The relationship of optokinetic nystagmus to pursuit eye movements, vestibular nystagmus and to saccades in humans. A clinical study

The relationship of mean velocity of optokinetic nystagmus (OKN) to pursuit eye movements (PEM), to vestibular nystagmus and to voluntary saccades was analysed in 10 patients with peripheral vestibular lesions and in 30 patients with central vestibular lesions. PEM and vestibular nystagmus were significantly correlated to OKN, suggesting that a common neural pathway is used in the generation of these eye movements. Weak or no correlation was found between saccadic peak velocity and slow phase velocity of OKN. Using multiple linear regression analysis, it was found that 78.5% of the variation in the slow-phase velocity of OKN could be explained by a synthesis of PEM and vestibular test data. PEM test data were more powerful than those of vestibular nystagmus in deduction of OKN. The possible appearance of slow build-up of OKN could not be deduced from the reduction of PEM. Hence, the relationship between PEM and OKN in man is not a simple linear one, but is more complex.     

Electronystagmographic analysis of caloric test parameters in vestibular disorders

The electronystagmographical analysis of the eye movements provoked by caloric stimulation is an important method in the evaluation and topical diagnostic procedure of several vestibular lesions. The aim of the study was to compare the electronystagmographical results of caloric response in several vestibular disorders. The patients were divided into five groups: right and left unilateral and bilateral peripheral lesions, central vestibular dysfunction, and normal vestibular function. In the normal vestibular system group the average caloric nystagmus SPV in normal vestibular system was 17.4°/s. In the peripheral lesion groups the average slow phase velocities are decreased in the affected side, as we expected. In the compensated vestibular lesion the average ASPV of caloric nystagmus is also decreased on the unaffected side. This might be caused by the effect of the central adaptive mechanisms. According to our observations, in central dysfunctions the average caloric ASPV and the spontaneous nystagmus ASPV is increased (25.0°/s). This suggests that in central vestibular lesions the central inhibiting mechanisms of the caloric response are impaired. Our results show that electronystagmographical analysis of spontaneous and caloric nystagmus is very important in the evaluation of dizzy patients.     

The optokinetic test: Interaction of the vestibular and optokinetic system in normal subjects and patients with vestibular disorders

Summary In 100 patients showing different lesions of the peripheral vestibular system and of the CNS, the influence of spontaneous vestibular nystagmus on optokinetic nystagmus was investigated. Considering the large interindividual differences in the results of vestibulo-visual interaction, the actual values of OKN slow-phase velocity obtained by visual stimulation are only of limited diagnostic value in a single case. However, by averaging the results obtained from various nosologic groups of patients very different but distinct patterns of vestibulo-visual interaction can be demonstrated: The diagnostic importance of quantitative assessment of optokinetic nystagmus is demonstrated by a statistical evaluation of test results obtained in normal subjects as well as in patients with peripheral and central vestibular disorders. The most important diagnostic parameters of a pathologic foveo-retinal optokinetic response are directional preponderance of slow phase velocity and gain of OKN. Increasing target velocity with decreasing gain clearly indicate the presence of a severe brainstem lesion involving the entire oculomotor control system which provides the coordination of head and eye movements.     

Wallenberg's syndrome: neurotological classification

Objectives: Visually induced eye movements were investigated in 26 patients with Wallenberg's syndrome. Methods: Slow-phase optokinetic nystagmus (OKN) velocities, pursuit gains, and percentage fixation suppression (%FS) of caloric nystagmus were recorded by DC electrooculography (EOG), and stored directly onto FM magnetic tape. Results: OKN velocities, pursuit gains, and %FS decreased toward the lesion side (group A), whereas OKN velocities and pursuit gains decreased toward the side contralateral to the lesion side. %FS decreased toward the lesion side (group B). MR images in group A showed that lesions were only in and near to the vestibular nuclei, and images in group B showed that lesions extended to the cerebellum. Conclusion: Visually guided eye movements allow classification of Wallenberg's syndrome into two types, one with brainstem lesions and one with both brainstem and cerebellar lesions. This demonstrates that assessing eye movements is helpful in supplementing MRI data.     

Vestibular-optokinetic interactions in normal subjects and in patients with peripheral vestibular dysfunction.

The vestibulo-ocular reflex (VOR) during rotation, optokinetic nystagmus (OKN), and interactions between the vestibulo-ocular and optokinetic systems were studied quantitatively in 10 normal human subjects, 15 patients with unilateral horizontal semicircular canal paralysis (UP), and 11 patients with bilateral horizontal semicircular canal paralysis (BP). The OKN gain (eye velocity/drum velocity) was not significantly different between the normal subjects and the patient groups. During tests in which rotatory and visual stimuli were presented simultaneously, the contribution to the observed eye movements by the VOR was only one-fourth to one-third of its gain during rotation in the dark in the normal subjects and UP patients. These interactive tests did not differentiate UP patients from normal subjects but did separate BP patients from normal subjects.     

Neurologic and otologic findings in Fisher's syndrome

We performed neurologic and otologic examinations in 14 patients with Fisher's syndrome to determine whether its manifestations inducing acute ophthaloplegia, ataxia and areflexia may involve the auditory and vestibular systems. Tests included pure tone audiometry, auditory brainstem response, observations of nystagmus, smooth pursuit test, saccade test, optokinetic nystagmus test, and the caloric test. One patient showed downbeat nystagmus and lateral gaze nystagmus without restriction of eye movement, two patients showed dysmetria on saccades without restriction of eye movement, and three patients showed superimposed saccadic eye movement on smooth pursuit without lateral gaze nystagmus. The abnormalities in those six cases could not be explained by solely muscular weakness, but also appeared to involve the central oculomotor system. In the other patients, nystagmus could be explained by muscular weakness alone. Additionally, three patients, including two patients with dysmetria on saccades, showed a unilateral diminished response to caloric testing with no severe restriction of eye movements. In evaluating the auditory brainstem response of these three patients, one patient, who showed abnormality on the saccade and caloric tests, showed an elongation of wave I latencies and of wave I-III interpeak latencies at both ears, and one other patient showed an elongation of wave III-V interpeak latencies at both ears. This disorder may involve the peripheral and central auditory systems as well as the peripheral vestibular system.     

Computerized study of the velocity of the rapid eye movements

The average velocity-amplitude characteristics of rapid eye movements (voluntary saccades, and fast phases of caloric and optokinetic [OKN] nystagmus) in normal humans were analyzed with an analogue-digital computer and compared among them. For the same amplitude of movement the velocity of the saccades is considerably greater than that of the fast phases of the OKN, and these in turn are greater than those of their vestibular counterparts. The complexity in oculomotor neurophysiology makes this observation difficult to explain.     

Can oculomotricity be altered in patients with tinnitus only? A preliminary study

The study of oculomotricity is performed by evaluating three systems: saccadic ocular movements (SOMs), optokinetic nystagmus (OKN), and smooth pursuit eye movements (SPEMs). Our aim was to study oculomotricity in patients with a complaint of only tinnitus and to compare it with the value of our control group. We studied the SOMs, OKN, and SPEMs in 25 patients complaining only about tinnitus and in 35 normal adults and compared the results. The data analysis showed a significant difference in the value of the SOMs and SPEMs between the two groups. Sensorineural tinnitus can originate in the organ of Corti, in the cochlear nerve, or in the auditory pathways of the central nervous system. The auditory cortex connects with visual areas and with the superior colliculus. The latter structure is involved in the origin of SOMs and OKN. In our study, we found an increased delay in saccadic tests. In the SPEMs, we observed an increase in the degree of distortion, and a reduction in the gain. This outcome is in accordance with the literature. However, we detected a few alterations in the OKN, and this finding is in partial agreement with the studies analyzed. Alterations in oculomotricity can indicate involvement of the central nervous system in patients with a complaint of only tinnitus.     

Periodic alternating nystagmus in Meniere's disease: the peripheral type?

Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus that reverses direction periodically. PAN has been reported in acquired and congenital forms. The lesion site of the acquired form of PAN has been attributed to the caudal brainstem or cerebellum. We report an extremely rare case (a 59-year-old woman) with bilateral Meniere's disease, who presented PAN. PAN in this patient was suppressed in the light. This patient had smooth pursuit and normal optokinetic nystagmus, although patients with PAN usually show saccadic pursuit and impaired optokinetic nystagmus. These findings were different features from those of the central or congenital form of PAN. It should be kept in mind that peripheral vestibular disorders such as Meniere's disease could produce PAN.     

Electronystagmogrpahic findings among 127 dizzy patients: correlation wiht the aetiology of dizziness

Electronystagmography (ENG) was performed on 127 dizzy patients and the findings were compared with the diagnosis obtained with a comprehensive neurological test battery. ENG was found to be abnormal in 49 (39%) of the patients: 19 with unilateral vestibular hyporeactivity, eight with directional preponderance, 12 with spontaneous or unidirectional positional nystagmus, eight with abnormal smooth pursuit, and 13 with other abnormalities. Among the patients with abnormal ENGs, established central nervous system lesions were found in 28 cases (19 of these infratentorial lesions); nine peripheral vestibular lesions and five undefined vestibular lesions were found. Patients with normal ENGs showed fewer peripheral vestibular lesions and more dizziness of psychogenic aetiology. Almost half the patients with infratentorial lesions had normal ENGs. Patients with roatory vertigo had fewer ENG abnormalities than those with other types of dizziness.     

Periodic alternating nystagmus in Meniere's disease: the peripheral type?

Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus that reverses direction periodically. PAN has been reported in acquired and congenital forms. The lesion site of the acquired form of PAN has been attributed to the caudal brainstem or cerebellum. We report an extremely rare case (a 59-year-old woman) with bilateral Meniere's disease, who presented PAN. PAN in this patient was suppressed in the light. This patient had smooth pursuit and normal optokinetic nystagmus, although patients with PAN usually show saccadic pursuit and impaired optokinetic nystagmus. These findings were different features from those of the central or congenital form of PAN. It should be kept in mind that peripheral vestibular disorders such as Meniere's disease could produce PAN.     

Electronystagmographic findings among 127 dizzy patients: correlation with the aetiology of dizziness

Electronystagmography (ENG) was performed on 127 dizzy patients and the findings were compared with the diagnosis obtained with a comprehensive neurological test battery. ENG was found to be abnormal in 49 (39%) of the patients: 19 with unilateral vestibular hyporeactivity, eight with directional preponderance, 12 with spontaneous or undirectional positional nystagmus, eight with abnormal smooth pursuit, and 13 with other abnormalities. Among the patients with abnormal ENGs, established central nervous system lesions were found in 28 cases (19 of these infratentorial lesions); nine peripheral vestibular lesions and five undefined vestibular lesions were found. Patients with normal ENGs showed fewer peripheral vestibular lesions and more dizziness of psychogenic aetiology. Almost half the patients with infratentorial lesions had normal ENGs. Patients with rotatory vertigo had fewer ENG abnormalities than those with other types of dizziness. These results suggest that ENG alone is of limited value in the diagnosis of dizziness. A comprehensive test battery is needed to establish the diagnosis.     

Multiple sclerosis. The value of clinical vestibular examination

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

Multiple sclerosis. The value of clinical vestibular examination.

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

Electronystagmography and horizontal directionalization

A series of 22 patients complaining of disorders of equilibrium or hearing thought to be due to Central Nervous System (CNS) dysfunction has been studied. Data were obtained for electronystagmography (ENG), horizontal directionalization (HD), the staggered spondee word test (SSW), brainstem auditory evoked responses (BSER) and the Chocholle test of binaural interaction of pure tones (CH). The central ENG abnormalities found were spontaneous central vestibular nystagmus, paroxysmal central positional nystagmus, gaze paretic nystagmus, impaired optokinetic nystagmus, impaired smooth pursuit eye movements and impaired fixation-suppression of caloric nystagmus. HD results showed a weak link with hearing loss (HL). The central ENG abnormality most closely associated with impairment of HD was abnormal smooth pursuit eye movements. No significant relationship could be established between any two of the tests studied. The limited localizing value of the tests is discussed together with the contribution they make towards the diagnosis of the patient complaining of dizziness.     

Evaluation of oculomotor tests in patients with tinnitus

Tinnitus as a symptom remains a serious multidisciplinary problem. Vertigo or dizziness is not noticed frequently in tinnitus patients, so vestibular function is not often studied. Because they are in close proximity to one another, the vestibular and hearing organs may influence each other. We decided to evaluate the results of the oculomotor reflex in tinnitus patients. We carried out clinical examinations and audiological and oculomotor tests in 50 tinnitus patients and 30 healthy persons. Such oculomotor tests as smooth-pursuit eye movement, optokinetic tests, and saccadic eye movement and gaze fixation were performed. Tinnitus was unilateral in 37 tinnitus patients (74%) and bilateral in 13 (26%). Twenty-two tinnitus patients (44%) reported previous remote episodes of vertigo and dizziness. Gaze-evoked nystagmus was absent in all cases. Morphological abnormalities and gain decreases in smooth-pursuit tests were recorded in 19 tinnitus patients (38%). Findings in the optokinetic test were incorrect in 10 (20%). The saccadic eye movement test showed disturbances in 18 tinnitus patients (36%). In 11 (22%), abnormal recordings were found in two tests and, in 10 (20%), abnormal recordings were found in all three tests. Our study suggests that computerized, quantitative electronystagmographic analysis in tinnitus patients should be interpreted carefully. A persistence of abnormal oculomotor recordings can suggest subclinical central vestibular system impairment.     

Comparison of vertical and horizontal optokinetic nystagmus in the squirrel monkey.

Horizontal and vertical optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) of squirrel monkeys were compared with those of rabbits, cats and humans that were previously described. Squirrel monkeys showed similar findings to cats, in which vertical optokinetic nystagmus (VOKN) is not as well elicited as horizontal optokinetic nystagmus (HOKN) and down-pursuit OKN is poorer than up-pursuit OKN. As to the reasons that bring about different responses of OKN and OKAN (and vestibular nystagmus) in different planes, we speculated two possibilities: compensatory activation of horizontal eye movement for narrowed visual field accompanied by frontally positioned eyes, and the gravity that restricts and modifies posture and locomotion. Directional difference of VOKN may be caused by a physiological mechanism that makes visual fixation not susceptible to downward movement of the ground surface during forward locomotion.     

Postural behaviour responses to visual stimulation in patients with vestibular disorders

Patients with different vestibular disorders exhibit changes in postural behaviour when they receive visual stimuli, reproducing environmental stimulation. Postural control was studied using an AMTI Accusway platform, measuring the confidential ellipse (CE) and sway velocity (SV). Postural responses were recorded according to the following stimulation paradigm: i) without specific stimuli; ii) smooth pursuit with pure sinusoids of 0.2 Hz (foveal stimulation); and iii) optokinetic stimulation (retinal stimuli). Patients with central vestibular disorders (CVD), cerebellar damage and unilateral peripheral vestibular lesions (UPVL) in asymptomatic periods were studied. A group of normal subjects was studied as control. Signal processing was done with a scalogram by wavelets in order to observe the relation between time and frequency in postural control. While patients with CVD and cerebellar disease showed a significant increase in CE and SV in the three conditions of the paradigm compared to the normal group, the patients with UPVL showed no change. Wavelets processing showed that the main sway occurs in the Y axis (antero-posterior) and below at 0.4 Hz in normal subjects, while the CVD and cerebellar patients showed sway frequencies in both the X and Y axes. The clinical implications of these findings are discussed.     

The value of the examination of visuooculomotor reflexes in diagnosis of posterior cranial fossa lesions

The aim of this study was to compare the frequency of pathological types of smooth-pursuit and saccadic movements in different localizations of vestibular lesions. We tested 112 patients using videonystagmography. The smooth pursuit was appreciated qualitatively on the basis of Malecki's patterns. We analyzed the saccadic movements taking three parameters into consideration: latency, velocity, and accuracy. The patients suffered from posterior cranial fossa lesions, supratentorial damage, and peripheral vestibular disorders. We discovered that testing of smooth pursuit and saccades was very helpful in pointing to the localization of the damage in the posterior fossa. The frequency of the pathological saccadic and eye-tracking movements was similar for the different sites of deficit inside the posterior fossa, so recognizing the precise localization of lesion in this anatomical region was difficult.     

Neuro-otological findings in patients with very small (border zone) cerebellar infarcts

CONCLUSIONS: The symptoms and signs in patients with very small (border zone) cerebellar infarcts (VSCIs) may mimic those in benign peripheral vestibular disorders, except that smooth pursuit eye movement is disturbed in patients with VSCI. OBJECTIVES: VSCIs are located at the boundary territories between well-defined cerebellar arteries and are frequently manifested by dizziness or vertigo. The aim of the current study was to clarify the clinical characteristics of vestibular symptoms and signs associated with VSCI. PATIENTS AND METHODS: We studied the neuro-otological findings in five vertiginous patients, who were diagnosed as having VSCI based on magnetic resonance imaging (MRI). RESULTS: Four patients complained of only dizziness or only vertigo, and one complained of dizziness with dysarthria. Horizontal spontaneous nystagmus and saccadic eye movement on eye tracking test were observed in all patients, but there were no abnormalities on examinations for saccade, optokinetic pattern, or visual suppression. Canal paresis was present in three patients.