Biomedical subjects

L Averbuch-Heller

Publications and source records attributed to L Averbuch-Heller.

At least 19 recordsLinked to original sources

PubMed2001

Supranuclear control of ocular motility.

Ocular motor behavior is dictated by visual demands. The entire brain is involved in programming and executing of eye movements. Gaze shifts performed under natural conditions require an elaborate supranuclear coordination between various motor and sensory mechanisms. Recently, a wealth of novel data emerging from animal studies along with functional imaging in humans expanded and modified traditional schemes of premotor organization of the ocular motor system. In this review, types of eye movements that provide clear and stable vision are delineated, neuroanatomical basis of ocular motor control is considered, and the clinical disorders of supranuclear motility are discussed.

Brain↗

PubMed2000

Acquired nystagmus.

Traditionally, acquired forms of nystagmus have been classified in descriptive terms based on their clinical features and recorded waveforms. In the past 20 years, the mechanisms of several major forms of nystagmus have been elucidated; animal and mathematical models for these ocular oscillations have been developed. These advances, which owe much to modern anatomical, physiological, and pharmacological techniques, have enhanced the diagnostic value of nystagmus and provide the basis for developing rational therapy.

Eye Movements↗

PubMed1999

Square-wave jerks induced by pallidotomy in parkinsonian patients.

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.

Adult↗

PubMed1999

Acquired Nystagmus.

Patients with acquired forms of nystagmus may suffer from oscillopsia and blurred vision; abolishing or reducing nystagmus ameliorates these symptoms. Ideally, treatment of nystagmus should be directed against the pathophysiologic mechanism responsible. Identification of nystagmus pattern is important in directing therapy and occasionally requires electronic eye movement recording for precise characterization. Patients with acquired pendular nystagmus, particularly those with multiple sclerosis, often benefit from gabapentin, a drug with few side effects. Scopolamine, clonazepam, and valproate are also useful in some patients. A new drug, memantine, was effective in treating pendular nystagmus in one study, but it has not yet been approved for use in the United States. Periodic alternating nystagmus usually responds to baclofen. Central vestibular nystagmus, including downbeating and upbeating forms, can be treated with baclofen or clonazepam. In some patients, treatment of an underlying condition, such as periodic ataxia, Whipple's disease, and Chiari malformation, abolishes nystagmus and improves vision. If pharmacologic therapy fails, optical devices can be considered in selected patients. Injections of botulinum toxin and surgery to weaken extraocular muscles are prone to induce diplopia and may precipitate plastic-adaptive ocular motor changes that eventually negate the beneficial effect.

Journal Article↗

PubMed1999

Disconjugate adaptation of saccades: contribution of binocular and monocular mechanisms.

We studied the effects of prism-induced disparity on static and intrasaccadic alignment in six normal human subjects. A ten diopter base-out prism, calling for convergence, was placed in front of the central field of the right eye, so that at the center the eye viewed through the prism; at left and right, outside the prism. During 15 min of training, subjects made repetitive saccades solely in the right field of vision (C-R-C sequence). This paradigm required relative divergence for centrifugal (C-R) saccades and relative convergence for centripetal (R-C) saccades, as well as increase of the amplitude for all saccades made by the right eye. We found that during training, all subjects incorporated the necessary change in alignment into the saccades. After training the resultant intrasaccadic disconjugacy persisted when tested during monocular viewing, indicating that motor learning had occurred. Subjects demonstrated increased divergence for C-R and increased convergence for R-C saccades, in accordance with the change acquired during adaptation to the prism. In addition, five subjects developed increased divergence for C-L saccades, for which they did not train. Smaller and less consistent divergence was also observed for L-C saccades. Changes in intrasaccadic alignment were accompanied by changes in the relative velocities of the two eyes' saccades and slowing of the peak velocities in both eyes during training. Static alignment showed a general tendency toward convergence that did not parallel the changes in the intrasaccadic alignment, suggesting that saccade adaptation is system-specific. The pattern of transfer of the intrasaccadic disconjugacy to saccades in the untrained field and the changes in the relative speeds of the two eyes cannot be explained by monocular adjustment of the saccades. Our results indicate that both a binocular mechanism--saccade-vergence interaction--and monocular adaptation contribute to disconjugate adaptation of saccades.

Adaptation, Psychological↗

PubMed1999

Whipple's disease mimicking progressive supranuclear palsy: the diagnostic value of eye movement recording.

Treatable causes of parkinsonian syndromes are rare; Whipple's disease is one of them. A patient is described who presented with a parkinsonian syndrome and abnormal vertical gaze. Measurement of eye movements showed marked slowing of upward saccades, moderate slowing of downward saccades, a full range of voluntary vertical eye movements, curved trajectories of oblique saccades, and absence of square wave jerks. These features, atypical of progressive supranuclear palsy, suggested the diagnosis of Whipple's disease, which was subsequently confirmed by polymerase chain reaction analysis of intestinal biopsy material. Precise measurement of the dynamic properties of saccadic eye movements in parkinsonian patients may provide a means of identifying treatable disorders.

Biopsy↗

PubMed1999

Latent and congenital nystagmus in Down syndrome.

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

Adult↗

PubMed1998

Pendular nystagmus in patients with peroxisomal assembly disorder.

BACKGROUND: Pendular nystagmus commonly occurs in congenital and acquired disorders of myelin. OBJECTIVE: To characterize the nystagmus in 3 siblings with an infantile form of an autosomal recessive peroxisomal assembly disorder causing leukodystrophy. DESIGN: We examined visual function and measured eye movements using infrared oculography. We noted changes in eye speed and frequency before and after the administration of gabapentin to 1 patient. RESULTS: All 3 siblings showed optic atrophy and pendular nystagmus that was predominantly horizontal, at a frequency of 3 to 6 Hz, with phase shifts of 45 degrees to 80 degrees between the oscillations of each eye. Gabapentin administered to 1 child caused a modest improvement of vision and the reduction of the velocity and frequency of oscillations in the eye with worse nystagmus. CONCLUSION: The pendular nystagmus in these patients was due to their leukodystrophy and may have a similar pathogenesis to the oscillations seen in other disorders affecting central myelin.

Adolescent↗

PubMed1998

Slow vertical saccades in motor neuron disease: correlation of structure and function.

We studied eye movements and brainstem pathology in 2 patients with slow vertical saccades and autopsy-proven amyotrophic lateral sclerosis (ALS). In both patients, the main ocular motor finding was supranuclear vertical gaze impairment with slow vertical saccades. The second patient had difficulty opening his eyes on command, with preserved spontaneous eyelid opening. Postmortem examination in both patients demonstrated cell loss in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and substantia nigra, along with histopathological findings consistent with ALS. The extent of the pathological changes in the riMLF correlated well with the degree of functional impairment as reflected in the slow vertical saccades. We suggest that motor neuron disease with early involvement of vertical saccades represents a distinct clinicopathological entity.

Amyotrophic Lateral Sclerosis↗

PubMed1998

Clinical evidence of extraocular muscle fiber-type specificity of botulinum toxin.

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.

Adult↗

PubMed1997

A double-blind controlled study of gabapentin and baclofen as treatment for acquired nystagmus.

We conducted a double-blind crossover trial comparing gabapentin (up to 900 mg/day) to baclofen (up to 30 mg/day) as therapy for acquired nystagmus in 21 patients. We measured visual acuity and the nystagmus before, and at the end of, 2 weeks on each medication. For a group of 15 patients with acquired pendular nystagmus (APN), visual acuity improved significantly with gabapentin, but not with baclofen. Gabapentin significantly reduced APN median eye speed in all three planes, but baclofen did so only in the vertical plane. In 10 patients with APN, the reduction of nystagmus with gabapentin was substantial and 8 of these elected to continue taking the drug. In 6 patients with downbeat or torsional downbeat nystagmus, changes in median slow-phase eye speed were less consistent with both drugs, either increasing or decreasing, and being dependent on viewing conditions. Only 1 patient showed consistent reduction of median eye speed, and this was achieved by either drug. Our findings suggest that gabapentin may be an effective treatment for many patients with APN and that occasional patients with downbeat nystagmus will respond to gabapentin or baclofen.

Acetates↗

PubMed1997

Neurology of the eyelids.

The role of eyelids is to provide maximal protection to the eyeball without interfering with vision. To accomplish this purpose, an intricate neural network coordinates the lid and eye movements. The lid-eye synkinesis is ultimately based on common innervation of the levator palpebrae superioris (LPS) and the superior rectus muscles. The LPS is variously affected in numerous neurologic disorders. Because the eyelids are readily accessible for inspection, and because they conform to the fundamental laws of neurophysiology, different syndromes of eyelid dysfunction are of great value in topologic diagnosis.

Animals↗

PubMed1997

Torsional eye movements in patients with skew deviation and spasmodic torticollis: responses to static and dynamic head roll.

We measured torsional eye movements induced by sinusoidal rotation or static tilt, of the head in roll while viewing a far or near target in 4 patients with skew deviation due to brainstem lesions, 4 patients with spasmodic torticollis (ST), 2 patients with unilateral eighth nerve section (VIIIS), and 10 normal subjects. Torsional nystagmus was present in all 4 patients with skew deviation. In subjects and patients, responses to both sinusoidal and static roll were larger while viewing the far target, consistent with factors dictated by geometry. Response gains to sinusoidal roll were abnormal in 3 patients with skew (increased in one, decreased in two), abnormal in 3 with ST (increased in 1, decreased in 2), and in abnormal both VIIIS patients (decreased). Greater abnormalities were evident in 3 skew patients while rolling away from the side of their brainstem lesions and in both VIIIS patients while rolling toward their lesioned ears. There were similar but less pronounced changes during static head roll. We conclude that patients with skew, ST, and VIIIS may all have abnormal ocular counter-rolling that is more evident during dynamic testing while viewing a far target. Such abnormalities endure because of the limited influence exerted by vision on torsional eye movements.

Adult↗

PubMed1997

Medical treatments for abnormal eye movements: pharmacological, optical and immunological strategies.

PURPOSE: To review current medical treatments for nystagmus and saccadic intrusions, and their visual consequences. METHODS: Evaluation of studies that have used reliable measurement of eye movements and visual acuity before and after treatment. Interpretation of results in light of physiological and pharmacological studies in animals, and recent immunological advances. RESULTS: There are many case reports of patients with abnormal eye movements being improved by a variety of drugs, but few double-blind, controlled studies have been carried out. Most promising are agents that mediate their effects through the neurotransmitter gamma-aminobutyric acid; such drugs include baclofen and gabapentin. Botulinum toxin, injected into selected extraocular muscles or the retrobulbar space, can abolish nystagmus for several months, but often produces troublesome side-effects, such as diplopia and ptosis, which limit its value. Optical measures to either reduce nystagmus by manipulating vergence angle, or reduce retinal image motion, help some patients. Opsoclonus occurring in association with cancer may be successfully treated with an immuno-adsorption technique using a protein A column. CONCLUSIONS: There is need for controlled, blinded studies to evaluate the many agents reported to improve visual symptoms in individual patients with abnormal eye movements.

Animals↗

PubMed1996

Bilateral ptosis and upgaze palsy with right hemispheric lesions.

Bilateral ptosis is reported with unilateral hemispheric lesions, suggesting partial lateralization of the control of the levator palpebrae superioris. There is a tight synkinesis between vertical eye and eyelid movements, but a similar, lateralized control of vertical gaze has not been previously described. We report 3 patients with right hemispheric infarctions, in whom bilateral ptosis was accompanied by impaired upward gaze. We postulate that this lateralization of ocular motor function reflects the special contribution that the nondominant hemisphere makes to attention.

Aged↗

PubMed1996

Comparison of horizontal, vertical and diagonal smooth pursuit eye movements in normal human subjects.

We compared horizontal and vertical smooth pursuit eye movements in five healthy human subjects. When maintenance of pursuit was tested using predictable waveforms (sinusoidal or triangular target motion), the gain of horizontal pursuit was greater, in all subjects, than that of vertical pursuit; this was also the case for the horizontal and vertical components of diagonal and circular tracking. When initiation of pursuit was tested, four subjects tended to show larger eye accelerations for vertical as opposed to horizontal pursuit; this trend became a consistent finding during diagonal tracking. These findings support the view that different mechanisms govern the onset of smooth pursuit, and its subsequent maintenance when the target moves in a predictable waveform. Since the properties of these two aspects of pursuit differ for horizontal and vertical movements, our findings also point to separate control of horizontal and vertical pursuit.

Adult↗

PubMed1996

Opsoclonus.

Opsoclonus is a rare disorder of the saccadic system, in which fixation is continuously interrupted by multivectorial, back-to-back saccades that at times can be seen only with an ophthalmoscope. To diagnose it reliably, eye movement recording is required. Opsoclonus may be a harbinger of an occult malignancy, though many cases are postinfectious, toxic-metabolic or idiopathic. The underlying malignancy is usually neural crest tumors in children and lung, breast, or gynecologic cancer in adults. Opsoclonus can be accompanied by myoclonus and ataxia. Concurrent appearance of oscillations affecting eyes and limbs suggests a common brainstem generator. Dysfunction of the glycinergic omnipause neurons in the nucleus raphe interpositus has been proposed. Autoantibodies against neural epitopes shared with a tumor are implicated in the pathogenesis of opsoclonus in paraneoplastic cases. Because of the association with malignancies, full oncological work-up is indicated in every case. Coexisting opsoclonus carries a relatively good prognosis for the cancer; however, the neurologic disability may remain even if the tumor has been arrested. New, potentially effective immunoadsorption therapy for opsoclonus is currently under investigation.

Adult↗

PubMed1996

Eye movements.

Recent discoveries emanating from basic electrophysiological, anatomical, and pharmacological studies have implications for the diagnosis and treatment of clinical disorders of eye movements caused by disease affecting the brainstem and cerebellum. Electrophysiological studies have better defined the role of the superior colliculus in programming of saccades, and the nucleus reticularis tegmenti pontis in saccade-vergence interaction. Pharmacological inactivation studies have demonstrated the important role played by gamma-aminobutyric acid in the normal control of gaze and lead to trials of new agents in the treatments of nystagmus.

Eye Diseases↗