Simple method of differential diagnosis of peripheral and central vertigo--development of diagnostic method and studies of 178 cases]

In patients who complain of vertigo or who have equilibrium disorders, it is often difficult to determine the etiology of the disorder, that is to determine whether it is dependent on a peripheral or central vestibular disorder. To attempt to determine the etiology in these cases, we divised a new method, the caloric eye tracking pattern test (CETP-Test). Seventeen normal subjects and 161 patients were tested. The latter group included 33 with peripheral disorders such as Meniere's disease, benign paroxysmal positional nystagmus, and others, and 128 with central disorders such as vertebral basilar artery insufficiency, cervical vertigo, and others, were tested. The cases of central disorders were limited to those patients whose eye tracking pattern before the caloric stimulation was normal. In normal subjects and in patients with peripheral disorders, it is well known that caloric nystagmus has little influence on the eye tracking pattern. In contrast, in patients with central vestibular disorders, caloric nystagmus evokes abnormalities on the eye tracking pattern, either superimposed or saccades, despite the fact that the eye tracking pattern before the caloric stimulation is normal. First we administer the eye tracking stimulation test using a target which moves horizontally at 0.3 cycle per second. Next, we perform the caloric test on the right ear, using 20 c.c. of ice water for 10 seconds. During the evoked caloric nystagmus we administer the eye tracking test once again. The eye tracking pattern is recorded for 20 seconds beginning 50 seconds after the start of the ice water injection. The procedure repeated on the left ear. The results on each case are presented as three patterns of ENG-recording. We may stat that in normal subjects and in patients with peripheral vestibular disorders, visual suppression of caloric nystagmus remains functional. Caloric induced nystagmus does not affect the CETP. In patients with central vestibular disorders, visual suppression of caloric nystagmus does not function properly because of defects in the visual suppression mechanism. Therefore, caloric nystagmus greatly influences the CETP. Consequently, the CETP may not be smooth when CETP test is administered to patients with central vestibular disorders. We may say also that the visual suppression to the vestibular nystagmus is evoked more strongly by pursuing a moving visual stimulus than by gazing a stational target. These results allow for a differential diagnosis between peripheral and central disorders.     

Abnormal visual-vestibular interaction and smooth pursuit tracking in psychosis: implications for cerebellar involvement.

The vestibulo-ocular response to caloric irrigation and the effect of vestibular activation on eye movements were examined during light and dark testing conditions--the latter to assess these measures under conditions attenuating possible cerebellar-vestibular interaction present in the light-adapting condition. Subjects were psychiatric patients (23 actively-ill psychotic patients and 23 remitted psychotic patients) and normal controls (23 with no history of psychiatric illness). Standardized clinical electronystagmographic procedures were used, together with electrographic measures to assess visual fixation and level of arousal. During the light condition previous findings of impaired smooth pursuit tracking and reduced fixation suppression in actively psychotic patients were replicated. These patients also exhibited hyperresponsive vestibulo-ocular responses. Remitted patients' performance levels on test measures fell between those of controls and actively-ill patients on the majority of response measures. However, remitted patients were found to have impaired smooth pursuit tracking and failure of fixation suppression relative to controls. The dark testing condition effected a normalization of several patient-control differences, including smooth pursuit tracking and the elimination of vestibular hyperresponsiveness. In many respects the present results parallel findings of eye movement aberrations in cerebellar patients. These similarities include evidence of an intact but hyperresponsive vestibular system, the normalization of previously disordered pursuit tracking during dark-testing, the failure of fixation suppression, and the decrease in this measure during dark conditions. These findings suggest that cerebellar dysfunction may contribute to irregularities in smooth pursuit tracking and fixation suppression found in psychotic patients.     

A quantitative analysis of saccades and smooth pursuit during visual pursuit tracking. A comparison of schizophrenics with normals and substance abusing controls.

The eye movements of schizophrenic patients are characterized by decreased smooth pursuit gain and an increased frequency of saccades. However, the nature of these saccades and their function during smooth pursuit has not been clearly defined. To address this issue we examined the eye movements of 22 schizophrenic patients, 20 substance abusing patients (primarily alcohol; some with concomitant cocaine and/or cannabis abuse), and 17 normal controls during a visual pursuit task using infra-red oculography. A computerized pattern recognition algorithm divided pursuit eye movements into two basic components: smooth pursuit and saccadic eye movements. The algorithm also determined eye position error and velocity error before and after each saccade. Schizophrenic patients had lower smooth pursuit gain (p less than 0.02) and made more saccades during smooth pursuit (p less than 0.02) than either comparison group. When saccades were assigned to subcategories based on direction and position error, only the frequency of 'catch-up' saccades differentiated schizophrenic patients from the comparison groups (p less than 0.05). Smooth pursuit gain was negatively correlated with saccadic frequency among all three subject groups. Eye velocity preceding saccades was significantly lower among the schizophrenic patients, but pre or post saccadic position error did not differ among the three groups. Discrete analysis of the fine structure of visual pursuit tracking may lead to a better understanding of eye movement abnormalities in schizophrenia.     

Ocular motor abnormalities in progressive supranuclear palsy

Eleven patients, 7 males and 4 females, of progressive supranuclear palsy (PSP) were examined neuro-otologically for the purpose of elucidating the characteristics of ocular motor abnormalities. All cases were admitted to our hospital and age at onset was from 52 to 71 years old, duration of illness was 2 to 11 years. Range of voluntary eye movements and abnormal eye movements including nystagmus were examined on naked eyes and with electronystagmography (ENG). Smooth pursuit movements and saccadic eye movements were tested both horizontally and vertically by using visual tracking method with ENG recordings. Optokinetic nystagmus test and caloric test with visual suppression test were also performed. These neurotological examinations were made repetitively in 5 cases and their progressions were observed. Vertical gaze palsy and convergence palsy were observed in all cases as the initial symptom. In this study downward gaze was more severely disturbed than upward gaze. Using ENG, saccadic eye movements (saccades) were disturbed earlier than smooth pursuit movements. Hypometric saccades and decreased saccadic velocity were common abnormalities. In the later stage of the disease, horizontal eye movements were also disturbed. In four cases bilateral adduction palsy was added to vertical gaze paralysis so that the lesion of the MLF to oculomotor nucleus was suggested to exist. These voluntary eye movements were worsened gradually as the disease progressed. By using ENG we could find so called abnormal eye movements more frequently than the previous reports. Eight patients demonstrated horizontal gaze nystagmus, and rebound nystagmus were observed in four cases.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of tobacco smoking on smooth pursuit eye movements

It has recently been shown that tobacco smoking in normal human subjects induces a transient primary-position upbeat nystagmus. We studied the effects of tobacco smoking on smooth pursuit eye movements and found defects in both vertical and horizontal tracking during the first 5 minutes after smoking one cigarette. The smooth pursuit defect consisted of a reduction in upward tracking velocity and the superposition of saccadic square-wave jerks on both vertical and horizontal tracking eye movements. The degree of impairment in upward smooth pursuit correlated with the intensity of tobacco-induced nystagmus present when recording in darkness. We suggest that these alterations are due to summation of nystagmus on normal tracking eye movements rather than primary defects in the smooth pursuit system.     

Smooth pursuit eye movements and neuropsychological tests in schizophrenic patients: Possible involvement of attentional components

The relationships among different components of frontal lobe dysfunction and voluntary attention were studied. Drug-free schizophrenic patients and matched normal controls were recruited and assessed for smooth pursuit eye movements, voluntary saccadic eye movements and by means of neuropsychological tests (Toluse-Pieron test and Wisconsin Card Sorting Test). No clear-cut relationship was found between eye movement performance and neuropsychological impairment.     

Disturbed Eye Movements after Whiplash Due to Injuries to the Posture Control System

Abstract

Self-reports after whiplash often indicate associations with vertigo and reading problems. Neuropsychological and otoneurological tests were applied to a group of whiplash patients (n =26) and to a carefully matched control group. The whiplash group deviated from the control group on measures of eye movements during reading, on smooth pursuit eye movements with the head in normal position, and with the body turned to the left or to the right. Clinical, caloric, and neurophysiological tests showed no injury to the vestibular system or to the CNS. Test results suggest that injuries to the neck due to whiplash can cause distortion of the posture control system as a result of disorganized neck proprioceptive activity.     

Smooth pursuit eye movements of normal and schizophrenic subjects tracking an unpredictable target

An experimental paradigm employed by several workers in the field of schizophrenic eye movements has involved finding sequences of stimuli that induce saccadic smooth pursuit in the eye movements of normal individuals. It is hoped that the identification of such stimuli will lead to clues concerning the etiology or nature of eye tracking dysfunction in schizophrenia. In this study, the pursuit eye movements of normal and schizophrenic subjects tracking an unpredictable target (composed of summed sine waves) were examined. Eye tracking performance was evaluated both qualitatively and quantitatively using percent root-mean-square (%RMS) error and pursuit gain scores. Schizophrenics are capable of tracking an unpredictable target. This finding has implications for our understanding of schizophrenic information processing during visual tracking.     

Disturbed smooth pursuit and saccadic eye movements in schizophrenia

Smooth pursuit and saccadic eye movements of schizophrenic patients were examined. In a pendulum (0.5 Hz) tracking task schizophrenic inpatients had a slightly lower smooth pursuit gain than outpatients and controls, who showed no significant differences. The number of saccades, counter-saccades and velocity arrests occurring in a 20 s tracking epoque was the same in patients and controls, but patients made larger saccades. When tracking a stepping target by saccadic eye movements, schizophrenic inpatients, and to a lesser extent outpatients, exhibited longer reaction times than controls and had a higher incidence of "non-fixation" (saccades away from the target while the target is stationary). Schizophrenic patients also showed a significantly larger proportion of dysmetric saccades (undershooting the target). While similar changes of reaction time and non-fixation score were observed in manic-depressives and alcoholics, dysmetria was more often found in schizophrenics and possibly constitutes the expression of a specific impairment of attention.     

Abnormalities of smooth eye and head movement control in parhson's disease

The control of horizontal head and eye movements was examined in 13 nondemented patients with Parkinson's disease (PD) of mild to moderate severity. During pursuit of single-frequency sine waves, smooth component eye velocity was lower in the PD group at frequencies of 1.2 Hz and above; but the differences in overall eye displacement were even greater, indicating an impaired ability to generate catch-up saccades at high frequencies. A corresponding deficit in saccadic performance was observed during a high-frequency saccadic tracking task where predictive saccades of reduced gain and variable timing were generated. During pursuit of pseudo-random target motion with varying degrees of predictability, small differences in smooth component eye velocity were observed, but prediction was otherwise well preserved in the patient group. Vestibulo-ocular reflex (VOR) suppression was also normal during head-free pursuit. No major improvement in smooth pursuit gain could be attributed to drug treatment, based on a comparison of patient results before and after administration of levodopa.     

The effects of dark adaptation on pursuit tracking dysfunction in psychotics with impaired vestibular suppression

Smooth pursuit eye tracking performance, evaluated by electronic processing and subjective ratings, was assessed in actively psychotic psychiatric patients and normal controls under conditions of light and dark adaptation and was related to subjects' ability to suppress vestibular nystagmus induced by caloric irrigation. Patients' tracking performance was significantly inferior during the light-adapted condition on all tracking measures. Dark-adaptation eliminated group differences based on electronic analyses, but subjective ratings--which showed a variable relationship to the other tracking measures--did not reflect this improvement. Vestibular nystagmus suppression was significantly impaired in patients relative to controls and this impairment, coupled with smooth pursuit dysfunction and marked improvement in tracking performance during dark-adaptation, suggests that cerebellar dysfunction contributes significantly to tracking dysfunction in psychotic patients.     

Effects of intravenous opioids on eye movements in humans: possible mechanisms

Oculomotor symptoms such as downbeat nystagmus can be due to side effects of drugs. We investigated the clinical effects as well as the eye movement symptoms after intravenous administration of opiates (pethidine and fentanyl). Eye movements were recorded with the magnetic search coil technique. All four normal subjects showed a transient disturbance of eye fixation with downbeat nystagmus, a range of saccadic intrusions and oscillations, including square wave jerks and saccadic pulses, lasting from 10 to 15 minutes. The gain of sinusoidal VOR and smooth pursuit was moderately decreased; in particular the vertical pursuit showed an upward velocity offset. On the basis of the clinical findings and of recent diprenorphine PET findings in humans, which detected opiod binding sites in the cerebellum and the known inhibitory action of opiates, we hypothesized that a cerebellar dysfunction occurs after opiate administration which could possibly be mediated by inhibition of the parallel fiber activation of the Purkinje cells. Furthermore, opiate binding sites in the vestibular nuclei could be responsible for the vertical vestibular tonus imbalance involved in the pathophysiolgy of downbeat nystagmus. Received: 4 April 2001, Received in revised form: 1 March 2002, Accepted: 12 March 2002     

Lorazepam-induced modifications of saccadic and smooth-pursuit eye movements in humans: attentional and motor factors

In a placebo-controlled, double-blind study, we measured the effects of low dose lorazepam on attentional and motor factors involved in saccadic and smooth pursuit eye movements. We manipulated the temporal interval between the extinction of the central fixation target and the appearance of a second eccentric target (gap/overlap step paradigm). The second target was either stationary (saccade trial) or moving in a direction opposite to the step (pursuit trial). Gap/overlap effects on the latency of saccadic and smooth pursuit eye movements were measured before and after oral intake of either lorazepam or placebo. Pharmacological effects on the dynamics and the accuracy of both types of eye movements were also investigated. In 14 healthy volunteers, we found that the temporal interval between fixation target offset and eccentric target onset modulates the latency of saccadic and smooth pursuit eye movements in a similar way. As compared to placebo, lorazepam significantly increased the latency of both types of eye movements, but did not modify the gap/overlap effect. Moreover, lorazepam significantly decreased the peak velocity of the first saccade towards the eccentric stationary target, as well as the gain of tracking towards the eccentric moving target. However, the overall accuracy of both behaviors was not significantly affected, indicating that systematic errors in foveating or tracking were detected and corrected by appropriate corrective or catch-up saccades, respectively. Results are discussed in terms of shared/different mechanisms for saccadic and pursuit systems in primates.     

Ataxia telangiectasia: a reappraisal of the ocular motor features and their value in the diagnosis of atypical cases

The eye movements of four patients with ataxia telangiectasia (AT), three of whom had an unusual neurological presentation, were studied. All had striking abnormalities of saccadic generation with markedly hypometric saccades, increased saccadic latency, but normal saccadic velocity. Three patients used head thrusts to aid refixation. In addition, there was absence of smooth pursuit and optokinetic nystagmus, and hyperactive vestibular responses. Two of the four patients had, in addition, periodic alternating nystagmus. This combination of an ocular motor apraxia with superadded cerebellar ocular motor abnormalities, and possibly periodic alternating nystagmus, should strongly suggest the diagnosis of AT, even if the clinical syndrome is otherwise atypical.     

Coordination of eye and head movements during smooth pursuit in patients with vestibular failure.

During pursuit of smoothly moving targets with combined eye and head movements in normal subjects, accurate gaze control depends on successful interaction of the vestibular and head movement signals with the ocular pursuit mechanisms. To investigate compensation for loss of the vestibulo-ocular reflex during head-free pursuit in labyrinthine-deficient patients, pursuit performance was assessed and compared under head-fixed and head-free conditions in five patients with isolated bilateral loss of vestibular function. Target motion consisted of predictable and unpredictable pseudo-random waveforms containing the sum of three or four sinusoids. Comparison of slow-phase gaze velocity gains under head-free and head-fixed conditions revealed no significant differences during pursuit of any of the three pseudo-random waveforms. The finding of significant compensatory eye movement during active head movements in darkness in labyrinthine-deficient patients, which were comparable in character and gain to the vestibular eye movement elicited in normal subjects, probably explains the similarity of the head-fixed and head-free responses. In two additional patients with cerebellar degeneration and vestibular failure, no compensatory eye movement response was observed, implying that the cerebellum is necessary for the generation of such responses in labyrinthine-deficient patients.     

Erratic eye tracking in schizophrenic patients as revealed by high-resolution techniques

Using high-resolution infrared oculography with digital recording and analysis techniques, we tested several types of eye movements in 19 schizophrenic patients and 11 normal controls. Abnormal slow pursuit eye movements, seen in about half of the patients, were characterized by erratic inaccuracies in position, velocity, and phase. Tracking errors were quantitatively assessed by their root mean square (RMS) error. Position RMS errors fell into two clearly separated groups, with 10 of 19 patients clustering about the normal controls and the remaining 9 having much higher errors than normal. Although several of these poor trackers had an excess of saccades or low pursuit gain, these abnormalities were not primarily responsible for the large erratic tracking errors. Saccades in response to unpredictable target jumps had normal latencies (reaction times) and velocities, but were more hypometric and variable in accuracy than those of controls. These saccadic abnormalities did not correlate with the patients' position RMS errors during slow pursuit.     

Electrooculographic findings in progressive supranuclear palsy

Progressive supranuclear palsy is a heterogeneous system degeneration. We studied three patients by means of electrooculography. There were severe disturbances in saccadic and smooth pursuit eye movements, and optokinetic nystagmus in both vertical and horizontal planes. Caloric reactions were absent in all patients. The absence of vestibular reflex responses in contrast to the normal results in doll's head manoeuvre seems contradictory and is discussed. From the results in our patients it is concluded that E.O.G. is an essential contribution in proving a multiple system pathology.     

Disruption of saccade production during oculomotor tracking in schizophrenia and the use of its changes across target velocity as a discriminator of the disorder.

A clear measure of eye movement disorder (EMD) that reliably separated schizophrenic individuals from others would both give insight into the brain control of the disorder and provide an aid in diagnosis. In the present study, a detailed analysis was carried out of the interactions between the pursuit and saccadic components of eye movements at different target velocities. The subjects comprised schizophrenic patients, unipolar depressed patients, and normal controls. The speed of the slow pursuit component did not differ among the groups, but schizophrenic subjects made more saccadic movements at low target velocities, though they started further away from the target at high target velocities. On the basis of these differences, a slope was computed of the linear function that related the number of saccadic eye movements to the velocity of a ramp visual target. Slope direction was negative for schizophrenic subjects but positive for unipolar depressive and normal subjects, and the correct classification rate for subjects was 84%.     

Visually and memory guided saccades in a case of cerebellar saccadic dysmetria.

Saccades under four specific test conditions (visually guided, visually remembered, vestibular remembered, and cervical remembered) were studied in a 38 year old man with ocular dysmetria due to an angioma of the dorsal cerebellar vermis. The aim of the study was to investigate if the saccadic disorder was specific to certain subsets of saccades elicited by different sensory modalities. The experiments showed that initial saccades were equally hypermetric in all four conditions and that final eye position was normal in all memory guided saccade tests. Eye movements differed after the initial saccade, however. Whereas corrective saccades were seen in most visually guided and visually remembered experiments, postsaccadic centripetal drifts were documented in non-visual (vestibular and cervical) remembered saccades. These results indicate that the cerebellar vermis modulates the amplitude of the initial saccade (pulse size of saccadic innervation) independently of the saccadic task. The finding that post-saccadic drift never occurred when saccades were programmed using visual positional information suggests that the dorsal vermis may participate in the process of pulse step integration of saccades elicited by memorised vestibulo-cervical information.     

Downbeat nystagmus during eye closure

We studied eye movements and clinical findings in 1225 patients with complaints of dizziness. Downbeat nystagmus was demonstrated in 11 patients during eye closure. Simultaneous vertical and horizontal eye recordings were examined to demonstrate vertical eye position during eye closure. Downbeat nystagmus appeared on midline position even during eye closure in six patients. An electrooculography was demonstrated in three out of above six patients. A 24-year-old woman (Case 1) complained of a single spell of vertigo. There was no remarkable finding on neurological examination. An audiogram was an abrupt type sensorineural hearing loss in both ears. A caloric test was normal. Horizontal and vertical smooth pursuit was normal. Optokinetic nystagmus showed normal response in both horizontal and vertical planes. Both eyes were elevated on eye closure. They were depressed to the midline position with mental task and downbeat nystagmus appeared. A 68-year-old man (Case 2) had a history of dizziness on walking of three-year duration. On examination neurological findings were normal. A caloric test was normal in both ears. Optokinetic nystagmus and smooth pursuit were normal in both horizontal and vertical eye recordings. He had a transient eye elevation on eye closure. Both eyes immediately came downward to midline position and downbeat nystagmus was demonstrated. His nystagmus had persisted for four years. A 68-year-old woman (Case 3) complained of positional vertigo of seven-month duration. Neurological findings were normal. A caloric test was normal. There was a conductive hearing loss on the left ear. The right ear showed a normal audiogram.(ABSTRACT TRUNCATED AT 250 WORDS)