. Electronystagmography findings in acoustic neuromas. J Postgrad Med 1985; 31: 128-33. 2. Hitselberger WE. Tumors of the cerebellopontine angle in relation to vertigo. Arch Otolaryngol
1967; 85: 539-41. 3. Linthicum FH, Churchill D. Vestibular test results in acoustic tumour cases. Arch Otolaryngol 1968; 88: 604-7. 4. Bergenius J, Magnusson M. The relationship between caloric response, oculomotor dysfunction and size of cerebello-pontine angle tumors. Acta Otolaryngol (Stockh) 1988; 106: 361 -7. 5 . Hulshof JH, Hilders GJM, Baarsman EA. Vestibular investigation in acoustic neuroma. Acta Otolaryngol (Stockh) 1989; 108: 38-44. 6. Barrs DM, Brackmann DE, Olson JE et al. Changing concept of acoustic neuroma diagnosis. Arch Otolaryngol 1985; 11 1: 17-21. 7. Linthicum FH, Klalessi MH, Churchill D. Electronystagmographic caloric bithermal vestibular test (ENG). In: House WF, Luetje CM, eds. Acoustic tumors, I. Diagnosis. Baltimore: University Park Press, 1979: 237-40. 8. Peponis TN. Diagnosis of acoustic neuroma. J Am Osteopath Assoc 1986; 86: 369-78. 9. Shiffman F, Dancer J, Rothballer AB. The diagnosis and evaluation of acoustic neuromas. Otolaryngol Clin North Am 1973; 6: 189-98. 10. Fukaya T, Okuno T, Komatsuzaki A. Early acoustic neuromas relation between the origin of the tumor and caloric testing. J Otolaryngol Jpn 1983; 86: 1461-4.
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156 Y. Okada et al. 11. Perez De Moura LF. Inner ear pathology in acoustic neurinoma. Arch Otolaryngol 1967; 85:
125-33. 12. Ylikoski J, Collan Y, Palva T. Vestibular findings in patients with acoustic neurinoma. Arch Otolaryngol 1980; 106: 723-6. 13. Neely JG. Gross and microscopic anatomy of the eighth nerve in relationship to the solitary schwannoma. Laryngoscope 1981; 91: 1512-31. 14. Ylikoski J, Collan Y, Palva T. Eighth nerve in acoustic neuromas. Special reference to superior vestibular nerve function and histopathology. Arch Otolaryngol 1978; 104: 532-7. 15. Ylikoski J, Collan Y , Palva T. Cochlear nerve in neurilemmomas. Audiology and histopathology. Arch Otolaryngol 1978; 104: 679-84.
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Address for correspondence: Y . Okada, Department of Otolaryngology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Electronystagmographic Findings in 147 Patients with Acoustic Neuroma Yukihiro Okada, Masahiro Takahashi, Akira Saito & Jin Kanzaki To cite this article: Yukihiro Okada, Masahiro Takahashi, Akira Saito & Jin Kanzaki (1991) Electronystagmographic Findings in 147 Patients with Acoustic Neuroma, Acta OtoLaryngologica, 111:sup487, 150-156, DOI: 10.3109/00016489109130461 To link to this article: http://dx.doi.org/10.3109/00016489109130461
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 10
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [UQ Library]
Date: 05 May 2016, At: 16:09
Acta Otolaryngol (Stockh) 1991; Suppl. 487: 150-156
Electronystagmographic Findings in 147 Patients with Acoustic Neuroma YUKIHIRO OKADA, MASAHIRO TAKAHASHI, AKIRA SAITO and JIN KANZAKI From the Department of Otolaryngology, Keio University School of Medicine, Tokyo 160, Japan
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Okada Y, Takahashi M, Saito A, Kanzaki J. Electronystagmographic findings in 147 patients with acoustic neuroma. Acta Otolaryngol (Stockh) 1991; Suppl 487: 150- 156. We report on the preoperative findings in 147 patients with surgically confirmed acoustic neuroma (AN). Gaze nystagmus, spontaneous nystagmus and positional nystagmus were present in 23.1%. 47.5% and 63.0% of the patient, respectively. Pathological findings in ETT, OKP and bithermal caloric test were found in 4 . 3 % , 45.3% and 77.0%, respectively. The ratio of pathological findings in ETT and OKP was larger in the large tumor group than in the small tumor group. Gaze nystagmus to both directions and direction-changing positional nystagmus were also found in the large tumor group. While the correlation between tumor size and CP% in caloric test was slightly significant (correlation coefficient, 0.52) in all 122 patients, it was more significant (correlation coefficient, 0.65) in 16 patients whose tumor origin was surgically confirmed to be the inferior vestibular nerve. These findings suggest that reduced caloric response is caused by compression of the nerve by tumor mass. On the other hand, 6 patients whose tumor originated from the superior vestibular nerve showed no significant correlation between CF% and tumor size. Key words: acoustic neuroma, ENG, caloric test, tumor size, tumor origin.
INTRODUCTION Only a limited number of electronystagmographic (ENG) findings is considered to be characteristic in acoustic tumor (AN) cases, and vestibular examinations such as the caloric test are thought to have less diagnostic value than CT and MR imaging or ABR. However, in certain cases ENG finding may be useful to determine the location of the tumor, i.e., the superior vestibular nerve or inferior vestibular nerve, and to evaluate the degree of CNS involvement. In this paper, we report on preoperative ENG findings in 147 patients with surgically confirmed AN and compare them with tumor size measured on CT films and surgical findings. SUBJECTS We studied 147 patients with AN who underwent examinations at Keio University Hospital between 1976 and 1988. Sixty-eight patients (46%) were male and 79 (54%) female. Age at the time of ENG examination ranged from 16 to 72 years, and the mean age was 46.5 years. METHODS ENG examinations for preoperative assessment of vestibular function consisted of tests of gaze nystagmus, spontaneous nystagmus, positional nystagmus, optokinetic pattern test (OKP), pendular eye tracking test (ETT), and bithermal caloric test (30°C and 44°C). Eye movements were recorded with a d.c. ENG with time constants of 3 s and 0.03 s. Gaze nystagmus was evaluated by frontal, 20" right lateral and 20" left lateral gaze. Spontaneous nystagmus was recorded with the eyes open in the dark and the eyes closed, with mental arithmetic in the spine position. Positional nystagmus was examined with the eyes open in
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Electronystugrnogruphy and AN
the dark at 6 head positions: frontal head position, right lateral head position, left lateral head position, head-hanging position, right lateral head-hanging position and left lateral head-hanging position. In ETT, patients were asked to track a light spot which moved horizontally and sinusoidally over a 40" amplitude across a flat screen which was placed 150 cm away from the patient. The OKP test was performed by using a Jung-type stimulator of 4"/s2 angular acceleration which reached maximum 120"/s. The bithermal caloric test was performed in the dark with the eyes open. In the test, 5 ml water at 30°C or 44°C was irrigated over a period of 10 s and pooled in the ear canal for 10 more s. Slow phase eye velocity was measured manually and caloric response (CP%) was calculated. CP% values exceeding 20% were considered pathological. The size of the tumor was decided by measuring the maximum diameter of the tumor shadow which protruded out of the internal auditory canal (IAC) on the CT films. Tumors confined within the IAC (IC tumor) were regarded as 0 mm in size. We analysed nystagmus of at least three successive beats in one direction as significant nystagmus on each nystagmus test. Similarly, eye tracking interrupted by 5 saccades during one cycle was diagnosed as pathological ETT, and optokinetic pursuit with apparently decreased pursuit velocity or abnormal fast phase as pathological OKP. We classified the findings of nystagmus tests into 3 grades, and tumor size, into 2 grades. Since there were several patients who did not undergo all of these examinations, the total patient number varied among the different ENG tests. RESULTS Nystagmus tests
Gaze nystagmus was found in 23.1% of the patients. Nystagmus to one direction was seen in 13.1% and nystagmus to both directions including Bruns nystagmus in 10.0%. Spontaneous nystagmus was found in 47.5%. Nystagmus to the intact side was seen in 34.5% and nystagmus to the affected side in 13.0%. For positional nystagmus, the rates of no nystagmus, direction-fixed positional nystagmus and direction-changing positional nystagmus were 37.0%, 55.0% and 8.O%, respectively. Caloric test
Caloric responses were classified into 4 grades according to values of CP%, i.e., normal response with CP% values of 20% or less (normal response group), slightly decreased response with CP% values of 21 -40% (slight CP group), moderately decreased response with CP% values of 41-60% (moderate CP group) and severely decreased response with CP% values larger than 60% (severe CP group). Normal response was found in 23.0% of the patients, slight CP in 21.3%, moderate CP in 19.7% and severe CP in 36.0%. ETT and OKP Normal findings on ETT and OKP were found in 55.7% and 54.7% of the patients, respectively. Pathological findings confined to one direction and those in both directions accounted for 11.5% and 32.8% on ETT, and 17.6% and 27.7% on OKP (Fig. 1). Relationship between ENG findings and tumor size Tumor size was divided into 20 mm or less and larger than 20 mrn. The results of these two groups on each ENG test are shown in Table I. The ratio of absence of nystagmus or normal findings was less in the large tumor group than in the small one. Gaze nystagmus to both
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Gaze Spontaneous Positional OKP
ETT Caloric test
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0
20
40
I
80
60
100%
Fig. I . The proportion of findings in ENG tests. 0:absence of nystagmus, normal finding (OKP, ETT) and CP% Q 20% (caloric test); 0:gaze nystagmus to one direction, spontaneous or positional nystagmus to the intact side, pathological finding gaze nystagmus in both confined to one direction (OKP, ETT) and slight CP (20% < CPA < 40%); 0: directions, spontaneous nystagmus to the affected side, direction-changing positional nystagmus, pathological finding in both directions (OKP, ETT) and moderate CP (40% < CP% < 60%); W : severe CP ( 60% < CP/u < 1OOo/o).
Table I. The ENGfindings in the large tumor group and the small tumor group Tumor size < 20 mm
Tumor size 2 21 mm
Findings
no.
Yo
no.
%
Average tumor size (mm)
Gaze nyst
Absence of nyst. Nyst. to one direction Nyst. to both directions
48 3 2
90.5%, 5.1% 3.8*h
52 14 11
61.5% 18.2% 14.3%1
23.1 39.1 38.2
Spontaneous nyst.
Absence of nyst. Nyst. to the intact side Nyst. to the affected side
35 16 4
63.5% 29.1% 7.4%i
38 32 14
45.2% 38.1% 16.1‘%1
23.1 30.0 36.4
Positional nyst.
Absence of nyst. Nyst. to one direction Direction changing nyst.
30 25 0
54.5% 45.5% 0.0Uh
21 51
\I
25.3% 61.5%) 13.2’Li
19.2 29.8 45.9
ETT
Normal finding Pathological finding to one direction Pathological finding to both directions
44
84.6%
29
36.8%
19.2
4
7.1%
11
13.9%
4
l.l”/u
39
49.3%
Normal finding Pathological finding to to one direction Pathological finding to both directions
31
82.2%
28
37.8%
6
13.4%
15
20.3%
2
4.4%
31
41.9%
Normal response Reduced response
24 30
44.4% 55.6%
4 64
6.1% 93.9%
OKP
Caloric test
37.1 20.5
36.1 10.6 30.5
Electronystugmography and A N
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0 00
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808
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Fig. 2. Relationship between tumor size and CP% in 122 cases. The correlation of coefficient was 0.52.
0
0
0
0
40 50 (1. c.) tumor size(mm)
10
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I I
20
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directions was found in 11 patients of the large tumor group; their average tumor size was 52.0 mm. Direction-changing positional nystagmus was found in 11 patients in the large tumor group; their mean tumor size was 45.9 mm. Differences in the proportion of pathological findings between the small and large tumor groups were more marked for tests of ETT and OKP than other nystagmus tests. The average tumor size in patients with normal finding on ETT OKP (19.2 mm and 20.5 mm on ETT and OKP, respectively) was smaller than that in patients with pathological findings on these tests (37.1 mm and 36.1 mm, respectively). The proportion of normal response on the caloric test was larger in the small group than in the large one. While mean tumor size was 10.6mm in normal response group, it was 30.5 mm in slight, moderate and severe CP groups. The relationship between tumor size and CP% is shown in Fig. 2. The correlation coefficient was 0.52, indicating a slight correlation between tumor size and CPYO. Cuioric response und surgical findings
We compared the relationship between tumor size, caloric response and origin of tumor in 22 patients whose origin of tumor was confirmed during surgery. The tumor originated in the superior vestibular nerve in 6 of 22 patients, and in the inferior vestibular nerve in 16 patients. The correlation coefficient between caloric response and tumor size was 0.65 in the group whose origin was in the inferior vestibular nerve, higher than the value obtained for all 122 patients (0.52) (Fig. 2). Whereas 5 of 6 patients with tumor origin in the superior vestibular nerve showed abnormal caloric response, 10 of 16 patients with tumor origin in the inferior vestibular nerve presented CP%Ivalues within the normal range (20% or less) (Fig. 3). As regards the findings of small tumors within the internal auditory canal (IC tumor), while 6 of 7 patients with origin in the inferior vestibular nerve showed normal caloric response, 5 of 6 patients with origin in the superior vestibular nerve showed significantly decreased response. One of these 6 patients presented the highest value of CP% of the 22 patients whose origin of tumor was surgically confirmed.
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DISCUSSION Gaze nystagmus, spontaneous nystagmus and positional nystagmus were present in 23.1%. 47.5% and 63.0%, respectively, of the patients in this study. According to previous reports, gaze nystagmus is observed in 40% ( I ) , spontaneous nystagmus in 9.4-40.0% ( I , 2, 3) and positional nystagmus in 21.5-70.0% of patients ( 1 , 3). The values in the present study seem to be almost equal to the reported values. The rates of occurrence of pathological findings in ETT and OKP (44.3% and 45.3%, respectively) were slightly higher than those in previous reports (4, 5). A significant decrease in caloric response (CPhhigher than 20%) was seen in 77% of the patients in this study, comparable to previously reported values (4-9). With respect to the relationship between tumor size and ENG findings, the ratio of pathological findings was apparently higher in the patient group with larger tumors than in the group with smaller tumors for all the tests examined. Two patients who showed Brunn's nystagmus and 11 patients who showed direction-changing positional nystagmus and appar-
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Electronystagmography and A N ent pathological findings on ETT and OKP belonged to the group with larger tumors. This finding suggests that space occupying lesions may have influenced the CNS, especially the brain stem. The severity of nystagmus findings increased as average tumor size increased (from absence of nystagmus or nystagmus confined to one direction or the the intact side, to nystagmus to both directions or to the affected side). The present study supports the idea that ENG examinations provide informations of CNS involvement in patients with AN, although they do not play a significant role in its diagnosis. Bergenius et al. reported a significant correlation between tumor size and caloric response (CF%) (4). We also found a slight correlation between the two in the present study, as shown in Fig. 2. The correlation was more significant in the group of 16 patients whose origin of tumor was confirmed, during surgery, to be the inferior vestibular nerve. On the other hand, in the group of 6 patients whose tumor originated in the superior vestibular nerve, no significant correlation was found. Even small tumors confined to the internal auditory canal presented high CP% values in the early stage of lesion, as reported by Fukaya et al. (10). Some reports have indicated that sensory epithelium in the vestibular end organs does not manifest damage in cases of AN (11, 12), suggesting that the vestibular dysfunction in AN patients is caused by impairment of the vestibular nerve function rather than inner ear lesions. If this were true in our cases, we can conclude that the reduced caloric response is caused by tumorization of the nerve in tumors originating in the superior vestibular nerve and that it results more from compression of the nerve by the tumor mass in cases of inferior vestibular nerve origin. On the other hand, there have been severat reports that dysfunction of the eighth nerve is caused by infiltration of the tumor onto the nerve, and others that reduced caloric response does not indicate a decrease in the number of vestibular nerve fibers ( 13, 14, 15). More information is needed to determine which hypothesis is correct regarding the mechanism that reduces caloric response. Despite the many possibilities, the present findings suggest that even a small tumor can cause a severe decline in caloric response in patients whose tumor originates in the superior vestibular nerve.
REFERENCES 1. Kirtane MV, Medikeri SB, Merchant SN. Electronystagmography findings in acoustic neuromas. J Postgrad Med 1985; 31: 128-33. 2. Hitselberger WE. Tumors of the cerebellopontine angle in relation to vertigo. Arch Otolaryngol
1967; 85: 539-41. 3. Linthicum FH, Churchill D. Vestibular test results in acoustic tumour cases. Arch Otolaryngol 1968; 88: 604-7. 4. Bergenius J, Magnusson M. The relationship between caloric response, oculomotor dysfunction and size of cerebello-pontine angle tumors. Acta Otolaryngol (Stockh) 1988; 106: 361 -7. 5 . Hulshof JH, Hilders GJM, Baarsman EA. Vestibular investigation in acoustic neuroma. Acta Otolaryngol (Stockh) 1989; 108: 38-44. 6. Barrs DM, Brackmann DE, Olson JE et al. Changing concept of acoustic neuroma diagnosis. Arch Otolaryngol 1985; 11 1: 17-21. 7. Linthicum FH, Klalessi MH, Churchill D. Electronystagmographic caloric bithermal vestibular test (ENG). In: House WF, Luetje CM, eds. Acoustic tumors, I. Diagnosis. Baltimore: University Park Press, 1979: 237-40. 8. Peponis TN. Diagnosis of acoustic neuroma. J Am Osteopath Assoc 1986; 86: 369-78. 9. Shiffman F, Dancer J, Rothballer AB. The diagnosis and evaluation of acoustic neuromas. Otolaryngol Clin North Am 1973; 6: 189-98. 10. Fukaya T, Okuno T, Komatsuzaki A. Early acoustic neuromas relation between the origin of the tumor and caloric testing. J Otolaryngol Jpn 1983; 86: 1461-4.
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156 Y. Okada et al. 11. Perez De Moura LF. Inner ear pathology in acoustic neurinoma. Arch Otolaryngol 1967; 85:
125-33. 12. Ylikoski J, Collan Y, Palva T. Vestibular findings in patients with acoustic neurinoma. Arch Otolaryngol 1980; 106: 723-6. 13. Neely JG. Gross and microscopic anatomy of the eighth nerve in relationship to the solitary schwannoma. Laryngoscope 1981; 91: 1512-31. 14. Ylikoski J, Collan Y, Palva T. Eighth nerve in acoustic neuromas. Special reference to superior vestibular nerve function and histopathology. Arch Otolaryngol 1978; 104: 532-7. 15. Ylikoski J, Collan Y , Palva T. Cochlear nerve in neurilemmomas. Audiology and histopathology. Arch Otolaryngol 1978; 104: 679-84.
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Address for correspondence: Y . Okada, Department of Otolaryngology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan
