Copyright 2020 The Korean Society of Neuro-Ophthalmology http://neuro-ophthalmology.co.kr S81
대뇌반구 병변으로 인한 안구운동이상
이익성
순천향대학교부천병원 신경과
Ocular Motor Syndromes Caused by Hemispheric Lesions
Eek-Sung Lee, MD
Department of Neurology, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
ISSN: 2234-0971 대한안신경의학회지: 제10권 Supplement 1
Clin Neuroophthalmol 10(Suppl 1):S81-83, November 2020
In this lecture on ocular motor syndromes caused by the cerebral hemispheres, first, I describe the effects of acute lesions; second, the persistent effects of large, unilateral lesions; and third, I discuss the effects of lesions limited to specific lobes. In the lecture on ocular motor syndromes caused caused by the cerebral hemisphere, first, functional neuroanatomy is introduced. Then the effects of the acute lesion are described. Third, the persistent effect of large and unilateral lesions; fourth, the effects of lesions localized to a specific lobe are discussed.
Lee ES • Ocular Motor Syndromes Caused by Hemispheric Lesions
Clin Neuroophthalmol 10(Suppl 1):S81-83, November 2020 S82 http://neuro-ophthalmology.co.kr
Topological Diagnosis of Acute Conjugate Deviations of the Eyes
• Sustained horizontal conjugate gaze deviation:
– Ipsilateral (“looks away from the hemiparesis”): destructive hemispheric lesions (e.g., infarcts), especially with large, posterior, and right-sided location
– Contralateral (“looks toward the hemiparesis”): pontine lesions; thalamic lesions, and rarely with other supratentorial disease (“wrong-way deviation”)
• Intermittent horizontal conjugate gaze deviation:
– Usually a manifestation of epileptic seizures
• Sustained upward gaze deviation:
– Following hypoxic-ischemic insult, early stages – Drug effects and oculogyric crisis
• Sustained downward gaze:
– Thalamic hemorrhage
– Lesions compressing or involving the dorsal midbrain, such as hemorrhage, tumor, hydrocephalus, or following hypoxic-ischemic insult, late stages
Leigh and Zee, Neurology of Eye Movements 5thed.
Enduring Effects of Large Unilateral Hemispheric Lesions on Ocular Motor Function
• Fixation:
– In darkness: eyes drift away from the side of the lesion
– During ophthalmoscopic examination: nystagmus with quick phases toward the side of the lesion (note that the direction of nystagmus appears inverted when viewed through a direct ophthalmoscope because you are seeing the retina behind the center of rotation of the globe)
– Square-wave jerks
• Saccades:
– Slower horizontal saccades to both sides, especially contralaterally – Latency longer for small saccades directed contralateral to the side of the lesion – Inaccurate (hypometric and hypermetric) saccades into the “blind” hemifield – Vertical saccades may have inappropriate ipsilesional horizontal component
• Smooth pursuit:
– Reduced pursuit gain toward the side of the lesion
– Smooth pursuit gain away from the side of the lesion may be increased for low-velocity targets
• Optokinetic:
– Reduced gain for stimuli directed toward the side of the lesion – Impaired optokinetic after-nystagmus
– May be relatively preserved compared with pursuit, with prolonged build-up of slow-phase velocity
• Vestibular:
– Asymmetric responses in darkness—greater for eye movements away from the side of the lesion – During attempted fixation of an imagined or real stationary target asymmetry increases – No asymmetry of responses to impulse head turns
• Forced eyelid closure:
– Eyes usually deviate conjugately away from the side of the lesion: Cogan’s spasticity of conjugate gaze
Ocular Motor Syndromes Caused by Hemispheric Lesions
Eric R. Kandel et al., Principles of Neural Science 5thed.
Cortical Areas Important for Eye Movements
Cortical Areas Important for Eye Movements
Leigh and Zee, Neurology of Eye Movements 5thed.
Paul W. Brazis et al., Localization in Clinical Neurology, 6thed.
Craniotopic vs. Retinotopic
Craniotopic (head-centered) Retinotopic (eye-centered)
대뇌반구 병변으로 인한 안구운동이상 • 이익성
Clin Neuroophthalmol 10(Suppl 1):S81-83, November 2020 http://neuro-ophthalmology.co.kr S83
Effects of Lesions of Posterior Cortical Areas
• Primary visual cortex:
– Acutely: Unable to make saccades or generate smooth pursuit in response to visual stimuli presented into the blind field
– Chronically: Strategies develop to scan the environment and place the image of an object of interest in the intact visual field
• Middle temporal visual area (MT, V5):
– Retinotopic defect of motion vision causing saccades and smooth pursuit to be impaired when visual stimuli fall in the affected visual field
• Medial superior temporal visual area (MST):
– Directional defect of smooth pursuit, with decreased gain for ipsilateral target motion
– Superimposed retinotopic defect, similar to MT lesions
• Posterior insula (“vestibular cortex”):
– Contralateral tilts of subjective visual vertical – Circularvection abolished during optokinetic stimulation
Effects of Parietal Lobe Lesions
• Unilateral lesions (especially right-sided):
– Contralateral inattention
– Ipsilateral gaze deviation or preference
– Increased latency for visually guided saccades (especially with distractor targets):
• Right-sided lesions: bilaterally
• Left sided lesions: contralaterally
– Errors on responses to double-step stimulus
– Impaired smooth pursuit to side of lesion for target moving across textured background
• Bilateral parietal lesions:
– Balint’s syndrome: peripheral visual inattention
(simultanagnosia), inaccurate arm pointing (“optic ataxia”), difficulty in making visually guided saccades (if all voluntary eye movements are affected, involvement of frontal lobes is likely and the term “ocular motor apraxia” has been used)
Effects of Frontal Lobe Lesions
• Effects of Lesions of the Frontal Eye Field (FEF)
– In monkeys, acute unilateral pharmacological inactivation of FEF with muscimol produces:
– An “ocular motor scotoma,” so that all voluntary contralateral saccades with sizes and directions corresponding to the injection site are abolished
– Gaze preference toward the side of the lesion – Impaired smooth pursuit, especially toward side of the lesion – In humans, chronic unilateral lesions affecting the FEF cause:
– Bilateral increase in reaction time of saccades made to visual targets in “overlap” task, to remembered target locations, and to imagined targets during the “antisaccade” task
– Hypometria of saccades made to visual or remembered targets located contralateral to the side of the lesion – Reduced ability to make saccades in anticipation of predictable stepping movement of a target when the target moves away from
the side of the lesion
– Impaired ability to inhibit inappropriate saccades to a novel visual stimulus
– Impairment of smooth pursuit and optokinetic following of targets moving toward the side of the lesion
• Effects of Lesions of the Supplementary Eye Field (SEF) – Lesions involving the SEF in humans do not affect visually guided saccades – Memory-guided saccades become inaccurate if gaze shifts during the memory period
– Impaired ability to make a remembered sequence of saccades to an array of visible targets (especially with left-sided lesions)
• Effects of Lesions of Dorsolateral Prefrontal Cortex (DLPC)
– Pharmacological blockade of D1dopamine receptors causes inaccuracy of saccades made to remembered target locations lying contralateral to the side of injection
– Patients with lesions affecting this area show defects of predictive saccades, memory-guided saccades and antisaccades
• Effects of Lesions of Anterior Cingulate Cortex
– Increased saccadic reaction time and decreased gain on overlap and memory-guided tasks – Bidirectional errors in the antisaccade task
– Errors of sequences of saccades made to remembered target locations
