Acta Oto-Laryngologica
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey Andreas Böhmer, Dominik Straumann, Naomi Kawachi, Yasuko Arai & Volker Henn To cite this article: Andreas Böhmer, Dominik Straumann, Naomi Kawachi, Yasuko Arai & Volker Henn (1992) Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey, Acta Oto-Laryngologica, 112:6, 916-926, DOI: 10.3109/00016489209137491 To link to this article: http://dx.doi.org/10.3109/00016489209137491
Published online: 08 Jul 2009.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [University of Cincinnati Libraries]
Date: 15 March 2016, At: 07:00
Acta Otolaryngol (Stockh) 1992; 112: 916-926
Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey ANDREAS BOHMER,' DOMINIK STRAUMANN,' NAOMI KAWACHI; YASUKO ARA13 and VOLKER HE"'
Downloaded by [University of Cincinnati Libraries] at 07:00 15 March 2016
From the Deparrmenis of 'Neurology and 'Ororhinolaryngology, University Hospital Zurich, Switzerland, and 'Department of Otolaryngology. Tokyo Women's Medical College, Daini Hospital, Tokyo, Japan
Bohmer A, Straumann D, Kawachi N, Arai Y , Henn V. Three-dimensional analysis of caloric nystagmus in the Rhesus monkey. Acta Otolaryngol (Stockh) 1992; 112: 916-926.
The aim of this study was to investigate whether caloric nystagmus contains response components that can be attributed to a stimulation of the vertical semicircular canals. Three dimensional eye movement recordings with a dual search coil technique revealed important horizontal, vertical and torsional nystagmus components following irrigation of the external ear canal with cold water in various head positions relative to gravity. Horizontal nystagmus components, i.e. lateral semicircular canal vectors, followed a cosine function of both the pitch and yaw angle of the head relative to gravity, confirming a mainly therrnovective mechanism for stimulation of the horizontal canals. Vertical and torsional nystagmus components behaved differently following left and right ear irrigations. Right-left symmetrical vectors emerged only when the vertical and torsional components were transposed into vectors of single semicircular canal directions. The intensity of these vertical semicircular canal vectors as a function of the position of the corresponding canal relative to gravity, however, excludes important thermovective mechanisms acting at the vertical canals. It remains an open question whether these vertical canal vectors represent a non-thermovective caloric stimulation of vertical canal afferents. Key words: eye movements, dual search coil, thermovection, semicircular canals.
INTRODUCTION Caloric nystagmus is still the most important tool for clinical examination of unilateral vestibular function. In the standard bithermal caloric test, irrigation of the outer ear canal is performed with the lateral semicircular canal in the earth vertical position and horizontal nystagmus is analyzed. Nystagmus components in other than horizontal directions may also be induced by caloric stimulation; torsional nystagmus, for instance, was described by Baldny as early as in 1907 (1). However, there are only few and inconsistent data on these components which depend in a complex way on head position relative to gravity. Vertical nystagmus in at least one of the four standard caloric irrigations (warm and cold stimulation of each ear) could be recorded in about every fourth subject (2, 3). These vertical responses were considered as originating from the vertical semicircular canals, but definite conclusions were not possible due to the variable Occurrence and even inconsistent direction of this vertical nystagmus. Hadj-Djilani, on the other hand, reported consistent upbeating/downbeating nystagmus following cold/warm stimulation in a supine position, but exclusively downbeating nystagmus following both cold and warm stimulation in a face down position (4). Following cold stimulation, horizontal nystagmus could be changed to a torsional nystagmus by changing the head position from the standard supine 30" face up to a 60" face down position ( 5 ) . This torsional nystagmus was considered to originate from the posterior canals. Experiments in space have shown that horizontal nystagmus can be elicited by caloric stimulation even in zero-gravity (6). Nevertheless, thermovection of the endolymph of the
Downloaded by [University of Cincinnati Libraries] at 07:00 15 March 2016
Acta Otolaryngol (Stockh) 112
Three-dimensional caloric nystagrnus
lateral semicircular canal seems to be the most important, but not exclusive mechanism for generation of caloric horizontal nystagmus in normal I-g conditions. Thermovective mechanisms have been demonstrated also in the vertical canals in preparations of frogs and pigeons, where calorization was applied directly to the walls of vertical canals (7, 8). However, it is not known whether the same thermovection is also induced by irrigation of the external ear canal. The magnetic search coil technique allows to record eye movements in three dimensions. Preliminary, i.e. uncalibrated, recordings of caloric nystagmus in monkeys with this technique revealed important vertical and torsional nystagmus components, which changed independently of each other when the irrigations were performed in supine and prone positions (9). The present paper for the first time reports on three-dimensional quantitative measurements of caloric nystagmus. We especially asked whether vertical and torsional components of caloric nystagmus can be attributed to stimulation of the vertical semicircular canals. Caloric stimulations were therefore performed in optimal and pessimal positions for thermovection of each semicircular canal. Definite responses from single vertical canals would allow to extend the diagnostic value of this clinical test, which at present is confined to the function of the lateral semicircular canal. METHODS Experiments were performed on 3 Rhesus monkeys, which were chronically prepared with stereotaxically implanted head bolts to fixate the head during the experiments in defined positions. The stereotaxic horizontal ( Horsley-Clarke) plane was defined by the outer acoustic meatus and the lower orbital rim. A dual search coil was implanted in one eye for three-dimensional recording of eye movements ( 10). Surgery was done under inhalative anaesthesia with 0 2 / N , 0 mixture, initiated by intraperitoneal pentobarbital and supplemented by halothane as required. Stimulation. Prior to the caloric tests the animals received amphetamine (either 1 mg i.m. or 2 mg orally) to induce a constant level of alertness. They were seated in a primate chair with the head firmly fixed with the horizontal stereotaxic plane in a 15" nose down position. The primate chair was placed inside the inner frame of a turntable with three axes that allowed to have the monkey oriented in any position relative to gravity. A thin polyethylene tube was introduced 24mm into the outer ear canal and imgations were performed with 2 ml of ice water (0 "C) in one monkey, and 5 ml water of 20'C in the 2 other monkeys. Calorically induced nystagmus was recorded in complete darkness in the following positions relative to gravity (Fig. 1): i) in the standard clinical supine position with the lateral semicircular canal in the earth vertical plane and the ampulla at the top of the semicircular canal, ii) in an upright, and iii) in a prone position (pitched 9 0 and 180about an interaural axis from the supine position). In the latter two positions the lateral canal was either earth-horizontal or earth-vertical with the ampulla at the bottom of the canal, it.) in a supine/prone position with the body rotated in the yaw plane 45 laterally either with the irrigated ear up (ELI) or down (ED). This manoeuvre brought one of the vertical semicircular canals in an earth-vertical, and the other one in an earth-horizontal plane. Maximally eight different irrigations were performed at a single experimental day with intervals of at least 10 min in the light. A few obviously poor responses-probably due to improper irrigation-were discarded and then repeated on another day.
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Acta Otolaryngol (Stockh) 112
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ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey Andreas Böhmer, Dominik Straumann, Naomi Kawachi, Yasuko Arai & Volker Henn To cite this article: Andreas Böhmer, Dominik Straumann, Naomi Kawachi, Yasuko Arai & Volker Henn (1992) Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey, Acta Oto-Laryngologica, 112:6, 916-926, DOI: 10.3109/00016489209137491 To link to this article: http://dx.doi.org/10.3109/00016489209137491
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 6
View related articles
Citing articles: 4 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [University of Cincinnati Libraries]
Date: 15 March 2016, At: 07:00
Acta Otolaryngol (Stockh) 1992; 112: 916-926
Three-dimensional Analysis of Caloric Nystagmus in the Rhesus Monkey ANDREAS BOHMER,' DOMINIK STRAUMANN,' NAOMI KAWACHI; YASUKO ARA13 and VOLKER HE"'
Downloaded by [University of Cincinnati Libraries] at 07:00 15 March 2016
From the Deparrmenis of 'Neurology and 'Ororhinolaryngology, University Hospital Zurich, Switzerland, and 'Department of Otolaryngology. Tokyo Women's Medical College, Daini Hospital, Tokyo, Japan
Bohmer A, Straumann D, Kawachi N, Arai Y , Henn V. Three-dimensional analysis of caloric nystagmus in the Rhesus monkey. Acta Otolaryngol (Stockh) 1992; 112: 916-926.
The aim of this study was to investigate whether caloric nystagmus contains response components that can be attributed to a stimulation of the vertical semicircular canals. Three dimensional eye movement recordings with a dual search coil technique revealed important horizontal, vertical and torsional nystagmus components following irrigation of the external ear canal with cold water in various head positions relative to gravity. Horizontal nystagmus components, i.e. lateral semicircular canal vectors, followed a cosine function of both the pitch and yaw angle of the head relative to gravity, confirming a mainly therrnovective mechanism for stimulation of the horizontal canals. Vertical and torsional nystagmus components behaved differently following left and right ear irrigations. Right-left symmetrical vectors emerged only when the vertical and torsional components were transposed into vectors of single semicircular canal directions. The intensity of these vertical semicircular canal vectors as a function of the position of the corresponding canal relative to gravity, however, excludes important thermovective mechanisms acting at the vertical canals. It remains an open question whether these vertical canal vectors represent a non-thermovective caloric stimulation of vertical canal afferents. Key words: eye movements, dual search coil, thermovection, semicircular canals.
INTRODUCTION Caloric nystagmus is still the most important tool for clinical examination of unilateral vestibular function. In the standard bithermal caloric test, irrigation of the outer ear canal is performed with the lateral semicircular canal in the earth vertical position and horizontal nystagmus is analyzed. Nystagmus components in other than horizontal directions may also be induced by caloric stimulation; torsional nystagmus, for instance, was described by Baldny as early as in 1907 (1). However, there are only few and inconsistent data on these components which depend in a complex way on head position relative to gravity. Vertical nystagmus in at least one of the four standard caloric irrigations (warm and cold stimulation of each ear) could be recorded in about every fourth subject (2, 3). These vertical responses were considered as originating from the vertical semicircular canals, but definite conclusions were not possible due to the variable Occurrence and even inconsistent direction of this vertical nystagmus. Hadj-Djilani, on the other hand, reported consistent upbeating/downbeating nystagmus following cold/warm stimulation in a supine position, but exclusively downbeating nystagmus following both cold and warm stimulation in a face down position (4). Following cold stimulation, horizontal nystagmus could be changed to a torsional nystagmus by changing the head position from the standard supine 30" face up to a 60" face down position ( 5 ) . This torsional nystagmus was considered to originate from the posterior canals. Experiments in space have shown that horizontal nystagmus can be elicited by caloric stimulation even in zero-gravity (6). Nevertheless, thermovection of the endolymph of the
Downloaded by [University of Cincinnati Libraries] at 07:00 15 March 2016
Acta Otolaryngol (Stockh) 112
Three-dimensional caloric nystagrnus
lateral semicircular canal seems to be the most important, but not exclusive mechanism for generation of caloric horizontal nystagmus in normal I-g conditions. Thermovective mechanisms have been demonstrated also in the vertical canals in preparations of frogs and pigeons, where calorization was applied directly to the walls of vertical canals (7, 8). However, it is not known whether the same thermovection is also induced by irrigation of the external ear canal. The magnetic search coil technique allows to record eye movements in three dimensions. Preliminary, i.e. uncalibrated, recordings of caloric nystagmus in monkeys with this technique revealed important vertical and torsional nystagmus components, which changed independently of each other when the irrigations were performed in supine and prone positions (9). The present paper for the first time reports on three-dimensional quantitative measurements of caloric nystagmus. We especially asked whether vertical and torsional components of caloric nystagmus can be attributed to stimulation of the vertical semicircular canals. Caloric stimulations were therefore performed in optimal and pessimal positions for thermovection of each semicircular canal. Definite responses from single vertical canals would allow to extend the diagnostic value of this clinical test, which at present is confined to the function of the lateral semicircular canal. METHODS Experiments were performed on 3 Rhesus monkeys, which were chronically prepared with stereotaxically implanted head bolts to fixate the head during the experiments in defined positions. The stereotaxic horizontal ( Horsley-Clarke) plane was defined by the outer acoustic meatus and the lower orbital rim. A dual search coil was implanted in one eye for three-dimensional recording of eye movements ( 10). Surgery was done under inhalative anaesthesia with 0 2 / N , 0 mixture, initiated by intraperitoneal pentobarbital and supplemented by halothane as required. Stimulation. Prior to the caloric tests the animals received amphetamine (either 1 mg i.m. or 2 mg orally) to induce a constant level of alertness. They were seated in a primate chair with the head firmly fixed with the horizontal stereotaxic plane in a 15" nose down position. The primate chair was placed inside the inner frame of a turntable with three axes that allowed to have the monkey oriented in any position relative to gravity. A thin polyethylene tube was introduced 24mm into the outer ear canal and imgations were performed with 2 ml of ice water (0 "C) in one monkey, and 5 ml water of 20'C in the 2 other monkeys. Calorically induced nystagmus was recorded in complete darkness in the following positions relative to gravity (Fig. 1): i) in the standard clinical supine position with the lateral semicircular canal in the earth vertical plane and the ampulla at the top of the semicircular canal, ii) in an upright, and iii) in a prone position (pitched 9 0 and 180about an interaural axis from the supine position). In the latter two positions the lateral canal was either earth-horizontal or earth-vertical with the ampulla at the bottom of the canal, it.) in a supine/prone position with the body rotated in the yaw plane 45 laterally either with the irrigated ear up (ELI) or down (ED). This manoeuvre brought one of the vertical semicircular canals in an earth-vertical, and the other one in an earth-horizontal plane. Maximally eight different irrigations were performed at a single experimental day with intervals of at least 10 min in the light. A few obviously poor responses-probably due to improper irrigation-were discarded and then repeated on another day.
9 17
Downloaded by [University of Cincinnati Libraries] at 07:00 15 March 2016
918 Andreas Bohmer et al.
Acta Otolaryngol (Stockh) 112
'>.--
