Experimental study on the eye movements induced by the electrical stimulation of the cerebellar nucleus in the rabbit

The purpose of this study is to investigate the induced eye movements by the cerebellar nuclei stimulation in the rabbits. Forty-five pigmented rabbits were used in this experiments. The cerebellar nuclei, especially medial nucleus, were stimulated electrically and the induced eye movements were observed. The results were as follows. 1. The horizontal nystagmus was produced by the electrical stimulation of the medial, anterior interposed, or posterior interposed nuclei. 2. The horizontal nystagmus towards the ipsilateral to the stimulated side was observed when the caudal portion of the medial nucleus was stimulated. On the other hand, the horizontal nystagmus towards the contralateral to the stimulated side was observed when the rostral portion of the medial nucleus was stimulated. 3. The latency of the field potential in the vestibular nucleus by stimulating the medial cerebellar nucleus, and that in the reverse situation, were 0.7 to 1.1 msec. 4. After the destruction of the lateral vestibular nucleus, no nystagmus was elicited by the stimulation of the medial cerebellar nucleus. From these results, it can be concluded that there is the monosynaptic connection between the medial cerebellar nucleus and the lateral vestibular nucleus. This indicates that the stimulation of the medial cerebellar nucleus produces the excitation of the vestibular nucleus via the cerebello-vestibular fibers and produces the nystagmus in the pigmented rabbits.     

Surgical treatment of posterior semicircular canal dehiscence syndrome caused by jugular diverticulum

Objective: We report a rare case of posterior semicircular canal dehiscence caused by a jugular diverticulum, and we describe its surgical treatment using a dehiscence resurfacing manoeuvre. Method: The clinical findings, surgical procedure and outcomes are presented. Results: A 66-year-old man presented with disequilibrium, sound-induced vertigo, a reduced ocular vestibular evoked myogenic potential threshold, and pressure-induced vertical and torsional nystagmus. Computed tomography revealed a right posterior semicircular canal dehiscence caused by a diverticulum of the jugular bulb. The defect in the posterior semicircular canal was localised and resurfaced with bone paté, temporalis muscle fascia and conchal cartilage, under direct visualisation. Post-operatively, the patient's symptoms disappeared and his ocular vestibular evoked myogenic potential threshold normalised. Conclusion: This case illustrates that posterior semicircular canal dehiscence can be surgically managed by resurfacing the defect site via a transmastoid approach.     

On the vertical caloric nystagmus

Eye movements in response to caloric stimuli are recorded traditionally in the horizontal plane only. Twin channel electronystagmographic traces of 124 patients undergoing evaluation of vertigo were reviewed. Thirty traces (24%) were found to include a "true" vertical component to the evoked nystagmus. There was no correlation between the existence and the nature of any vestibular pathology and the presence of the vertical nystagmus. Thus, a vertical component to the caloric nystagmus (the so-called "perverted" caloric nystagmus) is not necessarily a pathological sign, and can be a normal variant, caused by excitation of the vertical semicircular canal - most probably the posterior one. The mechanisms of heat transfer in the temporal bone and the source of this vertical caloric nystagmus are discussed in the context of the published literature.     

Eye movements evoked by the selective stimulation of the utricular nerve in cats

Objective: Eye movements evoked by otolith organ are not well-investigated compare with canal related eye movements due to the technical difficulties. We try to solve this problem by means of our methods. Methods: Eye movements evoked by selective utricular (UT) nerve stimulation were investigated using both electrooculography (EOG) and video recording in decerebrated cats in the presence or absence of anesthesia. Electrical stimulation was applied to the UT nerve through implanted acupuncture needles. Results: In the absence of anesthesia and with stimulus intensities less than 2.6±0.7×N₁T, we found ipsilaterally directed horizontal eye movements in both eyes in one cat, abduction in the ipsilateral eye in two cats, and adduction in the contralateral eye in another cat. Other types of eye movements (e.g., supraduction or diagonal eye movements) were observed in both eyes of cats in the absence of anesthesia at a stimulus intensity of 12.2±7.6×N₁T, an intensity in which current spread to the adjacent nerve could not be ruled out. In the presence of anesthesia, UT nerve stimulation alone failed to evoke horizontal eye movements, but with an intensity 13.8±6.4×N₁T, supraduction or diagonal eye movements were evoked. UT nerve stimulation at 2–3×N₁T facilitated horizontal eye movements induced by ipsilateral abducens (AB) nucleus stimulation or contralateral horizontal canal nerve stimulation. Conclusion: This is the first report to our knowledge in which UT nerve-evoked horizontal eye movements are documented. These results confirm the known monosynaptic and disynaptic anatomical connections from utricular primary afferents to the ipsilateral AB nucleus neurons.     

Eye movements evoked by selective saccular nerve stimulation in cats

OBJECTIVE: Because of technical obstacles in controlling current spread to adjacent peripheral nerve, eye movements evoked by activation of the otolith organs have not been investigated in detail compared to eye movements evoked by activation of the canal organs. We attempted to solve this problem by applying more sensitive methods using fine needle and strictly controlling stimulus current intensity compare with filed potential for selective stimulation. METHODS: Eye movements evoked by selective, unilateral saccular (SAC) nerve stimulation were investigated using both electrooculography (EOG) and video recording in decerebrated cats in the presence or absence of anesthesia. Electrical stimulation was applied to the SAC nerve through implanted acupuncture needles. RESULTS: In the absence of anesthesia and with stimulus intensities less than (3.1 +/- 2.7) x N(1)T, we found supraduction in both eyes or in either the ipsilateral or contralateral eye of different cats. We observed downward eye movements using a stronger stimulus intensity ((6.2 +/- 2.9)) x N(1)T). The threshold for downward eye movements was significantly greater than that for upward eye movements (P < 0.05). In anesthetized cats, only downward eye movements were observed when stimulus intensities less than 10 x N(1)T ((7.8 +/- 2.3) x N(1)T) were used. CONCLUSION: These results confirm the known sacculo-ocular anatomical connections, which are involved predominantly in vertical eye movements. Because the sacculo-ocular connections are relatively weak, the normal supraduction evoked by SAC activation can be easily modified by factors such as level of anesthesia and the method of stimulation.     

Three-dimensional eye rotation axis analysis of benign paroxysmal positioning nystagmus

We have developed a new technique for analyzing the rotation vector of eye movement with an infrared CCD camera [Imai et al.: Acta Otolaryngol 1999;119:24-28]. We used this technique to analyze the eye rotation axis of benign paroxysmal positioning nystagmus (BPPN) that was induced by the Dix-Hallpike maneuver in 14 patients with benign paroxysmal positioning vertigo (BPPV). Eye rotation axes of BPPN in 8 patients were closely perpendicular to the posterior canal of the undermost ear in the provocative head position. Under the hypothesis that BPPN is due to a mechanical stimulation of the posterior canal by canalolithiasis, this finding suggested that the posterior canal of the undermost ear is the lesion. On the other hand, eye rotation axes of BPPN in the other 6 patients were closely aligned with the naso-occipital axis. It is suggested that canalolithiasis induces endolymphatic flow in both posterior and anterior canals via the common crus and the summation of the eye movements induced by stimulation of both the posterior and anterior canals rotates the eye along the naso-occipital axis.     

Interaction between the saccules and the vertical semicircular canals.

For the experiments 39 cats were used. Selective sectioning of either the anterior or the posterior vertical ampullar nerves was performed bilaterally. Additionally in some cats the utricular nerves were cut, or the saccule extirpated on one or both sides. The otolith organs were stimulated by tilting around the bitemporal axis of the animals. Bilateral sectioning of the anterior ampullar nerve induced vertical nystagmus upwards, which disappeared, if the animals were tilted upside down. When the posterior ampullar nerves were cut bilaterally a vertical nystagmus downwards was obtained, and if the animals were tilted upside down there was a large increase in nystagmus frequency. After unilateral extirpation of the saccule, vertical nystagmus downwards was observed in 50 percent of these experiments. This nystagmus was modulated by tilting. However, if the saccules on both sides were extirpated, no nystagmus could be elicited. The cause of these results is discussed.     

Mechanism of posterior semicircular canal stimulation in patients with benign paroxysmal positional vertigo

A quantitative study of the stimuli and vestibulo-ocular response associated with benign paroxysmal positional vertigo (BPPV) was made to test and further develop the canalithiasis theory of BPPV. The angular velocities of the head in the planes of the semicircular canals during the Dix-Hallpike test were measured in four healthy subjects using electromagnetic sensors to record the position of the head in a six degrees of freedom paradigm. Next, the nystagmus reactions in seven patients diagnosed with idiopathic BPPV were recorded with video-oculography. The characteristics of the vestibulo-ocular reflex (VOR) response were analyzed using three-dimensional vector techniques. The angular velocity of the head was primarily, but not exclusively, in the plane of the posterior semicircular canal (PSC) in question. Both the anterior and horizontal canals were also stimulated by a lesser degree. The duration of the motion stimulus in the PSC was < 1.3 s with peak angular velocities of 150 deg/s. The eye response in BPPV patients began 4 s after the test and had a duration of 15-20 s. Peak slow-component eye velocities of about 42 deg/s were reached 3-5 s after onset of nystagmus. The motion of the eye, as predicted by the cupulolithiasis theory, is disconjugated and has torsional, vertical, and horizontal components. In the eye ipsilateral to the tested ear it is primarily torsional (0.80, 0.54, 0.16) and in the contralateral eye it is mainly vertical (0.57, 0.73, 0.08). These results suggest that particles, initially resting on the floor of the cupula dome in the PSC, are perturbed by the Dix-Hallpike test and disperse freely into the endolymph where they are propelled by gravity into the canal lumen. This creates abnormal pressure on the cupula and the specific VOR activation of the ipsilateral superior oblique and the contralateral inferior rectus muscles, whose force vectors are indistinguishable from the measured eye motion vectors. The estimated pressure exerted on the crista is approximately 10(-2) dyn/cm2.     

红外视频采集仪记录BPPV患者眼震的结果分析

目的探讨用红外视频眼动采集仪(CHARTR VNG)观察记录良性阵发性位置性眩晕(benign paroxys-mal positional vertigo,BPPV)患者的眼震特点。方法用红外视频采集仪详细记录78例BPPV患者在Dix-Hallpike试验及滚转试验中的眼震变化。结果40例(51.28%)为一侧后半规管病变;13例(16.67%)为一侧水平半规管病变;6例(7.7%)为一侧上半规管病变;19例(24.36%)出现多发位置性眼震,其中6例为双侧后半规管病变,2例双侧上半规管病变,3例为双侧水平半规管病变,8例患者在不同头位下出现眼震,提示混合半规管病变。结论红外视频眼动采集仪可以更直观地观察眼动变化,对诊断BPPV受累半规管提供可靠依据,特别是对非典型位置性的眼震,能更好的提示良性阵发性位置性眩晕患者非典型位置性的眼震发生率,包括水平半规管、上半规管病变和多个半规管联合病变。患者的治疗可以根据不同的受累半规管采取不同方法。     

垂直平面摆动试验检测垂直半规管功能及其正常值的研究

目的 利用垂直平面摆动试验检测垂直半规管功能并探讨中青年垂直半规管功能正常值.方法 运用自主研制的SRM-Ⅳ全自动前庭功能诊治系统,采用垂直平面180°正弦非阻尼摆动方法对100名18 ～59岁的健康受试者诱发垂直眼震,记录眼震视频和眼震曲线,采集眼震个数、持续时间、慢相速度等参数.将100名健康受试者以45岁为界分为青年组(68例)和中年组(32例)进行比较.试验中以右前半规管和左后半规管为一对(right anterior semicircular canal and left posterior semicircular canal,RALP),以左前半规管和右后半规管为一对(left anterior semicircular canal and right posterior semicircular canal,LARP),计算出两对垂直半规管垂直眼震平均慢相速度两侧不对称比( canal paresis,CP),采用SPSS 13.0软件进行统计学分析.结果 青年组和中年组平均慢相速度CP值差异无统计学意义(P＞0.05),总体CP值,RALP为10.2％±7.1％,LARP为10.4％±6.2％.健康中青年人群垂直半规管垂直眼震平均慢相速度CP值95％参考值范围,RALP为低于23.7％,LARP为低于22.9％;CP正常范围:≤20％为理想值,20％～ 25％为正常偏高.结论 垂直平面180°摆动试验可有效检测垂直半规管功能,此方法有望在临床得到应用.     

Ecological Aspects of Auditory Rehabilitation

A quantitative study of the stimuli and vestibulo-ocular response associated with benign paroxysmal positional vertigo (BPPV) was made to test and further develop the canalithiasis theory of BPPV. The angular velocities of the head in the planes of the semicircular canals during the Dix-Hallpike test were measured in four healthy subjects using electromagnetic sensors to record the position of the head in a six degrees of freedom paradigm. Next, the nystagmus reactions in seven patients diagnosed with idiopathic BPPV were recorded with video-oculography. The characteristics of the vestibulo-ocular reflex (VOR) response were analyzed using three-dimensional vector techniques. The angular velocity of the head was primarily, but not exclusively, in the plane of the posterior semicircular canal (PSC) in question. Both the anterior and horizontal canals were also stimulated by a lesser degree. The duration of the motion stimulus in the PSC was &;lt;1.3 s with peak angular velocities of 150 deg/s. The eye response in BPPV patients began 4 s after the test and had a duration of 15-20 s. Peak slow-component eye velocities of about 42 deg/s were reached 3-5 s after onset of nystagmus. The motion of the eye, as predicted by the cupulolithiasis theory, is disconjugated and has torsional, vertical, and horizontal components. In the eye ipsilateral to the tested ear it is primarily torsional (0.80, 0.54, 0.16) and in the contralateral eye it is mainly vertical (0.57, 0.73, 0.08). These results suggest that particles, initially resting on the floor of the cupula dome in the PSC, are perturbed by the Dix-Hallpike test and disperse freely into the endolymph where they are propelled by gravity into the canal lumen. This creates abnormal pressure on the cupula and the specific VOR activation of the ipsilateral superior oblique and the contralateral inferior rectus muscles, whose force vectors are indistinguishable from the measured eye motion vectors. The estimated pressure exerted on the crista is approximately 10^-2 dyn/cm².     

Multiple positional nystagmus suggests multiple canal involvement in benign paroxysmal positional vertigo

Conclusion. Video-oculography demonstrates a higher occurrence of atypical positional nystagmus in patients with benign paroxysmal positional vertigo (BPPV). This includes anterior and horizontal canal variants and multiple positional nystagmus, suggesting combined lesions affecting several canals. Objective. To analyse the video-oculographic findings of positional tests in patients with BPPV. Material and methods. Seventy individuals with symptoms of BPPV and positional nystagmus were included in this study. The diagnosis was based on a history of brief episodes of vertigo and the presence of positional nystagmus as confirmed by video-oculographic examination during the Dix–Hallpike test, the McClure test or the head-hanging manoeuvre. Patients were treated by means of different particle repositioning manoeuvres according to the affected canal (Epley's manoeuvre for the posterior or anterior canals and Lempert's manoeuvre for the lateral canal) and the effectiveness was evaluated at 7 and 30 days. Results. Twenty-nine individuals (41.43%) presented an affected unilateral posterior canal. Fifteen patients (21.43%) presented a pure horizontal direction-changing positional nystagmus consistent with a diagnosis of horizontal canal BPPV. Twelve individuals (17.14%) presented a unilateral down-beating nystagmus, suggesting possible anterior canal BPPV. In addition, 14 patients (20%) showed multiple positional nystagmus during the examination corresponding to simultaneous multi-canal BPPV, 5 had bilateral posterior canal BPPV and 2 presented a positional down-beating nystagmus in both left and right Dix–Hallpike manoeuvres and the head-hanging manoeuvre, which is highly suggestive of anterior canal BPPV. However, seven individuals showed positional horizontal and vertical side-changing nystagmus that could not be explained by single-canal BPPV. These patients with multiple positional nystagmus showed changing patterns of positional nystagmus at follow-up.     

Multiple positional nystagmus suggests multiple canal involvement in benign paroxysmal vertigo

CONCLUSION: Video-oculography demonstrates a higher occurrence of atypical positional nystagmus in patients with benign paroxysmal positional vertigo (BPPV). This includes anterior and horizontal canal variants and multiple positional nystagmus, suggesting combined lesions affecting several canals. OBJECTIVE: To analyse the video-oculographic findings of positional tests in patients with BPPV. MATERIAL AND METHODS: Seventy individuals with symptoms of BPPV and positional nystagmus were included in this study. The diagnosis was based on a history of brief episodes of vertigo and the presence of positional nystagmus as confirmed by video-oculographic examination during the Dix-Hallpike test, the McClure test or the head-hanging manoeuvre. Patients were treated by means of different particle repositioning manoeuvres according to the affected canal (Epley's manoeuvre for the posterior or anterior canals and Lempert's manoeuvre for the lateral canal) and the effectiveness was evaluated at 7 and 30 days. RESULTS: Twenty-nine individuals (41.43%) presented an affected unilateral posterior canal. Fifteen patients (21.43%) presented a pure horizontal direction-changing positional nystagmus consistent with a diagnosis of horizontal canal BPPV. Twelve individuals (17.14%) presented a unilateral down-beating nystagmus, suggesting possible anterior canal BPPV. In addition, 14 patients (20%) showed multiple positional nystagmus during the examination corresponding to simultaneous multi-canal BPPV, 5 had bilateral posterior canal BPPV and 2 presented a positional down-beating nystagmus in both left and right Dix-Hallpike manoeuvres and the head-hanging manoeuvre, which is highly suggestive of anterior canal BPPV. However, seven individuals showed positional horizontal and vertical side-changing nystagmus that could not be explained by single-canal BPPV. These patients with multiple positional nystagmus showed changing patterns of positional nystagmus at follow-up.     

Pathological localization of so-called posterior canal BPPV

OBJECTIVE: Based on the hypothesis that the origin of nystagmus is from the posterior canal (PC), the nystagmus in the head hanging and sitting position should be mirror images. To clarify the anatomical origin of positioning nystagmus in BPPV patients, we analyzed the positioning nystagmus of benign paroxysmal positioning vertigo (BPPV) patients three-dimensionally. METHODS: Twenty-six patients with BPPV participated in this study. The positioning nystagmus was recorded in complete darkness from the patient's left eye by means of an infrared CCD camera. We performed three-dimensional analysis of nystagmus using video image analysis system (VIAS). Subsequently, the rotation axis of the 3D eye movements of the positioning nystagmus was calculated. RESULTS: Among the 26 patients tested, 20 patients demonstrated the axes of nystagmus in good or relatively good alignment to the PC axis. However, in 11 of these 20 patients there was poor alignment of the axis of nystagmus in the sitting position to the PC axis. In addition, six patients showed axes of nystagmus with poor alignment to the PC in the head hanging position. Among them, two patients exhibited axes of nystagmus in good alignment with the anterior canal, in spite of diagnosis of these patients as PC BPPV by experienced examiner based on the positioning nystagmus test. CONCLUSION: These results demonstrated that only one-third of patients who were diagnosed as BPPV, could be diagnosed as true BPPV which originates from a PC pathology. Besides the possibility that the pathology may originate from the AC, it is still unclear which part of the inner ear may be the candidate site of origin of the pathology of BPPV in the other 15 patients.     

A novel maneuver for diagnosis and treatment of torsional-vertical down beating positioning nystagmus: anterior canal and apogeotropic posterior canal BPPV

IntroductionIn patients with benign paroxysmal positional vertigo, BPPV; a torsional-vertical down beating positioning nystagmus can be elicited in the supine straight head-hanging position test or in the Dix-Hallpike test to either side. This type of nystagmus can be explained by either an anterior canal BPPV or by an apogeotropic variant of the contralateral posterior canal BPPV Until now all the therapeutic maneuvers that have been proposed address only one possibility, and without first performing a clear differential diagnosis between them.ObjectiveTo propose a new maneuver for torsional-vertical down beating positioning nystagmus with a clear lateralization that takes into account both possible diagnoses (anterior canal-BPPV and posterior canal-BPPV).MethodsA prospective cohort study was conducted on 157 consecutive patients with BPPV. The new maneuver was performed only in those with torsional-vertical down beating positioning nystagmus with clear lateralization.ResultsTwenty patients (12.7%) were diagnosed with a torsional-vertical down beating positioning nystagmus. The maneuver was performed in 10 (6.35%) patients, in whom the affected side was clearly determined. Seven (4.45%) patients were diagnosed with an anterior canal-BPPV and successfully treated. Two (1.25%) patients were diagnosed with a posterior canal-BPPV and successfully treated with an Epley maneuver after its conversion into a geotropic posterior BPPV.ConclusionThis new maneuver was found to be effective in resolving all the cases of torsional-vertical down beating positioning nystagmus-BPPV caused by an anterior canal-BPPV, and in shifting in a controlled way the posterior canal-BPPV cases of the contralateral side into a geotropic-posterior-BPPV successfully treated during the followup visit. Moreover, this new maneuver helped in the differential diagnosis between anterior canal-BPPV and a contralateral posterior canal-BPPV.     

Dynamics of canal response to head-shaking test in benign paroxysmal positional vertigo

CONCLUSIONS: Time constant and maximum slow phase velocity (SPV) of head-shaking nystagmus (HSN) demonstrated a differential canal response to head shaking in 24% of patients with posterior canal benign paroxysmal positional vertigo (BPPV). We suggest that vestibular lithiasis has a limited contribution to the mechanism that generates HSN. OBJECTIVE: To determine the canal response to head shaking in BPPV. PATIENTS AND METHODS: This was a case-control study including 104 individuals with BPPV. The diagnosis was based on the presence of vertigo and nystagmus during the positional test. Subjects were examined by the horizontal and vertical head-shaking test. Eye movements were recorded on a video camera to analyze the nystagmus. The head was shaken passively in the horizontal and sagittal planes, respectively, for horizontal and vertical HSN at a frequency of 2 Hz. HSN was considered when six consecutive beats of nystagmus with an SPV of at least 2 degrees/s were detected. Main outcome measures were the presence of horizontal and vertical HSN, maximum SPV of HSN, time constant of HSN, and canal paresis. RESULTS: Maximum SPV of vertical HSN was higher in BPPV patients with posterior canal BPPV (n = 10) than in controls (p = 0.04). Moreover, the time constant of vertical HSN was significantly lower for posterior canal BPPV when compared with controls (p < 0.02).     

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.     

Selective stimulation of the equilibrium organ using monochromatic near infrared

BACKGROUND: The aim of this study was, to establish, if a selective thermal warm-stimulation using monochromatic near infrared radiation (NIR) in healthy persons, patients with chronic otitis media (chronic mucosal inflammation) and after radical surgery of one ear shows quantitative or qualitative changes of the nystagmus reaction. PATIENTS AND METHODS: Healthy persons (n = 3), patients with a large central defect of the tympanic membrane (n = 5) and after radical ear surgery (n = 6) were examined. In healthy persons a stimulation with monochromatic NIR (lambda = 980 nm) of several areals of the external auditory canal was performed. In patients with large defects of the tympanic membrane the promontorium was stimulated. In patients with a radical cave of the ear a selective NIR-stimulation of the region of the vertical and the anterior semicircular canal was performed. The horizontal semicircular canal was visible as a landmark. Registration of the nystagmus was performed by means of videonystagmography. RESULTS: In healthy persons the mean slow phase velocity of the nystagmus depended on the stimulated region. But there was no qualitative change of three dimensional eye movement. Stimulation of the promontorium showed a strong directional horizontal nystagmus. In patients with a radical cave the stimulation of the regions of the three semicircular canals showed a qualitative difference in three dimensional eye movement. NIR-stimulation showed in all cases a nystagmus into the stimulated ear. CONCLUSIONS: The method of monochromatic near infrared stimulation can be used for selective stimulation of several regions of the external auditory canal, the promontorium and the regions of the semicircular canals in a radical cave of the ear as well as to prove the warm reaction of the equilibrium organ. A specific nystagmus after stimulation of the semicircular canal-region in a radical cave of the ear could be an indication for a normal semicircular canal function.     

Paroxysmal positional vertigo syndrome.

INTRODUCTION: This study was initiated to investigate the differential diagnosis of patients with benign paroxysmal positional vertigo (BPPV) of different canals' origin. METHODS: The eye movements of 292 patients were evaluated with the use of Frenzel glasses and infrared video cameras after positional tests. Epley's canal repositioning procedure (CRP) was conducted, with appropriate modifications for individual cases, on every patient. RESULTS: Two different types of positional nystagmus were observed corresponding to the presence of otoliths in the lumen of each of the semicircular canals and on the cupola of the horizontal semicircular canal. The posterior canal was involved in 250 patients unilaterally and 23 patients bilaterally. The anterior canal variety was observed in four patients. In the horizontal canal, nine were of the cupulolithiasis and six of the canalithiasis variety. In seven patients. the affected canal converted to a different location. The canal repositioning procedure eliminated vertigo and abnormal eye movements in 88% of the unilateral posterior canal variety. The success rate of the procedure in the other varieties was 50%. CONCLUSION: Positional vertigo can have characteristics corresponding to the presence of otolith particles in each of the semicircular canals. The treatment requires different strategies to move the otoliths, depending on their location in the vestibule.     

Three-dimensional analysis of pressure nystagmus in labyrinthine fistulae.

In this study we analysed pressure nystagmus three-dimensionally in subjects with labyrinthine fistulae. The fistulae were localized in the lateral canal in five patients, in the posterior canal in one patient and in both lateral and anterior canals in two patients. The eye velocities during the fistula test in patients with lateral canal fistula and in a patient with posterior canal fistula were closely aligned with the anatomical axes. On the other hand, pressure nystagmus in cases with fistulae of both the lateral and anterior canals were not aligned with the anatomical axes of the combination of both canals.