A fuzzy set theoretical approach to automatic analysis of nystagmic eye movements

A mouse model of autoimmune inner ear disease without endolymphatic hydrops

Autoimmune inner ear disease (AIED) is an organ-specific disease characterized by irreversible, prolonged, and progressive hearing and equilibrium dysfunctions. The primary symptoms of AIED include asymmetric sensorineural hearing loss accompanied by vertigo, aural fullness, and tinnitus. AIED is divided into primary and secondary types. Research has been conducted using animal models of rheumatoid arthritis (RA), a cause of secondary AIED. However, current models are insufficient to accurately analyze vestibular function, and the mechanism underlying the onset of AIED has not yet been fully elucidated. Elucidation of the mechanism of AIED onset is urgently needed to develop effective treatments. In the present study, we analyzed the pathogenesis of vertigo in autoimmune diseases using a mouse model of type II collagen-induced RA. Auditory brain stem response analysis demonstrated that the RA mouse models exhibited hearing loss, which is the primary symptom of AIED. In addition, our vestibulo-oculomotor reflex analysis, which is an excellent vestibular function test, accurately captured vertigo symptoms in the RA mouse models. Moreover, our results revealed that the cause of hearing loss and vestibular dysfunction was not endolymphatic hydrops, but rather structural destruction of the organ of Corti and the lateral semicircular canal ampulla due to an autoimmune reaction against type II collagen. Overall, we were able to establish a mouse model of AIED without endolymphatic hydrops. Our findings will help elucidate the mechanisms of hearing loss and vertigo associated with AIED and facilitate the development of new therapeutic methods.

Effect of Sitting Position vs. Supine Position With the Head Turned to the Affected Side on Benign Paroxysmal Positional Vertigo Fatigue

Objective: In benign paroxysmal positional vertigo (BPPV), positional nystagmus becomes generally weaker when the Dix–Hallpike test is repeated. This phenomenon is termed BPPV fatigue. We previously reported that the effect of BPPV fatigue deteriorates over time (i.e., the positional nystagmus is observed again after maintaining a sitting head position). The aim of this study was to investigate whether the effect of BPPV fatigue attenuates after maintaining a supine position with the head turned to the affected side.

Methods: Twenty patients with posterior-canal-type BPPV were assigned to two groups. Group A received Dix–Hallpike test, were returned to the sitting position (reverse Dix–Hallpike test) with a sitting head position for 10 min, and then received a second Dix–Hallpike test. Group B received Dix–Hallpike test, were kept in the supine position with the head turned to the affected side for 10 min, and then received reverse Dix–Hallpike test followed by the second Dix–Hallpike test. The maximum slow phase eye velocity (MSPEV) of positional nystagmus induced by the first, reverse, and second Dix–Hallpike test were analyzed.

Results: The ratio of MSPEV of the positional nystagmus induced by the second Dix–Hallpike test relative to the first Dix–Hallpike test was significantly smaller in group B than that in group A. There was no difference in the MSPEV of the positional nystagmus induced by the reverse Dix–Hallpike test between group A and B.

Conclusions: The effect of BPPV fatigue is continued by maintaining a supine position with the head turned to the affected side, while the effect is weakened by maintaining a sitting head position. On the basis of the most widely accepted theory of the pathophysiology of BPPV fatigue, in which the particles become dispersed along the canal during head movement in the Dix–Hallpike test, we found an inconsistency whereby the dispersed otoconial debris return to a mass during the sitting position but do not return to a mass in the supine position with the head turned to the affected side. Future studies are required to determine the exact pathophysiology of BPPV fatigue.

Classification of Evidence: 2b.

Effects of cochlear implants on otolith function as evaluated by vestibulo-ocular reflex and vestibular evoked myogenic potentials

OBJECTIVE

The aim of this study was to investigate whether the insertion of an implant into the cochlea is accompanied by a deterioration in otolith function. Cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP) and linear vestibulo-ocular reflex (lVOR) during eccentric rotation were assessed before and after cochlear implantation (CI) to evaluate otolith function.

METHODS

Twelve patients with bilateral severe sensorineural hearing loss who had undergone CI surgery in our hospital between May 2016 and November 2017 were included in this study. cVEMP and oVEMP were assessed using the asymmetry ratio (AR), calculated with the following formula: [(peak-to-peak amplitude calculated as the sum of the p13 and n23 amplitudes in the non-operated side) - (that in the operated side)]/[(that in the non-operated side) + (that in the operated side)]. The ratio of VOR gain during eccentric rotation against VOR gain during center rotation was used to assess lVOR. For eccentric rotation, patients were rotated while displaced from the axis of rotation. At the same time, linear acceleration stimulated the utricle and induced lVOR. All patients underwent cVEMP and oVEMP tests and center and eccentric rotation tests before and about 30days after CI surgery.

RESULTS

Three patients with absent cVEMP responses before surgery were excluded, leaving pre-surgery cVEMP results for 9/12 patients. In five of these patients, the AR of cVEMP increased after CI, indicating that saccular function, as evaluated by cVEMP, did not deteriorate significantly postoperatively. One patient with an absent oVEMP response before CI was excluded, leaving pre-surgery oVEMP results for 11/12 patients. In 10 of these patients, the AR of oVEMP increased after CI surgery, indicating that utricular function, as evaluated by oVEMP, deteriorated significantly postoperatively. However, because the ratio of VOR gain during eccentric rotation against VOR gain during center rotation did not become worse after CI, utricular function, as evaluated by lVOR, did not deteriorate significantly postoperatively. Symptoms of vertigo became worse after CI in two of the 12 patients.

CONCLUSION

CI does not cause a deterioration in saccular function, as evaluated by cVEMP. Although CI does cause a deterioration in utricular function in oVEMP tests, this is not consistent in lVOR tests. These results indicate that CI causes a slight deterioration in utricular function that is insufficient to cause vertigo or deterioration of lVOR.

Effects of Interval Time of the Epley Maneuver on Immediate Reduction of Positional Nystagmus: A Randomized, Controlled, Non-blinded Clinical Trial

Objective: The Epley maneuver (EM) has an immediate effect: rapid reduction of positional nystagmus. Benign paroxysmal positional vertigo (BPPV) causes BPPV fatigue, which constitutes fatigability of positional nystagmus and vertigo with repeated performance of the Dix-Hallpike test; notably, BPPV fatigability becomes ineffective over time. We hypothesized that the immediate effect of the EM is caused by BPPV fatigue. Therefore, we suspected that performance of the EM with intervals between head positions would worsen the immediate reduction of positional nystagmus in patients with BPPV, because BPPV fatigability would become ineffective during performance of this therapy.

Methods: Forty patients with newly diagnosed BPPV were randomly assigned to the following two groups; one group performed the EM without intervals between positions (group A), and the other group performed the EM with 3 min intervals between positions (group B). The primary outcome measure was the ratio of maximum slow-phase eye velocity (MSPEV) of positional nystagmus soon after the EM, compared with that measured before the EM. Secondary outcome included whether a 30 min interval after the EM enabled recovery of MSPEV of positional nystagmus to the original value. This study followed the CONSORT 2010 reporting standards.

Results: In both groups A and B, the immediate effect of the EM could be observed, because MSPEV during the second Dix-Hallpike test was significantly smaller than MSPEV during the first Dix-Hallpike test (p < 0.0001 in group A, p < 0.0001 in group B). The primary outcome measure was larger in group B than in group A (p = 0.0029). The immediate effect faded 30 min later (secondary outcome).

Conclusions: This study showed that the EM had an immediate effect both with and without interval time in each head position of the EM. Because setting interval time in each head position of the EM reduced the immediate effect of the EM, interval time during the EM adds less benefit. This finding can reduce the effort exerted by doctors, as well as the discomfort experienced by patients with pc-BPPV, during EM. However, this immediate effect may be caused by BPPV fatigue, and may fade rapidly.

Classification of Evidence: 1b

Three-dimensional analysis of the vestibulo-ocular reflex and the ability to distinguish the direction of centripetal acceleration in humans during eccentric rotation with the right ear facing downwards

This study was conducted to evaluate the linear vestibulo-ocular reflex (lVOR) mediated by the saccule, and to investigate the relationship between the lVOR and the ability to distinguish the direction of centripetal acceleration during centric and eccentric rotation. Participants sat on a chair in darkness, with the right ear facing downwards, either directly above the center of rotation, or with their nose out, nose in, right shoulder out, or left shoulder out against the center of rotation (eccentric rotation). Participants were given no information about the chair position, and were rotated sinusoidally at 0.1-0.7 Hz. Three-dimensional eye movements during rotation were analyzed. Participants were asked to describe the position of the chair after rotation. Correctly reporting the five possible chair positions requires recognition of the direction of centripetal acceleration. We analyzed the rate of correct answers to assess participants' ability to identify the direction of centripetal acceleration. lVOR mediated by the saccule was observed only at high rotational frequencies. The rate of correct answers was higher at high rotational frequencies than that at low rotational frequencies. These results indicate that high rotational frequency is important for both lVOR mediated by the saccule and distinguishing the direction of centripetal acceleration.

Visual Target Strategies in Infantile Nystagmus Patients With Horizontal Jerk Waveform

The aim of this study was to propose a new pathophysiological hypothesis for involuntary eye oscillation in infantile nystagmus (IN): patients with IN exhibit impaired gaze fixation, horizontal smooth pursuit and optokinetic nystagmus (OKN) and use saccadic eye movements for these underlying impairments. In order to induce saccades, they make enough angle between gaze and target by precedent exponential slow eye movements. IN consists of the alternate appearance of the saccade and the slow eye movements. Unlike most previous theories, IN is therefore considered a necessary strategy allowing for better vision and not an obstacle to clear vision. In five patients with IN, eye movements were analyzed during the smooth pursuit test, saccadic eye movement test, OKN test and vestibulo-ocular reflex (VOR) test. Their gaze fixation, horizontal smooth pursuit, OKN and the last half of the slow phase of VOR were impaired. The lines obtained by connection of the end eye positions of fast phase of nystagmus coincided with the trajectories of targets. The findings indicate that patients followed the target by the fast but not the slow phase of nystagmus, which supports our hypothesis. By setting the direction of slow phase of nystagmus opposite to the direction of the OKN stimulation, enough angle can be effectively made between the gaze and target for the induction of saccade. This is the mechanism of reversed OKN response. In darkness and when eyes are closed, IN weakens because there is no visual target and neither the saccade for catching up the target or slow phase for induction of the saccade is needed.

Topology for gaze analyses - Raw data segmentation

Recent years have witnessed a remarkable growth in the way mathematics, informatics, and computer science can process data. In disciplines such as machine learning, pattern recognition, computer vision, computational neurology, molecular biology, information retrieval, etc., many new methods have been developed to cope with the ever increasing amount and complexity of the data. These new methods offer interesting possibilities for processing, classifying and interpreting eye-tracking data. The present paper exemplifies the application of topological arguments to improve the evaluation of eye-tracking data. The task of classifying raw eye-tracking data into saccades and fixations, with a single, simple as well as intuitive argument, described as coherence of spacetime, is discussed, and the hierarchical ordering of the fixations into dwells is shown. The method, namely identification by topological characteristics (ITop), is parameter-free and needs no pre-processing and post-processing of the raw data. The general and robust topological argument is easy to expand into complex settings of higher visual tasks, making it possible to identify visual strategies.

Assessment of endolymphatic hydrops and otolith function in patients with Ménière's disease

Ménière's disease is associated with hydrops of the inner ear endolymphatic space, and histopathologically, the cochlea and vestibule are usually involved. We used gadolinium-enhanced magnetic resonance imaging and measured cervical and ocular vestibular evoked myogenic potentials and the gain in the utricular induced linear vestibulo-ocular reflex to test the hypothesis that vestibular hydrops in Ménière's disease patients is associated with otolith organ dysfunction. We evaluated 21 patients diagnosed with unilateral definitive Ménière's disease using gadolinium magnetic resonance imaging to detect endolymphatic hydrops in the cochlea and vestibule. Cervical and ocular vestibular evoked myogenic potentials and the gain in utricular induced linear vestibulo-ocular reflex during eccentric rotation were measured to assess otolith organ function. For eccentric rotation, patients were rotated while displaced from the axis of rotation, while linear acceleration stimulated the utricle and induced the vestibulo-ocular reflex. Magnetic resonance imaging revealed vestibular hydrops in 14 of 20 patients (70%). Among the 14 patients, ten (71%) had abnormal cervical and three (21%) had abnormal ocular vestibular evoked myogenic potentials. Four patients (4/21, 19%) had abnormal linear vestibulo-ocular reflexes, three of whom also had abnormal ocular vestibular evoked myogenic potentials. Overall, 16 of 17 patients had normal linear vestibulo-ocular reflexes and normal ocular vestibular evoked myogenic potentials. Vestibular endolymphatic hydrops in Ménière's disease patients caused otolith organ dysfunction, mainly in the saccule. The number of Ménière's disease patients with abnormal ocular vestibular evoked myogenic potentials was low (19%), and they also had abnormal utricular induced linear vestibulo-ocular reflexes.

Three-dimensional analysis of otolith-ocular reflex during eccentric rotation in humans

When a participant is rotated while displaced from the axis of rotation (eccentric rotation, ER), both rotational stimulation and linear acceleration are applied to the participant. As linear acceleration stimulates the otolith, the vestibulo-ocular reflex (VOR) caused by the otolith (linear VOR; lVOR) would be induced during ER. Ten participants were rotated sinusoidally at a maximum angular velocity of 50°/s and at frequencies of 0.1, 0.3, 0.5, and 0.7Hz. The radius of rotation during ER was 90cm. The participants sat on a chair at three different positions: on the axis (center rotation, CR), at 90cm backward from the axis (nose-in ER, NI-ER) and at 90cm forward from the axis (nose-out ER, NO-ER). Their eye movements during rotation were recorded and analyzed three-dimensionally. The VOR gain during NI-ER was lower at 0.5 and 0.7Hz, and that during NO-ER was higher at 0.3, 0.5, and 0.7Hz than during CR. These results indicate that lVOR actually worked at 0.5 and 0.7Hz during ER and that the enhancement and decline of the VOR gain relative to the VOR gain during CR was seen in humans. Thus, we suggest that otolith function can be assessed via rotational testing of NI-ER and NO-ER.

Light cupula: the pathophysiological basis of persistent geotropic positional nystagmus

OBJECTIVE

To clarify the pathophysiological basis of persistent geotropic positional nystagmus (PGN) in patients with the horizontal canal type of benign paroxysmal positional vertigo (H-BPPV), the time constant (TC) of nystagmus and the relationship between its slow phase eye velocity (SPV) and the angle of head rotation in supine were defined.

METHODS

Geotropic or apogeotropic positional nystagmus was recorded by video-oculography and analysed three-dimensionally.

RESULTS

Geotropic positional nystagmuses in patients with H-BPPV were classified as transient geotropic positional nystagmus with a TC of ≤35 s or PGN with a TC of >35 s. Alternatively, the TC of persistent apogeotropic positional nystagmus (AN) in patients with H-BPPV was >35 s. The direction of the SPV of patients with PGN was opposite to that of patients with AN at each head position across the range of neutral head positions. The relationship between the SPV of patients with PGN and the angle of head rotation was linearly symmetrical against that of patients with AN with respect to a line drawn on the neutral head position.

CONCLUSIONS

Since its TC was >35 s, it is suggested that PGN is induced by cupula deviation in response to gravity at each head position. It is also suggested that the direction of cupula deviation in patients with PGN is opposite to that of patients with AN across the neutral head positional range with no nystagmus where the long axis of cupula is in alignment with the axis of gravity. Since the pathophysiological basis of AN is considered a heavy cupula, it is suggested that PGN is conversely induced by a light cupula.

Pseudo-anterior canalolithiasis

CONCLUSION

Because nystagmus induced by ampullopetal inhibition of the posterior semicircular canal (PSCC) rotates around the axis perpendicular to the plane of the anterior semicircular canal (ASCC) of the other side, when free-floating debris is initially located at the distal portion of the PSCC, a patient showing positional nystagmus appears to have the ASCC type of benign paroxysmal positional nystagmus. We name this 'pseudo-anterior canalolithiasis'.

OBJECTIVE

We report on pseudo-anterior canalolithiasis originating in the PSCC and discuss the differential findings between pseudo-anterior and true anterior canalolithiasis by means of three-dimensional (3D) analysis of the positional nystagmus.

METHODS

We performed 3D analysis of the positional nystagmus in a patient with true anterior canalolithiasis and in another patient with pseudo-anterior canalolithiasis.

RESULTS

In the patient with true anterior canalolithiasis, the direction of positional nystagmus during reverse Epley maneuver was constant and its axis was perpendicular to the plane of the right ASCC three-dimensionally. In contrast, in the patient with pseudo-anterior canalolithiasis, the first positional nystagmus of which the axis was perpendicular to the plane of the left ASCC became a second positional nystagmus of which the axis was perpendicular to the plane of the right PSCC during the reverse Epley maneuver.

Analysis of benign paroxysmal positional nystagmus in children

INTRODUCTION

Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder. However, BPPV in children has been studied less extensively than in the adult population. This is because the observation of benign paroxysmal positional nystagmus (BPPN) in children is technically very difficult and BPPV is rare in children. In this study, we present the only two cases of BPPV in children in which we successfully recorded and analyzed the BPPN.

METHODS

One case was an 11-year-old boy and the other was a 3-year-old girl. We analyzed their BPPN three-dimensionally.

RESULTS

Apogeotropic positional nystagmus was observed in the first case. We analyzed it to verify the presence of cupulolithiasis in the horizontal semicircular canal (HSCC). Geotropic positional nystagmus was observed in the second case, and the analyzed data indicated the presence of canalolithiasis in HSCC. Over the last decade, we have examined 3341 patients complaining of vertigo or dizziness. Among them, there were 63 children with the same complaint, so that the proportion of cases of BPPV in children was only 3% (2/63).

DISCUSSION

Among patients complaining of vertigo or dizziness, children with BPPV are rare (3%). However, we have recorded their BPPN to confirm that BPPV does occur in children and that their characteristics of positional nystagmus are generally identical to those in adults. We emphasize that this is the first report of a child as young as 3 years old being diagnosed with BPPV.

Neural network approaches to grade adult depression

Depression is a common but worrying psychological disorder that adversely affects one's quality of life. It is more ominous to note that its incidence is increasing. On the other hand, screening and grading of depression is still a manual and time consuming process that might be biased. In addition, grades of depression are often determined in continuous ranges, e.g., 'mild to moderate' and 'moderate to severe' instead of making them more discrete as 'mild', 'moderate', and 'severe'. Grading as a continuous range is confusing to the doctors and thus affecting the management plan at large. Given this practical issue, the present paper attempts to differentiate depression grades more accurately using two neural net learning approaches-'supervised', i.e., classification with Back propagation neural network (BPNN) and Adaptive Network-based Fuzzy Inference System (ANFIS) classifiers, and 'unsupervised', i.e., 'clustering' technique with Self-organizing map (SOM), built in MATLAB 7. The reason for using the supervised and unsupervised learning approaches is that, supervised learning depends exclusively on domain knowledge. Supervision may induce biasness and subjectivities related to the decision-making. Finally, the performance of BPNN and ANFIS are compared and discussed. It was observed that ANFIS, being a hybrid system, performed much better compared to the BPNN classifier. On the other hand, SOM-based clustering technique is also found useful in constructing three distinct clusters. It also assists visualizing the multidimensional data clusters into 2-D.

3D analysis of spontaneous upbeat nystagmus in a patient with astrocytoma in cerebellum

AIMS

We report the case of a 58-year-old female patient who consulted our Department complaining of positional vertigo and showing spontaneous upbeat nystagmus (UBN) in darkness.

METHOD

We analyzed her UBN three-dimensionally. The MRI scan revealed the astrocytoma in the left cerebellum involving the cerebellar vermis.

RESULT

Three-dimensional analysis showed a spontaneous UBN rotating around the intra-aural axis in the pitch plane.

CONCLUSION

Since the cerebellar vermis is known to plays an inhibitory role on the central vertical vestibule-ocular reflex (VOR), the present results suggest that the spontaneous UBN in darkness observed in this patient was induced by an imbalance of central vertical VOR tone.

An improved algorithm for automatic detection of saccades in eye movement data and for calculating saccade parameters

This analysis of time series of eye movements is a saccade-detection algorithm that is based on an earlier algorithm. It achieves substantial improvements by using an adaptive-threshold model instead of fixed thresholds and using the eye-movement acceleration signal. This has four advantages: (1) Adaptive thresholds are calculated automatically from the preceding acceleration data for detecting the beginning of a saccade, and thresholds are modified during the saccade. (2) The monotonicity of the position signal during the saccade, together with the acceleration with respect to the thresholds, is used to reliably determine the end of the saccade. (3) This allows differentiation between saccades following the main-sequence and non-main-sequence saccades. (4) Artifacts of various kinds can be detected and eliminated. The algorithm is demonstrated by applying it to human eye movement data (obtained by EOG) recorded during driving a car. A second demonstration of the algorithm detects microsleep episodes in eye movement data.

Waveform type evaluation in congenital nystagmus

Congenital nystagmus is an ocular-motor disorder characterised by involuntary, conjugated and bilateral to and fro ocular oscillations. In this study a method to recognise automatically jerk waveform inside a congenital nystagmus recording and to compute foveation time and foveation position variability is presented. The recordings were performed with subjects looking at visual targets, presented in nine eye gaze positions; data were segmented into blocks corresponding to each gaze position. The nystagmus cycles were identified searching for local minima and maxima (SpEp sequence) in intervals centred on each slope change of the eye position signal (position criterion). The SpEp sequence was then refined using an adaptive threshold applied to the eye velocity signal; the outcome is a robust detection of each slow phase start point, fundamental to accurately compute some nystagmus parameters. A total of 1206 slow phases was used to compute the specificity in waveform recognition applying only the position criterion or adding the adaptive threshold; results showed an increase in negative predictive value of 25.1% using both features. The duration of each foveation window was measured on raw data or using an interpolating function of the congenital nystagmus slow phases; foveation time estimation less sensitive to noise was obtained in the second case.

3D analysis of benign positional nystagmus due to cupulolithiasis in posterior semicircular canal

CONCLUSIONS

The characteristic of both the vertical-torsional positional nystagmus with long time constant and its disappearance at the neutral head position could diagnose cupulolithiasis in posterior semicircular canal (PSCC) in the eight patients with the PSCC type of benign paroxysmal positional vertigo (P-BPPV).

OBJECTIVE

The aim of the study was to diagnose cupulolithiasis in patients with P-BPPV.

PATIENTS AND METHODS

We used three-dimensional rotation axis analysis of nystagmus of the vertical-torsional positional nystagmus in 111 patients with P-BPPV and evaluated its time constant. We then examined whether the vertical-torsional positional nystagmus with long time constant disappeared at the neutral head position where the axis of the heavy cupula of the affected PSCC is aligned with gravity.

RESULTS

The first parameter showed a wide variation that could be divided into two groups: one lasting more than 40 s in 8 patients and another below 20 s in 103 patients. Since the time constant of the positional nystagmus induced by cupulolithiasis was much longer than that induced by canalolithiasis, this finding suggests that cupulolithiasis in the PSCC induced the vertical-torsional positional nystagmus with a long time constant in the group of eight patients. The vertical-torsional positional nystagmus disappeared in these patients at the neutral head position, where the axis of the cupula of affected PSCC aligned with gravity.

Differential diagnosis of true and pseudo-bilateral benign positional nystagmus

CONCLUSIONS

Two patients showing two rotational axes of their positional nystagmus had canalolithiasis in bilateral posterior semicircular canals (PSCCs), leading to the diagnosis of true bilateral benign paroxysmal positional nystagmus (P-BPPN). Another 18 patients had a single rotation axis of their positional nystagmus with short time constant (TC) on one side and long TC on the other. Since canalolithiasis in the uppermost PSCC may be transient cupulolithiasis, evoking positional nystagmus with long TC, the diagnosis of the latter patients should be pseudo-bilateral P-BPPN.

OBJECTIVE

To differentiate the true bilateral posterior canal type of P-BPPN from pseudo-bilateral P-BPPN.

PATIENTS AND METHODS

The rotational axis and TC of positional nystagmus were three-dimensionally analyzed in 20 patients showing geotropic torsional nystagmus on the left and right Dix-Hallpike (D-H) maneuvers.

RESULTS

Two patients showed two rotational axes of their positional nystagmus, which were perpendicular to the plane of the PSCCs. There were no differences in TCs of their positional nystagmus between bilateral D-Hs. Another 18 patients showed a single rotational axis of their positional nystagmus, which was perpendicular to the plane of either the left or right PSCC. TCs of their positional nystagmus were short on one side and long on the other.

Changes in slow phase eye velocity and time constant of positional nystagmus at transform from cupulolithiasis to canalolithiasis

Changes in slow phase eye velocity (SPEV) and time constant (TC) of benign paroxysmal positional nystagmus in horizontal canal type were examined at transitional period from cupulolithiasis (apogeotropic nystagmus) into canalolithiasis (geotropic nystagmus) in two patients. SPEV and TC of positional nystagmus were tri-dimensionally analyzed. The first patient showed an apogeotropic nystagmus. Head rotation to the left in supine position induced a right-beating nystagmus with an initial SPEVof 15.3 degrees/s and a TC of 133 s. The nystagmus then gradually declined with a TC of 31.3 s after reaching a maximum SPEV of 28.8 degrees/s. After the nystagmus disappeared, he showed a geotropic nystagmus. The second patient showed a left-beating nystagmus with an initial SPEV of 2.5 degrees/s and a TC of 141 s when his head was rotated to the right in supine position. The nystagmus then gradually declined with a TC of 8.05 s after reaching a maximum SPEV of 16.7 degrees/s. After the nystagmus disappeared, he showed a geotropic nystagmus. The present findings suggested that in both patients, at the period of an increase of SPEV of the positional nystagmus with the shortening of its TC, cupulolithiasis transformed into canalolithiasis.

Improved algorithm for classification of ocular nystagmus

An improved algorithm for classification of nystagmus was designed allowing the sorting of response segments even in severely non-linear patients and subjects with abnormally large phase shifts. The algorithm employs a model-based approach that was developed by Rey and Galiana. The improved classification algorithm consists of two essential stages. In the first stage the eye velocity response is classified to obtain initial estimates of the slow phase eye velocity intervals. In the second stage, the slow phase estimates are used to identify a response phase shift and nonlinearity, and compensate for their effects. Multiple tests on simulated data and experimental data obtained from clinical subjects are presented. The results of the tests demonstrate that the algorithm is able to analyze the patient data with a high accuracy even in the presence of noise, eye-blinks and other artifacts.

A Signal Analysis Technique of Vestibulo-Ocular Reflex Stimulated with Impulsive Head Movements

Eye movements have been investigated in several areas of medicine and also elsewhere, such as in psychology or even in the development of human-computer interfaces. In the last few years we have designed a technique to stimulate, measure and analyze vestibulo-ocular reflex eye movements. In the otoneurological literature these are seen as a novel and promising means of revealing certain disorders and diseases associated with vertigo. Vestibulo-ocular reflex is stimulated by impulsive head movements. We developed the present pattern recognition technique to detect the stimulus (impulsive head movements) and the vestibulo-ocular reflex (response eye movements) generated from signals and to compute the latency and the gain values between them. Using our technique to calculate these attributes, we obtained clearly different results for a group of 22 dizzy patients than for a group of 30 healthy subjects.

Three-Dimensional Analysis of Benign Paroxysmal Positional Nystagmus in a Patient with Anterior Semicircular Canal Variant

OBJECTIVE

To show the positional nystagmus in a patient who had suffered from benign paroxysmal positional vertigo (BPPV) that was thought to be caused by involvement of the anterior semicircular canal (ASCC) (A-BPPV).

STUDY DESIGN

Retrospective case report.

SETTING

City hospital.

PATIENT

The present study reports a rare case of A-BPPV in a 41-year-old woman.

CASE REPORT

The patient is 41-year-old woman who developed a positional vertigo after playing volleyball on March 22, 2005 and consulted our hospital the next day. When left Dix-Hallpike maneuver was performed, she showed a positional nystagmus of which fast phase direction of the torsional component was clockwise while that of the vertical component was downward. We plotted the slow phase eye velocity of the positional nystagmus during the left Dix-Hallpike maneuver on three-dimensional coordinates that showed the axis of the positional nystagmus to be perpendicular to the plane of the right ASCC.

CONCLUSION

These results suggested that the patient was suffering from A-BPPV.

Objective motor response onset detection in surface myoelectric signals

Precise detection of discrete motor events like the onsets of voluntary muscle contractions is a prerequisite for various psychophysiological approaches in sensorimotor system analysis. In biomedical research and clinical diagnosis, motor events frequently are determined from surface electromyographic (SEMG) signals by some computerized detection algorithm. However, little is known about the reliability and accuracy of these methods, which frequently rely on intuitive and heuristic criteria. Therefore, the systematic approach to computerized detection of discrete motor events from SEMG signals presented by this paper fills a basic gap in EMG signal processing. Based upon a dynamic process model for the SEMG signal, a formal detection scheme is established which incorporates the essential processing modules common to the majority of algorithms. In addition, using concepts of statistically optimal change detection in random processes, a new model-based algorithm is presented which serves as a reference for optimum performance. The validity of this concept is demonstrated for the specific example of accurate detection of muscle activation onsets in rapid voluntary contractions; the estimation error (i.e., the deviation between estimated and "true" onset time) was evaluated by statistical simulations for three representative methods. Results show a substantial decrease of performance of traditional methods in the case of highly variable dynamic muscle activation profiles and/or superimposed activation patterns (e.g., due to a secondary motor task simultaneously executed by the same muscle). The model-based approach provided significantly more accurate results, even when the exact model parameters were unknown but estimated from the SEMG signal actually measured. It is concluded that the detection algorithm has to be critically taken into consideration during interpretation of motor events resolved from SEMG signals. The process model together with the corresponding statistically optimal detector represents an efficient tool for selecting appropriate detection algorithms for a particular experimental condition, and it allows a quantitative assessment of their performance.

A self calibration method using a soft clustering procedure for eye movement recordings

A nearly automatic method for calibrating eye movement records has been developed. This very robust method is based on a soft clustering algorithm which allows exploration of the whole range of eye movement records for reliable calibration. In contrast to many other methods which carry out the calibration on several discrete points, this method is suitable for continuous determination of the transfer function of the eye movement transducer. Moreover it simultaneously uses the combined properties of vestibulo-ocular reflex, neck-to-eye reflex and smooth pursuit system to reach approximately a unity gain and zero phase lag (in subjects with no severe vestibular disorders or ocumomotor palsy). In addition, this method does not rely heavily on the degree of attention of the subject. The method is particularly suited for the calibration of non linear or noisy transducers like Electro Oculography (EOG). Calibration is performed within a few seconds. So when necessary in clinical applications it is possible to repeat calibrations frequently.

Changes in dorsal neck muscle activity related to imposed eye movement in the decerebrate pigeon

Movements of the head and eyes are known to be intimately related. Eye position has also been shown to be closely related to the electromyographic activity of dorsal neck muscles; however, extraocular muscle proprioception has not generally been considered to play a part in the control of such movements. We have previously shown that, in the pigeon, imposed movements of one eye modify the vestibular responses of several dorsal neck muscles in ways that are dependent on stimulus parameters such as the amplitude and velocity of imposed eye movement. The present study examines more closely the interactions between imposed eye movements and different muscle pairs. The three neck muscle pairs studied each responded to afferent signals from the extraocular muscles in discrete and specific ways which appeared to be correlated with their different actions. Complementary effects of imposed eye movements in the horizontal plane were seen for both the complexus and splenius muscle pairs, with imposed eye movements in one direction producing the largest inhibition of the ipsilateral muscle's vestibular response and imposed eye movements in the opposite direction the largest inhibition of the contralateral muscle's vestibular response. During roll tilt oscillation (ear-up/ear-down) in the frontal plane, similar complementary effects of imposed eye movement were seen in the complexus muscle pair, but the splenius muscle pair showed little tuning, with similar inhibition for imposed eye movement directed either upwards or downwards. In contrast to these complementary effects, the biventer cervicis muscle pair showed no vestibular modulation during vestibular stimulation in the horizontal plane and their spontaneous activity was not altered by imposed eye movement. During roll-tilt oscillation (ear-up/ear-down) in the frontal plane imposed eye movement directed vertically upwards increased both muscles' vestibular responses and imposed eye movement directed vertically downwards inhibited both muscles' vestibular responses. Section of the ophthalmic branch of the trigeminal nerve (deafferenting the eye muscles) abolished the effects of imposed eye movement on the neck muscle pairs. In conjunction with further control experiments these results provide compelling evidence that proprioceptive signals from the extraocular muscles reach the neck muscles and provide them with a functionally significant signal. We have previously shown that signals from the extraocular muscles appear to be involved in the control of the vestibulo-ocular reflex. It follows from the experiments reported here that proprioceptive signals from the extraocular muscles are also likely to be involved in the control of gaze.

Estimation of slowly changing components of physiological signals

A method for the estimation of slowly changing components of physiological signals is presented in this communication. The method is based on a sequential approximation of slowly changing components by a low-order polynomial function. The polynomial coefficients are obtained by minimizing the distance between the expected zero crossing density (ZCD) value of the fast components of the physiological signal and the estimated ZCD value of these components. The method has been tested and preliminary results were satisfactory.

A new method for approximation of physiological signals

A new robust method for the approximation of physiological signals is proposed. The noise must satisfy only one condition: that the probabilities for positive and negative values are equal. Our results illustrate that the proposed method provides a more accurate approximation of signals than either the least square error or the least absolute deviation method in cases that include unknown noise density.

A review of computerized electronystagmography technology

Analysis of nystagmus using manual methods is time consuming, reliant on considerable experience and subject to observer bias. Like many electrophysiological responses, nystagmus waveforms are suited to acquisition and analysis by digital computer techniques. Development of computerized eye movement analysis procedures commenced in the late 1960s. Initially programs were mostly researched-based with the data often acquired on FM tape recorders and evaluated on mini-computers. As computer technology evolved and equipment prices decreased, development of portable software and hardware for use in general clinical assessment became feasible. The development of computer programs for the acquisition and analysis of eye movements is described and the limitations of analysis procedures discussed.

A fuzzy pattern recognition method to classify esophageal motility records

Analysis and classification of esophageal motility records were investigated using signal processing and fuzzy-set pattern recognition techniques. A set of parameters has been extracted from the raw records and has previously been used as characterizing features. Improvements to these procedures were obtained by extracting these features from processed data, and some additional parameters were developed. The new set of features was used in the design of a fuzzy classifier, and classification accuracy was estimated using the leave-one-out technique. To our knowledge, this is the first report of the application of automatic classification to esophageal motility records.

Afferent signals from pigeon extraocular muscles modify the activity of neck muscles during the vestibulocollic reflex

Movements of the head and eye which, together, result in changes in the direction of gaze are linked in a number of species, including man, and eye position is known to affect the activity of neck muscles. This head-eye linkage has generally been ascribed to modification of neck muscle activity by internal estimates of eye position derived from motor commands. We have recently shown that afferent signals from stretch receptors in the extraocular muscles are involved in the moment-to-moment control of eye movements during the vestibuloocular reflex (VOR). We have now studied the interactions between head and eye movements by recording the electromyographic activity of several neck muscles during horizontal (yaw) or frontal (roll tilt) vestibular stimulation. Such a stimulus evokes a VOR in the eyes and a vestibulocollic reflex (VCR) in neck muscles. Imposing movements on one eye at saccadic velocities produced considerable inhibition of the VCR response of a number of neck muscles. The magnitude of these effects was dependent on the parameters of the imposed eye movement. Thus systematic changes were seen when the amplitude, velocity or direction of eye movement was varied. Movement of the eye in the opposite direction to that produced by a normal VOR produced a large inhibition of the VCR response, whereas movements in the same direction as the VOR produced only modest inhibition of the VCR response of the neck muscles tested. Slow, sinusoidal, imposed eye movements that mimicked the slow phase of the VOR produced changes in the gain of the VCR response which appear to correct for errors in the imposed eye velocity and thus tend to maintain the direction of gaze. The results show that changes in eye position have striking effects on the electromyographic activity of neck muscles during the VCR, and strongly suggest that extraocular muscle afferent signals are involved in head-eye coordination.

An algorithm separating saccadic from nonsaccadic eye movements automatically by use of the acceleration signal

An algorithm is described to discriminate automatically between saccades and slow eye movements. Sampled data of the eye position have been used to calculate the momentary acceleration of the eye. The higher acceleration values of the saccadic eye movements as opposed to the slow compensatory or pursuit eye movements served to differentiate between the two. The method is demonstrated by search-coil data in squirrel monkeys.

Afferent signals from the extraocular muscles of the pigeon modify the electromyogram of these muscles during the vestibulo-ocular reflex

There is no general agreement on whether afferent signals from the extraocular muscles play any part in oculomotor control. However, we have previously shown that they modify the responses of cells in the oculomotor control system during the vestibulo-ocular reflex (VOR). If, as we suspect, these signals have an important role in the control of the VOR from moment-to-moment, we should be able to demonstrate similar, functionally significant, modifications at the output of the reflex. We have recorded the electromyographic activity of several extraocular muscles of the right eye during the VOR and while imposing movements on the left eye. We describe how the activity of the muscles, reflected in the electromyogram, is modified in specific ways depending on the parameters of the imposed eye movements. The effects of the extraocular afferent signals on the eye-muscle responses to vestibular drive during the slow phase of the VOR appear to be corrective. Thus the present results provide strong evidence that afferent signals from the extraocular muscles are concerned in the control of the reflex from moment-to-moment, and suggest that the wider question of their role in oculomotor control merits further consideration.

Afferent signals from pigeon extraocular muscles modify the vestibular responses of units in the abducens nucleus

Although the extraocular muscles contain stretch receptors it is generally believed that their afferents exert no influence on the control of eye movement. However, we have shown previously that these afferent signals reach various brainstem centres concerned with eye movement, notably the vestibular nuclei, and that the decerebrate pigeon is a favourable preparation in which to study their effects. If the extraocular muscle afferents do influence oculomotor control from moment-to-moment they should exert a demonstrable effect on the oculomotor nuclei. We now present evidence that extraocular muscle afferent signals do, indeed, alter the responses of units in an oculomotor nucleus (the abducens, VI nerve nucleus, which supplies the lateral rectus muscle) to horizontal, vestibular stimulation induced by sinusoidal oscillation of the bird. Such stimuli evoke a vestibulo-ocular reflex in the intact bird. The extraocular stretch receptors were activated by passive eye movement within the pigeon's saccadic range; such movements modified the vestibular responses of all 19 units studied which were all, histologically, in the abducens nucleus. The magnitude of the effects, purely inhibitory in 15 units, depended both on the amplitude and the velocity of the eye movement and most units showed selectivity for particular combinations of plane (e.g. horizontal versus vertical) and direction (e.g. rostral versus caudal) of eye movement. The results show that an afferent signal from the extraocular muscles influences vestibularly driven activity in the abducens nucleus to which it carries information related to amplitude, velocity, plane and direction of eye movement in the saccadic range. They thus strongly support the view that extraocular afferent signals are involved in the control of eye movement.

Parametric classification of segments in ocular nystagmus

A new method for nystagmus classification, using system identification techniques, is presented. We formulate a system whose input is head position and whose output is eye position. We approximate this system with an autoregressive with exogenous input (ARX) model which relates the input and output (transfer function) regardless of the temporal profile for the sensory stimulation. The system is then identified using a least squares criteria and three indicators are produced. From these a flag is produced that marks slow and fast phases as well as blinks and bad data segments. Tests with simulated and real data are presented and indicate that the segment classification is remarkably insensitive to recording noise and that it is more robust than previous techniques. Operator intervention is minimal. We expect the method to be applicable for all types of ocular nystagmus. Here, however, we illustrate our results only in the context of the vestibuloocular reflex (VOR). A discussion explains how this method can also be applied for optokinetic (OKN) or pursuit nystagmus.

Optokinetic nystagmus in the ferret: including selected comparisons with the cat

The aim of this study was to evaluate the functional significance of similarities observed in the anatomy and the physiology of cat and ferret visual systems. Optokinetic nystagmus (OKN) in response to movement of the entire visual field, and optokinetic after nystagmus (OKAN) were measured in 8 ferrets with binocular stimulation. A shift of the beating field in the same direction as the fast phase of eye movements was observed both in ferret and cat. The absence of a fast rise in slow phase velocity (SPV) and similarities in the time constant to reach the steady state OKN gain, using step velocity stimuli are noted. As in the cat, primary OKAN was observed with a gradual decrease in its SPV. Following termination of stimulation, no sudden fall in SPV was noted for either species. However, for the ferret, the decrease was more rapid. With monocular stimulation, small differences were observed in OKN gain when responses to temporonasal and nasotemporal directions of the stimulus were compared in the two species. In contrast, the ferret displays a OKN gain which is approximatively twice that of the cat at stimulus velocities of 100 degrees/sec. Even at 200 degrees/sec., visual movement still induces a discernable OKN response (gain .0.07). Secondary OKAN, always present in the cat, was observed in only 43% of ferret records. Taken together with other considerations, these findings recommend the ferret as an alternative to the cat for the study of OKN and of other visuo-motor capacities in carnivores.