Torsional nystagmus: quantitative features and possible pathogenesis

We measured eye rotations in three planes in a patient with acquired, torsional nystagmus. This nystagmus had linear or increasing-velocity waveforms, was increased after active pitch rotations of the head, and was suppressed by convergence. Magnetic resonance imaging demonstrated a midpontine lesion that was probably a venous angioma. We postulate that torsional nystagmus in this patient was due to disruption of central vestibular connections.     

Unilateral pursuit-induced congenital nystagmus

We describe two patients with a lifelong history of oscillopsia only when following objects moving toward their left side. Neurologic examination was normal except for eye movements. The patients showed nystagmus during any tasks that required visual following toward the left (ie, smooth pursuit, optokinetic nystagmus, and vestibulo-ocular-reflex-suppression), but had no nystagmus during fixation of stationary targets or visual following tasks to the right. Eye-movement recordings showed waveforms during pursuit to the left that were typical of congenital nystagmus.     

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.     

Assessment of vestibulo-ocular reflexes in congenital nystagmus

The vestibulo-ocular reflex and its suppression by fixation of a target rotating with the subject were tested in 18 subjects with congenital nystagmus using steps of constant velocity rotation and sinusoidal stimuli swept in frequency between 0.01 and 1.0 Hz. Responses to stopping stimuli were abnormal in waveform and of short duration in most subjects tested. This pattern was attributed to masking of the response by spontaneous eye movements and to adaptation. In contrast, during both oscillation in the dark and attempted suppression of the vestibulo-ocular reflex, all subjects had nystagmus that was modulated with the stimulus during all frequencies of stimulation. The phase relationship of the nystagmus to the motion stimulus was the same as in normal subjects. Estimates of the gain of the vestibulo-ocular reflex response were not meaningful because of contamination of the vestibular response by the congenital nystagmus waveforms. Modulation of amplitude and reversal of nystagmus in phase with the vestibular stimulus at all frequencies of oscillation were shown most clearly during attempted suppression of the vestibulo-ocular reflex. This finding is clinically useful because it establishes suppression as a test of the presence of vestibular function in congenital nystagmus.     

Latent and congenital nystagmus in Down syndrome.

OBJECTIVES: Although nystagmus has been reported in Down syndrome (DS), it has been poorly characterized, because most investigators have relied on clinical observations rather than on eye movement recordings. This study was conducted to investigate nystagmus in DS, using quantitative measurements of eye movements. METHODS: Ocular motility and visual functions were examined in 26 unselected adults with DS and compared with those in an age-matched group of 35 subjects with other causes of mental retardation. The eye movements of those with clinically evident nystagmus were recorded with the infrared technique. We also recorded the eye movements of a child with DS and nystagmus. RESULTS: Nystagmus was identified in six (23%) adults with DS and in none in the control group. All six patients showed latent/manifest latent nystagmus (LMLN), prominent with the covering of one eye, and esodeviations of 10 to 30 prism diopters. Eye movement recordings confirmed LMLN with its exponentially decaying waveform. Frequencies ranged from 2 to 5 Hz and amplitudes from 5 degrees to 20 degrees. While attempting to fixate straight ahead in the absence of visual cues, three subjects exhibited shifts in the mean eye position. In contrast with the findings in adults, the only child with DS examined had both congenital nystagmus and LMLN waveforms. CONCLUSIONS: The predominant type of nystagmus in the study subjects with DS is LMLN. The high prevalence of LMLN may reflect abnormal integration of visuospatial information that is typical of DS. The concurrent presence of congenital nystagmus in a child but only LMLN in the adults with DS raises the possibility of age-related waveform changes or could reflect sample variation.     

The torsional component of "horizontal" congenital nystagmus.

OBJECTIVES: To study the relationship between the major horizontal and minor torsional components of congenital nystagmus to elucidate the diagnostic importance, effects on vision, and pathogenetic implications of the torsional components. METHODS: We recorded the eye movements of 13 subjects with congenital nystagmus using a three-dimensional magnetic search coil technique over a 15-year period. The subjects fixated on stationary targets straight ahead and along the horizontal and vertical meridians. Six of the 10 subjects with horizontal congenital nystagmus were asymptomatic; the remaining 4 (plus two with a vertical component to their congenital nystagmus) had adult-onset symptoms. An additional subject without symptoms had a vertical congenital nystagmus component plus seesaw nystagmus; one of the symptomatic subjects also had seesaw nystagmus. RESULTS: In all 13 subjects, the horizontal and torsional cycles were phase-locked, and positive horizontal (rightward), vertical (upward, if any), and torsional (clockwise) motion coincided in 10 subjects. That is, rightward horizontal eye rotation coincided with clockwise curvilinear motion (rightward and downward) of the upper pole of each eye. During the horizontal foveation periods, torsional motion was also of low velocity. In 2 of 13 subjects, the torsional waveforms differed from those in the horizontal plane; in others, the direction or the variation with gaze angle differed from that predicted by Listing. In each of the 13 subjects, the torsional components ranged from 8.16% to 94.42% (median, 32.94%) of the peak-to-peak magnitudes of the congenital nystagmus. In most cases, the measured torsion was far greater than that predicted by Listing's law for a worst-case analysis (range, 0.69-11.83%; median, 4.91%). The torsional components of the two subjects with seesaw nystagmus were 60.48% and 264.02%. CONCLUSIONS: The manner in which the horizontal and torsional components of "horizontal" congenital nystagmus were phase-locked made clinical detection of the torsional component difficult. Most "horizontal" congenital nystagmus is actually horizontal-torsional congenital nystagmus. Visual acuity during horizontal foveation periods is not significantly diminished by torsional motion. In only one subject did the torsional component of the congenital nystagmus have an amplitude equivalent to Listing torsion; in the other 12 subjects, torsion exceeded our estimate of what Listing's law would predict. The torsional components of the seesaw nystagmus in two subjects also greatly exceeded the torsion predicted by Listing torsion. The most parsimonious explanation for our data is that the cyclic torsion in congenital nystagmus was generated centrally and not a result of Listing torsion, mechanical crosstalk, or normal or abnormal extraocular-muscle (plant) dynamics. Further measurements are needed to confirm this hypothesis.     

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.     

Horizontal pursuit defect nystagmus.

A teenage girl with a chronic large posterior fossa tumor had primary position right-beating nystagmus with a constant-velocity slow phase. Smooth pursuit was normal to the left but absent to the right. Vestibuloocular movements were present in both directions. The findings are analogous to downbeat and upbeat nystagmus, in which unidirectional pursuit palsies have been postulated as the pathogenic mechanism. This is the first reported case of a horizontal pursuit defect causing nystagmus.     

Pharmacology of vertigo/nystagmus/oscillopsia

PURPOSE OF REVIEW: To describe recent developments in the pharmacological treatment of vertigo and nystagmus while focusing on vestibular neuritis, Meniere's disease, downbeat nystagmus, periodic alternating nystagmus, acquired pendular nystagmus, and superior oblique myokymia. RECENT FINDINGS: In the last 2 years several studies have been published on possible pharmacological treatment options for nystagmus and oscillopsia. In the treatment of vestibular neuritis two studies showed that cortisone treatment was effective for restoring labyrinthine function. This benefit seems more likely if treatment is started within the first 2 days of onset. For recurrent vertigo attacks due to Meniere's disease, the titration technique with daily or weekly doses of intratympanic gentamicin until onset of vestibular symptoms, change in vertigo or hearing loss rated best for complete vertigo control. A new pharmacological treatment option for downbeat nystagmus is the administration of potassium channel blockers (e.g. 4-aminopyridine). They are thought to reinforce the inhibitory action of cerebellar Purkinje cells. Several case reports have proven the beneficial effect of baclofen on periodic alternating nystagmus, of gabapentin and memantine on acquired pendular nystagmus, and of carbamazepine and gabapentin on superior oblique myokymia. SUMMARY: There have been several new developments in the treatment of nystagmus and vertigo over the last 2 years. These include potassium channel blockers for the treatment of downbeat nystagmus, early cortisone treatment to improve recovery of the labyrinth function in vestibular neuritis, and intratympanic gentamicin treatment for Meniere's disease. Other pharmacological treatment options are baclofen for periodic alternating nystagmus, gabapentin and memantine for acquired pendular nystagmus, and carbamazepine for superior oblique myokymia.     

What We Know about the Generation of Nystagmus and Other Ocular Oscillations: Are We Closer to Identifying Therapeutic Targets?

Mechanisms underlying acquired nystagmus are better understood than those leading to infantile nystagmus. Accordingly, further progress has been made in the development of effective therapies for acquired nystagmus, mainly through pharmacological interventions. Some of these therapies have been developed under the guidance of findings from experimental animal models. Although mechanisms behind infantile nystagmus are less understood, progress has been made in determining the genetic basis of nystagmus and characterizing associated sensory deficits. Pharmacological, surgical, and other treatments options for infantile nystagmus are now emerging. Further investigations are required for all forms of nystagmus to produce high-quality evidence, such as randomized controlled trials, upon which clinicians can make appropriate treatment decisions.     

Oculomotor abnormalities in Friedreich's ataxia.

A clinical neuro-ophthalmological and electro-oculographic study was made on fourteen patients with Friedreich's ataxia. None had evidence of optic nerve dysfunction. No patient complained of oscillopsia although all had ocular motor deficits of varying degrees, which appeared to be related to the severity of the general manifestations of the disease. The defects comprised square wave jerks, jerky pursuit with inability to maintain eccentric gaze resulting in gaze paretic nystagmus and rebound nystagmus. There was failure to suppress by fixation the vestibulo-ocular reflex. The slow phase velocity of caloric nystagmus was always of reduced velocity. There was inability to augment the slow phase velocity of optokinetic nystagmus with increasing stimulus velocity. Abnormalities of the saccadic system were manifest particularly as hypermetria. These signs in combination are suggestive of disease involving the cerebellar flocculus and vermis or their brain stem connections. No abnormalities were found in 17 parents or siblings.     

The differential diagnosis of congenital nystagmus.

The decision whether a nystagmus is congenital or acquired may be difficult and is of importance in patients presenting with neurological complaints. In this article, established diagnostic criteria are critically reviewed with particular emphasis on types of nystagmus waveform and their relationship to pursuit and optokinetic responses. Attention is drawn to certain acquired nystagmus which may have similar features which have hitherto been accepted as pathognomonic of congenital nystagmus. Symptoms due to congenital nystagmus are discussed and related to the oculomotor abnormalities. The importance of the characteristics of congenital nystagmus are evaluated for use in differential diagnosis.     

Apogeotropic central positional nystagmus as a sole sign of nodular infarction

Positional vertigo and nystagmus without associated neurological symptoms and signs are characteristic features of benign paroxysmal positional vertigo (BPPV). Although positional nystagmus may occur with caudal cerebellar infarction including the nodulus, positional nystagmus is usually associated with other neurological signs such as spontaneous or gaze-evoked nystagmus, perverted head-shaking nystagmus, cerebellar dysmetria, or severe gait ataxia with falling. We present a patient with nodular infarction who had positional vertigo with nystagmus as a sole manifestation. Video-oculography showed apogeotropic positional horizontal nystagmus during head turning while supine, which was consistent with apogeotropic BPPV involving the horizontal canal. MRI disclosed acute infarct in the nodulus. Nodulus infarction should be considered in a patient with positional nystagmus, especially when the presenting symptoms and signs are consistent with BPPV involving the horizontal canal.     

Central nystagmus induced by deep-brain stimulation for epilepsy

PURPOSE: The goal of the present study was to describe the localization of central nystagmus induced as a side effect of electrical deep-brain stimulation for epilepsy. METHODS: Bilateral deep-brain stimulating electrodes were inserted in the centromedian nucleus of the thalamus to control seizures in a patient with intractable epilepsy. RESULTS: Cathodal high-frequency stimulation through the deepest contact of each electrode elicited cycles of slow ipsiversive conjugate eye deviations, each followed by rapid contralateral jerks. The involved electrode contacts were situated at the mesodiencephalic junction just inferior to the centromedian nucleus of the thalamus and rostral to the superior colliculus. Right-sided stimulation evoked left beating nystagmus and left-sided stimulation evoked right beating nystagmus. Stimulation through other electrode contacts did not induce nystagmus. Electronystagmography showed the nystagmus to have constant velocity slow phases. CONCLUSIONS: A central nystagmogenic area exists in humans that appears to be homologous to the nucleus of the optic tract, a region described in nonhuman primates to play a role in the generation of optokinetic nystagmus.     

Primary position upbeat nystagmus reversed with carbamazepine

A 16-year old girl presented with primary position upbeat nystagmus (PPUN). MRI showed a small lesion at the perihypoglossal nuclei of the dorsal medulla oblongata. The case was diagnosed as a demyelinating disease for its response to prednisone, and the nystagmus decreased after administration of carbamazepine. Primary position upbeat nystagmus might be caused by an abnormal firing of neurons in the nuclei resulting in a tonic imbalance of vertical gaze. Also this is the first report to confirm the attenuation of PPUN by carbamazepine.     

Pharmacotherapy of central oculomotor disorders

Nystagmus causes blurred vision due to oscillopsia, as well as impaired balance. Depending on etiology, additional cerebellar and brain stem signs may occur. We present the current pharmacotherapy of the most common forms of central nystagmus: downbeat nystagmus (DBN), upbeat nystagmus (UBN), acquired pendular nystagmus (APN), and congenital nystagmus (CGN). Recommended medical therapies are aminopyridines (4-AP) for DBN and UBN, gabapentin and memantine for CGN and APN, and baclofen for periodic alternating nystagmus (PAN).     

Seesaw nystagmus caused by giant pituitary adenoma: case report

Giant pituitary adenomas are uncommonly large tumors, greater than 4 cm in size that can produces endocrine symptoms, visual loss and cranial nerve palsies. We report the rare occurrence of seesaw nystagmus as the presenting sign of giant pituitary adenoma. A 50-year-old man presented with headache associated with visual loss and seesaw nystagmus. Perimetry revealed bitemporal hemianopia and magnetic resonance imaging showed a giant pituitary adenoma. After surgery, nystagmus disappeared. Our case is relevant in understanding its pathogenesis since it documents seesaw nystagmus in a patient bitemporal hemianopia due to a large tumor but without mesencephalic compression.     

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)     

VERTICAL OPTOKINETIC NYSTAGMUS

Among 6377 investigations for optokinetic nystagmus the authors found 97 patients with abnormal vertical optokinetic nystagmus and normal horizontal optokinetic nystagmus. This is 10 % of the approx. 1000 patients with manifest organic lesion of the central nervous system. In 30 the vertical optokinetic nystagmus was abnormal in one direction, in 67 cases in both. Abnormality of the vertical optokinetic nystagmus in both directions was found in unilateral cerebral lesions, unilateral brain-stem lesions, and in more diffuse lesions of the central nervous system. Total absence of vertical optokinetic nystagmus was observed in only 7 patients, 5 of whom had vertical gaze paralysis, 4 of them due to pseudobulbar paralysis. Abnormality of the vertical optokinetic nystagmus in both directions in cases with definitely unilateral signs from the cerebrum or mesencephalon indicates that both vertical gaze centres have to function simultaneously to elicit normal optokinetic nystagmus. This is also confirmed by the fact that the severity of the abnormal vertical optokinetic nystagmus is greatest in lesions high in the mesencephalon, where the paths for vertical optokinetic nystagmus assemble in the two vertical gaze centres. Abnormality of the vertical optokinetic nystagmus as an isolated finding is interpreted as a sign of organic disease in the central nervous system and should lead to further special investigations for a more detailed diagnosis.     

EFNS task force--therapy of nystagmus and oscillopsia.

An overview of possible treatment options for oculomotor disorders that prevent clear vision is given. Downbeat nystagmus, upbeat nystagmus, seesaw nystagmus, periodic alternating nystagmus, acquired pendular nystagmus, and saccadic oscillations such as opsoclonus/ocular flutter are discussed. In addition, superior oblique myokymia and vestibular paroxysmia are reviewed. All treatment recommendations available in the literature are classified as class C only. In general, only some of the patients benefit from the treatment.