Vertical Semicircular Canal Function Research Articles

A Clinical Infrared Video-Oculoscopy Suppression Head Impulse (IR-cSHIMP) Test.

We propose a Suppression Head IMPulse (SHIMP) test method that provides for equipment only through the use of InfraRed Video-OculoScopy (IR-VOS) and allows horizontal and vertical semicircular canal function evaluation in bedside mode. We therefore named the test InfraRed clinical SHIMP (IR-cSHIMP). To check IR-cSHIMP diagnostic efficiency, we studied 22 normal subjects, 18 patients with unilateral, and 6 with bilateral deficient vestibulopathy. Each subject first underwent a vestibular examination and, only later, an IRc-SHIMP test. When the IR-cSHIMP test was performed in the horizontal plane, all normal subjects showed anti-compensatory saccades. When the vertical semicircular canal function was evaluated, the same result was obtained in all normal subjects except three, which were considered false positives. In patients with vestibular deficits, the test performed in the horizontal and vertical planes were always pathological, with 100% agreement between clinical and instrumental tests. Our bedside method proved to be fast, simple, and effective in discriminating between healthy and pathological subjects. It required only the same skill as the better-known cHIT. For these reasons, we believe that the IR-cSHIMP should be part of daily clinical practice as a useful tool in the selection of patients to undergo more sophisticated investigations.

Isolated bilateral posterior semicircular canal hypofunction: comparison with bilateral vestibulopathy

Background Chronic unsteadiness is a common complaint at vestibular clinics. Bilateral vestibulopathy (BVP) is a major cause of chronic unsteadiness but is often overlooked. Although diagnostic criteria for BVP have been established by the Barany Society, isolated vertical canal hypofunction can remain undiagnosed. Recently, the video head-impulse test has enabled clinicians to assess vertical semicircular canal function at clinics. Objective This study aimed to compare the features of isolated bilateral posterior semicircular canal hypofunction (IBPH) with those of BVP diagnosed based on the Barany criteria. Methods The clinical data of 8 IBPH patients that had been diagnosed using our diagnostic criteria (sex, age, subjective symptoms, questionnaire, video head-impulse test and stabilometry) were analyzed and compared with those of 6 BVP patients diagnosed using the Barany criteria. Results The IBPH patients were all aged >70 years, while the age range of the BVP patients was wider. While the BVP patients complained of both oscillopsia during body movement and unsteadiness in darkness, the IBPH patients complained of unsteadiness in darkness without oscillopsia during body movement. The IBPH patients exhibited milder clinical findings than the BVP patients. Conclusion IBPH can cause mild unsteadiness in the elderly. Significance Clinicians should be aware that IBPH can cause unsteadiness in the elderly.

VHIT Testing of Vertical Semicircular Canals With Goggles Yield Different Results Depending on Which Canal Plane Being Tested.

Objective: The use of goggles to assess vertical semicircular canal function has become a standard method in vestibular testing, both in clinic and in research, but there are different methods and apparatus in use. The aim of this study was to determine what the cause of the systematic differences is between gain values in testing of the vertical semicircular canals with two different video head impulse test (vHIT) equipment in subjects with normal vestibular function.Study Design: Retrospective analysis of gain values on patients with clinically deemed normal vestibular function (absence of a corrective eye saccade), tested with either Interacoustics or Otometrics system. Prospective testing of subjects with normal vestibular function with the camera records the eye movements of both eyes. Finally, 3D sensors were placed on different positions on the goggles measuring the actual vertical movement in the different semicircular planes.Results: In the clinical cohorts, the gain depended on which side and semicircular canal was tested (p < 0.001). In the prospective design, the combination between the stimulated side, semicircular canal, and position of the recording device (right/left eye) highly influenced the derived gain (p < 0.001). The different parts of the goggles also moved differently in a vertical direction during vertical semicircular canal testing.Conclusion: The gain values when testing the function of the vertical semicircular canals seem to depend upon which eye is recorded and which semicircular plane is tested and suggests caution when interpreting and comparing results when different systems are used both clinically as well as in research. The results also imply that further research and development are needed to obtain accurate vertical semicircular canal testing, in regard to both methodology and equipment design.

The role of vertical semicircular canal function in the vertical component of skull vibration-induced nystagmus

Background: Generally, vertical component of the skull vibratory nystagmus (VCN) is ignored in the clinical practise. Thus, the relative contribution of the vestibular organs in the presence of VCN remains unknown.Objectives: To determine the association between vertical semicircular canal (vSCC) function and the presence of VCN.Material and methods: Comparisons were made between Video Head Impulse Test and SVINT (100 Hz) results at the time of the acute peripheral vestibular lesion (PVL) and at the post-acute phase in patients diagnosed PVL. Later on, a paired analysis was performed restricting the assessments to patients with vestibular explorations in both the acute and post-acute phases.Results: In an univariable analysis, larger mean total gain differences (TGD) between vSCC VOR gains, significantly related with the appearance of VCN in nystagmography in the acute phase (p = .001), unlike the post-acute phase (p = .46). After a multivariate analysis, mean TGD was the only predictive factor of the VCN (p = .013). In the paired analysis, we found an increase in the post-acute phase mean TGD, approaching zero value.Conclusions and significance: Global relation between all vertical canals has at least a contributory role in the presence of the vertical component of nystagmus in SVINT.

The Video Head Impulse Test: Our Experience in 45 Cases.

To evaluate the role of video head impulse test in the diagnosis of peripheral vestibular disorders, we performed an observational study in the outpatient department in a tertiary setup in which the clinical head impulse test and the video head impulse test were performed on 45 patients with clinically suspected peripheral vestibular disorders, and their results were correlated. To analyse our results, each ear was counted individually and hence, among 45 patients, 12 out of 90 ears showed abnormal clinical head impulse test for lateral semicircular canals and 27 out of 90 ears showed abnormal video head impulse test for lateral semicircular canals. This gave us an additional diagnostic accuracy of 21.1% on using video head impulse test for the lateral semicircular canals as compared to the clinical head impulse test. Video head impulse test is a physiological, quick and well tolerated test for assessing the vestibular function, and the only practical test for assessing the vertical semicircular canal function. Video head impulse test provides valuable information in localising the site of lesion as it assesses the semicircular canals individually. Video head impulse is merely not an objectification and registration system for the clinical head impulse test as it provides additional information such as vestibulo-ocular reflex gain, and occurrence of covert refixation saccades which cannot be picked up by naked eyes.

Disease-specific sparing of the anterior semicircular canals in bilateral vestibulopathy.

Bilateral vestibular loss (BVL) is often diagnosed with great delay and an underlying cause is only identified in 50-80%. We measured horizontal and vertical semicircular canal function using the video-head-impulse test (vHIT) and hypothesized that specific vHIT-patterns may be linked to certain etiologies. We retrospectively analyzed 109 BVL-patients linked to aminoglycoside vestibulotoxicity (n=16), Menière's disease (n=10), infectious inner-ear disorders (n=11), sensorineural hearing-loss (n=11), cerebellar-ataxia-neuropathy-vestibular-areflexia-syndrome (CANVAS, n=5), other causes (n=19) as well as those with unknown origin (n=47). Vestibulo-ocular reflex gains and cumulative saccade amplitudes were measured with vHIT, and the functional integrity of all semicircular canals was rated. Overall, anterior canal hypofunction (n=86/218) was identified significantly (p<0.001) less often than horizontal (n=186/218) and posterior (n=194/218) hypofunction. Preserved anterior canal function was associated with aminoglycoside vestibulotoxicity, Menière's disease and BVL of unknown origin, while no such sparing was found for inner-ear infections, CANVAS and sensorineural hearing loss. Semicircular canal function in BVL shows disease-specific dissociations, potentially related to reduced vulnerability or superior recovery of the anterior canals. In patients with suspected BVL we recommend quantifying vHIT gains and saccade amplitudes for all semicircular canals as the pattern of canal hypofunction may help identifying the underlying disorder.

Functional analysis of the vertical semicircular canal using vertical plane swing test and study of its normal values

The purpose of this study was to set up a method to analyze the vertical semicircular canal function and study the normal values of the vertical semicircular canal function using the vertical plane swing test. A prospective analysis of 100 normal persons (aged from 18 to 59 years), who were treated by using the vertical plane swing test with the newly developed automatic vestibular function diagnosis and therapy system (SRM-IV). These persons were rotated 180° at a sinusoidal speed (acceleration 45°/s, maximum speed 90°/s) in the vertical semicircular canal plane. Using a PC, evoked vertical nystagmus was analyzed in order to evaluate the excitability of vertical semicircular canals, including the number and the duration of nystagmus, the slow phase velocity and other parameters. Meanwhile, the all persons were divided into two groups, order and younger than 45 years respectively. In the test procedure, with the two pairs of the right anterior vertical semicircular canal and left posterior vertical semicircular canal (RALP) as well as the left anterior vertical semicircular canal and the rear right vertical semicircular canals (LARP), the average slow phase velocity of the vertical nystagmus and the canal paresis (CP) of the two pairs of vertical semicircular canals were calculated using PC and SPSS13.0 software for statistical analysis. There was no significant difference between the two groups (P > 0.05). The general CP of RALP was 10.2% ± 7.1%, and LARP was 10.4% ± 6.2%. The normal CP range of the vertical semicircular canal in the health group was identified (idea: ≤ 20%; normal high: 20% - 25%). The 180° vertical plane sinusoidal swing method is effective in functional analysis of the vertical semicircular canal, it is expected to be reliably used in clinical treatment.

A new rotational test for vertical semicircular canal function

Objective: We developed a new rotating chair in order to assess the function of the vertical semicircular canal (VSCC) by analyzing VSCC-induced post-rotatory nystagmus (PRN). Methods: We examined 14 healthy subjects, wearing goggles equipped with an infrared CCD camera, and sitting on a chair which was designed to stimulate a pair of the VSCCs by tilting the head 60° backward with a 45° rotation to the left or right side from the sagital plane. The time constant (TC) or maximal slow phase eye velocity (MSPEV) of the vertical component of four kinds of PRN were analyzed in four corresponding rotatory conditions, and used as functional index of the corresponding VSCC. Results: The mean values of MSPEV in both anterior semicircular canal (ASCC) and posterior semicircular canal (PSCC)-induced PRN tended to be lower ( P<0.10) than those induced by the lateral semicircular canal (LSCC). The result suggests that the threshold to the angular velocity in the VSCC is lower than that in the LSCC. The mean values of TC in both ASCC and PSCC-induced PRN were significantly lower ( P<0.05) than those induced by the LSCC. Conclusion: The significant reduction of TC in VSCC-induced PRN compared with LSCC-induced PRN indicates that VSCC function is less affected by velocity storage mechanisms than LSCC function. The rotational test with respect to the VSCC can be used as a tool for assessing vertical canal function.

Vertical Semicircular Canal Function: A Study in Patients with Benign Paroxysmal Positional Vertigo

Vertical Semicircular Canal Function: A Study in Patients with Benign Paroxysmal Positional Vertigo

Vertical Semicircular Canal Function: A Study in Patients with Benign Paroxysmal Positional Vertigo

A pendular rotation test in a head-tilted position (60° backwards and rotated 45° to either the right or left) was performed in 7 patients with benign paroxysmal positional vertigo (BPPV). Patients were rotated 360° at a frequency of 0.1 Hz (maximum speed 114°/s). The excitability of vertical semicircular canals was evaluated using this test procedure. Using an infrared CCD camera and a PC, evoked nystagmus was analyzed in order to determine the morbidity of BPPV. A statistically significant difference ( p <0.05) was found in the maximal slow-phase eye velocity between nystagmus from the anterior semicircular canal and nystagmus from the posterior semicircular canal. The excitability of the posterior semicircular canal in the affected ear was lower than that of the anterior semicircular canal. However, when vertigo and nystagmus disappeared, the difference in excitability was improved. The present results indicate some functional deterioration of the posterior semicircular canal in BPPV cases, suggesting the participation of both mechanical (dumping by mass) and organic (peripheral end organ) factors in causing morbidity.

垂直半規管の回転検査 頭位別の眼球運動解析

Benign Paroxysmal positioning vertigo and acoustic tumors are thought to be related to the function of the vertical semicircular canal (VSCC). Therefore, we developed a new test to assess VSCC function by analyzing VSCC-induced nystagmus. We examined 11 healthy subjects, wearing goggles equipped with an infrared CCD camera and sitting on a chair designed to bilaterally stimulate the VSCCs by tilting the head backward during 45° rotation to the right on the sagital plane. The stimuli used were sinusoidal rotation with a maximal angular velocity of 100°/sec at a frequency of 0.033 Hz. The result was that the maximum slow phase eye velocity (MSPEV) of horizontal nystagmus decreased parallel to the head-tilted angle and the MSPEV of the vertical nystagmus was maximal when the head was tilted 60° or 70° backward. From the perspective of VSCC anatomy, the direction of horizontal nystagmus is reversed when head is tilted 60° backward. However, we could not observe the reverse of the direction of horizontal nystagmus even when head tilted 80° backward. We considered that vertical nystagmus was maximal when the head was tilted 60-70° backward because this position applied the optimal stimulation to the VSCC. This finding is in agreement with the position of the vertical VSCC in skull. We concluded that rotational test with respect to the VSCC can be used to analyze VSCC function.

Evaluation of the vertical semicircular canal function by the pendular rotation test: a study on patients with benign paroxysmal positional vertigo.

The pendular rotation test (non-damped) in a head-tilted position, 60 degrees backward and then rotated 45 degrees either to the right or left, was performed in 6 patients with benign paroxysmal positional vertigo. The stimulus mode was amplitude = 360 degrees, frequency = 0.1 Hz, and the maximal speed = 114 degrees/s. By this test procedure, it was possible to evaluate the excitability of vertical semicircular canals. Using an infra-red CCD camera and a personal computer system, the evoked nystagmus was analysed. A statistically significant difference (p < 0.05) in the maximal slow-phase eye velocity of vertical nystagmus was found between those from the anterior semicircular canal and those from the posterior semicircular canal. The excitability of the posterior semicircular canal in the affected ear was found to be lower than that of the anterior semicircular canal.

垂直半規管刺激性回転後眼振 健常耳での外側半規管刺激との比較

To test vertical semicircular canal function, we developed a new and convenient type of rotation-chair, in which subjects sat with their heads and backs tilting backward 60°and with their heads rolling laterally 45°. A CCD camera and infrared video system was used to record eye movement in the dark. Normal subjects were rotated with an acceleration of 2°/sec2 until the angular velocity reached 60°/sec. The rotation was then stopped with a deceleration of 100°/sec2 after per-rotation nystagmus subsided. The maximal slow phase eye velocity (MSPEV) of vertical components of vertical semicircular canal (VSCC)-induced post-rotatory nystagmus (PRN) were analysed.Subjects were first rotated with laterally rolling head angles of 30°, 45° and 60°to examine the optimal angle for stimulating VSCC.MSPEV of posterior semicircular canal (PSCC)-induced PRN was largest with a head angle of 60°. While MSPEV of anterior semicircular canal (ASCC)-induced PRN did not vary with the laterally rolling head angle. MSPEV of the vertical components of VSCC-induced PRN was then compared with that of the horizontal components of lateral semicircular canal (LSCC)-induced PRN. MSPEV of both PSCC- and ASCC-induced PRN were significantly smaller than that of LSCC-induced PRN.MSPEV of ASCC-induced PRN was slightly smaller than that of PSCC-induced PRN, though individual differences varied widely. However, there were very small leftright differences in MSPEV of both PSCC- and ASCC-induced PRN. Therefore, it is suggested that our PRN function test involving VSCC can diagnose vestibular diseases.

Vestibulo-ocular reflex

Recent animal and clinical studies on the vestibulo-ocular reflex deal with a number of physiological and clinical aspects from which three were chosen for this review: (1) the torsional vestibulo-ocular reflex and its disorders; (2) the otolith contribution to the vestibulo-ocular reflex; and (3) neurotransmitters, neuropharmacological aspects, and medical treatment. Disorders of the vestibulo-ocular reflex can be classified according to the three major planes of action, yaw plane, pitch plane, and roll plane, which equate with horizontal nystagmus, upbeat or downbeat nystagmus, and torsional nystagmus, respectively. The particular interest in the torsional vestibulo-ocular reflex arises from new methods for measuring ocular torsion, especially the three-dimensional eye-movement recordings with scleral coils. These methods make it possible to do three-dimensional analysis of the differential effects of horizontal and vertical semicircular canal function and their individual disorders of the torsional vestibulo-ocular reflex. Otolith and semicircular canal inputs converge at the level of the vestibular nuclei to subserve static graviceptive and dynamic torsional and pitch function. The elaboration of the particular sensorial weight of the input from either the otoliths or the semicircular canal is currently a challenge for both physiologists and neurologists. Disorders of otolith function, still absent from the diagnostic repertoire of most neurologists, are increasingly being reported. The most promising developments in therapeutic measures may come from research on vestibular neurotransmitters, their agonists and antagonists. A number of pharmacological agents are effective suppressants of pathological eye movements. However, systematic prospective studies are needed.(ABSTRACT TRUNCATED AT 250 WORDS)

TORSIONAL NYSTAGMUS

Thirty-five patients with torsional nystagmus (TN) underwent vestibular and ocular motor assessment and magnetic resonance image (MRI) scanning of the head. Patients were divided into two groups according to whether TN was predominant and present in primary gaze (Group I, 23 patients) or elicited by head positioning or gaze deviation and less prominent than other concurrent nystagmus (Group II, 12 patients). The main aetiologies in both groups were demyelination, vascular disease and posterior fossa tumours. In Group I, a frequent pattern of findings, occurring in 30-50% of cases, was a caloric canal paresis contralateral to the direction of the fast phases ('beat') of the TN, whereas the duration of horizontal caloric/rotational nystagmus and the slow-phase eye velocity of pursuit and of optokinetic nystagmus were all reduced in the direction of beating. The TN was more frequently and consistently modulated by vertical canal stimuli (head oscillation in roll) than by otolith stimuli (static tilt). Statistical analysis of the MRI showed significant overlap of abnormal MRI signals in the area of the vestibular nuclei, on the side opposite to the beat direction of TN. These results suggest that TN originates in a central imbalance of vertical semicircular canal function, resulting from lesions involving the vestibular nuclei on the opposite side of the TN. Group II was heterogeneous with no consistent pattern of neuro-otological findings, although lesions ipsilateral to the TN were frequent occurrence; in these cases cerebellar system lesions may have produced ipsilateral vestibular nuclei disinhibition.