Acta Otolaryngol83: 245-251, 1977
VISUAL SUPPRESSION OF CALORIC NYSTAGMUS IN NORMAL INDIVIDUALS
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
I . Kato, Y. Kimura, M. Aoyagi, K. Mizukoshi and T. Kawasaki’ From rhe Depcirtment of Otolaryngology. Niigcrtrr University School of Medicittc~. cr nil th e Depart ni en t of’ Neuruphy s iology , Brtr it? R es ecirch Itr st itrr t e , ’ Niignttr University. Niigtrfn, J~rpan (Received November 24, 1975)
caloric nystagmus, on the other hand, has also been carried out by some investigators. Demanez & Ledoux developed an “ocular fixation index (OFI)” (1970). Alpert (1974) also indicated that OF1 based on slow-phase velocity was found to be the best method of separating a normal from an abnormal fixation suppression of caloric nystagmus. Maccario et al. (1972) calculated an “EO/EC‘’ ratio of caloric nystagmus, defined as the average deflection with the eyes open divided by the average deflection with the eyes closed. Molnar & Torok (1974) studied the effect of fixation and nonfixation upon the caloric nystagmus in both I t is well known that caloric-induced nystag- weak and strong caloric stimulation and conmus is definitely suppressed by ocular fixa- cluded that slow-phase velocity and amplitude tion (Mahoney et al., 1957; Anderson et al., measurements following the strong stimulus 1958; Sokolovski, 1966; Hart, 1967; Hood & were more informative. As outlined above, Dix, 1973; Alpert 1974; Molnar & Torok, attention has hitherto been directed toward 1974). In some instances of disorders of the reliable parameters, with which to test the central nervous system, on the contrary, a fixation suppression of caloric nystagmus. As lesser degree of (or no) suppressive effect of regards test conditions, on the other hand, ocular fixation upon the caloric nystagmus has little attention has been paid. In the present study we have attempted also been recognized, which state has been termed “Failure of Fixation-Suppression of to assess the standardization of our modified Caloric Nystagmus (FFS)” (Coats, 1970), caloric test. Particular attention was focused “paradoxical caloric response (PCR)” (Mac- upon the effects of eye opening and ocular cario et al., 1972), and also “ocular fixation fixation upon caloric nystagmus from the folreversal phenomenon” (Torok, 1973). Quanti- lowing points of view: ( I ) whether or not the tative evaluation of fixation suppression of effects of eye opening and ocular fixation upon
Ahsfrcrc/.The effects of opening of the eyes and of ocular fixation upon caloric nystagmus were investigated during the period of maximum intensity of caloric nystagmus in a series of 32 normal individuals. The percentage reduction in slow-phase velocity induced depended upon the test conditions, but, o n the other hand, did not depend upon the temperature of the water applied a s caloric stimulus. This latter fact favors the theory of. visual suppression of the caloric test. Another striking finding was that a clear correlation definitely existed between the percentage reduction of suppression in slow-phase velocity and that in the multiplication product of amplitude by nystagmus frequency (P.A.F.) during the period of eye opening and ocular fixation. T h e percentage of suppression in slow-phase velocity is interchangeable with that in P.A.F., which broadens the practical scope of the routine test.
Acto Urolarwgol 83
1. Kato et al.
246
H 1oseC
I
Test Condition
caloric nystagmus are dependent upon the temperature of the water applied as caloric stimulus; (2) whether or not the degree of visual suppression of caloric nystagmus varies according to the test conditions; (3) whether or not a reduction in slow-phase velocity induced by eye opening and ocular fixation can be replaced by a reduction in P.A.F. during the period of eye opening and ocular fixation.
30('Lt
' "' TwTryTest Conditbon
[I
(30°CL t ) E y e s Open
End of Irrigation
3 1
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
3
METHOD
Test Condition
11
All subjects used were medical and paramedical students, 17 females and IS males with ages ranging from 18 to 25 years and in good general physical condition. None of them had any past history of otoneurological disorders or had any experience of exposure to caloric tests. None had taken drugs or alcohol for at least 2 days prior to tests. The subjects were examined prior to tests for evidence of spontaneous nystagmus, and abnormalities of tympanic membrane and audiogram.
(30'CLt)
(30°C L t )
Test Condition
Test P r u c t h r e
In attempting to assess the influence of eye opening and ocular fixation, the following test conditions were employed.
-
~
~
~
Fig. 1. ENGs representing visual suppression of caloric
nystagmus under each test condition in the same individual studied on different days. All traces under each test condition are horizontal ENG recorded biternporally. Upward deflections in the figures represent eye movements to the right. Upper traces in each test condition show eye velocity, and bottom traces in each test condition exhibit slow-phase eye velocity. Calibration and time scale are indicated by the vertical and horizontal bar respectively on the upper right of most of the traces. Reduction in slow-phase velocity induced by eye opening and ocular fixation was dependent upon each test condition. Mean percentage reduction in slow-phase velocity in each test condition, 69.0%. 5 8 . 5 % . 64.1% and 84.2% respectively.
ACIU0 1 o l u r v n ~ ~ o l 8 3
Test Condition I Control- test. A d modirm Fitzgerald 7 v & Hallpike ~ (1942) modified by Otani (1962), caloric stimulus was 50 ml water. most often 30°C or 44"C, sometimes of 17"C, for an irrigation period of 20 sec with 5- min rest intervals between the end of one trial and the beginning of the next. All subjects were investigated with one test condition only per day. Prior to each trial, calibration was performed to adjust a pen deflection of about 20 mm per 20 degrees of eye movement. A test trial was made in all subjects, with room illuminated and eyes closed. All subjects were always required to perform mental arithmetic throughout the period of the trial. In 32 subjects, maximum slow-phase eye
v i s r i u i .siipprrs.sion oj Slow-Phase Eye Velocity 100
r
Iw
!
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
m
11 Frenzel Glasses
White Paper ( 5 L u x ’
r
tr
ii
-t
0 17 30 44 T E M P OF W A T E R ‘‘C
Iv
Whlte Paper ‘Z,OClOLux\
0 1 7 3 0 4 4 TEMP O F W A T E R ( ‘ C )
V
Fixatlon a t Man
r
!
carried out during this maximum intensity of caloric nystagmus according to each test condition. Test Condirion I1 Frc>n,-cl gltrssc~s.Mean maximum intensity of slow-phase eye velocity was determined during the control period from 50-55 sec after the onset of irrigation. At 55 sec after the onset, subjects were asked to open their- eyes under Frenzel glasses for 10 sec and then to close them until there was no detectable nystagmus. A comparable value for the slowphase velocity was established during the first half of the 10 sec period ( 5 5 4 0 sec after the onset of irrigation) in the period of eye opening under Frenzel glasses (Figs. 1 and 2). Visual suppression was defined as the percentage reduction in slow-phase velocity (SP Vel) (Takemori & Cohen. 1974). Crc Visual suppression (V.S.) - SPVel control-SP Vel eye opening x 100 -
S P Vel control
’L’i T0E M P 17 O F W30A T E 44 Rf~C)
TEMP 0 17 O F W30 A T E R (-C)
Fig. 2. Mean percentage reduction in slow-phase velocity induced by each test condition was established as compared with the control period (see text). The amounts of percentage reduction tended to be almost equal in each test condition without any correlation to water ternperature applied as caloric test. Of the four test conditions. on the other hand. amounts of percentage reduction were dependent upon test conditions. The first was Test Condition V . in which caloric nystagmus was most strongly suppressed. The second was Test Conditions 11 and IV. The third, Test Condition 111. This classification proved significant @ < O . O l ) .
velocity occurred at about 49 sec after the onset of irrigation and was maintained for about 30 sec whether the water temperature of caloric stimulus applied was 30°C or 44°C (Fig. I). The visual suppression test was
Test Conditiori 111 Homogeneous white paper, the surface of which reflected 5 lux. Subjects were required to open their eyes at 55 sec after the onset of irrigation, at which time their eyes were covered with thick white paper at about 10 cm distance. A comparable value for the slowphase velocity was determined during the same time course as that of Test Condition I1 (Figs. I and 2).
Test Condition IV White paper, the surface of which reflected 2000 lux. Test procedure was the same as that of Test Condition I l l , except that in this test, the surface of the white paper facing the eyes was maintained at 2 000 lux illuminated evenly with a flash lamp behind the subject during the eye opening. A comparable reduction in the slow-phase velocity induced was calculated during the same time course as that of Test Condition I 1 (Figs. I and 2). A ( 10 O t o I ( i r i i i q o / 8
VISUAL SUPPRESSION OF CALORIC NYSTAGMUS IN NORMAL INDIVIDUALS
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
I . Kato, Y. Kimura, M. Aoyagi, K. Mizukoshi and T. Kawasaki’ From rhe Depcirtment of Otolaryngology. Niigcrtrr University School of Medicittc~. cr nil th e Depart ni en t of’ Neuruphy s iology , Brtr it? R es ecirch Itr st itrr t e , ’ Niignttr University. Niigtrfn, J~rpan (Received November 24, 1975)
caloric nystagmus, on the other hand, has also been carried out by some investigators. Demanez & Ledoux developed an “ocular fixation index (OFI)” (1970). Alpert (1974) also indicated that OF1 based on slow-phase velocity was found to be the best method of separating a normal from an abnormal fixation suppression of caloric nystagmus. Maccario et al. (1972) calculated an “EO/EC‘’ ratio of caloric nystagmus, defined as the average deflection with the eyes open divided by the average deflection with the eyes closed. Molnar & Torok (1974) studied the effect of fixation and nonfixation upon the caloric nystagmus in both I t is well known that caloric-induced nystag- weak and strong caloric stimulation and conmus is definitely suppressed by ocular fixa- cluded that slow-phase velocity and amplitude tion (Mahoney et al., 1957; Anderson et al., measurements following the strong stimulus 1958; Sokolovski, 1966; Hart, 1967; Hood & were more informative. As outlined above, Dix, 1973; Alpert 1974; Molnar & Torok, attention has hitherto been directed toward 1974). In some instances of disorders of the reliable parameters, with which to test the central nervous system, on the contrary, a fixation suppression of caloric nystagmus. As lesser degree of (or no) suppressive effect of regards test conditions, on the other hand, ocular fixation upon the caloric nystagmus has little attention has been paid. In the present study we have attempted also been recognized, which state has been termed “Failure of Fixation-Suppression of to assess the standardization of our modified Caloric Nystagmus (FFS)” (Coats, 1970), caloric test. Particular attention was focused “paradoxical caloric response (PCR)” (Mac- upon the effects of eye opening and ocular cario et al., 1972), and also “ocular fixation fixation upon caloric nystagmus from the folreversal phenomenon” (Torok, 1973). Quanti- lowing points of view: ( I ) whether or not the tative evaluation of fixation suppression of effects of eye opening and ocular fixation upon
Ahsfrcrc/.The effects of opening of the eyes and of ocular fixation upon caloric nystagmus were investigated during the period of maximum intensity of caloric nystagmus in a series of 32 normal individuals. The percentage reduction in slow-phase velocity induced depended upon the test conditions, but, o n the other hand, did not depend upon the temperature of the water applied a s caloric stimulus. This latter fact favors the theory of. visual suppression of the caloric test. Another striking finding was that a clear correlation definitely existed between the percentage reduction of suppression in slow-phase velocity and that in the multiplication product of amplitude by nystagmus frequency (P.A.F.) during the period of eye opening and ocular fixation. T h e percentage of suppression in slow-phase velocity is interchangeable with that in P.A.F., which broadens the practical scope of the routine test.
Acto Urolarwgol 83
1. Kato et al.
246
H 1oseC
I
Test Condition
caloric nystagmus are dependent upon the temperature of the water applied as caloric stimulus; (2) whether or not the degree of visual suppression of caloric nystagmus varies according to the test conditions; (3) whether or not a reduction in slow-phase velocity induced by eye opening and ocular fixation can be replaced by a reduction in P.A.F. during the period of eye opening and ocular fixation.
30('Lt
' "' TwTryTest Conditbon
[I
(30°CL t ) E y e s Open
End of Irrigation
3 1
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
3
METHOD
Test Condition
11
All subjects used were medical and paramedical students, 17 females and IS males with ages ranging from 18 to 25 years and in good general physical condition. None of them had any past history of otoneurological disorders or had any experience of exposure to caloric tests. None had taken drugs or alcohol for at least 2 days prior to tests. The subjects were examined prior to tests for evidence of spontaneous nystagmus, and abnormalities of tympanic membrane and audiogram.
(30'CLt)
(30°C L t )
Test Condition
Test P r u c t h r e
In attempting to assess the influence of eye opening and ocular fixation, the following test conditions were employed.
-
~
~
~
Fig. 1. ENGs representing visual suppression of caloric
nystagmus under each test condition in the same individual studied on different days. All traces under each test condition are horizontal ENG recorded biternporally. Upward deflections in the figures represent eye movements to the right. Upper traces in each test condition show eye velocity, and bottom traces in each test condition exhibit slow-phase eye velocity. Calibration and time scale are indicated by the vertical and horizontal bar respectively on the upper right of most of the traces. Reduction in slow-phase velocity induced by eye opening and ocular fixation was dependent upon each test condition. Mean percentage reduction in slow-phase velocity in each test condition, 69.0%. 5 8 . 5 % . 64.1% and 84.2% respectively.
ACIU0 1 o l u r v n ~ ~ o l 8 3
Test Condition I Control- test. A d modirm Fitzgerald 7 v & Hallpike ~ (1942) modified by Otani (1962), caloric stimulus was 50 ml water. most often 30°C or 44"C, sometimes of 17"C, for an irrigation period of 20 sec with 5- min rest intervals between the end of one trial and the beginning of the next. All subjects were investigated with one test condition only per day. Prior to each trial, calibration was performed to adjust a pen deflection of about 20 mm per 20 degrees of eye movement. A test trial was made in all subjects, with room illuminated and eyes closed. All subjects were always required to perform mental arithmetic throughout the period of the trial. In 32 subjects, maximum slow-phase eye
v i s r i u i .siipprrs.sion oj Slow-Phase Eye Velocity 100
r
Iw
!
Acta Otolaryngol Downloaded from informahealthcare.com by University of Oxford on 11/08/14 For personal use only.
m
11 Frenzel Glasses
White Paper ( 5 L u x ’
r
tr
ii
-t
0 17 30 44 T E M P OF W A T E R ‘‘C
Iv
Whlte Paper ‘Z,OClOLux\
0 1 7 3 0 4 4 TEMP O F W A T E R ( ‘ C )
V
Fixatlon a t Man
r
!
carried out during this maximum intensity of caloric nystagmus according to each test condition. Test Condirion I1 Frc>n,-cl gltrssc~s.Mean maximum intensity of slow-phase eye velocity was determined during the control period from 50-55 sec after the onset of irrigation. At 55 sec after the onset, subjects were asked to open their- eyes under Frenzel glasses for 10 sec and then to close them until there was no detectable nystagmus. A comparable value for the slowphase velocity was established during the first half of the 10 sec period ( 5 5 4 0 sec after the onset of irrigation) in the period of eye opening under Frenzel glasses (Figs. 1 and 2). Visual suppression was defined as the percentage reduction in slow-phase velocity (SP Vel) (Takemori & Cohen. 1974). Crc Visual suppression (V.S.) - SPVel control-SP Vel eye opening x 100 -
S P Vel control
’L’i T0E M P 17 O F W30A T E 44 Rf~C)
TEMP 0 17 O F W30 A T E R (-C)
Fig. 2. Mean percentage reduction in slow-phase velocity induced by each test condition was established as compared with the control period (see text). The amounts of percentage reduction tended to be almost equal in each test condition without any correlation to water ternperature applied as caloric test. Of the four test conditions. on the other hand. amounts of percentage reduction were dependent upon test conditions. The first was Test Condition V . in which caloric nystagmus was most strongly suppressed. The second was Test Conditions 11 and IV. The third, Test Condition 111. This classification proved significant @ < O . O l ) .
velocity occurred at about 49 sec after the onset of irrigation and was maintained for about 30 sec whether the water temperature of caloric stimulus applied was 30°C or 44°C (Fig. I). The visual suppression test was
Test Conditiori 111 Homogeneous white paper, the surface of which reflected 5 lux. Subjects were required to open their eyes at 55 sec after the onset of irrigation, at which time their eyes were covered with thick white paper at about 10 cm distance. A comparable value for the slowphase velocity was determined during the same time course as that of Test Condition I1 (Figs. I and 2).
Test Condition IV White paper, the surface of which reflected 2000 lux. Test procedure was the same as that of Test Condition I l l , except that in this test, the surface of the white paper facing the eyes was maintained at 2 000 lux illuminated evenly with a flash lamp behind the subject during the eye opening. A comparable reduction in the slow-phase velocity induced was calculated during the same time course as that of Test Condition I 1 (Figs. I and 2). A ( 10 O t o I ( i r i i i q o / 8
