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A 60-year-old patient had progressive imbalance. Examination revealed saccadic smooth pursuit, downbeat nystagmus, ataxia of stance and gait, and reduced vibration sense. Video head impulse and caloric testing both showed vestibulo-ocular reflex (VOR) deficits (figure). The patient has cerebellar ataxia with neuronopathy and vestibular areflexia syndrome.1,2 Slow head turns while looking at an earth-fixed target produce saccadic rather than smooth compensatory eye movements (Videos 1) due to impairment of both the VOR and smooth pursuit (the visually enhanced VOR): 1 simple bedside test, 2 clinical signs, and 1 precise diagnosis.

Athletes exhibit better dynamic visual acuity (DVA) compared with nonathletes, whereas action video game players (VGPs) perform more similarly to controls despite having similar static visual acuity and refractive errors. The differences in DVA between groups were not related to differences in static visual acuity, refractive error, or smooth pursuit gain.The purpose of the study was to examine whether athletes and VGPs have superior DVA than controls (nonathletes, nongamers).Forty-six participants (15 athletes, 11 VGPs, 20 controls) aged 21.7 years (standard deviation, 2.8 years) were recruited. Participants were emmetropic with equivalent monocular and binocular static visual acuity between groups. Dynamic visual acuity was assessed using predictable (horizontal) and unpredictable (random) motion targets at velocities of 5, 10, 20, and 30°/s. Smooth pursuit eye movements were assessed using a horizontal motion step-ramp stimulus at the same speeds. This study was pre-registered with the Center for Open Science (https://osf.io/eu7qc).At 30°/s, there were significant main effects of group (F = 4.762, P = .01) and motion type (F = 9.538, P = .004). Tukey post hoc analysis for groups indicated that athletes performed better than did the control group (t = -2.919, P.02). An omnibus (group × motion type × speed) repeated measures ANOVA showed a main effect of speed (F = 110.137, P.001) and a speed × motion-type interaction (F = 27.825, P.001). Dynamic visual acuity decreased as speed increased, and the slope of the change was greater for random than for horizontal motion. Smooth pursuit gains were not significantly different between groups (P.05).Athletes have superior dynamic visual acuity performance compared with controls at 30°/s. This between-group difference cannot be fully explained by differences in smooth pursuit eye movements and therefore may reflect other differences between the groups.

SIGNIFICANCE. Oculomotor tests in concussion commonly show impairment in smooth pursuit and saccadic function. Honing in on the systems likely to be affected by concussion will streamline use of oculomotor function as a supplemental diagnostic and prognostic tool, as well as improve our understanding of the pathophysiology of concussion. PURPOSE. This study investigates oculomotor function between concussed and healthy collegiate athletes, as well as determines measurement test-retest reliability of those tools. METHODS. Eighty-seven healthy athletes were recruited from a US Division 1 sports university and completed a 30-minute vestibular ocular testing battery in an enclosed rotary chair system equipped with 100Hz eye-tracking goggles. Forty-three individuals completed the battery twice. Twenty-eight individuals with a current diagnosis of concussion also completed the battery. All participants were ages 18–24. Bivariate statistical tests examined differences in scores across groups, and intraclass coefficients were computed to test reliability. RESULTS. Concussed individuals had significantly longer saccadic, visual, and dual-task reaction times and reduced saccadic accuracy. There was no difference in optokinetic reflex gain, but few concussed individuals tolerated the task. Reaction time latencies and optokinetic gain show moderate test-retest reliability. Smooth pursuit tasks and saccadic accuracies showed poor test-retest reliability. CONCLUSIONS. Saccadic latency was the most sensitive oculomotor function to change following concussion and was reliable over time. Saccadic accuracy was significantly lower in the concussed group but had poor retest-reliability. Optokinetic gain may warrant more investigation due to its high test-retest reliability and symptom provocation in concussion, despite not showing a significant difference between groups.

OBJECTIVE: Symptom factors present the first week following concussion may predict subsequent concussion outcomes and recovery duration. We hypothesized that a high loading on cognitive-fatigue-migraine and somatic factors would be predictive of neurocognitive impairment following concussion. We also hypothesized that the affective factor would be related to vestibular symptoms and impairment. DESIGN: Prospective repeated measures SETTING: Concussion specialty clinic PARTICIPANTS: Athletes ages 13–20 years diagnosed with a concussion within the past 7 days INDEPENDENT VARIABLE: Symptom factors at initial visit 1–7 days post-injury. MAIN OUTCOME MEASURE: Symptom factor score, neurocognitive testing, and vestibular/ocular motor assessment at second visit (2–4 weeks post-injury) RESULTS: The somatic symptom factor from initial visit was significant (p.05) at the second visit. The cognitive-migraine-fatigue and affective symptom factors predicted symptom burden at the second visit(p

Study design Cross-sectional study. Objective To determine whether adolescent idiopathic scoliosis (AIS) at onset is associated with oculomotor dysfunction and whether these oculomotor anomalies are correlated to the amplitude of the spine deformation. Summary of background data AIS is related to abnormalities of postural control. To date, few studies have focused on visuo-oculomotor and vestibulo-ocular functions at early-stage AIS. Methods Fifty-three adolescent girls were diagnosed with AIS (mean age: 11.6 ± 2.1 yr) on clinical and radiological criteria (mean Cobb angle: 14.8° ± 5.0°). Visuo-oculomotor and vestibulo-ocular functions were studied with video-oculography, including saccades, smooth pursuit, caloric test, and pendular rotation, with visual vestibular ocular reflex and vestibulo-ocular reflex sequences. Two patient groups were defined according to the mean Cobb angle: group 1 included 29 patients with a Cobb angle from 5° to 14° and group 2 included 24 patients with a Cobb angle from 15° to 25°. Results The group 2 showed different saccade characteristics than group 1: higher latencies for saccade sequences characterized by temporal uncertainty and predictive direction; lower velocity regardless of the type of the saccades. No difference was observed for saccadic accuracy and smooth-pursuit gain. For the visual vestibular ocular reflex, group 2 showed lower total maximal slow-phase velocity than group 1, whereas the vestibulo-ocular reflex (tested in dark) did not differ between groups. No difference was observed concerning the caloric vestibular test. Conclusion Patients with a Cobb angle of 15° or more presented normal vestibulo-ocular responses but altered visuo-oculomotor functions, especially for the saccadic latency and velocity. This could be the result of a dysfunction of oculomotor pathways at cerebellar and/or brainstem level. These central disorders may be incriminated in the development of AIS.

OBJECTIVE: To compare performance of children with acquired brain injury (ABI) on static versus dynamic visuomotor tasks with that of control children. PARTICIPANTS: Twenty-eight children with ABI and 28 normal age- and gender-matched controls (aged 6-16 years). MAIN MEASURES: Two visuomotor tasks on a digitizing tablet: (1) a static motor task requiring tracing of a flower figure and (2) a dynamic task consisting of tracking an accelerating dot presented on a monitor. RESULTS: Children with ABI performed worse than the control group only during the dynamic tracking task; the duration within the target was shorter, the distance between the centers of cursor and target was larger, and the number of velocity peaks per centimeter and the number of stops (ie, the number of submovements) were higher than those of the control group. Rather than resulting from movement execution problems, this might be due to less adequate processing of fast incoming sensory information, resulting in a decreased ability to anticipate the movement of the target (predictive control). CONCLUSION: Deficits in eye-hand coordination require careful attention, even in the postinjury chronic phase. Language: en

Background: In standard perimetry, subjects fixate so that saccades are reduced and testing precision is increased. However, because vision in daily life requires eye movements, it is appropriate to assess visual fields during eye movement. Methods: Perimetry was carried out in 8 healthy subjects and in 16 patients with visual field defects under conditions of a stable and moving fixation spot. Eye movements were simultaneously recorded with an eye tracker. Outcome measures included stimulus detection, variability of visual field border, and saccade amplitudes. Results: Perimetric performance during stable fixation was comparable to that during eye movement. All subjects showed 92%-96% correct detections of the fixation controls and a stable and comparable blind spot position in the stable and moving fixation spot conditions. The eye tracker revealed that 97% of the time the eyes were positioned within ±1 from fixation. Conclusions: Visual fields obtained by perimetry while moving the eyes is comparable to standard perimetry in which a stable fixation spot minimizes eye movements.

Patients with bilateral vestibular de¢cits experience unsteady gait and oscillopsia that can reduce the quality of life, though many patients adapt remarkably well and lead mostly normal lives. One source of adaptation could be the ability of sensory-motor systems to compensate for the vestibular loss by adaptive enhancement of their performance. We studied smooth-pursuit eye movements in ¢ve patients and six healthy control subjects using a step-ramp paradigm. Eye movements were measured with scleral search coils. Patients showed open- and closed-loop pursuit gains that were about 9% higher than controls. We suggest that the challenge of living with a de¢cient vestibular system caused an enhancement in the pursuit system, which contributes to the patient’s overall compensation. NeuroReport 15:2617^2620 � c 2004 Lippincott Williams &W ilkins.

Here, I report that rhesus monkeys are able to generate anticipatory smooth pursuit eye movements in the transient absence of a moving target, if this target moves periodically. The eye velocity before target reappearance was significantly larger if the target trajectory was predictable compared with the control condition consisting of unpredictable target trajectory. Parallel to the registration of the eye movements, single-unit activity was recorded from neurons in the middle superior temporal (MST) area of the two monkeys. The neuronal activity of visual-tracking neurons resembled the observed eye movements, i.e. these neurons increased their activity earlier if the movement of the target was predictable compared with the unpredictable control. These results provide further evidence for the existence of extra-retinal signals in the activity of visual-tracking neurons located in area MST.

Blinks are known to change the kinematic properties of fast eye movements, probably by changes in the brain stem circuits. To determine whether slow disconjugate (slow vergence) eye movements are affected by blinks under natural viewing conditions, we elicited airpuff-evoked trigeminal blinks randomly during ongoing steady slow vergence eye movements. Lid and binocular eye movements were recorded by the scleral search coil method. Slow vergence eye movements showed a peak of vergence velocity during the final part of the blink, which depends on the stimulus direction. We propose that the direction-specific blink effect on slow vergence may be caused by changes in brain stem premotor circuits.

Stimulus motion is a prominent feature that is used by the visual system to segment figure from ground and perceptually bind widely separated objects. Pursuit eye movements can be influenced by such perceptual grouping processes. We have examined the subjects' ability to detect small amounts of coherent motion in random dot kinematograms during pursuit. We compared performance on tests of coherent motion perception while subjects fixated a stationary spot or while they tracked a moving target. The results indicate that smooth pursuit can improve subjects' ability to detect the presence of coherent motion. We tentatively propose that an efference copy of the eye movement signal can enhance the ability of the visual system to detect correlations between sparsely placed targets among noisy distractors.

We present a new method for the analysis of reading eye movements based on the methods of nonlinear dynamics. In this preliminary study, the eye movements of normal and abnormal readers were analyzed for evidence of chaotic, nonlinear dynamical behavior. Both power spectral density analysis and fractal dimension determination showed evidence of nonlinearity as manifest in chaotic behavior. The computed fractal dimension of the system's presumed attractor seemed directly related to qualitative assessment of reading ability. Representative subjects did not differ in a similar analysis of pursuit movements. Although fractal analysis did not distinguish unconditionally between normal and abnormal reading in this preliminary study, it nevertheless offers a promising hitherto unused approach to the analysis of eye movements and the modeling of oculomotor behavior.

We studied the neural substrate of anticipation and learning of smooth pursuit eye movements in humans using fMRI. Both predictable and non-predictable eye movements, compared to baseline, activated a common network previously associated with oculomotor function. The temporal dynamics of activity in a subset of these areas suggested a strong correlation with type of condition. Specifically, differential decreases in activity were seen in dorsolateral prefrontal cortex and the intraparietal sulcus during the predictable condition. During the non-predictable condition the same areas exhibited evidence of high levels of activity that further increased throughout the condition. In contrast, differential increases associated with the predictable condition were seen in anterior cingulate and preSMA cortex regions. These changes in activity mirror the time course of the short-term learning of eye movements seen behaviourally, and are congruent with learning-related changes that have been reported for other motor paradigms.

Using infrared oculography, we compared saccades toward predictable and pseudo-random visual targets in 19 neuroleptic-free patients with schizophrenia (including 13 neuroleptic-naïve patients) and in 29 age- and gender-matched healthy volunteers. Externally driven saccades were not different between patients and controls, whether or not the target was predictable. Anticipated saccades were specifically less accurate in the patients compared to the controls. The difference between primary gain of anticipated and non-anticipated saccades was markedly higher in the patients compared to controls (p=0.003). These results point to a deficit in the early step of internally driven oculomotor planning in schizophrenia.

Our detailed understanding of the physiology and anatomy of the ocular motor system allows an accurate differential diagnosis of pathological eye movement patterns. This review covers important clinical studies and studies in basic research relevant for the neurologist published during the past year.

Each year brings new scientific knowledge that builds on itself in a geometric fashion. Ocular motility basic and clinical neurosciences continue to advance with this accelerating pace. The years 1997 and 1998 brought new knowledge to the motility world. This review focuses on the clinical advances within this realm. Part I of this review appeared in the June 2000 (20:2) issue.

Objectives: To develop a hypothetical scheme to account for clinical disorders of vertical gaze based on recent insights gained from experimental studies.Methods: The authors critically reviewed reports of anatomy, physiology, and effects of pharmacologic inactivation of midbrain nuclei.Results: Vertical saccades are generated by burst neurons lying in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Each burst neuron projects to motoneurons in a manner such that the eyes are tightly coordinated (yoked) during vertical saccades. Saccadic innervation from riMLF is unilateral to depressor muscles but bilateral to elevator muscles, with axons crossing within the oculomotor nucleus. Thus, riMLF lesions cause conjugate saccadic palsies that are usually either complete or selectively downward. Each riMLF contains burst neurons for both up and down saccades, but only for ipsilateral torsional saccades. Therefore, unilateral riMLF lesions can be detected at the bedside if torsional quick phases are absent during ipsidirectional head rotations in roll. The interstitial nucleus of Cajal (INC) is important for holding the eye in eccentric gaze after a vertical saccade and coordinating eye–head movements in roll. Bilateral INC lesions limit the range of vertical gaze. The posterior commissure (PC) is the route by which INC projects to ocular motoneurons. Inactivation of PC causes vertical gaze-evoked nystagmus, but destructive lesions cause a more profound defect of vertical gaze, probably due to involvement of the nucleus of the PC. Vestibular signals originating from each of the vertical labyrinthine canals ascend to the midbrain through several distinct pathways; normal vestibular function is best tested by rotating the patient’s head in the planes of these canals.Conclusions: Predictions of a current scheme to account for vertical gaze palsy can be tested at the bedside with systematic examination of each functional class of eye movements.

In order to accomplish desired movements, the nervous system must specify the movement dynamics: it must provide a signal that compensates for the mechanical constraints encountered during movement. Here we tested whether the population activity of Purkinje cells in the cerebellum specifies the dynamics for pursuit eye movements. We first estimated the population activity by computing weighted averages of Purkinje cell firing on a millisecond time scale. We then generated predicted eye movements by transforming this pooled neural activity with a description of eye mechanics. We found that the equally weighted average of Purkinje cell outputs produced a close match between the predicted and actual eye movements. These findings demonstrate that neural circuits through the cerebellum are capable of providing the dynamic compensation necessary to achieve desired movements.

Motion perception and associated involuntary eye movements depend on factors such as the physical attributes of the stimulus and visual attention. Cues from spatial changes in luminance (first-order motion in the Fourier domain) or more complicated transitions involving two-dimensional patterns (second-order, non-Fourier) require rather different kinds of analyses to detect their net motion. During a fixation task we monitored eye movements induced by the onset of motion to examine the functional properties of the monkey cortical motion processing system. Eye movement velocity was indistinguishable to first- and second-order motion; concomitant response latency confirmed an additional calculation is required to detect the direction and velocity of second-order motion.

It has been demonstrated in normal subjects that smooth pursuit latency is reduced in gap pursuit tasks. We have now measured smooth pursuit latency in a group of schizophrenic subjects in both gap and non-gap conditions. In non-gap tasks pursuit latency was longer in the schizophrenic subjects than in controls. While the addition of gaps produced reductions in pursuit latency in the schizophrenic subjects, the effect was more variable than in controls, with a greater asymmetry between rightward and leftward pursuit latencies. Our results are consistent with the hypothesis that pursuit initiation is modified in schizophrenia and that as with the gap effect on saccades, the gap effect on pursuit is also modified.

The present investigation examined how attention is distributed across both space and time during smooth pursuit eye movements. This was accomplished by measuring manual button pressing latencies to the sudden appearance of a peripheral target during the onset, maintenance, or offset of the pursuit response to a step-ramp target motion. The results showed that manual response latencies were shorter for stimuli flashed ahead of the pursuit target than for those presented in its wake. In addition, the latencies to the peripheral target appearance were shorter overall during pursuit maintenance compared to pursuit onset or offset. Taken together, these results indicate that attention is significantly modulated both in space and time during smooth pursuit eye movements.

Involuntary eye movements to foveal stimulation were measured in a monkey while it performed a fixation task. Second-order plaid motion generated higher velocities of eye movements than did first-order gratings, yet the latency of the early following response was no different for grating or plaid motion. Nevertheless, early suppressed ocular following responses to isoluminant motion continue to be titrated by stimulus velocity and spatial frequency. Motion defined by 60% luminance contrast gratings and plaids generated a motion signal gain of 60% over chrominance motion. The 20% longer latency of eye movements to chrominance motion may reflect the longer conduction latency of the parvocellular channel and an additional stage in cortical processing en route to motion areas and eye movement control.

Objective: To compare the effects of botulinum toxin on static and dynamic aspects of eye movements, and thereby elucidate the mechanisms of its action on eye muscles.Background: Laboratory evidence indicates that static alignment and saccades are subserved by different extraocular muscle fiber types, and botulinum toxin may cause specific dysfunction of the fibers controlling static alignment. Diplopia is a well-known side effect of periorbital botulinum toxin injections in humans, and may be a clinical correlate of the laboratory findings.Methods: Search coil recording of eye movements was performed in one patient with systemic botulism, and in three patients with diplopia following periorbital injection of botulinum toxin A.Results: In the patient with acute botulism, eye movement alignment, range, and saccadic velocity profiles were abnormal. In three patients with iatrogenic diplopia, static alignment was abnormal but movement range and saccadic velocities were within normal limits. Edrophonium improved the range of movements and saccadic velocities in the patient with systemic botulism but was ineffective in reversing ocular misalignment in the one iatrogenic patient to whom it was administered.Conclusions: Precise alignment is subserved by orbital singly innervated muscle fibers, and the effects of botulinum toxin are greatest on these fibers. This predilection is apparent when the toxin dose is very small, as must have been the case in our patients with iatrogenic diplopia. The lack of a response to edrophonium probably reflects structural damage to muscle fibers. In contrast, larger doses of toxin produce an acute dysfunction of all extraocular muscle fiber types, which is responsive to edrophonium and consequently reflects partial blockade at the neuromuscular junction.

Visuomotor performance is known to be disturbed in patients who have advanced Parkinson's disease (PD). The degree of impairment in the early stages of PD was investigated in both the symptomatic and asymptomatic hand of patients with unilateral disease. We examined the visuomotor performance of 10 early unilateral parkinsonian patients and 15 control subjects by using several tracing and tracking tasks that were performed with unseen hands, in which feedback was given through a screen cursor. Significant impairment in control of movement direction was found in tracing of screen paths but not in tracking. Significant slowing of movement was found in target tracking, whereas tracing velocity was normal. Although all patients were judged by standard clinical criteria to be unilaterally affected, visuomotor functions were found to be impaired equally in both hands. Visuomotor control of movement direction and movement velocity is performed independently. Performance along both control dimensions is impaired in the mild stages of parkinsonism, even before the appearance of motor symptoms.

We found a selective loss of vestibular hair cells in a patient followed for more than 10 years with imbalance and oscillopsia due to idiopathic progressive loss of vestibular function. Hearing function and cochlear hair cells were normal. The vestibulo-ocular reflex (VOR) gain at high frequencies was relatively maintained despite marked shortening of the dominant VOR time constant (to less than 500 ms). Ultrastructural examination of remaining hair cells showed mitochondrial abnormalities. The ultrashort VOR time constant probably resulted from changes in firing patterns of the primary afferent nerves due to loss of hair cells and impaired energy metabolism in remaining hair cells.

I recorded smooth pursuit and saccadic eye movements in six patients with unilateral cerebral infarction. By comparing responses within the hemiranges of eye position to the right and left of the orbital midline and in rightward and leftward directions, I quantified craniotopic and directional ocular motor deficits. Two patients had ipsiversive gaze deviation and severe craniotopic defects in which they could not generate smooth pursuit or saccadic eye movement into the contralateral orbital hemirange. Three patients without gaze deviation generated worse smooth pursuit in the contralateral hemirange than in the ipsilateral hemirange, but each had symmetric saccades according to eye position. All patients with craniotopic pursuit defects also had directional smooth tracking asymmetries in which eye velocities were lower for targets moving ipsilaterally than for targets moving contralaterally. Craniotopic and directional defects were associated with damage in the frontal eye field region. Orbital position is taken into account by cerebral circuits that govern smooth pursuit and saccades.

The utility of L-tyrosine (10 g/day in four divided doses) as an adjuvant to molindone (150 mg/day) in the treatment of schizophrenia was investigated using a placebo-controlled, double-blind crossover design (3 weeks on L-tyrosine, 3 weeks on placebo). The objective of this inpatient study was to increase dopaminergic neural transmission along mesocortical projections in patients by increasing the precursor availability of L-tyrosine for dopamine biosynthesis. Theoretically, this approach might lessen both negative and positive symptoms of schizophrenia and improve frontal lobe-mediated neuropsychological performance. There was no evidence of statistically significant improvement conferred by L-tyrosine as measured by weekly Brief Psychiatric Rating Scale (BPRS), Schedule for the Assessment of Negative Symptoms (SANS), or Clinical Global Impressions (CGI) scales. The 12-h trough plasma level of L-tyrosine was significantly higher in all patients during the L-tyrosine phase of the study (t = -3.9, df = 20, p = 0.0009). At the end of each 3-week study period, no significant differences could be found in Wisconsin Card Sorting Test (WCST) or memory test performance. Smooth-pursuit eye movement (SPEM) performance had significantly more saccadic intrusions during the L-tyrosine supplementation phase compared to the placebo period. This increase in saccades during SPEM suggests that the tyrosine supplementation might have had some central effect.

The internal representation of saccade commands has been shown to combine with visual information for saccade programming. In normative studies saccade parameters have been found consistent across tests. Their variability is highly correlated in both eyes suggesting a common saccade generator. Experimental and clinical studies specify the role of frontal eye fields in the volitional, inhibitory control of visually triggered saccades. The parietal lobe instead seems mainly concerned with privileged target selection. A parallel processing of saccade related signals occurs in corticostriatal circuits. Pursuit movements elicited by intermittently illuminated moving targets result from a predictive estimate of eye velocity based on previous eye velocity and visual feedback. Evidence for peristriate and parietal cortical areas to encode the information relevant to smooth pursuit generation is provided by clinical studies.

In this correlation study of visual parameters as related to learning disabilities, we considered several deficits: uncorrected refractive error, accommodative infacility, inaccurate pursuits, and vertical fixation disparity. Because vision is the primary sensory input involved in reading, it is nothing new to find a correlation between visual deficits and learning problems; however, vertical fixation disparity, unique in its relation to other sensory systems, deserves a great deal of attention. The high incidence of vertical fixation disparity measured in 5th and 6th graders with learning disabilities suggests that there is a plausible causal relation. Vertical oculomotor imbalance, vestibular problems, and learning disability are discussed.

Responses of Purkinje cells were compared in the monkey flocculus and ventral paraflocculus. During vestibuloocular reflex (VOR) eye movements, flocculus Purkinje cells exhibited simple spike modulation related to head velocity, while ventral paraflocculus Purkinje cells exhibited modulation with no such head velocity preference. During smooth tracking of a sinusoidally moving small target, ventral paraflocculus Purkinje cells exhibited simple spike modulation related to target velocity or position, while the flocculus Purkinje cells exhibited a smaller modulation with no such target preference. Visual suppression of the VOR enhanced the simple spike responses in the ventral paraflocculus, but not in the flocculus. These results suggest that the primate flocculus and the ventral paraflocculus control differentially VOR and smooth pursuit eye movements, respectively.

A 27-year-old man developed sudden dysarthria and left-sided weakness and paresthesia. Gaze-evoked nystagmus (GEN) was evident in bilateral horizontal gazes (see the video on the Neurology Web site at www.neurology.org). Rightward pursuit was interrupted by catch-up saccades while leftward pursuit was normal (figure, A, and video). Saccadic eye movements and vestibulo-ocular reflex were normal. Brain MRI …

Article abstract Square-wave jerks (SWJs) are small, inappropriate saccades that intrude on steady fixation by taking the eye away from the target and then returning it after approximately 200 msec. The pathophysiology of SWJs is unknown; they have not been attributed to any specific lesion. We found that unilateral pallidotomy substantially increased the frequency of SWJs in three patients with Parkinson’s disease. This effect is likely due to imbalance in the fixation system caused by asymmetric reactivation of prefrontal cortex via ascending thalamocortical projections. Alternatively, disruption of nigral projections to the superior colliculus might be responsible.

A 60-year-old man developed diplopia and experienced difficulty moving his eyes. Vertical movement of each eye, including vestibulo-ocular reflex and smooth pursuit, was extremely limited. Horizontal eye movements were normal. His head position was tilted toward his left. There was 10 prism diopters of exotropia and 10 prism diopters of right hypertropia. Fundus photographs revealed a clockwise torsion of both eyes. These signs indicate leftward ocular tilt reaction. Magnetic resonance imaging showed a small area of an increased signal intensity localized in the midbrain dorsomedial to the red nucleus on the right side. Based on recent experimental evidence, it may be assumed that the unilateral lesion involving the right interstitial nucleus of Cajal most probably caused leftward ocular tilt reaction in our patient.

Three patients who presented with episodic vertigo followed by gait imbalance and oscillopsia had profound bilateral vestibular loss despite normal hearing. All had a parent with similar findings. The patients, their affected parent, and multiple other family members had a history of migraine headaches, although several of the latter had normal vestibular function. Acetazolamide stopped or markedly decreased the frequency of vertigo attacks in the three patients treated but had little effect on the chronic vestibular loss. This is the first report of a dominantly inherited bilateral vestibulopathy associated with normal hearing.

We recorded horizontal smooth pursuit in 23 patients with discrete unilateral cerebral hemispheric lesions and in 12 normal subjects. Most patients had bidirectional reduction of smooth pursuit gain, indicating that each cerebral hemisphere participates in smooth pursuit in both directions. Pursuit gain fell proportionately more with increasing target acceleration in patients than in normals. A normal phase relationship between eye and target motion in patients indicated an intact predictor mechanism for smooth pursuit. Ten patients had pursuit asymmetry with lower gain when tracking toward the side of cerebral damage; none had lower gain when tracking away. Two patients with lower ipsilateral gain had frontal lobe lesions. Areas of anatomic overlap of lesions associated with asymmetric pursuit in 8 patients provide evidence for a pursuit pathway that originates from Brodmann areas 19 and 39 and descends to the brainstem through the posterior limb of the internal capsule.

Albino mammals are known to suffer from misrouted optic projections and there is a growing body of evidence suggesting that human albinos have similar aberrant anatomical pathways. The present study examined the possible consequences of such aberrant pathways on the oculomotor performance of five adult human albinos. Optokinetic nystagmus to drifting grating patterns and pursuit eye movements were measured. The subjects' congenital nystagmus was also measured under different conditions of gaze position and ambient room illumination. Two of the subjects showed clear instances of an inversion in the optokinetic response and there were probable inversions observed for a third subject. The magnitude of the optokinetic nystagmus was appropriate for the rate of pattern drift, but inverted in direction. In all cases smooth pursuit was severely impaired, but reversals of the appropriate direction of pursuit eye movements were not observed. Changes in the congenital nystagmus under conditions of light and darkness were found for four of the five subjects and varied greatly between subjects. The results suggest that human albinos share many of the oculomotor deficits found in other albino species.

Smooth pursuit eye movements (SPEM) to a sinusoidally modulated target moving horizontally across a cathode ray tube screen were examined for 17 patients with dementia of the Alzheimer type (DAT) and for 14 age-matched control subjects. There were 3 target-motion conditions at frequencies representing varying ranges of target velocity. DAT patients differed from controls on all measures of smooth pursuit quality: their gain was reduced at high target velocities and lower target accelerations, they made more frequent directionally appropriate saccades and had more saccadic intrusions, they led the target with their eyes (phase lead) in all 3 conditions, and lag-adjusted cross-correlation coefficients, computed between digitized eye-movement and target signals, were lower among patients. The cross-correlation measure was most sensitive to between-group variability. These results suggest that the impaired SPEM observed in DAT patients reflect degeneration of cortical oculomotor centers, either through inappropriate saccadic intrusions in smooth pursuit as a result of physiologic disinhibition or through effects on attentional processes or both.

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.

Smooth ocular pursuit was measured by magnetic search coil oculography in 13 patients with Alzheimer's disease and compared with control subjects. Smooth eye movement gain was uniformly reduced in Alzheimer's disease at all target velocities for several frequencies of sinusoidal target motion, signifying impairment of steady-state gain. Normal phase relationships between the target and eyes indicated an intact predictor mechanism for smooth pursuit. When peak target velocity was held constant, pursuit gain decreased markedly in response to small increments of target acceleration, indicating involvement of an acceleration saturating nonlinear element that limits smooth pursuit. Large-amplitude saccadic intrusions, in the direction of target motion, often disrupted pursuit; smooth eye movements continued in response to target velocity despite large position errors of the fovea from its target. These disorders of smooth eye movement control can quantify motor dysfunction in Alzheimer's disease.

Smooth pursuit was studied during predictable L-dopa dose-related "off" periods of morning akinesia and wearing off and during "on" periods in eight patients with idiopathic Parkinson's disease. Smooth pursuit gain was significantly reduced in patients during both on and off phases. Despite marked fluctuations between parkinsonism and periods of near normal skeletal motion, there were no changes in smooth pursuit gain. We conclude that unvarying paresis of smooth pursuit in Parkinson's disease signifies involvement of neural circuits that are distinct from the dopaminergic mechanisms that mediate the on-off phenomenon of somatic motor control.