The vertical component in a caloric nystagmus and the existence of a second phase of the nystagmus--the possibility of canal otolithic interaction in normal subjects]

To clarify the existence of the vertical component during a caloric nystagmus and the existence of a second phase of the nystagmus, 194 induced incidents of a caloric nystagmus in 29 normal subjects have been analyzed. Each nystagmus episode was recorded by using ENG and an infra-red video camera. The caloric stimuli were given by pouring 5 ml of water at 20 degrees C into the ear at an ear-up position. After irrigation, each subject then assumed a supine or a prone position, with the head bent 30 degrees forward in either position. All recordings contained vertical components that depended on the supine or prone head position and not on the side of the stimulated ear, i.e., an up-beating nystagmus resulted in the supine position and a down-beating nystagmus in the prone position. Further, the vertical component was far stronger in the prone position. In contrast, the horizontal component had larger velocities and was of longer duration in the supine position than in the prone position. When the first phase of the caloric nystagmus ended, the body position was changed 90 degrees, i.e., to a sitting position or a right-ear-down or left-ear-down position. All trials showed a horizontal component during the secondary phase when the head assumed the sitting position. As for the ear-down positions, only when the irrigated ear was moved upwards from the prone position during the secondary phase, an up-beating vertical nystagmus resulted in almost all the trials. These findings suggest that a caloric nystagmus may originate not only from the lateral semicircular canal but also from the vertical canals, and the second phase of a caloric nystagmus may be strongly influenced by the otolithic organs.     

Vertical component of the caloric response, including a caloric second phase provoked by positional change: a preliminary report

We measured the horizontal and vertical components of caloric nystagmus in 120 ears of 60 vertiginous patients who had moderate to vigorous caloric first-phase response in both ears, no spontaneous nystagmus, and no severe disorders in the central nervous system. We provoked a caloric first phase in the supine position with 5 ml of water at 20 degrees C for 15 seconds. We provoked a caloric second phase by changing the position of a patient from supine to sitting after the end of the first phase. The horizontal component of the caloric second phase was recorded in 108 of 120 ears (90%). The vertical component was recorded in 57 of 120 ears (48%) during the caloric first phase and in 51 of 120 ears (43%) during the caloric second phase. We suspected that the vertical component of the caloric first phase was mainly due to the inhibition of the anterior semicircular canal.     

Caloric nystagmus in three dimensions under otolithic control in rhesus monkeys. A preliminary report

The caloric nystagmus of rhesus monkeys in the 'optimum' supine or prone position was recorded three-dimensionally using magnetic search coils. The horizontal component of the nystagmus was in the direction expected from the convection flow theory of Bárány. The torsional component changed its direction according to the side of caloric stimulation independent of head position with regard to gravity, i.e., counterclockwise nystagmus by right ear stimulation and clockwise nystagmus by left ear stimulation both in the supine or in the prone positions. The direction of the vertical component depended upon the head position and not upon the side of stimulation, i.e., up-beating nystagmus in the supine position and down-beating nystagmus in the prone position. The durations and the contours of slow phase velocity of the horizontal, vertical and torsional components were different from each other. The origins of the first phase of caloric nystagmus in three dimensions may be explained by activation of all the three semicircular canals. As for the second phase of caloric nystagmus in the supine or in the prone position, the torsional component was comparatively strong and lasted the longest among the three components. The second phase of caloric nystagmus was markedly modified by head position with regard to gravity. These findings suggest that it is the otolithic organs that determine the moving plane of second phase caloric nystagmus.     

Three-component analysis of caloric nystagmus in humans.

Three-component analysis of caloric nystagmus, focusing on the horizontal, vertical, and torsional, using a computerized eye movement analysis system, was carried out in 10 normal human subjects. The caloric response was induced by cold stimulation to the right ear of the subjects in the supine and prone positions. In the supine position, the three components of nystagmus were toward the left (10 subjects), upward (eight subjects) or downward (two subjects), and clockwise (10 subjects). In the prone position, on the other hand, the three components were directed toward the right (10 subjects), downward (five subjects), upward (three subjects), and counterclockwise (10 subjects); there was no vertical direction in two subjects. These findings indicate that caloric stimulation activates the three semicircular canals simultaneously. Also the changes in the nystagmus direction in the supine and prone positions could be explained, at least partially, by the nonconvective component of caloric stimulation.     

Clinical significance of vertical component of caloric response including its second phase in vertiginous patients

CONCLUSIONS: Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s). OBJECTIVE: To investigate the origin of a vertical component in caloric response. MATERIALS AND METHODS: We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG. RESULTS: We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).     

Clinical significance of vertical component of caloric response including its second phase in vertiginous patients

Conclusions. Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s). Objective. To investigate the origin of a vertical component in caloric response. Materials and methods. We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG. Results. We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).     

Effect of angular acceleration on the localization performance of a remembered target

Both the influence of a remembered "earth-fixed" target (RT) on the vestibulo-ocular reflex and the effect of "unilateral cold caloric vestibular stimulation" on the localization of a RT have previously been proved. As "unilateral caloric stimulation" is not a physiological stimulus, the aim of the present study was to analyze whether even physiological "bilateral vestibular stimulation" (rotation) is able to affect the RT position. The pointing error (PE) towards an RT both without and following angular acceleration was investigated in 24 healthy volunteers. Postrotatory nystagmus response was recorded by electronystagmography. Evaluation parameters were "nystagmus frequency", "total amplitude" and "velocity of the slow phase"; the horizontal and vertical PE. The fixation of an RT led to a significant reduction of about 28% in nystagmus amplitude compared to the test condition in darkness. "After rotatory stimulation" a systematic horizontal PE in the direction of the fast phase of the postrotatory nystagmus (direction of "illusory self-rotation") occurred and the magnitude of this PE increased significantly compared to the test situation "without vestibular stimulation", but showed only a non-uniform negative correlation with two of the nystagmus parameters. It has to be concluded that "after rotatory stimulation", in contrast to "unilateral cold caloric vestibular stimulation", the subjective sense of "illusory self-motion" leads to a horizontal PE in the direction of the nystagmus fast phases.     

Three dimensional analysis of caloric nystagmus using computerized image recognition]

Three-component analysis of caloric nystagmus, focusing on horizontal, vertical, and torsional directions, using a newly developed computerized eye movement analysis system was carried out in ten normal human subjects. The caloric response was induced by cold stimulation to the right ear while the subjects were in supine and prone positions. The directions of the three components of nystagmus, were left in ten subjects (10), upward (8) or downward (2), and clockwise (10) in the supine position. In the prone position, on the other hand, the three components were directed toward the right (10), downward (5), upward (3), and counterclockwise (10) or were not present (2). These findings indicate that caloric stimulation activates the three semicircular canals simultaneously. In addition the changes in the direction of nystagmus in the supine and prone positions could not be explained in detail by the convection theory of caloric response alone.     

Results of Air Caloric and Other Vestibular Tests in Patients with Chronic Otitis Media

Objectives

Air caloric results are supposed to be influenced by anatomic changes of the middle ear. The aims of our study were to evaluate the incidence and characteristics of abnormal air caloric results in patients with unilateral chronic otitis media and without any history of vertigo, and to compare caloric results with there of other vestibular function tests (VFTs).

Methods

Twenty five patients with unilateral chronic otitis media (COM) who were scheduled for surgery underwent VFTs preoperatively. Hearing was assessed using pure-tone audiometry and vestibular function was assessed using a set of VFTs: air caloric, head-shaking nystagmus (HSN), vibration-induced nystagmus (VIN), and subjective visual vertical (SVV) tests.

Results

Six patients (24%) showed pathologic canal paresis (CP) on COM-sided ears. Two patients showed pathologic CP on the contralateral side. However, both of the two showed inverted nystagmus to warm air stimulation on the COM-side and hyperactive nystagmus to cold air stimulation on the COM-side, which means that the COM-sided ear was stimulated too much. There was pathologic HSN in 12 patients (48%), pathologic VIN in 7 (28%), and pathologic SVV in 5 (20%). Overall, 20 (80%) patients showed abnormal findings through a set of VFTs. Patients with an interaural difference of bone-conduction hearing thresholds ≥10 dB tended to show more abnormal VFT results than those for whom the interaural difference of bone-conduction hearing thresholds was <10 dB.

Conclusion

Our data show that one-fourth of patients with unilateral COM show abnormal caloric results on the COM side. However, subclinical latent vestibular imbalances were found to be common, which might be related to the gradual vestibular involvement in inflammatory processes, regardless of the caloric results. Results of a set of VFTs should be referred to when determining vestibular imbalance in patients with COM.     

鼓膜穿孔眩晕者的冷热气试验结果分析

目的：分析冷热气刺激下鼓膜穿孔患者的试验结果特点,探讨鼓膜穿孔者冷热气试验的可行性。方法：慢性中耳炎鼓膜穿孔伴眩晕的患者43例（49耳）,行双耳冷热气试验,观测眼震特点、慢相角速度（SPV）和眼震不对称比（UW）。结果：穿孔耳冷热气刺激诱发眼震呈现4种类型：①增强型：穿孔耳诱发性眼震SPV增强并超过正常范围,或强于非穿孔耳、UW＞15％者15例（17耳）;②“正常型”：穿孔、非穿孔耳眼震SPV均在正常范围,UW〈15％者7例;③减弱型：穿孔耳眼震SPV弱于非穿孔耳,UW〉15％者9例;④反向型：非穿孔耳冷热气刺激眼震正常,穿孔耳热气刺激眼震反向者12例（14耳）。反向型眼震均出现在近期慢性中耳炎复发、鼓膜穿孔且有渗出或潮湿者;其余类型均为慢性中耳炎静止期患者。结论：对于穿孔耳,冷热气成为强刺激,半规管功能正常时诱发的眼震强于非穿孔耳;穿孔耳半规管功能不同程度减弱时,诱发眼震可为正常或减弱反应;活动期的中耳炎患者,穿孔耳热气刺激可转化为冷刺激效应,诱发出反向眼震;冷热气试验可用于鼓膜穿孔伴眩晕患者的前庭功能评定。     

Three-dimensional analysis of caloric nystagmus in the rhesus monkey.

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 thermovective 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.     

Multiple sclerosis. The value of clinical vestibular examination

A clinical vestibular examination was carried out on 82 patients with multiple sclerosis (MS) selected on McAlpine's criteria. Spontaneous nystagmus, positional nystagmus or pathological caloric test were found in 49 (60%) patients. Pathological horizontal optokinetic nystagmus occurred in 47 (57%) patients. In 36 cases horizontal optokinetic nystagmus was pathological to both sides, in 28 cases combined with a pathological vertical optokinetic nystagmus, indicative of diffuse intracerebral lesions. Lesions in the central vestibular system and in the optokinetic pathways were frequently discovered in early or atypical cases of MS.     

Multiple sclerosis. The value of clinical vestibular examination.

A clinical vestibular examination was carried out on 82 patients with multiple sclerosis (MS) selected on McAlpine's criteria. Spontaneous nystagmus, positional nystagmus or pathological caloric test were found in 49 (60%) patients. Pathological horizontal optokinetic nystagmus occurred in 47 (57%) patients. In 36 cases horizontal optokinetic nystagmus was pathological to both sides, in 28 cases combined with a pathological vertical optokinetic nystagmus, indicative of diffuse intracerebral lesions. Lesions in the central vestibular system and in the optokinetic pathways were frequently discovered in early or atypical cases of MS.     

Caloric vertical nystagmus: the vertical semicircular canal in caloric testing

Vertical nystagmus elicited by caloric testing does not necessarily mean there is central pathology. In a patient with confirmed peripheral vestibular disease, caloric stimulation produced an intense vertical nystagmus, which showed all the features of a caloric nystagmus. The patient had bilateral mastoid cavities, allowing easy stimulation of the posterior semicircular canal, using air. At the same time, a unilateral horizontal semicircular canal functional loss was observed, raising the possibility of dissociated canal dysfunction.     

The effect of mental alerting on peripheral vestibular nystagmus during spontaneous, gaze (30 degrees left, 30 degrees right) and body positional (left & right lateral lying) testing using electronystagmography (ENG)

The performance of mental alerting during caloric testing has always been considered important, however its use/benefit during electronystagmography (ENG)/videonystagmography (VNG) testing has been questioned. The aim of this study was to investigate the effect of mental alerting tasks on peripheral type vestibular nystagmus recorded during ENG. Thirty patients with significant spontaneous/gaze or positional nystagmus (slow phase velocity >or= 6 degrees /s) were recruited from consecutive referrals for vestibular assessment. Nystagmus was recorded by ENG both in the presence and absence of mental alerting for each patient. Investigation of nystagmus by analysis of variance (ANOVA) revealed significantly larger nystagmus (higher value SPV) with mental alerting than with no alerting (p<0.001), and for some patients nystagmus traces were reduced to a flat line (no nystagmus) with no alerting. The study demonstrates the importance of mental alerting in helping overcome central suppression of nystagmus and highlights its importance to help identify peripheral type nystagmus during ENG.     

The effect of mental alerting on peripheral vestibular nystagmus during spontaneous,gaze (30° left, 30° right) and body positional (left & right lateral lying) testing using electronystagmography (ENG)

The performance of mental alerting during caloric testing has always been considered important, however its use/benefit during electronystagmography (ENG)/videonystagmography (VNG) testing has been questioned. The aim of this study was to investigate the effect of mental alerting tasks on peripheral type vestibular nystagmus recorded during ENG. Thirty patients with significant spontaneous/gaze or positional nystagmus (slow phase velocity ≥ 6°/s) were recruited from consecutive referrals for vestibular assessment. Nystagmus was recorded by ENG both in the presence and absence of mental alerting for each patient. Investigation of nystagmus by analysis of variance (ANOVA) revealed significantly larger nystagmus (higher value SPV) with mental alerting than with no alerting (p<0.001), and for some patients nystagmus traces were reduced to a flat line (no nystagmus) with no alerting. The study demonstrates the importance of mental alerting in helping overcome central suppression of nystagmus and highlights its importance to help identify peripheral type nystagmus during ENG.     

The Torsion Swing Chair test: a ratio method for quantifying nystagmus

In a Torsion Swing Chair (TSC) test for nystagmus, S is oscillated sinusoidally around the vertical axis with successive cycles diminishing in extent. Channel II of a standard recording ENG traces the chair's movement (differing among Ss according to their weight) while Channel I records S's ENG. A method was devised to quantify S's nystagmus by calculating, for each pair of succeeding cycles, the ratio of the decline in amplitude of the slow phase nystagmic velocity to the decline in amplitude of chair movement. This ratio, relatively constant across cycles, is greater with labyrinthine pathology. Ratios were established with 15 normal young adults as cut-offs for normalcy. The method was applied to 30 patients with peripheral hearing loss whose only complaint was slight vertigo following an acute stage of vertigo. The TSC test was validated by comparing it to the severity of vertigo and to the presence/absence of abnormal results on a standard clinical caloric test in ENG and on standard clinical ECoG. All but 1 of the 30 pts exhibited abnormal results on the TSC test, as compared with 18 for the caloric and 16 for the ECoG. Furthermore, abnormality on the TSC test was more likely to be associated with abnormal results on one or both of the other two tests than were either of the other two tests. It can be concluded that the TSC test is a valid and objective tool useful in ENG practice.     

Air Caloric Stimulation With Tympanic Membrane Perforation

Warm air caloric stimulation in an ear with tympanic membrane perforation or mastoidectomy cavity often causes contralateral nystagmus. Secondary nystagmus is common. Our evidence with squirrel monkeys and patients indicates that the primary “inversion” results from endolymph cooling due to evaporative cooling of the mucus lining the middle ear cavity, by the dry air stimulus. Disconjugate horizontal nystagmus was found in a patient with large eardrum perforation, after cold air caloric stimulation. The effect probably resulted from stimulation of the anterior or posterior vertical semicircular canal. Inverted or disconjugate caloric nystagmus after air stimulation is much more frequently due to tympanic membrane perforation, or moisture in the external ear, than to central nervous system disease.     

Vestibulo-ocular reflex (VOR) preserved in bilateral severe vestibular malformations with internal auditory canal stenosis

A 60-year-old woman, who has suffered from bilateral deafness throughout her life, visited our outpatient clinic. Computed tomography (CT) revealed inner ear malformations, which comprise cochlear aplasia with hypoplastic vestibule in the right ear and a common cavity in the left ear, and narrow internal auditory canals. We performed electronystagmography with caloric stimulation and stimulation of earth-vertical axis rotation (EVAR) or off-vertical axis rotation (OVAR), and studied vestibular evoked myogenic potentials (VEMPs) and vestibular ocular reflex (VOR). Slight horizontal nystagmus was induced by the stimulation of EVAR but not by caloric stimulation. Slight vertical nystagmus was observed during OVAR, whereas the VEMP test elicited no response. The result of horizontal or vertical VOR performed in the dark was almost normal. These findings suggest that VOR can be acquired even with severe malformation of the inner ear whose labyrinthine functions markedly reduce bilaterally until nystagmus is slightly induced by rotation stimulation.