"Saccadic nystagmus" in cerebellar cortical atrophy.

An ocular dyskinesia designated "saccadic nystagmus" was observed in a patient with cerebellar cortical atrophy. Saccadic nystagmus is a sustained ocular dyskinesia present during visual fixation and abolished by eye closure. It is difficult to distinguish visually from either pendular or jerk nystagmus without eye movement recordings. The oscillations are horizontal and rapid and may be influenced by direction of gaze. Caloric nystagmus (eye closed) and optokinetic nystagmus were normal in our patient. Visual fixation abolished caloric nystagmus, which was replaced by saccadic nystagmus.     

Translocation of cortical migraine phosphenes through eye movements and vestibular stimulation]

Self-observations of migraine-phosphenes demonstrate the influence of gaze and vestibular stimuli upon cortical foci in the human are 17. The scintillating phosphenes appearing in one half-field are seen as moving during voluntary gaze shifts: Saccades and pursuit movements translocate the phosphenes besides the fixation point within a stable outer visual surround. Vestibular stimuli cause a shift and deformation of the phosphene towards the slow phase direction of vestibular nystagmus. In contrast to voluntary eye movements the phosphenes do not transgress the midline during vestibular nystagmus and the translocation is much smaller than the sum nystagmus amplitudes elicited by head acceleration.     

Study of nystagmus suppression in the rotatory tests

Thirty one healthy subjects ranging in age between 21 and 50, participated voluntarily in the following experiment: they underwent programmed sequential alternating rotations, while their nystagmus was recorded by way of electronystagmography. The direction of rotation was changed every minute, and the total rotation time was 36 minutes. The subjects were rotated under external conditions which were altered every six minutes; these conditions included the following:

1. Rotation in the light with visual fixation and convergence.
2. Rotation in the light with visual fixation without convergence (one eye closed, the other looking at the target).
3. Rotation in the light without visual fixation (both eyes covered by a shade or by Frenzel's glasses).
4. Rotation in the dark without convergence (looking straight ahead).
5. Rotation in the dark with convergence (looking at the thumb, closely placed in front of the nose).

The purpose of the experiment was to study the phenomenon of nystagmus suppression observed with visual fixation and often attributed to cortical activity. The conclusion of the study is that nystagmus may be suppressed by light alone as well as by visual stimuli, convergence and proprioceptive stimuli. The inference is that the mechanism involves brain stem reflexes and not necessarily visual cortex activity.     

Vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and its interaction in active head movements

Summary In normal adults the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) were investigated during passive and active head or body movements, respectively. Sinusoidal rotations around the vertical axis of the body at frequencies of 0.05, 0.1, and 0.2 s^–1 and total amplitudes of 20°, 40°, 60°, or 80° were employed.The average eye deviations (Schlagfeld) during VOR were directed opposite to the direction of the head turning. During COR, however, slow eye deviations of higher amplitude were anticompensatory relative to the fixed head. During active head turnings the average eye deviations showed the same anticompensatory direction as in COR, but were still larger. They increased with stimulus amplitudes up to 60°.At least a weak cervical nystagmus was elicited in all subjects, with its fast phases beating in the direction of the relative head movement. Its gain reached marked values up to 0.5, but only for peak stimulus velocities below 25°/s. The nystagmus gain during active head turnings was only slightly higher than during VOR.With higher stimulus velocities, large anticompensatory saccades appeared just before the change of stimulus direction; these are typical for active head movements, but were also found during COR.Supported by Sonderforschungsbereich Hirnforschung und Sinnesphysiologie (SFB 70) der Deutschen Forschungsgemeinschaft (DFG)     

Eye movements in patients with superior canal dehiscence syndrome align with the abnormal canal

BACKGROUND: The superior canal dehiscence (SCD) syndrome consists of sound- or pressure-induced nystagmus and vertigo caused by a defect in bone overlying the superior semicircular canal. The SCD syndrome is diagnosed based upon characteristic symptoms, signs, and findings on CT imaging of the temoral bones. However, SCD syndrome is often misdiagnosed as perilymphatic fistula (PLF), and the symptoms of sound- and pressure-induced vertigo are more commonly attributed to the vestibular utricle, rather than to the superior semicircular canal. This study explored the role of the superior canal and the utricle in the pathophysiology of SCD syndrome. METHODS: Three-dimensional scleral search coils were used to record eye movements in 11 patients with SCD syndrome. RESULTS: Ten patients developed nystagmus with upward torsional slow phases characteristic of superior canal activation when loud tones were presented to the affected ear or when the patients performed a Valsalva maneuver. Visual fixation led to a suppression of the nystagmus and the appearance of a sustained torsional deviation of the eyes. Two patients also had sound-evoked head movements in the same direction as the ocular slow phases. The response of the affected superior canal to rapid head rotations was tested in nine patients. The response was diminished in those with large (>/=5 mm) defects in the bone overlying the superior canal. CONCLUSIONS: The evoked eye movements in patients with SCD syndrome arise from the superior canal, not the utricle. The syndrome is recognized by the characteristic nystagmus evoked by tones or maneuvers that change middle ear or intracranial pressure. Examination for this nystagmus should be performed under conditions that prevent visual fixation.     

INFRARED METHODS FOR STUDYING NYSTAGMUS AND EYE DEVIATIONS IN COMPLETE DARKNESS WITH SPECIAL REFERENCE TO VERTICAL NYSTAGMUS

Two infrared methods for direct evaluation of oculostatic signs in darkness are presented. Both methods are suitable for clinical work. In this first study they were used to observe vertical darkness nystagmus under reliable control of the ocular position. Fifty healthy subjects had no nystagmus in any gaze position in ordinary light. In darkness a slight, but distinct, somewhat irregular up-beat nystagmus on forward gaze was observed in five of these (in addition, a slight horizontal nystagmus appeared in nine subjects). Down-beat nystagmus, which was not observed in any of the cases, is consequently of unique importance as a pathological sign. Twenty-two patients with multiple sclerosis showed no vertical nystagmus at straight forward gaze in ordinary light. On examination in darkness, a vertical nystagmus appeared in the straight forward (primary) position of the eyes in twelve of the patients. The rapid phase was directed downward in eight, upward in four patients. In five patients the vertical nystagmus was associated with a tonic eye deviation in the direction of the slow phase. In one patient, nystagmus persisted at voluntary gaze in the direction of the slow phase. Thus, in these six patients it may be designated as third degree vertical nystagmus in darkness. (At gaze deviation towards the rapid phase it became visible (group I) in ordinary light as a “gaze-deviational” nystagmus.) The relation between the so-called gaze deviation nystagmus, spontaneous vertical darkness nystagmus in multiple sclerosis and vestibular nystagmus is briefly discussed.     

Functional localization in the three floccular zones related to eye movement control in the cat

Anatomically, the cat's cerebellar flocculus can be divided into 3 zones on the basis of differences in their efferent projection sites^13,14. The functional differences of these 3 zones in relation to eye movement control were investigated by observing the eye movements evoked by electric stimulation of each zone of the flocculus in ketamine-anesthetized cats. Stimulation of the flocculus elicited a slow eye movement. The direction of the slow eye movement was mapped. A downward eye movement was evoked by stimulation of the caudal zone. An ipsilateral horizontal eye movement was induced from the middle zone. An upward eye movement was elicited from the rostral zone. When prolonged stimulation was applied to the flocculus, the slow eye movement was followed by nystagmus in the opposite direction. This nystagmus persisted for many seconds after cessation of stimulation (afternystagmus). Nystagmus and afternystagmus could not be elicited in deeply anesthetized cats. Possibilities as to how the stimulation leads to various eye movements are discussed.     

Paroxysmal alternating skew deviation and nystagmus after partial destruction of the uvula

A patient with suspected brain stem glioma involving the area of the left vestibular nuclei and cerebellar peduncle, developed paroxysmal alternating skew deviation and direction changing nystagmus after biopsy of the inferior cerebellar vermis resulting in destruction of the uvula. Between attacks she had right over left skew deviation with asymptomatic right beating horizontal nystagmus. Slow phases of the resting nystagmus showed increasing velocity, similar to congenital nystagmus. At intervals of 40-50 seconds, paroxysmal reversal of her skew deviation occurred, accompanied by violent left beating horizontal torsional nystagmus lasting 10-12 seconds and causing severe oscillopsia. It is proposed that this complex paroxysmal eye movement disorder results from (1) a lesion in the left vestibular nuclei causing right over left skew and right beating resting nystagmus and (2) a disruption of cerebellar inhibition of vestibular nuclei, causing alternating activity in the vestibular system with intermittent reversal of the skew deviation and paroxysmal nystagmus towards the side of the lesion.     

Drug therapy for acquired pendular nystagmus in multiple sclerosis

Acquired pendular nystagmus (APN) is regularly accompanied by oscillopsia and impairment of static visual acuity. Therapeutic approaches to APN remain controversial, and there is no generally accepted therapeutic approach. We tested 14 patients who had suffered from APN caused by multiple sclerosis for several years; 12 patients presented with fixational pendular nystagmus (increasing during fixation) and 2 with spontaneous pendular nystagmus. All 11 patients with fixational pendular nystagmus who were given memantine, a glutamate antagonist, experienced complete cessation of the nystagmus. In contrast, scopolamine caused no (6 of 8) or only a minor (10–50%) reduction of the nystagmus (2 of 8). It was concluded that memantine is a safe treatment option for APN. Received: 29 August 1995 Received in revised form: 6 August 1996 Accepted: 19 August 1996     

Pathologic nystagmus and related phenomena. A review

Pathological nystagmus may be spontaneous, positional, or gaze-evoked. Peripheral vestibular nystagmus is usually rotatory, the horizontal component being most prominent. It is - in contrast to a central vestibular nystagmus - strongly inhibited by fixation. Spontaneous congenital nystagmus is also prominent with fixation, but it can usually be distinguished from acquired fixation nystagmus based on its long duration, atypical waveforms and high frequency. Two general types of positional nystagmus can be identified on the basis of nystagmus regularity: static and paroxysmal. The most common variety of positional nystagmus is the so-called benign paroxysmal positional nystagmus, which in the majority of cases occurs as an isolated symptom of unknown cause. Gaze-evoked nystagmus, prominent with fixation, includes dissociated, rebound and gaze-paretic nystagmus forms. Symmetrical gaze-evoked nystagmus is most commonly produced by ingestion of certain drugs. Phenomena related to nystagmus include: amblyopic, voluntary, and convergence-retraction nystagmus, ocular dysmetria, ocular flutter, opsoclonus, ocular bobbing, and ocular myoclonus.     

Nystagmus only with fixation in the light: a rare central sign due to cerebellar malfunction

Journal of Neurology - Fixation nystagmus refers to the nystagmus that appears or markedly increases with fixation. While relatively common in infantile (congenital) nystagmus, acquired fixation...     

Abnormal visual--vestibular interactions in psychosis

Vestibular reactivity and suppression of caloric nystagmus by visual fixation were examined in 40 psychiatric patients (36 schizophrenics and 4 manic-depressives) and 20 normal control subjects. Indices of reactivity commonly considered to reflect vestibular integrity, namely, slow-phase velocity and bilateral symmetry of response, did not discriminate patients from controls. However, response irregularities in the form of dysrhythmia and slower velocity of the nystagmus fast (saccadic) component were present to a significant degree in patients. Visual fixation effectively suppressed caloric nystagmus in normal controls, but not in hospitalized patients. This failure of fixation suppression was most marked in patients showing active symptomatology. These results indicate a central regulatory dysfunction of visual-vestibular interaction in psychiatric patients which varies with intensity of psychotic symptomatology and which does not seem attributable to medication or attentional factors.     

Failure of fixation suppression of caloric nystagmus and ocular motor abnormalities

Caloric nystagmus is substantially suppressed by visual fixation. The degree of suppression of caloric nystagmus is influenced by the condition of visual fixation. We studied the percent reduction in slow-phase velocity of caloric nystagmus by visual fixation and certain abnormalities in optokinetic nystagmus, smooth pursuit, and maintenance of ocular position of gaze in 38 patients with disorders of the CNS. The inability to suppress caloric nystagmus by visual fixation correlated with reduction in optokinetic nystagmus, deficit in smooth pursuit eye movements, and presence of gaze nystagmus. It seems probable that modulation of the vestibulo-ocular reflex is influenced by the same mechanisms that are concerned with optokinetic nystagmus, maintenance of ocular position of gaze, and smooth pursuit eye movements.     

Vertical nystagmus in Wernicke’s encephalopathy: pathogenesis and role of central processing of information from the otoliths

Patients with Wernicke’s encephalopathy (WE) often have unusual patterns of vertical nystagmus. Initially there is often a spontaneous upbeating nystagmus that may change to downbeat nystagmus with a change in the direction of gaze, convergence or with vestibular stimuli. Patients also often show a profound loss of the horizontal but not the vertical vestibulo-ocular reflex (VOR). Furthermore, the acute upbeat nystagmus may change to a chronic downbeat nystagmus. We present hypotheses for these features based on (1) the location of vertical gaze-holding networks near the area postrema of the dorsomedial medulla where the blood–brain barrier is located, which we suggest becomes compromised in WE, (2) the location of the vestibular nuclei in the brainstem, medially for the horizontal VOR, and laterally for the vertical VOR, (3) neuronal circuits differ in susceptibility to and in the ability to recover from thiamine deficiency, and (4) impaired processing of otolith information in WE, normally used to modulate translational vestibulo-ocular reflexes, leads to some of the characteristics of the spontaneous vertical nystagmus including the peculiar reversal in its direction with a change in gaze or convergence.

     

Vestibular involvement in spasmodic torticollis.

Vestibular findings in a group of 35 patients with spasmodic torticollis without other otological or neurological symptoms were reviewed. The most consistent abnormality, present in more than 70% of cases, was a directional preponderance of vestibular nystagmus in the dark in a direction opposite to the head (chin) deviation. Rigidly clamping the head to a rotating chair did not abolish the directional preponderance. In the presence of optic fixation the directional preponderance was less frequent and its severity tended to diminish as a function of the duration of the disease. Smooth pursuit and optokinetic nystagmus were only occasionally affected. The results are indicative of primary involvement of the vestibular system in spasmodic torticollis and are discussed in terms of a break-down of the central mechanisms conveying sensory information responsible for head and eye orientation.     

Lateralizing value of epileptic nystagmus

Epileptic nystagmus is a relatively rare clinical seizure presentation. The direction is usually determined by the fast component of the eye movement. We retrospectively reviewed 1838 consecutive patients admitted to the Epilepsy Monitoring Unit at Cleveland Clinic and identified 9 patients (0.5%) with epileptic nystagmus. Only two of them were adults. The direction of the nystagmus was contralateral to the epileptogenic zone in all patients. In contrast, eye version was seen ipsiversive to the epileptic nystagmus in four of the six patients in whom both signs were observed. Epileptic nystagmus is a helpful lateralizing sign, particularly in pediatric patients.     

Absence of nystagmus during REM sleep in patients with vestibular neuritis

Saccades, including fast phases of nystagmus, disappear during drowsiness and non-rapid eye movement (NREM) sleep, but are present during the alert state and REM sleep. The purpose of this study was to determine whether spontaneous nystagmus is present in patients with vestibular neuritis during REM sleep. Eight patients with spontaneous nystagmus due to vestibular neuritis and eight control patients without any nystagmus underwent at least one night of polysomnography. Fast phases of nystagmus were analyzed. The number of right and left horizontal saccades were counted, first during 3-5 minute samples of the awake state before sleep onset, then during the first REM episode and the last REM episode of nocturnal sleep, and finally during the alert state in the morning after nocturnal sleep. All patients with vestibular neuritis showed significantly more saccades (fast phases) towards the side contralateral to their vestibular lesion in the awake state before and after the polysomnography. This reflects their spontaneous nystagmus. By contrast, during REM sleep the patients with vestibular neuritis showed no preponderance in saccade direction. The eye movement pattern in REM was the same for patients and controls. In conclusion, peripheral vestibular imbalance producing nystagmus in vestibular neuritis in the awake state is not active at the brain stem level during REM sleep.     

Lateralizing value of epileptic nystagmus

Epileptic nystagmus is a relatively rare clinical seizure presentation. The direction is usually determined by the fast component of the eye movement. We retrospectively reviewed 1838 consecutive patients admitted to the Epilepsy Monitoring Unit at Cleveland Clinic and identified 9 patients (0.5%) with epileptic nystagmus. Only two of them were adults. The direction of the nystagmus was contralateral to the epileptogenic zone in all patients. In contrast, eye version was seen ipsiversive to the epileptic nystagmus in four of the six patients in whom both signs were observed. Epileptic nystagmus is a helpful lateralizing sign, particularly in pediatric patients.     

Diagnostic accuracy of a smartphone bedside test to assess the fixation suppression of the vestibulo-ocular reflex: when nothing else matters

Objective

Validation of a bedside test to objectify the fixation suppression of the vestibulo-ocular reflex (FS-VOR) in patients with a cerebellar syndrome and healthy controls.

Methods

The vestibulo-ocular reflex and its fixation suppression were assessed by video-nystagmography (VNG) in 20 healthy subjects (mean age 56 ± 15) and 19 patients with a cerebellar syndrome (mean age 70 ± 11). The statistical cutoff delineating normal from pathological FS-VOR was determined at the 2.5th percentile of the normal distribution of the healthy cohort. VNG was then compared to a bedside test, where eye movements were recorded with a smartphone while patients were rotated on a swivel chair at a defined speed and amplitude. These videos were rated as normal or pathological FS-VOR by six blinded raters, and results compared to VNG.

Results

VNG in healthy controls showed FS-VOR with a reduction of nystagmus beats by 95.0% ± 7.2 (mean ± SD). The statistical cutoff was set at 80.6%. Cerebellar patients reduced nystagmus beats by only 26.3% ± 25.1. Inter-rater agreement of the smartphone video ratings was 85%. The sensitivity of the video ratings to detect an impaired FS-VOR was 99%, its specificity 92%. Inter-test agreement was 91%.

Conclusion

The smartphone bedside test is an easily performed, reliable, sensitive, specific, and inexpensive alternative for assessing FS-VOR.

     

Periodic alternating nystagmus.

Three patients with periodic alternating nystagmus (PAN) are described in detail. Digital computer methods were used to quantify their disordered eye movement in an attempt to understand the pathophysiology. One of the patients was unusual in showing rebound nystagmus with fixation and PAN without fixation. Each patient had hyperactive vestibular responses and the phase and gain of the PAN cycles were altered in a predictable fashion by vestibular stimuli. It is postulated that PAN represents cyclical firing between reciprocally connected groups of inhibitory neurons within the vestibular and oculomotor nuclei. The cyclical firing is initiated by a critical imbalance of tonic input to either group of normally functioning neurons.