1
|
Helmchen C, Heide W, Strupp ML, Straumann D. [Update on central oculomotor disorders and nystagmus]. Laryngorhinootologie 2024; 103:413-421. [PMID: 38195848 DOI: 10.1055/a-2192-7319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
The diagnosis of ocular motor disorders and the different forms of a nystagmus is based on a systematic clinical examination of all types of eye movements: eye position, spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, as well as testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR. Relevant anatomical structures are the midbrain, pons, medulla, cerebellum, and cortex. There is a simple clinical rule: vertical and torsional eye movements are generated in the midbrain, horizontal in the pons. The cerebellum is relevant for almost all types of eye movements; typical pathological findings are saccadic smooth pursuit, gaze-evoked nystagmus or dysmetric saccades.Nystagmus is defined as a rhythmic, most often involuntary eye movement. It normally consists of a slow (pathological) drift of the eyes and a fast central compensatory movement of the eyes back to the primary position (re-fixation saccade). There are three major categories: first, spontaneous nystagmus, i. e. nystagmus which occurs in the gaze straight ahead position as upbeat or downbeat nystagmus; second, nystagmus that becomes visible at eccentric gaze only and third, nystagmus which can be elicited by certain maneuvers, e. g. head-shaking, head positioning, air pressure or hyperventilation, most of which are of peripheral vestibular origin. The most frequent central types of spontaneous nystagmus are downbeat and upbeat, infantile, pure torsional, pendular fixation, periodic alternating, and seesaw nystagmus. Many types of central nystagmus allow a precise neuroanatomical localization: for instance, downbeat nystagmus, which is most often caused by a bilateral floccular lesion or dysfunction, or upbeat nystagmus, which is caused by a lesion in the mesencephalon or medulla oblongata. Examples of pharmacotherapy are the use of 4-aminopyridine for downbeat and upbeat nystagmus, memantine or gabapentin for fixation pendular nystagmus or baclofen for periodic alternating nystagmus.
Collapse
Affiliation(s)
| | - Wolfgang Heide
- Klinik für Neurologie, Allgemeines Krankenhaus Celle, Celle, Deutschland
| | - Michael Leo Strupp
- Neurologische Klinik und Deutsches Schwindel und Gleichgewichtszentrum, Klinikum der Ludwig-Maximilians-Universität, München
| | - Dominik Straumann
- Klinik für Neurologie, Universitätsspital Zürich und Universität Zürich,
| |
Collapse
|
2
|
Kim MK, Lee WH, Yang X, Kim HJ, Choi JY, Kim JS. Opsoclonus Induced by Head-Shaking in Vestibular Migraine. CEREBELLUM (LONDON, ENGLAND) 2024; 23:856-860. [PMID: 37227606 DOI: 10.1007/s12311-023-01571-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/18/2023] [Indexed: 05/26/2023]
Abstract
Opsoclonus refers to saccadic oscillations without an intersaccadic interval occurring in multiple planes. Opsoclonus mostly indicates dysfunction of the brainstem or cerebellum. We report opsoclonus induced by horizontal head-shaking without other signs of brainstem or cerebellar dysfunction in two patients with vestibular migraine (VM). The development of opsoclonus after horizontal head-shaking indicates unstable or hyperactive neural circuits between the excitatory and inhibitory saccadic premotor burst neurons in these patients with VM.
Collapse
Affiliation(s)
- Min-Ku Kim
- Department of Neurology, Dizziness Center, Clinical Neuroscience Center, Seoul National University Bundang Hospital, 82, Gumi-Ro 173 Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea
| | - Won-Hyeong Lee
- Department of Neurology, Dizziness Center, Clinical Neuroscience Center, Seoul National University Bundang Hospital, 82, Gumi-Ro 173 Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea
| | - Xu Yang
- Department of Neurology, Aerospace Center Hospital, Peking University Aerospace School of Clinical Medicine, Beijing, China
| | - Hyo-Jung Kim
- Biomedical Research Institute, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Jeong-Yoon Choi
- Department of Neurology, Dizziness Center, Clinical Neuroscience Center, Seoul National University Bundang Hospital, 82, Gumi-Ro 173 Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea
- Department of Neurology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Ji-Soo Kim
- Department of Neurology, Dizziness Center, Clinical Neuroscience Center, Seoul National University Bundang Hospital, 82, Gumi-Ro 173 Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea.
- Department of Neurology, Seoul National University College of Medicine, Seoul, Republic of Korea.
| |
Collapse
|
3
|
Grossman SN, Rucker JC. Opsoclonus and ocular flutter: evaluation and management. Curr Opin Ophthalmol 2023; 34:465-469. [PMID: 37603546 DOI: 10.1097/icu.0000000000000998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
PURPOSE OF REVIEW Opsoclonus and ocular flutter are saccadic intrusions characterized by spontaneous, back-to-back, fast eye movements (saccades) that oscillate about the midline of central visual fixation without intervening inter-saccadic intervals. When this type of movement occurs exclusively in the horizontal plane, it is called ocular flutter. When it occurs in multiple planes (i.e. horizontal, vertical, and torsional) it is called opsoclonus. The most common etiologic categories are parainfectious and paraneoplastic diseases. Less common are toxic-metabolic, traumatic, or idiopathic origins. The mechanism of these movements relates to dysfunction of brainstem and cerebellar machinery involved in the generation of saccades. In this review, we discuss the characteristics of opsoclonus and ocular flutter, describe approaches to clinical evaluation and management of the patient with opsoclonus and ocular flutter, and review approaches to therapeutic intervention. RECENT FINDINGS Recent publications demonstrated eye position-dependent opsoclonus present only in left gaze, which may be related to dysfunction of frontal eye fields or structures in the cerebellar vermis. SUMMARY Opsoclonus and ocular flutter originate from a broad array of neuropathologies and have value from both a neuroanatomic and etiologic perspective.
Collapse
Affiliation(s)
| | - Janet C Rucker
- Department of Neurology
- Department of Ophthalmology, New York University Grossman School of Medicine, New York, New York, USA
| |
Collapse
|
4
|
Sun YR, Beylergil SB, Gupta P, Ghasia FF, Shaikh AG. Monitoring Eye Movement in Patients with Parkinson's Disease: What Can It Tell Us? Eye Brain 2023; 15:101-112. [PMID: 37519412 PMCID: PMC10377572 DOI: 10.2147/eb.s384763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 06/01/2023] [Indexed: 08/01/2023] Open
Abstract
Parkinson's disease (PD) affects approximately 10 million individuals worldwide. Visual impairments are a common feature of PD. Patients report difficulties with visual scanning, impaired depth perception and spatial navigation, and blurry and double vision. Examination of PD patients reveals abnormal fixational saccades, strabismus, impaired convergence, and abnormal visually-guided saccades. This review aims to describe objective features of abnormal eye movements in PD and to discuss the structures and pathways through which these abnormalities may manifest.
Collapse
Affiliation(s)
- Yue Ran Sun
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, OH, USA
| | - Sinem B Beylergil
- Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA
| | - Palak Gupta
- Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | | | - Aasef G Shaikh
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, OH, USA
- Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| |
Collapse
|
5
|
Saccadic premotor burst neurons and histochemical correlates of their firing patterns in rhesus monkey. J Neurol Sci 2022; 439:120328. [DOI: 10.1016/j.jns.2022.120328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 06/14/2022] [Accepted: 06/15/2022] [Indexed: 11/20/2022]
|
6
|
Shaikh AG. Classics to Contemporary of Saccadic Dysmetria and Oscillations. CEREBELLUM (LONDON, ENGLAND) 2022:10.1007/s12311-022-01443-y. [PMID: 35881321 DOI: 10.1007/s12311-022-01443-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Clear vision requires accurate gaze shift from one object to the other and steadily maintaining it when eyes are at the target. The rapid gaze shifts are assured by the high-frequency burst in the brainstem neuronal firing, the mechanism relying on the tight cerebellar supervision. The cerebellar oversight is equally essential for maintaining gaze on the object of interest. The cerebellar significance on the motor control of gaze and the consequences of cerebellar illness are known for almost three quarters of the century - since David Cogan published the classic paper titled "Ocular Dysmetria, Flutter Like Oscillations of the Eyes, and Opsoclonus." In this classic series of cases, three disorders of gaze shifting and gaze holding were described in a number of etiologies, ultimately manifesting in a final common pathway involving the cerebellum. Since the 1950s, there had been substantial progress in contemporary neurology, experimental neuroscience literature has expanded, and computational models of ocular motor control have flourished in the field. In this short commentary, I will highlight Cogan's cerebellar classic in the context of contemporary research on motor control of saccades.
Collapse
Affiliation(s)
- Aasef G Shaikh
- Department of Neurology, University Hospitals, 11100 Euclid Avenue, Cleveland, OH, 44110, USA.
- Neurology Service and Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA.
- Departments of Neurology and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
| |
Collapse
|
7
|
"Leaky" and "Unstable" Neural Integrator Can Coexist-Paradox Observed in Multiple Sclerosis. J Neuroophthalmol 2021; 40:226-233. [PMID: 32304478 DOI: 10.1097/wno.0000000000000955] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The mechanism for stable gaze-holding requires a neural integrator that converts pulse of neural discharge to steady firing rate. The integrator is feedback-dependent, impaired feedback manifests as either "unstable" integration when it is too much or "leaky" when it is too little. The "unstable" integrator is known to cause sinusoidal oscillations of the eyes called pendular nystagmus, whereas the "leaky" integrator causes jerky eye oscillations called gaze-evoked nystagmus. We hypothesized that integrator can be simultaneously leaky and unstable. Mechanistically, some parts of network are served by increased feedback gain (unstable network), while other part would be decreased feedback gain (leaky). Both leaky and unstable, the network converges on the ocular motor plant, leading to simultaneously present gaze-evoked jerk and sinusoidal nystagmus. We tested our hypothesis by measuring eye movements with search coil technique in 7 multiple sclerosis patients. Five of these patients had gaze-evoked nystagmus and superimposed pendular nystagmus. The gaze-evoked nystagmus depicted all the features of "leaky" integrator, that is, the drifts were always toward the null that was located at the central eye-in-orbit orientation, there were no drifts at null, and the drift velocity increased as the eyes moved farther away from the null. The pendular nystagmus had all the features of "unstable" integrator, that is, constant 4- to 6-Hz frequency, eye-in-orbit position dependence of the oscillation amplitude, and the voluntary saccade causing an oscillatory phase reset. These features were then simulated in a computational model conceptualizing our hypothesis of simultaneously leaky and unstable neural integrator.
Collapse
|
8
|
Schall JD, Paré M. The unknown but knowable relationship between Presaccadic Accumulation of activity and Saccade initiation. J Comput Neurosci 2021; 49:213-228. [PMID: 33712942 DOI: 10.1007/s10827-021-00784-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 01/06/2021] [Accepted: 02/16/2021] [Indexed: 12/01/2022]
Abstract
The goal of this short review is to call attention to a yawning gap of knowledge that separates two processes essential for saccade production. On the one hand, knowledge about the saccade generation circuitry within the brainstem is detailed and precise - push-pull interactions between gaze-shifting and gaze-holding processes control the time of saccade initiation, which begins when omnipause neurons are inhibited and brainstem burst neurons are excited. On the other hand, knowledge about the cortical and subcortical premotor circuitry accomplishing saccade initiation has crystalized around the concept of stochastic accumulation - the accumulating activity of saccade neurons reaching a fixed value triggers a saccade. Here is the gap: we do not know how the reaching of a threshold by premotor neurons causes the critical pause and burst of brainstem neurons that initiates saccades. Why this problem matters and how it can be addressed will be discussed. Closing the gap would unify two rich but curiously disconnected empirical and theoretical domains.
Collapse
Affiliation(s)
- Jeffrey D Schall
- Centre for Vision Research, Vision Science to Application, Department of Biology, York University, Ontario, M3J 1P3, Toronto, Canada.
| | - Martin Paré
- Department of Biomedical & Molecular Sciences and of Psychology, Queen's University, Ontario, ON K7L 3N6, Kingston, Canada
| |
Collapse
|
9
|
Lee JY, Kwon E, Kim HJ, Choi JY, Oh HJ, Kim JS. Opsoclonus Following Downbeat Nystagmus in Absence of Visual Fixation in Multiple System Atrophy: Modulation and Mechanisms. THE CEREBELLUM 2019; 20:724-733. [PMID: 31838647 DOI: 10.1007/s12311-019-01090-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report atypical opsoclonus in a patient with multiple system atrophy and propose a mechanism based on the patterns of modulation by visual, vestibular, and saccadic and vergence stimulation. Firstly, the 6-Hz opsoclonus mostly in the vertical plane occurred only after the development of downbeat nystagmus in darkness without visual fixation. Even after a substantial build-up, visual suppression of the opsoclonus was immediate and complete. Furthermore, the latency for re-emergence of opsoclonus in darkness was greater when the duration of preceding visual fixation was longer. Secondly, the effect of preceding downbeat nystagmus on the development of opsoclonus was evaluated by changing the head position. The opsoclonus did not occur in the supine position when the downbeat nystagmus was absent. After horizontal head shaking, the opsoclonus in the vertical plane gradually evolved into horizontal plane and resumed its vertical direction again after vertical head shaking. Thirdly, any opsoclonus was not triggered by imaginary saccades in the supine position. Lastly, combined vergence and saccadic eye movements during the Müller paradigm did not induce opsoclonus. From these findings of modulation, we suggest that the opsoclonus observed in our patient was invoked by vestibular signals. When the function of the omnipause neurons and saccadic system was impaired, the centrally mediated vestibular eye velocity signals may activate the saccadic system to generate opsoclonus. These atypical patterns of opsoclonus, distinct from the classic opsoclonus frequently observed in para-neoplastic or para-infectious disorders, may be an unrevealing sign of degenerative brainstem or cerebellar disorders.
Collapse
Affiliation(s)
- Ju-Young Lee
- Dizziness Center and Clinical Neuroscience Center, Seoul National University Bundang Hospital, Seongnam, South Korea.,Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, 13620, South Korea
| | - Eunjin Kwon
- Dizziness Center and Clinical Neuroscience Center, Seoul National University Bundang Hospital, Seongnam, South Korea.,Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, 13620, South Korea
| | - Hyo-Jung Kim
- Research Administration Team, Seoul National Univertisy Bundang Hospital, Seongnam, South Korea
| | - Jeong-Yoon Choi
- Dizziness Center and Clinical Neuroscience Center, Seoul National University Bundang Hospital, Seongnam, South Korea. .,Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, 13620, South Korea. .,Department of Neurology, College of Medicine, Seoul National University, Seoul, South Korea.
| | - Hui Jong Oh
- The MTV (Migraine, Tinnitus, and Vertigo) Clinic, Oh Neurology Center, Daegu, South Korea
| | - Ji-Soo Kim
- Dizziness Center and Clinical Neuroscience Center, Seoul National University Bundang Hospital, Seongnam, South Korea. .,Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, 13620, South Korea. .,Department of Neurology, College of Medicine, Seoul National University, Seoul, South Korea.
| |
Collapse
|
10
|
Shaikh AG, Zee DS. Eye Movement Research in the Twenty-First Century-a Window to the Brain, Mind, and More. THE CEREBELLUM 2019; 17:252-258. [PMID: 29260439 DOI: 10.1007/s12311-017-0910-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The study of eye movements not only addresses debilitating neuro-ophthalmological problems but has become an essential tool of basic neuroscience research. Eye movements are a classic way to evaluate brain function-traditionally in disorders affecting the brainstem and cerebellum. Abnormalities of eye movements have localizing value and help narrow the differential diagnosis of complex neurological problems. More recently, using sophisticated behavioral paradigms, measurement of eye movements has also been applied to disorders of the thalamus, basal ganglia, and cerebral cortex. Moreover, in contemporary neuroscience, eye movements play a key role in understanding cognition, behavior, and disorders of the mind. Examples include applications to higher-level decision-making processes as in neuroeconomics and psychiatric and cognitive disorders such as schizophrenia and autism. Eye movements have become valued as objective biomarkers to monitor the natural progression of disease and the effects of therapies. As specific genetic defects are identified for many neurological disorders, ocular motor function often becomes the cornerstone of phenotypic classification and differential diagnosis. Here, we introduce other important applications of eye movement research, including understanding movement disorders affecting the head and limbs. We also emphasize the need to develop standardized test batteries for eye movements of all types including the vestibulo-ocular responses. The evaluation and treatment of patients with cerebellar ataxia are particularly amenable to such an approach.
Collapse
Affiliation(s)
- Aasef G Shaikh
- Neurological Institute, University Hospitals Health System, Cleveland, OH, USA. .,Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA. .,Department of Neurology, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH, 44110, USA.
| | - David S Zee
- Department of Neuroscience, The Johns Hopkins University, Baltimore, MD, USA.,Department of Neurology, The Johns Hopkins University, Baltimore, MD, USA.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, MD, USA.,Department of Ophthalmology, The Johns Hopkins University, Baltimore, MD, USA
| |
Collapse
|
11
|
Shaikh AG, Ghasia FF. Saccades in Parkinson's disease: Hypometric, slow, and maladaptive. PROGRESS IN BRAIN RESEARCH 2019; 249:81-94. [DOI: 10.1016/bs.pbr.2019.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
12
|
Paraneoplastic seesaw nystagmus and opsoclonus provides evidence for hyperexcitable reciprocally innervating mesencephalic network. J Neurol Sci 2018; 390:239-245. [DOI: 10.1016/j.jns.2018.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/28/2018] [Accepted: 05/01/2018] [Indexed: 11/18/2022]
|
13
|
Serra A, Chisari CG, Matta M. Eye Movement Abnormalities in Multiple Sclerosis: Pathogenesis, Modeling, and Treatment. Front Neurol 2018; 9:31. [PMID: 29467711 PMCID: PMC5807658 DOI: 10.3389/fneur.2018.00031] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/15/2018] [Indexed: 01/13/2023] Open
Abstract
Multiple sclerosis (MS) commonly causes eye movement abnormalities that may have a significant impact on patients’ disability. Inflammatory demyelinating lesions, especially occurring in the posterior fossa, result in a wide range of disorders, spanning from acquired pendular nystagmus (APN) to internuclear ophthalmoplegia (INO), among the most common. As the control of eye movements is well understood in terms of anatomical substrate and underlying physiological network, studying ocular motor abnormalities in MS provides a unique opportunity to gain insights into mechanisms of disease. Quantitative measurement and modeling of eye movement disorders, such as INO, may lead to a better understanding of common symptoms encountered in MS, such as Uhthoff’s phenomenon and fatigue. In turn, the pathophysiology of a range of eye movement abnormalities, such as APN, has been clarified based on correlation of experimental model with lesion localization by neuroimaging in MS. Eye movement disorders have the potential of being utilized as structural and functional biomarkers of early cognitive deficit, and possibly help in assessing disease status and progression, and to serve as platform and functional outcome to test novel therapeutic agents for MS. Knowledge of neuropharmacology applied to eye movement dysfunction has guided testing and use of a number of pharmacological agents to treat some eye movement disorders found in MS, such as APN and other forms of central nystagmus.
Collapse
Affiliation(s)
- Alessandro Serra
- Neurology, Louis Stokes VA Medical Center, University Hospitals and Case Western Reserve School of Medicine, Cleveland, OH, United States
| | | | - Manuela Matta
- Neurology, Ospedale San Luigi Gonzaga, Orbassano, Italy
| |
Collapse
|
14
|
Puri S, Shaikh AG. Basic and translational neuro-ophthalmology of visually guided saccades: disorders of velocity. EXPERT REVIEW OF OPHTHALMOLOGY 2017; 12:457-473. [PMID: 30774705 PMCID: PMC6377082 DOI: 10.1080/17469899.2017.1395695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
INTRODUCTION Saccades are rapid, yoked eye movements in an effort to direct a target over fovea. The complex circuitry of saccadic eye movements has been exhaustively described. As a result clinicians can elegantly localize the pathology if it falls on the neuraxis responsible for saccades. Traditionally saccades are studied with their quantitative characteristics such as amplitude, velocity, duration, direction, latency and accuracy. AREAS COVERED Amongst all subtypes, the physiology of the visually guided saccades is most extensively studied. Here we will review the basic and pertinent neuro-anatomy and physiology of visually guided saccade and then discuss common or classic disorders affecting the velocity of visually guided saccades. We will then discuss the basic mechanism for saccade slowing in these disorders. EXPERT COMMENTARY Prompt appreciation of disorders of saccade velocity is critical to reach appropriate diagnosis. Disorders of midbrain, cerebellum, or basal ganglia can lead to prolonged transition time during gaze shift and decreased saccade velocity.
Collapse
Affiliation(s)
- Sushant Puri
- Dept. of Neurology, University Hospitals Cleveland Medical Center and Case Western Reserve University, Cleveland, Ohio, United States
| | - Aasef G. Shaikh
- Dept. of Neurology, University Hospitals Cleveland Medical Center and Case Western Reserve University, Cleveland, Ohio, United States
- Daroff-DelOsso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, Ohio, United States
| |
Collapse
|
15
|
Shaikh AG, Wilmot G. Opsoclonus in a patient with increased titers of anti-GAD antibody provides proof for the conductance-based model of saccadic oscillations. J Neurol Sci 2016; 362:169-73. [PMID: 26944142 DOI: 10.1016/j.jns.2016.01.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 12/20/2015] [Accepted: 01/18/2016] [Indexed: 11/18/2022]
Abstract
Paucity in gamma-amino butyric acid (GABA) due to blockage in the action of glutamic acid decarboxylase (GAD), as seen in the syndrome of anti-GAD antibody, causes adult onset cerebellar ataxia, muscle rigidity, and episodic spasms. Downbeat nystagmus, saccadic dysmetria, impaired ocular pursuit, and impaired cancelation of vestibular ocular reflex are typical ocular motor deficits in patients with syndrome of anti-GAD antibody. We describe opsoclonus, in addition to downbeat nystagmus, in a patient with increased titers of anti-GAD antibody. Paucity in GABA leading to disinhibition to Purkinje target neurons at deep cerebellar and vestibular nuclei might have caused downbeat nystagmus in our patient. Anti-GAD antibody can also increase levels of glutamate the precursor of GABA and the substrate for the action of GAD. We propose that opsoclonus might be due to increased levels of glutamate and subsequent hyperexcitability of excitatory and inhibitory burst neurons leading to reverberation in their reciprocally innervating circuit.
Collapse
Affiliation(s)
- Aasef G Shaikh
- Department of Neurology, Case Western Reserve University, Cleveland, OH, United States; Daroff-DelOsso Ocular Motility Laboratory and Neurology Service, Cleveland VA Medical Center, Cleveland, OH, United States.
| | - George Wilmot
- Department of Neurology, Emory University, Atlanta, GA, United States
| |
Collapse
|
16
|
Moskovitz Y, Yang H. Modelling of noble anaesthetic gases and high hydrostatic pressure effects in lipid bilayers. SOFT MATTER 2015; 11:2125-2138. [PMID: 25612767 DOI: 10.1039/c4sm02667e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Our objective was to study molecular processes that might be responsible for inert gas narcosis and high-pressure nervous syndrome. The classical molecular dynamics trajectories (200 ns) of dioleoylphosphatidylcholine (DOPC) bilayers simulated by the Berger force field were evaluated for water and the atomic distribution of noble gases around DOPC molecules in the pressure range of 1-1000 bar and at a temperature of 310 K. Xenon and argon have been tested as model gases for general anaesthetics, and neon has been investigated for distortions that are potentially responsible for neurological tremors in hyperbaric conditions. The analysis of stacked radial pair distribution functions of DOPC headgroup atoms revealed the explicit solvation potential of the gas molecules, which correlates with their dimensions. The orientational dynamics of water molecules at the biomolecular interface should be considered as an influential factor, while excessive solvation effects appearing in the lumen of membrane-embedded ion channels could be a possible cause of inert gas narcosis. All the noble gases tested exhibit similar order parameter patterns for both DOPC acyl chains, which are opposite of the patterns found for the order parameter curve at high hydrostatic pressures in intact bilayers. This finding supports the 'critical volume' hypothesis of anaesthesia pressure reversal. The irregular lipid headgroup-water boundary observed in DOPC bilayers saturated with neon in the pressure range of 1-100 bar could be associated with the possible manifestation of neurological tremors at the atomic scale. The non-immobiliser neon also demonstrated the highest momentum impact on the normal component of the DOPC diffusion coefficient representing the monolayer undulation rate, which indicates that enhanced diffusivity rather than atomic size is the key factor.
Collapse
Affiliation(s)
- Yevgeny Moskovitz
- Department of Chemistry, Middle Tennessee State University, Murfreesboro, TN 37130, USA
| | | |
Collapse
|
17
|
Ghasia FF, Shaikh AG. Source of high-frequency oscillations in oblique saccade trajectory. Exp Eye Res 2014; 121:5-10. [PMID: 24560678 DOI: 10.1016/j.exer.2014.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 01/28/2014] [Accepted: 02/04/2014] [Indexed: 11/16/2022]
Abstract
Most common eye movements, oblique saccades, feature rapid velocity, precise amplitude, but curved trajectory that is variable from trial-to-trial. In addition to curvature and inter-trial variability, the oblique saccade trajectory also features high-frequency oscillations. A number of studies proposed the physiological basis of the curvature and inter-trial variability of the oblique saccade trajectory, but kinematic characteristics of high-frequency oscillations are yet to be examined. We measured such oscillations and compared their properties with orthogonal pure horizontal and pure vertical oscillations generated during pure vertical and pure horizontal saccades, respectively. We found that the frequency of oscillations during oblique saccades ranged between 15 and 40 Hz, consistent with the frequency of orthogonal saccadic oscillations during pure horizontal or pure vertical saccades. We also found that the amplitude of oblique saccade oscillations was larger than pure horizontal and pure vertical saccadic oscillations. These results suggest that the superimposed high-frequency sinusoidal oscillations upon the oblique saccade trajectory represent reverberations of disinhibited circuit of reciprocally innervated horizontal and vertical burst generators.
Collapse
Affiliation(s)
- Fatema F Ghasia
- Cole Eye Institute, Cleveland Clinic Foundation, 2022 E 105th Street, Cleveland, OH 44106, USA.
| | - Aasef G Shaikh
- Department of Neurology, Emory University, Atlanta, GA, USA
| |
Collapse
|
18
|
Abstract
Saccadic oscillations are continuous back-to-back saccades that cause excessive image motion across fovea and threaten clear vision. Acquired processes, related to immune or metabolic mechanisms, are common culprits. Saccadic oscillations are also seen in degenerative cerebellar disease or as a part of a familial syndrome of saccadic oscillations and limb tremor. Some normal individuals have innate ability to voluntarily trigger saccadic oscillations (i.e. voluntary nystagmus). Contemporary theory for the pathogenesis for saccadic oscillations has emphasized hyperexcitable or disinhibited state of the brainstem saccadic burst neuron membrane. This review discusses etiologies and treatment of saccadic oscillations in light of novel cell membrane based theory.
Collapse
Affiliation(s)
- Aasef G Shaikh
- Department of Neurology, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, OH
| |
Collapse
|
19
|
|