Diagnosing disconjugate eye movements

Serra, Alessandro; Liao, Ke; Matta, Manuela; Leigh, R. John

doi:10.1212/01.wnl.0000327525.72168.57

Cited by 20 publications

(24 citation statements)

References 31 publications

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“…In a prior study of patients with slow horizontal saccades due to brainstem stroke, we have provided evidence that vergence movements may play a substantial role in gaze shifts. 11 Furthermore, improvement of conjugacy during the fatigue test was observed in those patients with a more severe degree of INO (initial VDI Ͼ1.9), who may already have well developed substitution of vergence eye movements for saccades. These different forms of behavior during the fatigue test were evident in some time plots, such as the representative data shown in figure 2.…”

Section: Representative Records Of Horizontal Saccades Made During Thmentioning

confidence: 94%

“…We applied 3 measures of conjugacy of horizontal saccades from data segments collected during the first and last minute of the fatigue test: 1) amplitude ratio (AR) of the size of the abducting saccade to the size of the corresponding adducting saccade, measuring this ratio of change in eye position from the onset of the saccade until the time of the peak velocity, corresponding to the pulse of innervation; 2) the ratio of abducting/adducting peak velocity (versional disconjugacy index [VDI]) 9 ; and 3) the normalized, interocular velocity difference (IVD) measured at 20% of eye displacement on phaseplane plots. This last technique has been described previously, 11 and is summarized briefly here. The displacement (change in position) and velocity of each eye were normalized by assigning a value of 1.0 to the maximum displacement, and to the peak velocity, of the eye making the larger movement.…”

Section: Methodsmentioning

confidence: 99%

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Using fast eye movements to study fatigue in multiple sclerosis

Matta¹,

Leigh²,

Pugliatti³

et al. 2009

Neurology

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Objective: To investigate whether internuclear ophthalmoparesis (INO) due to demyelination of the medial longitudinal fasciculus (MLF) provides a model for studying the poorly understood symptom of fatigue in multiple sclerosis (MS). We asked whether repetitive horizontal saccades increased eye movement disconjugacy in patients with MS with INO, but not in healthy subjects. Methods:We compared conjugacy of horizontal saccades in 9 patients with INO (4 bilateral, total 13) and 8 controls during minute 1 and minute 10 of a fatigue test; we measured the ratio of abducting/adducting peak velocity (versional disconjugacy index [VDI]).Results: VDI values were greater in patients than controls. During the fatigue test, controls showed no changes of VDI, but patients did (p Ͻ 0.005) for 10/13 INOs, with increased ratios in 5 cases and a decrease in the other 5. Conclusion:Fatigue-induced worsening of conjugacy was observed in milder internuclear ophthalmoparesis (INO), and may reflect deteriorated fidelity of saccadic pulse transmission along demyelinated medial longitudinal fasciculus. Improved conjugacy was observed in the more severe INOs, and may be due to adaptive mechanisms, such as recruitment of vergence to aid gaze shifts. INO may provide an accessible, reductionist model to study how decreased neural transmission influences fatigue in multiple sclerosis, how the brain adapts to it, and whether drugs may prove therapeutic. Neurology Fatigue is a disabling symptom of MS but its pathogenesis is not understood.1,2 Internuclear ophthalmoparesis (INO) is common in multiple sclerosis (MS), being evident when patients make rapid gaze shifts (saccades) between 2 horizontally separated targets.3,4 Normal subjects show conjugate horizontal saccades but, in INO, the saccade made by the adducting eye is slowed more than the abducting eye ("adduction lag"). The pathogenesis of INO is well understood (figure 1). [4][5][6] Burst neurons lying in the paramedian pontine reticular formation generate a pulse of innervation that projects to 2 populations of neurons in the abducens nucleus: abducens motor neurons and abducens internuclear neurons. The pulse of innervation passes on axons of abducens motoneurons to the lateral rectus muscle, and the eye accelerates to high speeds. 7,8 Abducens internuclear neurons convey the pulse of innervation, via the medial longitudinal fasciculus (MLF), to medial rectus motoneurons in the contralateral oculomotor nucleus that cause the medial rectus muscle to contract rapidly. In normal subjects, the eyes turn rapidly together, as a conjugate saccade. The initial portion of horizontal saccades, which corresponds to the saccadic pulse, is machine-like and normal limits can be defined for the speed of abducting and the adducting eyes.4,7 INO in MS is due to demyelination of the MLF, which causes slowing of the adducting eye, which can no longer conduct high-frequency From Clinical Neurology (M.M., M.P., I.A., A.S.),

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Section: Representative Records Of Horizontal Saccades Made During Thmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Using fast eye movements to study fatigue in multiple sclerosis

Matta¹,

Leigh²,

Pugliatti³

et al. 2009

Neurology

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“…Comparison of the conjugacy of vertical saccades using phase plane analysis was possible in 9 PSP patients (Serra et al, 2008). We found no asymmetry of upward or downward movements.…”

Section: Fast Eye Movements: Saccades and Quick Phases Of Nystagmusmentioning

confidence: 99%

The Disturbance of Gaze in Progressive Supranuclear Palsy: Implications for Pathogenesis

Chen¹,

Riley²,

King³

et al. 2010

Front. Neur.

112

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Progressive supranuclear palsy (PSP) is a disease of later life that is currently regarded as a form of neurodegenerative tauopathy. Disturbance of gaze is a cardinal clinical feature of PSP that often helps clinicians to establish the diagnosis. Since the neurobiology of gaze control is now well understood, it is possible to use eye movements as investigational tools to understand aspects of the pathogenesis of PSP. In this review, we summarize each disorder of gaze control that occurs in PSP, drawing on our studies of 50 patients, and on reports from other laboratories that have measured the disturbances of eye movements. When these gaze disorders are approached by considering each functional class of eye movements and its neurobiological basis, a distinct pattern of eye movement deficits emerges that provides insight into the pathogenesis of PSP. Although some aspects of all forms of eye movements are affected in PSP, the predominant defects concern vertical saccades (slow and hypometric, both up and down), impaired vergence, and inability to modulate the linear vestibulo-ocular reflex appropriately for viewing distance. These vertical and vergence eye movements habitually work in concert to enable visuomotor skills that are important during locomotion with the hands free. Taken with the prominent early feature of falls, these findings suggest that PSP tauopathy impairs a recently evolved neural system concerned with bipedal locomotion in an erect posture and frequent gaze shifts between the distant environment and proximate hands. This approach provides a conceptual framework that can be used to address the nosological challenge posed by overlapping clinical and neuropathological features of neurodegenerative tauopathies.

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“…We used phase-plane plots of velocity versus displacement (change in position) to make this distinction (Serra et al 2008); an example is shown in Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

The role of the medial longitudinal fasciculus in horizontal gaze: tests of current hypotheses for saccade-vergence interactions

et al. 2010

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Rapid shifts of the point of visual fixation between equidistant targets require equal-sized saccades of each eye. The brainstem medial longitudinal fasciculus (MLF) plays a cardinal role in ensuring that horizontal saccades between equidistant targets are tightly yoked. Lesions of the MLF—internuclear ophthalmoparesis (INO)—cause horizontal saccades to become disjunctive: adducting saccades are slow, small, or absent. However, in INO, convergence movements may remain intact. We studied horizontal gaze shifts between equidistant targets and between far and near targets aligned on the visual axis of one eye (Müller test paradigm) in five cases of INO and five control subjects. We estimated the saccadic component of each movement by measuring peak velocity and peak acceleration. We tested whether the ratio of the saccadic component of the adducting/abducting eyes stayed constant or changed for the two types of saccades. For saccades made by control subjects between equidistant targets, the group mean ratio (±SD) of adducting/abducting peak velocity was 0.96 ± 0.07 and adducting/abducting peak acceleration was 0.94 ± 0.09. Corresponding ratios for INO cases were 0.45 ± 0.10 for peak velocity and 0.27 ± 0.11 for peak acceleration, reflecting reduced saccadic pulses for adduction. For control subjects, during the Müller paradigm, the adducting/abducting ratio was 1.25 ± 0.14 for peak velocity and 1.03 ± 0.12 for peak acceleration. Corresponding ratios for INO cases were 0.82 ± 0.18 for peak velocity and 0.48 ± 0.13 for peak acceleration. When adducting/abducting ratios during Müller versus equidistant targets paradigms were compared, INO cases showed larger relative increases for both peak velocity and peak acceleration compared with control subjects. Comparison of similar-sized movements during the two test paradigms indicated that whereas INO patients could decrease peak velocity of their abducting eye during the Müller paradigm, they were unable to modulate adducting velocity in response to viewing conditions. However, the initial component of each eye’s movement was similar in both cases, possibly reflecting activation of saccadic burst neurons. These findings support the hypothesis that horizontal saccades are governed by disjunctive signals, preceded by an initial, high-acceleration conjugate transient and followed by a slower vergence component.

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Diagnosing disconjugate eye movements

Cited by 20 publications

References 31 publications

Using fast eye movements to study fatigue in multiple sclerosis

Using fast eye movements to study fatigue in multiple sclerosis

The Disturbance of Gaze in Progressive Supranuclear Palsy: Implications for Pathogenesis

The role of the medial longitudinal fasciculus in horizontal gaze: tests of current hypotheses for saccade-vergence interactions

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